Energy & Technology
Agricultural Emissions in the United States
The agricultural sector affects the climate system in four distinct, but interrelated, ways outlined below and explored further in the subsequent sections of this overview.
- Greenhouse gas emissions associated with agriculture - Agriculture is directly responsible for 7 percent of total U.S. greenhouse gas emissions, largely from soil management (fertilizer use) and livestock; the agricultural sector is also an end user for electricity and transportation fuels.
- Agriculture and carbon storage - Agriculture affects the global carbon cycle because agricultural practices and land use alter the amount of carbon stored in plant matter and soil, and consequently, the amount of carbon dioxide (CO2) in the atmosphere.
- Energy and product substitution from agriculture - Biomass from the agricultural sector can be used to displace fossil fuels for energy purposes and to make a variety of bio-based products.
- Agriculture and the climate system: beyond greenhouse gases - Agriculture also interacts with the climate system in an important way that is not related to greenhouse gas emissions or storage by changing the amount of heat absorbed or reflected by the earth’s surface.
Although this overview does not aim to address the wide range of observed and projected impacts of climate change on agriculture, it is important to note that agriculture will be affected in a variety of ways as temperatures rise and precipitation patterns change (see Climate Change 101: Science and Impacts). The impacts of climate change on agriculture will vary by crop, across regions, and through time. Since the linkages between climate and agriculture are dynamic, the impacts of the climate on agriculture will in turn alter the way agriculture affects the climate.
Greenhouse Gas Emissions Associated with Agriculture in the United States
Direct greenhouse gas emissions from the U.S. agricultural sector account for 7 percent of total U.S. emissions (see Figure 1). Direct emissions from the U.S. agricultural sector account for 7 percent of total U.S. emissions (see Figure 1). Direct emissions from agriculture include methane (CH4) and nitrous oxide (N2O) emissions from a relatively small number of sources (see Figure 2). Distributing emissions from electricity and transportation among end-use sectors modestly increases the amount of greenhouse gas emissions attributable to the agricultural sector to roughly 7 percent of total U.S.
Figure 1: U.S. Greenhouse Gas Emissions by Economic Sector (2010)
Source: Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010, Table ES-7, 2012. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Direct greenhouse gas emissions from agriculture include methane (CH4) and nitrous oxide (N2O) emissions from a relatively small number of sources (see Figure 2). Distributing emissions from electricity and transportation among end-use sectors modestly increases the amount of greenhouse gas emissions attributable to the agricultural sector to roughly 7 percent of total U.S. emissions.
Agricultural soil management, including the application of nitrogen-based fertilizers, accounts for more than 40 percent of all agricultural emissions. Enteric fermentation, a normal digestive process in animals that produces methane, is the second largest source (nearly 30 percent) of agricultural emissions; beef and dairy cattle account for nearly 95 percent of emissions from enteric fermentation. Livestock manure management accounts for an additional 14 percent of emissions. Other emissions sources, including rice cultivation and the field burning of agricultural residues, account for 6 percent of non-energy related direct greenhouse gas emissions from agriculture.
Energy use is the fourth largest source of emissions, accounting for 10 percent of total agricultural emissions (see Figure 2). Both direct energy use in support of farming activities, such as the electricity used to power irrigation pumps and the liquid fuels for vehicles used in the fields, and indirect energy use, which includes the emissions from the production of commercial fertilizers and other energy-intensive farm inputs, produce emissions.
Figure 2: Emissions from Agriculture by Source (2010)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010, Table 2-12, 2012. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Agriculture and Carbon Storage
Plants, including agricultural crops, play an integral role in the global carbon cycle. The carbon cycle consists of four major stocks of carbon: the atmosphere, the oceans, the terrestrial biosphere (vegetation and soils), and sediments and rocks. Carbon moves from one stock to another at different rates through a variety of pathways. Plants, for example, convert atmospheric CO2 into a usable form of chemical energy, sugar, through photosynthesis. As the plants use the sugar’s energy, some of the carbon is released back into the atmosphere as CO2, and the rest of the carbon is used by the plant to grow new biomass. The carbon embodied by terrestrial plants can then replenish the carbon in soil, for example, through the decomposition of fallen leaves.
The agricultural sector affects carbon storage in two main ways:
- Land use conversion: Converting land from one use to another can result in significant changes to the amount of stored carbon; forests and wetlands generally store more carbon than grasslands, which in turn tend to store more carbon than croplands.
- Land management practices: A variety of land management practices help maintain and increase the amount of stored carbon on agricultural lands. These practices include agroforestry, improved cropping systems, improved nutrient and water management, conservation tillage, water management, and maintenance of perennial crops.
The U.S. Department of Agriculture classifies 62 percent of land in the contiguous 48 states as agricultural and 52 percent of land in all 50 states (see Figure 3).
Figure 3: Land Use in the Contiguous 48 States (2011)
Source: USDA Economic Research Service. Major Land Uses in the Continguous United States, 2007 (2011) http://www.ers.usda.gov/data-products/major-land-uses.aspx#25988 Note: Special use is defined as rural transportation, rural parks and wildlife, defense and industrial, plus miscellaneous farm and other special uses. Other land is unclassified uses such as marshes, swamps, bare rock, deserts, tundra and other uses not estimated, classified, or inventoried.
The U.S. Environmental Protection Agency (EPA) has estimated the annual carbon fluxes associated with land use, land-use change, and forestry for the contiguous 48 states. Land-use practices and land-use change can result in either a net release of carbon stored in the plants and soil (making the system a carbon source) or a net uptake of carbon by the plants and soil (making the system a carbon sink).
For agricultural lands, specifically croplands and grasslands, the annual carbon flux values include changes to the amount of carbon stored in soils due to land management and changes in land use, as well as the CO2 emissions resulting from the application of lime and urea fertilizer. Collectively, agricultural lands in the United States act as a small carbon sink, storing more carbon than they release (see Figure 4). For comparison, forests act as a much larger carbon sink in the United States, storing about 20 times more carbon than the total carbon sink provided by all agricultural lands.
Figure 4: Changes in Carbon Storage of Agricultural Land in 2010
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009, Table 7-1, 2011. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Based on the emissions measured by the EPA, agricultural land use and land-use change act as a small net sink for greenhouse gas emissions. However, when greenhouse gas emissions (Figure 2) and carbon storage (Figure 4) are totaled, the sector is a net source of greenhouse gas emissions on a CO2-equivalent basis.
Energy and Product Substitution from Agriculture
The agricultural sector is one source of biomass for bio-based products and energy. Bio-based products include a broad range of commercial and industrial items, excluding food and feed, that range from plastics to bedding made completely or in large part from agricultural and forestry products. Agricultural biomass, which can include waste materials or dedicated energy crops, can also be used to produce electricity, heat, and liquid fuels, broadly referred to as bioenergy.
Substituting biomass for fossil fuels in energy production has the potential to reduce greenhouse gas emissions. The combustion of fossil fuels adds to the atmosphere CO2 that has been stored in deep rock formations for millions of years. The combustion of biomass returns the atmospheric CO2 taken up through photosynthesis and converted into new plant material, making bio-based fuels theoretically carbon neutral. However, the full climate impact of bioenergy requires a broader assessment that accounts for the life-cycle emissions associated with the biomass, including land management practices, land use change, conversion processes and associated energy use, and transportation.
In 2011, biomass (including biofuels, biomass from wood and municipal solid waste from biogenic sources, landfill gas, sludge waste, agricultural byproducts and other biomass) provided 4.5 percent of total energy consumed in the United States, or nearly half of all renewable energy (see Figure 5). For more information on biofuels, see Climate TechBook: Biofuels Overview.
Figure 5: U.S. Energy Consumption by Energy Source with Biomass Breakdown, 2011
Source: Energy Information Administration (EIA), Annual Energy Review, Energy Consumption by Energy Sector, (Topic 2.1b – f), Renewable Energy (Topic 10.1). September 2012. http://www.eia.gov/totalenergy/data/annual/index.cfm
Agriculture and the Climate System: Beyond Greenhouse Gases
The interface between terrestrial ecosystems and the climate system encompasses a wide range of complex interactions that includes, but is not limited to, greenhouse gas emissions and carbon storage. Agriculture also affects the amount of solar energy that the land surface absorbs or reflects. The fraction of solar energy reflected by a surface is known as the albedo; bright surfaces like ice and snow that reflect a lot of solar energy have a high albedo, while dark surfaces, like the ocean, have a low albedo and tend to absorb greater amounts of solar energy.
Albedo is important to the climate system because absorbed sunlight warms the surface and is released back into the atmosphere as heat. Darker vegetation and exposed soils tend to absorb more sunlight and, therefore, release more heat into the atmosphere, producing a local warming effect. This warming can play an important role in the overall climate system.
Agricultural land, which includes cropland, managed grassland, and permanent crops, occupies about 40-50 percent of the world’s total land surface. In 2005, non-energy direct greenhouse gas emissions from agriculture accounted for 10-12 percent of total global greenhouse gas emissions from human-made sources. Agriculture accounts for 60 percent of global N2O emissions and 50 percent of CH4 emissions. A combination of population growth and changing diets has led to increased emissions of these gases from the agricultural sector since at least 1990. This increase can be attributed to the increased use of nitrogen-based fertilizers and the increased number of livestock being raised, especially cattle.
Population growth, changing diets, and changing standards of living will continue to affect the amount and type of food demanded. Recent years have also seen greater interest in and demand for dedicated energy crops. These trends have several possible implications on greenhouse gas emissions:
- Increasing land use change to increase the amount of cropland available for food or energy crops will affect carbon storage. The effect of land use change on carbon change will depend on a variety of factors, including previous land use, land management practices, and type of crops grown. An expansion of croplands could result in an overall loss of plant and soil carbon.
- Increasing crop yields will likely require more inputs, such as water and fertilizer, for a given a unit of land. Increasing agricultural inputs will result in higher emissions per unit of agricultural output because more energy will be required to produce the inputs and direct emissions from fertilizer use will increase.
- Rising demand for meat and dairy products will increase methane emissions from enteric fermentation and manure production. The Intergovernmental Panel on Climate Change (IPCC) projects that methane emissions from livestock could increase 60 percent by 2030, depending on whether greenhouse gas-mitigating feeding practices and manure management are used. Larger livestock populations could also result in land use change to create grazing lands.
Growing interest in the lifecycle carbon emissions of food may also change patterns of food production and consumption. Lifecycle emissions arise from agricultural inputs (including water and fertilizer), equipment for cultivating and harvesting crops, and transportation to consumers. Possible outcomes of using lifecycle analysis include more localized production—producing food close to its point of consumption—and using organic farming methods that minimize fertilizer use. Particularly in today’s globalized food market, accounting for life cycle emissions will be crucial in reducing greenhouse gas emissions associated with agriculture and livestock.
Agriculture Sector Mitigation Opportunities
The agricultural sector can contribute to climate change mitigation in a variety of ways. Mitigation efforts can reduce the direct greenhouse gas emissions from agriculture, increase carbon storage, substitute bio-based products and feedstocks for fossil fuels, and reduce the amount of heat absorbed by the earth’s surface. Some of these mitigation opportunities provide relatively straightforward solutions, but others face a variety of challenges, including the accurate measurement of greenhouse gas fluxes.
Mitigation opportunities can be identified from each of the four types of interactions that agriculture has with the climate system. A wide range of options exist, but with different levels of technical feasibility, cost-effectiveness, and measurement certainty. A number of the mitigation options for the agricultural sector, including soil management practices, also bring a variety of co-benefits, such as improved water quality and reduced erosion. To date, a number of policies thought to have climate benefits have been pursued in order to achieve one or more of these co-benefits.
Reduce greenhouse gas emissions
- Reduce greenhouse gas emissions from energy use: Energy-related greenhouse gas emissions from the agricultural sector can be reduced in a number of ways, including the use of more fuel-efficient machinery and the installation of on-site renewable energy systems for electricity.
- More efficient fertilizer use: Increasing the efficiency of nitrogen use reduces the need for additional fertilizer inputs. This can be achieved by fertilizing during the most appropriate period for plant uptake, fertilizing below the soil surface, and balancing nitrogen fertilizers with other nutrients that can stimulate more efficient uptake. These measures can reduce N2O emissions.
- Improved manure management: When manure is held in an oxygen-poor (anaerobic) environment—such as a holding tank—for an extended period of time, bacteria decompose this material and release methane as a byproduct. Reducing the moisture content and the amount of storage time are two options for reducing methane emissions from manure.
- Improved animal feed management : Facilitating the digestive process for livestock—such as using easy-to-digest feed—can reduce methane emissions from enteric fermentation.
- Improved rice cultivation practices: When rice paddies are flooded, the oxygen-poor (anaerobic) environment allows certain bacteria to create methane through a process called methanogenesis. Periodically draining rice paddies can inhibit this process by aerating the soil.
Increase vegetation and soil carbon stocks
- Land-use changes to increase soil carbon: Reforestation and afforestation initiatives can increase the amount of biomass in a given area of land, thereby sequestering carbon in plant material.
- Land management practices that increase soil carbon: A variety of land management practices can be implemented to increase soil carbon. These include the use of high-residue crops, such as sorghum, that produce a large amount of plant matter left in the field after harvest; the reduction or elimination of fallow periods between crops; the efficient use of manures, nitrogen fertilizers, and irrigation; and the use of low- or no-till practices. Importantly, local conditions will determine the best practices for a given location, and all of these practices do not increase carbon storage in all locations.
Substitute biomass feedstocks and products for fossil fuels
The use of bio-based products as fuels and product substitutes has the potential to reduce fossil fuel combustion and associated greenhouse gas emissions. However, careful life-cycle analysis is necessary to ensure that the substitution yields a net reduction of greenhouse gas emissions.
Non-greenhouse gas related climate interactions
Less attention has been given to mitigation options that do not affect greenhouse gas emissions, but a 2009 study did suggest that crops could be bred or genetically engineered to be more reflective to help reduce warming by reflecting more solar energy from the land surface.
Uncertainty and Mitigation Potential
Key aspects of the agricultural sector’s climate interactions involve complex biological processes. These processes continue to be studied by scientists to fill gaps in our understanding of how these processes work and to reduce the uncertainty associated with current data on greenhouse gas fluxes from agricultural systems. Although the agricultural sector is sometimes identified as having a potentially large role in mitigating climate change, especially by increasing carbon storage in developing countries, further scientific advances will be necessary for the agricultural sector to achieve its full mitigation potential.
Estimates of agriculture’s mitigation potential in the United States vary for different practices. For example, emissions of N2O could be reduced by 30 to 40 percent with improved fertilization practices. Methane (CH4) emissions could be reduced by 20 to 40 percent by improving livestock and methane management. Croplands could store up to 83 MMT of carbon per year, equivalent to about 1 percent of total U.S. greenhouse gas emissions, through widespread adoption of best management practices.
Our work at C2ES covers a wide variety of agriculture-related topics, including climate policy and how it interacts with the sector, low-carbon technology status and outlook, and agricultural practice innovation. We track and inform policymaking at the state, federal, and regional levels, collaborate on papers and briefs, blog about current issues, and educate policymakers and others with up-to-date online resources about important developments in the sector and those relevant to the sector.
Tracking policy - We track policy progress at the state, federal, and international level. Our state maps provide information about which states have implemented policies that promote the use of bio-based products and feedstocks as substitutes for fossil fuels. We also track and analyze policy at the national level, including what is happening in Congressand the Executive Branch.
Climate Compass Blog - Our blog includes posts about current issues related to agriculture, and you can view relevant posts here.
Climate Techbook - The agriculture section of the Climate Techbook provides an overview of the sector as well as briefs describing technologies and practices related to agriculture and GHG emissions. Below is a list of the Techbook factsheets that pertain to agriculture.
|Anaerobic Digesters||Cellulosic Ethanol|
Intergovernmental Panel on Climate Change (IPCC)
- Climate Change 2007: Mitigation, Contribution of Working Group III to the Fourth Assessment Report, 2007
- Climate Change 2007: Impacts, Adaptation, and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report, 2007
U.S. Global Change Research Program
U.S. Climate Change Science Program
- The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States, 2008
U.S. Department of Agriculture
U.S Environmental Protection Agency (EPA)
Related Business Environmental Leadership Council (BELC) Companies
|DTE Energy||PG&E Corporation|
 For more information, see Intergovernmental Panel on Climate Change (IPCC). “Food, fibre and forest products.” In Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report. Cambridge: Cambridge University Press, 2007. http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter5.pdf
 To calculate this value, two datasets are used. Emissions from energy use come from: U.S. Department of Agriculture (USDA), U.S. Agriculture and Forestry Greenhouse Gas Inventory: 1990-2008, 2011. http://www.usda.gov/oce/climate_change/AFGGInventory1990_2008.htm. Emissions from non-energy use come from: Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009, 2011. http://www.epa.gov/climatechange/emissions/usinventoryreport.html.
 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007, 2009. http://www.epa.gov/climatechange/emissions/usinventoryreport.html.
 One million metric ton is equal to one teragram. For reference, one million metric ton of CO2e is equal to 280,000 new cars each being driven 12,500 miles or 90 minutes of U.S. energy consumption or 1 day of U.S. energy emissions from lighting buildings, see U.S. Department of Energy (DOE). 2008 Buildings Energy Data Book. Prepared for U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by D&R International, Ltd. Silver Spring, MD, 2008. http://buildingsdatabook.eren.doe.gov/.
 Chapin, F. S., P.A. Matson, H. A. Mooney. Principles of Terrestrial Ecosystem Ecology. New York: Springer Science + Business Media, Inc. 2002.
 Richards, K. R., R. N. Sampson, and S. Brown. Agricultural & Forestlands: U.S. Carbon Policy Strategies. Prepared for the Pew Center on Global Climate Change, 2006. /global-warming-in-depth/all_reports/ag_forestlands
 EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009, 2011. http://www.epa.gov/climatechange/emissions/usinventoryreport.html.
 The emissions of a gas, by weight, multiplied by its "global warming potential." Global warming potential is a system of multipliers devised to enable warming effects of different gases to be compared. The cumulative warming effect, over a specified time period, of an emission of a mass unit of CO2 is assigned the value of 1. Effects of emissions of a mass unit of non-CO2 greenhouse gases are estimated as multiples. For example, over the next 100 years, a gram of methane (CH4) in the atmosphere is currently estimated as having 23 times the warming effect as a gram of carbon dioxide; methane's 100-year GWP is thus 23. Estimates of GWP vary depending on the time-scale considered (e.g., 20-, 50-, or 100-year GWP) because the effects of some greenhouse gases are more persistent than others.
 Department of Agriculture. Final Rule. “Designation of Biobased Items for Federal Procurement,” Federal Register 71, no. 51 (16 March 2006): 13686. http://www.epa.gov/EPAFR-CONTENTS/2006/March/Day-16/contents.htm
 DOE, Energy Efficiency and Renewable Energy. “Biomass FAQs.” http://www1.eere.energy.gov/biomass/printable_versions/biomass_basics_fa.... Updated 16 January 2009.
 Paustian, K., J. M. Antle, J. Sheehan, and E. A. Paul. Agriculture’s Role in Greenhouse Gas Mitigation. Prepared for the Pew Center on Global Climate Change, 2006. /global-warming-in-depth/all_reports/agriculture_s_role_mitigation
 Chapin et al. 2002.
 Intergovernmental Panel on Climate Change (IPCC). “Agriculture.” In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report. Cambridge University Press: Cambridge, 2007. http://www.ipcc.ch/ipccreports/ar4-wg3.htm.
 IPCC 2007.
 IPCC 2007.
 Ridgwell, A., J. S. Singarayer, A. M. Hetherington, and P. J. Valdes. “Tackling Regional Climate Change by Leaf Albedo Bio-Geoengineering” Current Biology 19 (2). (2009).
 IPCC 2007.
 Paustian et al. 2006.
Residential and Commercial Emissions in the United States
Greenhouse gas emissions data can be reported either by economic sector, which includes electric power generation as a separate sector, or by end-use sector, which distributes the emissions from electricity generation across the economic sectors where the electricity is used. The residential and commercial sectors are large consumers of electricity, so it is appropriate to address both emissions from direct sources and electricity end-use for these sectors.
Direct emissions from the residential and commercial sectors respectively account for 5.6 and 5.4 percent of total greenhouse gas emissions in the United States (see Figure 1).
Figure 1: U.S. Greenhouse Gas Emissions by Economic Sector (2010)
Source: Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010, Table ES-7, 2012. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Ninety-three percent of the residential sector’s direct greenhouse gas emissions come from the combustion of fossil fuels, primarily for heating and cooking. Less than 7 percent of direct emissions come from the substitution of ozone depleting substances and other minor sources. In the commercial sector, nearly 60 percent of direct emissions come from on-site fossil fuel combustion. Other sources of direct commercial emissions include landfills, wastewater treatment, the substitution of ozone depleting substances, and other minor sources (see Figure 2).
Figure 2: Direct Emissions of Greenhouse Gases in the U.S. Commercial Sector (2010)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010, Table 2-12, 2012. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
U.S. electricity sales are split among the residential, commercial, and industrial sectors, with the residential and commercial sectors accounting for 39 and 35 percent of sales, respectively.(see Figure 3).
Figure 3: Retail Sales of Electricity to Ultimate Customers, Total by End-Use Sector(2010)
Source: U.S. Energy Information Administration (EIA), Electric Power Monthly, Table 5.1, September 2012. http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_01
When emissions from electricity generation are attributed to end-use sectors, the residential and commercial sectors are responsible for 18 and 17 percent of total U.S. emissions, respectively (see Figure 4). Electricity-related geenhouse gas emissions account for 70 percent of total residential emissions and 67 percent of total commercial emissions.
Figure 4: Direct and Electricity-Related Greenhouse Gas Emissions by End-Use Sector (2010)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010, Table 2-14, 2012. http://epa.gov/climatechange/emissions/usinventoryreport.html
Buildings: Key Drivers of Residential and Commercial Emissions
Emissions from the residential and commercial sectors, including both direct emissions and end-use electricity consumption, can largely be traced to energy use in buildings. Diverse factors determine how much energy buildings consume; these include the size of the building, the design and materials used, and the kinds of lighting and appliances installed.
Building Trends for Greenhouse Gas Emissions, Size, and Energy Use Intensity
Total greenhouse gas emissions, including both direct and end-use emissions, from residential and commercial buildings in the United States accounted for about 40 percent of total U.S. carbon dioxide (CO2) emissions and 7 percent of global CO2 emissions in 2010. Greenhouse gas emissions attributable to buildings have been steadily increasing; in recent decades, emissions from the on-site combustion of fossil fuels have remained relatively steady while electricity consumption has increased (see Figure 5).
Figure 5: CO2 Emissions for U.S. Residential and Commercial Buildings
Source: DOE, 2011 Buildings Energy Data Book, Section 1.4.1, March 2012. http://buildingsdatabook.eren.doe.gov/.
Greenhouse gas emissions from buildings have increased as building size has increased. In the residential sector, the number of homes and the size of these homes have been increasing over time. As homes grow larger, more energy is generally needed for heating, cooling, and lighting. Over time, homes also have added more appliances and consumer electronics.
Even as residential energy use has increased overall, the amount of energy used per square foot of residential buildings, a measure of energy intensity, has decreased, due to the increased efficiency of consumer appliances and recent regional building trends, such as improved residential building energy codes. (see Figure 6) Energy intensity indicators are used to compare energy use in buildings through time. These indicators are used to examine energy-use trends in the different types of buildings in the residential and commercial sectors. They show how the amount of energy used per unit of output or activity has changed over time. Using less energy per unit of output reduces energy intensity; using more energy per unit increases the energy intensity. A weather factor is used to take into account the impacts of annual weather variation on energy consumption.
Figure 6: Residential Energy Use, Energy Use Intensity, and Energy Use Factors
Source: DOE, Energy Efficiency and Renewable Energy (EERE), “Trend Data: Residential Buildings Sector,” updated 14 May 2008. Note: The indicators on this chart are based on an Energy Use Index that is calibrated to 1985 levels.
In the commercial sector, both energy use and energy intensity have generally increased in recent decades. The general rise in energy intensity since 1985 has shown, however, a modest decline in recent years (see Figure 7). Commercial buildings have shown steady growth in size in recent years, as reflected by the increase in average floor space through time.
Figure 7: Commercial Energy Use, Energy Use Intensity, and Energy Use Factors
Source: DOE, EERE, “Trend Data: Commercial Buildings Sector,” updated 14 May 2008. Note: The indicators on this chart are based on an Energy Use Index that is calibrated to 1985 levels.
Energy End Use in Buildings
In the residential sector, space heating and cooling accounts for 43 percent of total primary energy use. Therefore, total energy demand from this sector is fairly sensitive to weather and varies considerably by region in a single year and over time in a given location. Other significant end uses of energy in the residential sector include water heating, lighting, refrigeration, electronics, wet cleaning and cooking (see Figure 8).
Figure 8: Residential Buildings Primary Energy End Use Splits (2010)
Source: DOE, 2011 Buildings Energy Data Book, Section 2.1.5, March 2012. http://buildingsdatabook.eren.doe.gov/.
In the commercial sector, space heating, ventilation and space cooling accounts for 43 percent of total primary energy use and lighting accounts for one-fifth. Refrigeration, water heating, electronics, computers, and cooking also use significant quantities of energy in the commercial sector (see Figure 9). The commercial sector encompasses a variety of different building types, including schools, restaurants, hotels, office buildings, banks, and stadiums. Different building types have very different energy needs and energy intensities.
Figure 9: Commercial Buildings Primary Energy End Use Splits (2010)
Source: DOE, 2011 Buildings Energy Data Book, Section 3.1.4, March 2012. http://buildingsdatabook.eren.doe.gov/.
For more information on buildings, see Climate TechBook: Buildings Overview.
On a global scale, energy use and greenhouse gas emissions data for the residential and commercial sectors can be difficult to quantify. Globally, the quantity of energy use attributed to buildings, as a proxy for the residential and commercial sectors, varies by country and climate. Energy consumption levels and primary fuel types of buildings in a specific country depend on economic and social indicators, such as national income and level of urbanization. Some key trends observed include:
- In general, developed countries consume more energy per capita than developing countries; developed countries tend to have bigger building sizes for comparable building functions, and they tend to use more appliances and other energy-using equipment than developing countries.
- Urban areas in developed countries use less energy per capita than rural areas; this is because of , district heating in higher-density areas, decreased transportation-related energy consumption, and other factors. However, the opposite effect can be seen in many developing countries where energy useis higher in cities than in rural areas because residents often have higher incomes and greater access to energy services.
- In some countries, grid-connected power remains unavailable or unaffordable for households. In these areas, which include large portions of sub-Saharan Africa, as well as parts of India and China, biomass and coal are often the primary fuels for heating and cooking. This has important implications both for global greenhouse gas emissions and development goals, including:
- Global data on GHG emissions often do not account for emissions from biomass that is collected and burned locally. Household-level combustion of biomass and coal are estimated to account for about 10 percent of global energy use and 13 percent of direct carbon emissions.
- The use of woody biomass, unless sustainably managed, can lead to widespread deforestation. Forests play important roles as local resources and as global carbon sinks.
- Indoor combustion of biomass and coal is a significant health concern; high rates of respiratory illness have been documented in areas that predominantly use biomass or coal for heating and cooking. Reducing GHG emissions through appropriate technology advances, energy efficiency improvements, and the use of alternative fuels will have important health co-benefits.
- Commercial energy intensity in developed countries, the energy use per dollar of income as measured by GDP, is currently almost twice that of developing countries. Commercial buildings’ energy consumption is projected to be the fastest-growing end-use sector for energy in developing countries. Economic growth in developing countries will likely lead to increased global demand for energy, and, without energy efficient products and practices, could lead to substantially higher global energy consumption and GHG emissions.
Residential and Commercial Sector Mitigation Opportunities
Reducing emissions from the residential and commercial sectors can be done in a variety of ways and on a number of scales:
- Addressing landfills
Landfill waste can be reduced (thereby lowering the volume of decomposing material that produces methane, a powerful greenhouse gas) or harnessed as an energy source. Methane-capture systems in landfills prevent greenhouse gases from being released into the atmosphere.
- Reducing embodied energy in building materials
Embodied energy refers to the energy used to extract, manufacture, transport, install, and dispose of building materials. Choosing low carbon materials—such as local materials, materials that sequester carbon, and products manufactured at efficient industrial facilities reduces emissions.
- Improving building design and construction
Building designs and construction techniques can maximize the use of natural light and ventilation, which minimizes the need for artificial light and HVAC equipment. Using building shading techniques, installing windows to minimize or maximize solar intake (depending on the region), and properly insulating against unwanted air flow between indoor and outdoor spaces improve energy use. Many other options are available and “green” builders are continually creating innovative ways to maximize efficiency in building spaces.
- Increasing end-use energy efficiency
Using efficient appliances can minimize energy consumption and concomitant GHG emissions from electricity and direct fossil fuel combustion.
- Adopting new energy-use habits
Following conservation guidelines and making personal choices to reduce the use of appliances, artificial lighting, and HVAC equipment (for example, by shutting them off when they are not in use) will reduce energy use. Also, opting for smaller residential and commercial spaces can reduce the energy needed for building construction and operation.
Our work at C2ES focuses on all types of commercial and residential building topics, including policy and low-carbon building technologies. We track state and federal building and efficiency policies, blog about building-related energy issues, and create and maintain a current online resource of building technologies.
Tracking Policy – Our state maps provide useful overviews of state policies supporting energy-related building codes and standards, such as Commercial Building Energy Codes. We also track and analyze policy at the national level, including what is happening in Congress and the Executive Branch.
Research – We produce research, including reports, white papers, and briefs, on climate and clean energy issues.
Climate Compass Blog – On our blog we inlclude posts related to the residential and commercial sectors. See our blog posts.
Climate Techbook – The Residential & Commercial section of the Climate Techbook provides an overview of these sectors and decriptions of technologies related to improving building energy efficiency. Below is a list of all the buildings-related Techbook factsheets.
|Residential & Commercial Overview||Natural Gas|
|Buildings Overview||Residential End-Use Efficiency|
|Building Envelope||Smart Grid|
U.S. Department of Energy (DOE)
U.S. Energy Information Administration
U.S. Environmental Protection Agency (EPA)
Related Business Environmental Leadership Council (BELC) Companies
|Bank of America||HP|
|Duke Energy||Johnson Controls, Inc.|
 Hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) are used as alternatives to several classes of ozone-depleting substances (ODSs) that are being phased out under the terms of the Montreal Protocol and the Clean Air Act Amendments of 1990. Ozone depleting substances—chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl chloroform, and hydrochlorofluorocarbons (HCFCs)—are used in a variety of industrial applications including refrigeration and air conditioning equipment, solvent cleaning, foam production, sterilization, fire extinguishing, and aerosols. Although HFCs and PFCs are not harmful to the stratospheric ozone layer, they are potent greenhouse gases. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2010, 2012. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
 Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009, 2011. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
 U.S. Department of Energy (DOE). 2011 Buildings Energy Data Book. Section 1.4.1. Prepared for the DOE Office of Energy Efficiency and Renewable Energy by D&R International, 2012. http://buildingsdatabook.eren.doe.gov/.
 One million metric ton is equal to one teragram. For reference, one million metric ton of CO2e is equal to 280,000 new cars each being driven 12,500 miles or 90 minutes of U.S. energy consumption or 1 day of U.S. energy emissions from lighting buildings, see DOE, 2010 Buildings Energy Data Book, 2011.
 DOE, Energy Efficiency Trends in Residential and Commercial Buildings, August 2010. http://apps1.eere.energy.gov/buildings/publications/pdfs/corporate/build... U.S. Census Bureau, Housing Vacancies and Homeownership, http://www.census.gov/hhes/www/housing/hvs/historic/index.html.
 DOE 2010
 The weather factor is included to show variations in weather conditions that may have had an impact on energy use in a given year. Data that is weather-adjusted shows how the indicator would have performed under “normal” weather conditions; for example, data in years with extreme weather (such as unusually cool weather that would increase energy consumption for indoor heating) is adjusted to show performance without the influence of weather. As the figure indicates, weather conditions have remained fairly stable while other indicators have risen; this indicates that weather conditions do not have as much of an impact on energy use as other factors.
 International Energy Agency (IEA). World Energy Outlook, 2010 Edition. Paris: IEA, 2010. http://www.worldenergyoutlook.org/2010.asp.UNEP, Urban Density and Transport-related Energy Consumption, http://maps.grida.no/go/graphic/urban-density-and-transport-related-energy-consumption.
 Smith, K. R. and E. Haigler. “Co-Benefits of Climate Mitigation and Health Protection in Energy Systems: Scoping Methods.” Annual Review of Public Health 29 (2008): 11-25.
Electricity Emissions in the United States
The electricity sector is responsible for about one-third of all U.S. greenhouse gas emissions (see Figure 1) and 38 percent of total carbon dioxide (CO2) emissions.
Figure 1: U.S. Greenhouse Gas Emissions by Sector (2014)
Source: U.S. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table ES-7, 2014. http://www.epa.gov/climatechange/ghgemissions/usinventoryreport.html.
A snapshot of the fuels used in the United States for electricity shows that coal-fueled generation provides a little more than 39 percent of all electricity, down from nearly 50 percent in 2006. Filling this gap, natural gas now provides more than a quarter of all electricity, and renewables, including wind and large hydroelectric power, provide about 13 percent. Nuclear power continues to provide around one-fifth of net generation (see Figure 2).
Figure 2: U.S. Net Electricity Generation by Energy Source (2013)
Source: Energy Information Administration (EIA), Monthly Energy Review, May 2014, Table 7.2a, 2014. http://www.eia.gov/totalenergy/data/monthly/#electricity.
The greenhouse gas emissions associated with different sources of electricity vary significantly, depending on the carbon content of the fuel being used. Carbon dioxide makes up almost 99 percent of the greenhouse gas emissions from electricity generation, and carbon dioxide emissions from coal combustion account for almost 80 percent of total electricity generation-related emissions. The combustion of natural gas and petroleum account for most of the remaining carbon dioxide emissions (see Figure 3). Electricity generation-related greenhouse gas emissions have decreased more than 16 percent since 2007.
Figure 3: Electricity Generation-Related GHG Emissions (2012)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table 2-13, 2014. http://www.epa.gov/climatechange/ghgemissions/usinventoryreport.html.
Key Generation Technologies in Use
Coal-fueled electricity is generated almost exclusively by pulverized coal (PC) power plants. These plants crush coal into a fine powder and then burn it in a boiler to heat water and produce steam. The steam is then used to spin one or more turbines to generate electricity. Natural gas, oil or biomass can be used as a fuel in conjunction with steam turbine technology. Similarly, in a nuclear reactor, fission is used to heat water, which directly or indirectly produces steam to drive a turbine and generate electricity. Large coal and nuclear steam units on the order of 500 – 1000 MW or greater are typically used to provide baseload  generation, meaning that they supply electricity nearly continuously.
Figure 4: Steam Turbine
Combustion (or single-cycle) turbines are another widespread power generation technology. In a combustion turbine, compressed air and burning fuel (diesel, natural gas, propane, kerosene, biogas, etc) are ignited in a combustion chamber. The resulting high temperature, high velocity gas flow is directed at turbine blades that spin the turbine and common shaft, which drives the air compressor and the electric power generator. Combustion turbine plants are typically operated to meet peak  load demand, as they are able to be switched on relatively quickly. Newer turbines are able to be switched on and off frequently, so they can provide a firm backup to intermittent wind and solar on the power grid if needed. The typical size is 100 – 400 MW.
Figure 5: Combustion Turbine
Source: Duke Energy. http://www.duke-energy.com/about-energy/generating-electricity/oil-gas-f....
A basic combined cycle power plant combines a single gas (combustion) turbine and a single steam unit all in one, although there are other possible configurations. As combustion turbines became more advanced in the 1950s, they began to operate at ever higher temperatures, which created a significant amount of exhaust heat. In a combined-cycle power plant, this waste heat is captured and used to boil water for a steam turbine generator, thereby creating additional generation capacity. Historically, they have been used as intermediate  power plants, generally supporting higher electricity use during daytime hours. However, newer natural gas combined cycle plants are now providing baseload support.
Figure 6: Combined-Cycle Turbine
Source: Global-Greenhouse-Warming.com. http://www.global-greenhouse-warming.com/gas-vs-coal.html.
The industrial sector accounts for 26 percent of U.S. electricity sales, with the residential and commercial sector evenly sharing the remainder. (see Figure 7).
Figure 7: Retail Sales of Electricity to Ultimate Customers, Total by End Use Sector (2013)
Source: EIA, Electric Power Monthly, Table 5.1, May 29, 2014. http://www.eia.doe.gov/cneaf/electricity/epm/table5_1.html.
The primary end uses of electricity vary by sector. In the residential sector, space heating, water heating, space cooling and lighting together account for more than half of household electricity use (see Figure 8). In the commercial sector, lighting is the largest electricity end use (see Figure 9). In the manufacturing sector, half of all electricity use is for powering electric motors (see Figure 10).
Figure 8: Residential Electricity Consumption by End Use (2010)
Source: DOE, Buildings Energy Data Book, Table 2.1.5, March 2012. http://buildingsdatabook.eren.doe.gov/ChapterIntro2.aspx.
Figure 9: Commercial Electricity Consumption by End Use (2010)
Source: DOE, Buildings Energy Data Book, Table 3.1.5, March 2012. http://buildingsdatabook.eren.doe.gov/ChapterIntro3.aspx.
Figure 10: Manufacturing Electricity Consumption by End Use (2006)
Source: EIA, Manufacturing Energy Consumption Survey (MECS), Table 5.2, 2006. http://www.eia.doe.gov/emeu/mecs/.
Since 1949, U.S. electricity generation has grown dramatically, with an average annual growth rate of 4.2 percent (see Figure 11). Since 2000, however, U.S. electricity generation has grown at an average rate of less than 1 percent. During this time, generation from natural gas has increased at an average annual rate of 4.9 percent, and non-hydro renewable generation has increased at an average annual growth rate of 9.2 percent. Coal generation has decreased at an average annual rate of 1.6 percent, and in 2013 fell below the level generated in 1990.
Figure 11: U.S. Net Electricity Generation by Source (1949-2013)
Source: EIA, Total Energy, Electricity Net Generation, 2014. http://www.eia.gov/totalenergy/data/monthly/index.cfm#electricity.
From 1990 to 2013, U.S. electricity generation-related greenhouse gas emissions grew an average of 0.5 percent per year, with a general decrease in annual emissions over the past several years (see Figure 12). During this time, the proportion of electricity generation-related greenhouse gas emissions from coal combustion, which peaked in 1996 at around 85 percent, has fallen to 77 percent in 2013. The share of emissions from natural gas combustion has grown from around 9 percent in 1990 to just over 21 percent in 2013, and the share of emissions from petroleum has fallen from around 5 percent to a little more than 1 percent over the same period.
From 1990 to 2013, CO2 emissions from electricity generation, electricity generation, and real gross domestic product (GDP) grew at annual average rates of 0.5, 1.3, and 2.5 percent, respectively (see Figure 13). This illustrates that the U.S. economy grew less electricity-intensive per value of output while the electricity generation also became less carbon intensive over this period.
Figure 12: U.S. Electricity Generation-Related Greenhouse Gas Emissions (1990-2012)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table 2-13, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html.
Figure 13: Relative Growth of Electricity Generation, CO2 Emissions from Electricity Generation, and GDP
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 – 2012, Table 2-13, 2014; EIA, Total Energy, Table 7.2a, 2014. http://www.eia.gov/totalenergy/data/annual/index.cfm#electricity; Bureau of Economic Analysis, Gross Domestic Product, http://www.bea.gov/national/index.htm.
Globally, CO2 is the most abundant anthropogenic greenhouse gas, accounting for 76 percent of total anthropogenic greenhouse gas emissions in 2008; the CO2 emissions from fossil fuel use alone account for 62 percent of total greenhouse gas emissions. ,  Electricity generation is by far the largest single source of CO2 emissions (see Figure 14).
Figure 14: Sources of Global CO2 Emissions (1970-2004, Direct Emissions by Sector Only)
Source: Intergovernmental Panel on Climate Change (IPCC), "Introduction." In Mitigation of Climate Change. Contribution of Working Group III to the Fourth Assessment Report. Cambridge: Cambridge University Press, 2007. Figure 1.2. http://www.ipcc.ch/ipccreports/ar4-wg3.htm
Notes: (1) Including fuel wood at 10% net contribution, large-scale biomass burning averaged data for 1997–2002, including decomposition and peat fires, excluding fossil fuel fires; (2) other domestic surface transport, non-energetic use of fuels, cement production, and venting/flaring of gas from oil production; (3) including aviation and marine transport.
The generation profile of global electricity production is similar to that of the United States, with coal being the largest energy source for electricity production (see Figure 15). Globally, 5.1 percent of electricity is generated by oil, whereas in the United States oil makes up less than 1 percent. Also, hydropower makes up a larger share of global electricity generation, while the United States gets a greater proportion of its electric power from nuclear. The United States contributes more than one-fifth of global carbon dioxide emissions from electricity and heat production; China and the United States are the largest single emitters (see Figure 16).
Figure 15: World Electricity Generation by Fuel (2011)
Source: Energy Information Administration (EIA), International Energy Statistics, 2014.
Notes: Other includes geothermal, solar, wind, combustible renewables & waste, and heat.
Figure 16: CO2 Emissions from Fossil Fuel Combustion for Electricity and Heat (2011)
Source: IEA, CO2 from Fossil Fuel Combustion 2013. Paris: IEA, 2013. http://www.iea.org/Textbase/publications/free_new_Desc.asp?PUBS_ID=1825.
Electricity Sector Mitigation Opportunities
In general terms, greenhouse gas emission reductions from the electric power sector can be achieved through efficiency (i.e., eliminating waste), conservation (i.e., reducing the amount of electricity generated), switching fuel sources (i.e., from coal to lower-emitting natural gas), and by incorporating low- and zero-carbon electricity generation technologies (i.e., reducing the emissions associated with electricity generation), such as renewable energy, carbon capture and storage, and nuclear power.
Many studies have analyzed the most cost-effective mix of emission-reduction options. Some of the most widely cited studies include:
- Electric Power Research Institute (EPRI), “The Full Portfolio,” see http://mydocs.epri.com/docs/CorporateDocuments/AboutEPRI/DiscussionPaper2007.pdf.
- Intergovernmental Panel on Climate Change, “Special Report on Renewable Energy Sources and Climate Change Mitigation,” see http://srren.ipcc-wg3.de.
- International Energy Agency (IEA), “Energy Technologies for a Low-Carbon Future: Insights from Energy Technology Perspective 2008,” see http://www.scribd.com/doc/5534059/IEA-Energy-Technologies-for-a-Low-Carbon-Future.
- Google’s Clean Energy 2030 Plan, see http://knol.google.com/k/-/-/15x31uzlqeo5n/1#.
Over the past 20 years U.S. electricity generation has become less carbon intensive, and the U.S. economy has grown less electricity-intensive. Further mitigating greenhouse gas emissions from electricity generation will require a comprehensive approach, including lower-, low- and zero-carbon electricity generation technologies, incorporating renewable energy, switching to lower-emitting fuels, coal or gas with carbon capture and storage, and nuclear power, as well as energy efficiency and conservation. Several types of policies can be employed to promote these mitigation techniques, including emissions pricing (e.g. carbon tax or cap and trade), electricity portfolio standards (also known as clean energy standards), emission performance standards, financial incentives for clean energy deployment and energy efficiency, and research and development to support innovative technologies.
Our work at C2ES covers all types of electricity-related topics, including policy and regulation, low-carbon technology status and outlook, and technology innovation. We track and inform policymaking at the state, federal, and regional levels, collaborate on research for papers and briefs, blog about current energy issues, and educate policymakers and others with up-to-date online resources about important low-carbon technologies.
Tracking policy - We track policy progress at the state, federal, and international level. Our state maps provide information about which states have implemented policies that promote low-carbon electricity technologies and energy efficiency. We also track and analyze policy at the national level, including what is happening in Congress and the Executive Branch.
Research - We produce research, including reports, white papers, and briefs, on climate and clean energy issues. For example, our 2005 report titled The U.S. Electric Power Sector and Climate Change Mitigation is a comprehensive look at reducing greenhouse gas emissions from the electricity sector.
Climate Compass Blog - Our blog includes posts about current issues related to electricity, and you can view relevant posts here.
Climate Techbook - The Climate Techbook provides briefs describing technologies related to electricity generation and energy efficiency. Below is a list of the Techbook factsheets that pertain to electricity.
International Energy Agency (IEA)
U.S. Department of Energy (DOE)
U.S. Energy Information Administration (EIA)
U.S Environmental Protection Agency (EPA)
Related Business Environmental Leadership Council (BELC) Companies
 Baseload generation describes electric power plants that typically run all day and night, seven days a week.
 Peak generation describes electric power plants that run only during times of the highest demand. For example, high demand can occur in the morning when many consumers are waking up and switching on electric appliances or on hot summer afternoons when many air conditioners are running simultaneously.
 Intermediate generation describes electric power plants that typically run only during daytime hours to support higher use of electrical appliances, computers, lighting and so on.
 International Energy Agency (IEA), CO2 Emissions From Fuel Combustion (2011). Section III, Figure 1, p III.4.
Industrial Emissions in the United States
Greenhouse gas emissions data can be reported either by economic sector, which includes electric power generation as a separate sector, or by end-use sector, which distributes the emissions from electricity generation across the economic sectors where the electricity is used. The industrial sector encompasses a wide range of activities (manufacturing, agriculture, mining and construction), including all facilities and equipment used for producing, processing, or assembling goods. Greenhouse gas emissions are produced from diverse processes, including the combustion of fossil fuels for heat and power, non-energy use of fossil fuels, and numerous industrial processes. The industrial sector is a large consumer of centrally generated electricity (26 percent of total U.S. electricity sales), so it is appropriate to address both emissions from direct sources and electricity end use for this sector. When electric power sector emissions are assigned to the end-use sectors that consume the electricity, the industrial sector accounts for 28 percent of total U.S. greenhouse gas emissions.
Direct emissions from the industrial sector account for 20 percent of total greenhouse gas emissions in the United States (see Figure 1).
Figure 1: U.S. Greenhouse Gas Emissions by Economic Sector (2012)
Source: Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table ES-7, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Emissions from the industrial sector come from fossil fuel combustion from manufacturing facilities (57 percent) and from non-energy use of fuels and industrial processes (43 percent). For example, heating iron ore to produce iron directly releases carbon dioxide (CO2). Similarly, the cement manufacturing process requires heating limestone, which also results in the release of CO2.
In addition to on-site fossil fuel combustion, the main sources of industrial emissions in the United States (Figure 2) include: natural gas systems (13 percent), the non-energy use of fuels (7 percent), coal mining (4 percent), iron and steel production (4 percent), cement production (3 percent), petroleum systems (2 percent), and a variety of other sources (9 percent). Industrial process emissions, which excludes on-site fossil fuel combustion, mobile combustion, natural gas systems and non-energy use of fuels, account for 5 percent of total U.S. greenhouse gas emissions.
Figure 2: Direct Emissions of Greenhouse Gases from the U.S. Industrial Sector (2012)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table 2-12, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Industrial process emissions include numerous greenhouse gases, including several gases with high global warming potentials, like hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). Global warming potential (GWP) is a metric used to compare the warming effects of different gases. Over a 100-year time horizon, carbon dioxide (CO2) is assumed to have a GWP of one. In comparison, SF6 has a GWP of 23,900, which means that over 100 years one ton of SF6 will have the same effect as 23,900 tons of CO2 (see Table 1).
The industrial sector is responsible for 25 percent of total non-CO2 emissions, specifically 40 percent of total U.S. methane (CH4), 7 percent of nitrous oxide (N2O), and 19 percent of other (HFCs, PFCs and SF6) emissions.
Table 1: Global Warming Potentials for 100-year Time Horizon
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table ES-1, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
Between 1990 and 2012, total industrial process emissions increased a little less than 6 percent, as emission decreases from some sources have been offset by increases from other sources. Notably, HFCs have increased more than 300 percent during this time period as a result of phasing out ozone depleting substances, such as chlorofluorocarbons (CFCs) (see Figure 3). Also, the economic downturn and slow recovery (2008 – 12) has reduced CO2 emissions from cement production more than 23 percent below their 2006 peak.
Figure 3: Industrial Process Emissions by Greenhouse Gas Type in Million Metric Tons of CO2e
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table 2-6, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
U.S. electricity sales are split among the residential, commercial, and industrial sectors, with the industrial sector accounting for almost 26 percent of sales (see Figure 4).
Figure 4: Retail Sales of Electricity to Ultimate Customers, Total by End-Use Sector (2012)
Source: U.S. Energy Information Administration (EIA), Electric Power Monthly, Table 5.1, September 2014. http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_01
When greenhouse gas emissions from electricity generation are distributed across the end-use sectors, the industrial sector is the second largest source of greenhouse gas emissions, responsible for almost 28 percent of total U.S. emissions (see Figure 5). Emissions from the use of electricity generated off-site (“electricity-related emissions” in the graph below) are also called indirect emissions to distinguish them from the direct emissions released on site.
Figure 5: Direct and Electricity-related Greenhouse Gas Emissions by End-Use Sector (2012)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table 2-14, 2014. http://epa.gov/climatechange/emissions/usinventoryreport.html
Relative to the residential and commercial sectors, a smaller percentage of the industrial sector’s greenhouse gas emissions come from electricity use. The industrial sector relies less on purchased electricity in part because of the on-site production of heat and power, also known as cogeneration or combined heat and power (CHP).
Industrial Emission Sources and Types
The industrial sector encompasses a diverse collection of businesses that have a variety of energy and feedstock needs to create products that range from paper to gasoline to pharmaceuticals. While greenhouse gas emissions from the electricity sector depend largely on the type of fuel used, and emissions from the residential and commercial sectors come largely from buildings, similar generalizations cannot be made about the industrial sector. Examining industrial emissions on an industry-by-industry basis shows that the magnitude of emissions associated with different industries varies significantly (see Figure 6).
Figure 6: Greenhouse gas Emissions for Key Industrial Sub-sectors in Million Metric Tons (MMT) of CO2e (2002)
Source: EPA, Quantifying Greenhouse Gas Emissions from Key Industrial Sectors in the United States, Working Draft, Table 1-3, 2008. http://www.epa.gov/ispd/
Figure 6 also shows the relative importance of different types of emissions to individual industries. For example, five industries (oil and gas, chemicals, iron and steel, mining, and cement) produce the majority of non-combustion-related direct emissions. Similarly, oil and gas, chemicals, construction, forest products, and food and beverages produce large amounts of greenhouse gas emissions from on-site fossil fuel combustion.
Certain industries are termed energy-intensive because they require large energy inputs per unit of output or activity. The largest energy-consuming industries in the United States are bulk chemicals, oil and gas, steel, paper, and food products; these five industries account for 60 percent of industrial energy use, but only 22 percent of the value of the products. Other energy-intensive industries include glass, cement, and aluminum. In general, energy-intensive industries are growing more slowly in the United States than industries with lower energy intensities.
Total industrial emissions in the United States have gradually declined over the past decade in both absolute and relative terms (see Figure 7). From 1990 to 2012 U.S. industrial output increased by 55 percent, while CO2 emissions from industrial processes decreased by a little more than 23 percent. Several factors have contributed to this reduction, including development of new methods (less carbon intensive), fuel switching, increased efficiency, and changes to the U.S. economy from a more manufacturing-based to a more service-based economy and from more energy-intensive industries to less energy-intensive industries. Over time, the proportion of industrial greenhouse gas emissions from electricity use has increased, while the proportion of greenhouse gases from direct emissions has decreased.
Figure 7: Greenhouse Gas Emissions by End-Use Sector (2012)
Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table 2-14, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
The industrial sector is the largest end-user of energy in the United States. Since 1973, total energy consumption has increased across all end-use sectors except the industrial sector (see Figure 8). This is due to three primary factors: a shift away from manufacturing and towards a more service-oriented economy; a move towards less energy-intensive manufacturing, and energy efficiency in the industrial sector.
Figure 8. Total Energy Consumption by End-Use Sector 1973 – 2013
Source: U.S. Energy Information Administration (EIA), Monthly Energy Review, September 2014. http://www.eia.gov/totalenergy/data/monthly/pdf/sec2_3.pdf
At the global level, the industrial sector is a key energy consumer and greenhouse gas producer. Manufacturing industries account for more than one-third of total energy consumption and 37 percent of CO2 emissions from energy use. At the global level, data on non-CO2 gases and non-combustion CO2 emissions have higher levels of uncertainty. A small number of industries account for a large percentage of global industrial emissions. In 2007, five industries (chemicals and petrochemicals, iron and steel, non-metallic minerals, pulp and paper, and non-ferrous metals) accounted for 50 percent of total industrial energy use.
Trends in global industrial energy use and emissions include:
- Overall industrial energy use increased between 1971 and 2004, with demand growing especially rapidly in emerging economies.
- Energy efficiency in energy-intensive manufacturing industries has increased, with Japan and Korea generally achieving the highest levels of energy efficiency.
- Cost-effective greenhouse gas mitigation opportunities exist for the industrial sector but are currently under-utilized in both developed and developing countries. The adoption of best practice commercial technologies by manufacturing industries could reduce industrial sector CO2 emissions by 19-32 percent annually by, for example, improving the efficiency of motor systems.
- Since 1970, several energy-intensive industries have seen significant growth. For example, production of steel increased 84 percent; paper, 180 percent; ammonia, 200 percent; aluminum 223 percent; and cement, 271 percent.
- Developed economies usually have a more energy-efficient industrial sector, and a larger fraction of their output comes from non-energy-intensive sectors than is the case for developing economies. On average, industrial energy intensity, which is the industrial sector’s energy consumption per dollar of economic output, is double in developing countries. Energy-intensive manufacturing industries are growing in many developing countries. Industrial energy use frequently accounts for a larger portion of total energy consumption in these countries; for example, an estimated 75 percent of delivered energy in China was used by the industrial sector in 2007.
- In 2007 the industrial sector comprised 51 percent of global energy use, and is projected to grow at an annual rate of 1.3 percent.
Industrial Sector Mitigation Opportunities
There is a diverse portfolio of options for mitigating greenhouse gas emissions from the industrial sector, including energy efficiency, fuel switching, combined heat and power, renewable energy sources, and the more efficient use and recycling of materials. The diverse opportunities for reducing emissions from the industrial sector can be broken down into three broad categories:
Some mitigation options can be used across many different industries, for example energy efficiency improvements for cross-cutting technologies, such as electric motor systems, can yield benefits across diverse sub-sectors. Other sector-wide mitigation options include the use of fuel switching, combined heat and power, renewable energy sources, more efficient electricity use, more efficient use of materials and materials recycling, and carbon capture and storage.
Certain mitigation opportunities come from improvements to specific processes and are not applicable across the entire sector. For energy-intensive industries, process improvements can reduce energy demand and, therefore, greenhouse gas emissions and energy costs. Other improvements can reduce emissions of non-CO2 gases with high global warming potentials.
Case studies can help illuminate the effectiveness of these process-specific options. For example, Alcoa’s aluminum smelters collectively reduced their emissions of perfluorocarbons (PFCs) from anode effects, which occur when a particular step in the smelting process is interrupted, by more than 1.1 million tons in 2008.
A variety of mitigation opportunities can be achieved through improvements to standard operating procedures. These options can include making optimal use of currently available technologies, such as improving insulation and reducing air leaks in furnaces.
A variety of public and private efforts have been developed to help reduce industrial greenhouse gas emissions, energy use, or energy intensity. Some of these programs include:
- Climate Leaders – U.S. Environmental Protection Agency (EPA)
- Partnership between industry and government to develop comprehensive climate change strategies. http://www.epa.gov/stateply/
- Climate VISION – Interagency program, including U.S. Department of Energy (DOE), U.S. EPA, U.S. Department of Transportation, and U.S. Department of Agriculture
- Voluntary program to reduce U.S. greenhouse gas emissions intensity. http://climatevision.gov/
- ENERGY STAR® for Industry – U.S. EPA
- Program to improve corporate energy management. http://www.energystar.gov/index.cfm?c=industry.bus_industry
- Save Energy Now – U.S. DOE, Industrial Technologies Program
- Program to achieve the goal of reducing industrial energy intensity 25 percent by 2017, per the Energy Policy Act of 2005. http://www1.eere.energy.gov/industry/saveenergynow/
- Voluntary Programs to Reduce High Global Warming Potential Gases – U.S. EPA
- A variety of programs to reduce gases with high global warming potentials, including perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6). http://www.epa.gov/highgwp/voluntary.html
At C2ES we work on several issues related to climate change and the industrial sector, including emissions reduction policy, energy efficiency, and adaptation. We track and inform policymakers about pragmatic policy options at the state, federal, and international level, collaborate on white papers and reports, blog about current issues impacting the industrial sector, and keep up-to-date online resources on innovative technologies.
Tracking Policy - We keep track of state, federal, and international policy that will impact the industrial sector. Our state maps have information about which states have adopted various GHG mitigation policies. We also track and analyze federal policy, including what is happening in Congress and the Executive Branch.
Research - At C2ES, we produce research, including reports, white papers, and briefs, on issues related to climate change and industry. C2ES's Corporate Energy Efficiency Project is a multi-year research and communications effort to identify and highlight the most effective methods used by companies, including many industrial firms, to reduce their energy consumption and lower their related GHG emissions. Other examples of relevant C2ES work include The Competitiveness Impacts of Climate Change Mitigation Policies and Adaption to Climate Change: A Business Approach.
Climate Compass Blog - Our blog includes entries about current perspectives on GHG emissions from Industry, and can be viewed here.
Climate Techbook - The industrial section of the Climate Techbook includes an overview of GHG emissions from the industrial sector as well as technologies that can be used to reduce those emissions. Below is a list of the Techbook factsheets that pertain to the industrial sector.
|Industrial Overview||Carbon Capture and Storage (CCS)|
|Anaerobic Digesters||Cogeneration / Combined Heat and Power (CHP)|
|Building Envelope||High Global Warming Potential Gas Abatement|
|Buildings Overview||Natural Gas|
Alliance to Save Energy
- Review of GHG Policies, Programs, Initiatives, and Energy Efficiency Opportunities for U.S. Industry
American Council for an Energy-Efficient Economy
Intergovernmental Panel on Climate Change (IPCC)
U.S. Department of Energy (DOE)
U.S. Energy Information Administration (EIA)
- Energy-Related Carbon Dioxide Emissions in U.S. Manufacturing, 2006
- Industry Analysis Briefs
- Manufacturing Energy Consumption Survey (MECS)
U.S. Environmental Protection Agency (EPA)
- ENERGY STAR - Inustries in Focus
- 2011 US Greenhouse Gas Emissions Inventory
- Quantifying Greenhouse Gas Emissions from Key Industrial Sectors in the United States Working Draft
- Sector Performance Report, 2008
Related Business Environmental Leadership Council (BELC) Companies
|DTE Energy||Rio Tinto|
|Duke Energy||Royal Dutch / Shell|
 U.S. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012. 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
 One million metric ton is equal to one teragram. For reference, one million metric ton of CO2e is equal to 280,000 new cars each being driven 12,500 miles or 90 minutes of U.S. energy consumption or 1 day of U.S. energy emissions from lighting buildings, see U.S. Department of Energy (DOE), 2009 Buildings Energy Data Book. Prepared for U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by D&R International, Ltd. Silver Spring, MD. 2009. http://buildingsdatabook.eren.doe.gov
 Global warming potential is a system of multipliers devised to enable warming effects of different gases to be compared. The cumulative warming effect, over a specified time period, of an emission of a mass unit of CO2 is assigned the value of 1. Effects of emissions of a mass unit of non-CO2 greenhouse gases are estimated as multiples. For example, over the next 100 years, a gram of methane (CH4) in the atmosphere is currently estimated as having 23 times the warming effect as a gram of carbon dioxide; methane's 100-year GWP is thus 23. Estimates of GWP vary depending on the time-scale considered (e.g., 20-, 50-, or 100-year GWP) because the effects of some GHGs are more persistent than others.
 U.S. EPA, 2014
 U.S. EPA, 2014
 U.S. EPA, 2014
 Carbon dioxide equivalent (CO2e) is a unit used to measure the emissions of a gas, by weight, multiplied by its global warming potential.
 U.S. EPA, 2014
 Department of Energy. Industrial Total Energy Consumption. April 14, 2008. http://www1.eere.energy.gov/ba/pba/intensityindicators/total_industrial....
 Intergovernmental Panel on Climate Change (IPCC), “Industry.” In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report. Cambridge: Cambridge University Press, 2007. http://www.ipcc.ch/ipccreports/ar4-wg3.htm
 IPCC, 2007.
 EIA, International Energy Outlook 2010. July 2010. http://www.eia.doe.gov/oiaf/ieo/pdf/0484(2010).pdf
 IPCC, 2007.
 EIA, July 2010.
 IPCC, 2007.
 Alcoa, “Alcoa Smelters Meet Challenge to Reduce Greenhouse Gas Emissions by One Million Tons Annually,” http://www.alcoa.com/global/en/about_alcoa/sustainability/case_studies/2009/case_ghg_million_ton.asp. Accessed 6 May 2009.
More than one-quarter of total U.S. greenhouse gas emissions come from the transportation sector (see Figure 1), making transportation the second largest source of greenhouse gas emissions in the United States after the electric power sector.
Figure 1: U.S. Greenhouse Gas Emissions by Sector (2012)
Source: U.S. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, Table ES-7, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html.
The transportation sector consists of passenger vehicles (a category including both passenger cars and light-duty trucks), medium- and heavy-duty trucks, buses, and rail, marine, and air transport. Of the various transportation modes, passenger vehicles consume the most energy (see Figure 2). Greenhouse gas emissions mirror energy use by each mode, because all modes use petroleum fuels with similar carbon contents and thus greenhouse gas emissions.
Figure 2: Transportation Energy Use by Mode (2012).
Source: U.S. Department of Energy. Transportation Energy Data Book, Table 2.5, 2014. http://cta.ornl.gov/data/chapter2.shtml
The vast majority of transportation emissions (95 percent) are composed of carbon dioxide (CO2), which is released during fossil fuel combustion. An additional one percent of total transportation GHG emissions come from methane (CH4) and nitrous oxides (N2O), emissions also associated with fossil fuel combustion. The leakage of hydrofluorocarbons (HFCs) from vehicle air conditioning systems is responsible for the remaining four percent of transportation GHG emissions. Transportation sources also emit hydrocarbons (which are ozone precursors), carbon monoxide (CO), and aerosols. These substances are not counted as greenhouse gases in transportation emissions inventories but are believed to have an indirect effect on global warming, although their impact has not been quantified with certainty.
Factors Affecting Transportation Emissions
Transportation energy use and emissions are determined by four interrelated but distinct factors: the type of fuels or energy sources, the vehicles, the distance traveled, and the overall system infrastructure.
- Fuel Types and Energy Sources
The transportation sector is the largest consumer of petroleum-based fuels in the United States. Importantly, transportation accounts for about 70 percent of U.S. oil consumption, which greatly affects U.S. energy security.
Figure 3: Petroleum and Other Liquids Production and Consumption, 1970–2013.
Source: U.S. Energy Information Agency (EIA), Monthly Energy Review 2014, Table 3.1, 3.7c, 2014. http://www.eia.gov/totalenergy/data/monthly/index.cfm#petroleum
Nearly all fossil fuel energy consumption in the transportation sector is from petroleum-based fuels (92 percent), with a small amount from renewable sources (5 percent) and natural gas (3 percent). There are several types of petroleum fuels used for transportation. Table 1 lists the major petroleum-based transportation fuels and the volume consumed in the United States in 2013.
Table 1: Estimated U.S. Transportation Sector Petroleum Consumption (2013), Million Gallons.
Distillate Fuel Oil (Diesel)
Residual Fuel Oil
Liquefied Petroleum Gases
Source: U.S. Energy Information Administration (EIA), Monthly Energy Review, Table 3.7c, 2014. http://www.eia.gov/totalenergy/data/monthly/index.cfm#petroleum
Petroleum fuels are supported by an extensive and well-functioning infrastructure and have the benefit of high energy density, low cost, and a demonstrated ability to adapt to a range of operating conditions.
The production and consumption of biofuels has increased significantly since 2005, due to the state and federal renewable fuel standards, which mandate minimum annual consumption levels of ethanol and biodiesel, the two renewable biofuels. Ethanol is an alcohol produced from crops such as corn, vegetable waste, wheat, and others; it is usually combined with gasoline to increase octane levels and more efficient fuel utilization. Biodiesel is produced from natural oils like soybean oil and functions only in diesel engines. In 2013, ethanol (4 percent) and biodiesel (0.7 percent) made up nearly five percent of the total primary energy consumed in the transportation sector.
- Vehicle Efficiency
Over the last 35 years, the fuel economy (miles per gallon, mpg) of new passenger vehicles in the United States has improved significantly, increasing by more than 50 percent. Until very recently, most of the gains occurred in the early years of fuel economy regulation under the Corporate Average Fuel Economy (CAFE) program. Fuel economy improvements were nearly stagnant from the late 1980s to the early 2000s. Over this period, the technical efficiency (amount of energy needed to move a given vehicle mass) of light-duty vehicles improved, although fuel economy (the amount of gasoline consumed per mile traveled) remained unchanged, as consumer preferences shifted to larger, heavier, and more powerful vehicles. Fuel economy standard for light trucks were increased slightly in 2003, and recent federal vehicle standards adopted in 2010 and 2012 are expected to raise average fuel economy as high as 54.5 mpg for model year 2025.
Transportation modes other than passenger vehicles also have efficiency improvement opportunities. For instance, aircraft energy intensity has historically improved at an average rate of 1.2-2.2 percent per year, although aircraft energy intensity steadily plateaued through the 1990s and early 2000s due to both historically low fuel prices and a tripling in the average age of aircraft and engine production lines since 1989. In addition, federal vehicle standards for medium- and heavy-duty vehicles were adopted in 2011, and should improve fuel efficiency significantly.
Figure 4: Corporate Average Fuel Economy (CAFE) Standards vs. Sales-Weighted Fuel Economy Estimates.
Source: NHTSA, Summary of Fuel Economy Performance, 2014.http://www.nhtsa.gov/fuel-economy
- Vehicle Use and Distance Traveled
The third factor that affects transportation emissions is the amount of vehicle use and distance traveled. Transportation demand is influenced by the geographic distribution of people and places, especially the density of development and zoning. Over the past 50 years, on-road vehicle miles traveled (VMT) increased steadily (Figure 5). Because of high fuel costs and slowing economic growth, VMT decreased in 2008. However, in 2006, the absolute number of VMT in the United States peaked, while the distance driven per person and per licensed driver peaked in 2004. The decline of these indicators prior to the 2008 recession were likely the result of non-economic factors such as increased use of public transportation, increases in telecommuting, an aging population (decreases in driving by ederly) and increased urbanization. Economic and non-economic factors contributing to the persistence of the flat absolute number of VMT in the post-recession period continue to be studied.
The absolute growth in distance traveled for modes has been similar. The use of all transportation modes (particularly freight transport and air travel) is still projected to grow rapidly in the future.
Figure 5: Annual On-Road Vehicle Miles Traveled (VMT).
Source: U.S. Department of Energy, Transportation Energy Data Book, Table 3.7, 2014. http://www-cta.ornl.gov/data/chapter3.shtml
- System Efficiency
The overall operation of the transportation system also plays an important role in GHG emissions. For example, congestion results when transportation demand exceeds capacity and poses a challenge for almost all modes of transportation, from on-road and highway transport, air, and rail. Shifting travel to other modes can reduce congestion, as can electronic signaling and other measures to smooth traffic flows. Reducing congestion has the benefit of lowering fuel consumption and GHG emissions by decreasing the time spent idling. For freight (via rail, truck, and ship) and air traffic, system improvements that allow vehicles to take more direct routes from origin to destination can reduce energy use and emissions.
Transportation activity is expected to grow significantly in all countries of the next 25 years. Over the next two decades, vehicle ownership is expected to double worldwide, with most of the increase occurring in non-OECD countries. The U.S. Energy Information Administration projects that non-OECD transportation energy use will increase by an average of 2.8 percent per year from 2010 to 2040, compared to an average decrease of 0.3 percent per year for OECD countries. Figure 6 shows projected worldwide energy consumption in the transportation sector.
Figure 6: Global Projections for Transportation Sector, Liquids Consumption, 2010-2040.
Source: U.S. Energy Information Agency, International Energy Outlook 2014. http://www.eia.gov/forecasts/ieo/more_overview.cfm
Transportation Sector GHG Mitigation Opportunities
Reducing GHG emissions from transportation will require a systematic approach to address the four interdependent yet distinct components of the sector.
- On the fuels side, transitioning to low-carbon energy sources, such as advanced biofuels or electricity produced from renewable sources, can directly reduce the carbon emissions from fuel consumption.
- Significantly more efficient transportation equipment is needed to complement the transition to low-carbon fuel sources. Alternative vehicle designs include flexible fuel vehicles that can run on a mix of biofuels and petroleum-based fuels or are powered by electricity and stored on-board in batteries or by hydrogen fuel cells.
- Vehicle travel demand is affected by a number of factors. Changing land use patterns and increasing alternative travel options, such as biking, walking or rail, can reduce the use of more energy-intensive modes of transportation.
- Increasing the efficiency of the transportation system would require both improving accessibility to and performance of the various modes of transportation and using more efficient ones. Advanced traffic monitoring and signaling can reduce congestion and improve the overall efficiency of the transportation system.
A strategy to reduce GHG emissions from the transportation sector will need to take into account the potential efficiency improvements for each mode of transportation and determine the appropriate reduction strategy for each. Policies that facilitate the adoption of low-carbon technologies and align infrastructure development and land use planning with GHG reduction goals can lead to further GHG reductions in these areas.
Several studies have analyzed the most cost-effective approach to emission reductions in transportation. Some of these studies include:
- Greene, D. and S. Plotkin, Reducing Greenhouse Gas Emissions from U.S. Transportation. Prepared for the Center for Climate and Energy Solutions, 2011.
- Cambridge Systematics, Inc. (2009). Moving Cooler: An Analysis of Transportation Strategies for Reducing Greenhouse Gas Emissions. Washington, D.C.: Urban Land Institute.
- Intergovernmental Panel on Climate Change (IPCC), “Transport and its infrastructure.” In Mitigation of Climate Change, 2007.
- International Energy Agency (IEA), “Transport.” In Energy Technology Perspectives 2008: Scenarios and Strategies to 2050, 2008.
Achieving emission reductions and oil savings from the transportation sector requires a multi-pronged approach that includes improving vehicle efficiency, lowering the carbon content of fuels, reducing vehicle miles traveled, and improving the efficiency of the overall transportation system.
At C2ES, we focus on all aspects of transportation from improving vehicle technology to the benefits of land-use planning. We produce cutting-edge research; track policy progress at the state, federal, and international level; blog on current transportation issues; and create and maintain an online resource of transportation technology.
Cutting-Edge Research - In our 2011 report titled Reducing Greenhouse Emissions from U.S. Transportation, we identify cost-effective solutions that will significantly reduce transportation's impact on our climate while improving our energy security. See all our transportation-related publications.
Convening Stakeholders - We've run a multi-year stakeholder dialogue to help enable a national electric vehicle market in the United States. The PEV Dialogue Initiative is a one-of-a-kind effort aimed at identifying policies and actions by public and private stakeholders to accelerate the deployment of electric vehicles.
Policy Progress - We track action at the state, federal, and international level. Our state maps provide useful overviews of action to promote alternative technologies. We also summarize action in Congress and in the Executive Branch, such as our summaries of the Renewable Fuel Standard and Vehicle Fuel Economy and Emission Standards. Lastly we track action at the international level, such as our comparison of international fuel economy standards.
Climate Compass Blog - On our blog, we provide C2ES's take on the latest news from the transportation sector. See our transportation blog postings.
Climate TechBook - The transportation section of the Climate TechBook introduces different modes of transportation along with policies to help mitigate GHG emissions and save oil. Below is a list of all the transportation-related factsheets within the TechBook.
|Advanced Biohydrocarbons||Freight Transportation|
|Aviation||Hydrogen Fuel Cell Vehicles|
U.S. Department of Transportation (DOT)
- Research and Innovative Technology Administration (RITA)
- National Household Travel Survey (NHTS)
- Federal Highway Office of Planning, Enviornment and Realty (HEP)
U.S. Department of Energy (DOE)
U.S. Environmental Protection Agency (EPA)
Joint Federal Programs
Related Business Environmental Leadership Council (BELC) Companies
|Air Products||Johnson Controls, Inc.|
|Dow Chemical Company||Weyerhaeuser|
 Source: U.S. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012, 2014. http://www.epa.gov/climatechange/emissions/usinventoryreport.html
 EIA, Annual Energy Review 2012, Table 2.1e, 2014. http://www.eia.gov/totalenergy/data/annual/index.cfm#consumption
 EIA, Annual Energy Review 2012, Table 10.2b, 2014. http://www.eia.gov/totalenergy/data/annual/index.cfm#renewable
 McCollum, D., Gould, G. and Greene, D., Aviation and Marine Transportation: GHG Mitigation Potential and Challenges. Prepared for the Center for Climate and Energy Solutions, 2009. http://www.c2es.org/technology/report/aviation-and-marine
|Photos by Dennis Schroeder / NREL, Iberdrola Renewables, Inc., U.S. Department of Energy|
Wind and solar power were once considered expensive and were not widely deployed. Today, skeptics say the same about technology to capture, use and store carbon dioxide emissions (CCUS or carbon capture).
So what lessons can we draw from the experience of the wind and solar industries as they’ve become more mainstream to facilitate a faster and broader deployment of carbon capture technology?
The cost of wind energy has declined by more than 60 percent since 2009 and average nameplate capacity increased 180 percent between 1998-99 to 2015. These improvements have led to an installed wind capacity of 74,821 MW in the United States, enough electricity to power nearly 20 million average U.S. homes every year.
These wind energy milestones in cost reduction, performance improvements, and scale of deployment were supported by the Production Tax Credit (PTC), a federal deployment incentive. It’s reasonable to assume that the PTC would have been even more successful if it had been maintained consistently instead of experiencing periods of uncertainty regarding its fate, leading to boom-and-bust wind power development cycles.
Ongoing federal research and development (R&D) also spurred improved wind industry technology. For example, in 2007, the National Renewable Energy Laboratory initiated the Gearbox Reliability Collaborative in response to industry-wide technology challenges. That research led to improved gearbox designs, reducing the overall cost of wind energy and showing how collaborative industry efforts and federal support for R&D can resolve performance challenges.
Solar photovoltaic (PV) technologies experienced similar dramatic cost declines due to economies of scale and improved manufacturing and performance. The cost of utility-scale solar has fallen more than 54 percent since 2011. The efficiency of all PV cells steadily improved between 1975 and 2010, supported by multi-decade R&D programs like the Department of Energy’s Thin Film PV Partnership.
These cost declines and performance improvements were facilitated by the Investment Tax Credit, another federal deployment-focused incentive, and the Section 1603 Treasury program, a federal loan guarantee mechanism to support project financing. Strong state policies like the California Renewables Portfolio Standard enabled developers to enter into above-market power purchase agreements. The experience of utility-scale solar PV demonstrates that overlapping policies are essential to achieve financing for first-of-a-kind projects.
Lessons for carbon capture
We can draw three key conclusions from wind and solar energy’s experience:
- Stable, long-term deployment incentives that build on previous public and private investments in technology research, development and demonstration (RD&D) are essential to facilitate a large volume of projects;
- As more projects are deployed, costs are reduced through economies of scale, learning from experience, and technological innovation;
- Ongoing government support for RD&D can deliver cost reductions by supporting innovation and overcoming performance challenges.
In contrast to wind and solar, the U.S. lacks an effective federal incentive for commercial deployment of CCUS—despite being a world leader in public and private RD&D for early stage technology demonstration. Fifteen commercial-scale CCUS projects are operating globally; eight of those are in the United States. But that’s not nearly enough to meet our mid-century climate goals.
Carbon capture can be used at coal- or natural gas-fired power plants, which are baseload generation resources. It’s also the only way to reduce carbon emissions from some industrial plants, such as facilities producing chemicals, steel, and cement. Also, over the long-term, we’ll need to integrate biomass energy systems with carbon capture (BECCS). Combining the capture of photosynthetic carbon from biomass with CCUS can enable negative emissions.
While first-of-a-kind, commercial-scale CCUS projects are expensive, we know that as more projects come online, they will become cheaper. SaskPower estimates it could cut costs by up to 30 percent on the next unit to be retrofitted following its current experience operating the world’s first commercial-scale, coal-fired power plant carbon capture project. Developers are exploring novel approaches, including the Exxon and Fuel Cell Energy partnership and the Exelon-supported NET Power project, that have the potential to reduce costs still further.
It’s essential to extend and expand tax incentives for carbon capture, update state laws to include CCUS technology in clean energy standards, and fund continued carbon capture RD&D, among other things, if we are going to reach our emissions-cutting goals.
This year we will witness a number of milestones in technology to capture, use and store carbon dioxide from industrial sources and power plants – technology we need to reach our goals to reduce greenhouse gas emissions. We will need continued policy and financing support, however, to accelerate deployment worldwide. Innovative research in finding uses for captured carbon will also be essential.
In 2016, the Emirates Steel Industries project in Abu Dhabi will be the world’s first steel plant with carbon capture, use and sequestration (CCUS) technology to begin operations. Globally, seven commercial-scale CCUS projects are under construction and many more are in the planning stages.
In the U.S., two notable CCUS projects are expected to come online soon, including the first-ever incorporation of CCUS technology at a bioethanol refinery at the Archer Daniels Midland project in Illinois and the incorporation of CCUS technology at the coal-fired power plant at the Southern Company Kemper project in Mississippi. Not far behind, in 2017, the NRG Energy Petra Nova project in Texas will also incorporate CCUS technology on coal-fired power generation.
These anticipated project developments reflect the fact that CCUS technology is advancing around the world. Fifteen commercial-scale CCUS projects are operating. Eight of those are in the United States, which has been a leader in this area.
Recent North American milestones include the retrofit of the SaskPower Boundary Dam coal-fired power plant project in Canada with CCUS technology in 2014. In April 2016, the company announced it had exceeded the carbon capture reliability goals established for the technology. SaskPower estimates it could cut costs up to 30 percent on future units based on the experience it has acquired. Also in Canada, in November 2015, Shell incorporated CCUS technology on hydrogen production at the Quest project in Alberta.
CCUS technology grows increasingly important as nations begin to implement their emission reduction pledges under the Paris Agreement. The Intergovernmental Panel on Climate Change Fifth Assessment Synthesis Report concluded that CCUS technology will be essential to meet mid-century climate goals of keeping global temperature rise within 2 degrees Celsius of preindustrial levels. In fact, without CCUS, mitigation costs will rise by 138 percent.
Even as nations take on climate change and diversify their energy portfolios, fossil fuels are expected to serve 78 percent of the world’s energy demand in 2040. The most recent Energy Information Administration analysis suggests that global energy consumption is expected to rise by 48 percent over the next 30 years led by significant increases in the developing world. In Asia in particular, power generation from fossil fuels is expected to continue to grow over the near term.
Earlier this spring, the International Energy Agency (IEA) published a study on retrofitting China’s coal-fired power plants with CCUS technology, which will be critical because China has roughly 900 GW of installed coal-fired power plant capacity and has committed to peaking its CO2 emissions by 2030. The IEA study concludes that one-third of the coal fleet in China is suitable for retrofitting with CCUS technology.
Aside from the power sector, CCUS is a critical technology for the industrial sector, which contributes roughly 25 percent of global emissions. Carbon dioxide (CO2) is a by-product of many manufacturing processes for chemicals, steel, and cement production as well as refining. There are no practical alternatives to CCUS for achieving deep emissions reduction in the industrial sector.
In some cases, the cost of incorporating CCUS technology into industrial processes may be lower than in the power sector because the CO2 stream in the industrial sector is often relatively pure, i.e. less mixed with other gases. A number of industrial CCUS projects are already operational including the Uthmaniyah natural gas processing project in Saudi Arabia that came online in 2015. In the U.S., the Air Products Port Arthur project in Texas incorporating CCUS technology on hydrogen production has been operational since 2013.
As new projects begin operating around the world, the Global CCS Institute concluded that policymakers can learn lessons for CCUS from the development of offshore wind in Europe. Those projects benefited from policy support from national governments through feed-in tariffs and long-term offshore wind capacity targets in national energy plans. The report also concludes that a multi-source approach to finance, including project finance, export credit agency support, multilateral institution lending, and green bank funding, will be helpful for CCUS technology.
Finding uses for the captured carbon will also be essential. At the January World Economic Forum meeting in Davos, Switzerland, the Global CO2 Initiative was launched to develop innovative approaches to transform CO2 into commercial products. Promising options include construction materials, plastics, chemicals, and agricultural products.
As researchers continue exploring new uses for captured carbon, CCUS project developments this year and next continue to highlight the significant potential for CCUS technology to contribute to global emissions reduction.
This blog post first appeared in the Summer 2016 edition of The Current, a publication of the Women's Council for Energy and the Environment.
California and New York are leaders in setting ambitious climate goals. Both have committed to producing half their electricity from renewable sources by 2030. Both have set identical goals of reducing greenhouse gas emissions 40 percent below 1990 levels by 2030.
Where they part ways, however, is on nuclear power, which supplies the majority of zero-emission electricity in the United States. California is letting its nuclear plants ride off into the sunset while New York, which just approved a Clean Energy Standard that specifically includes nuclear power, is actively trying to preserve them.
This summer, Pacific Gas & Electric Company (PG&E) announced it will close its Diablo Canyon nuclear plant – the last one in the state of California – by 2025. After striking an agreement with environmental and labor groups, PG&E said it will seek to replace Diablo Canyon’s roughly 18,000 GWh of annual electricity – almost 10 percent of California’s in-state electricity – through improved energy efficiency, which will decrease demand, and renewable energy.
Many experts think it will be a stretch to reach that goal, especially by 2025, and that natural gas will have to fill the gap, as it has where nuclear plants have closed elsewhere in California, Vermont and Wisconsin. In New England, emissions increased 5 percent in 2015 after the Vermont Yankee nuclear plant shut down and was largely replaced by natural gas-fired electricity.
Diablo Canyon might have kept going if PG&E had gotten its way in negotiations with the state last year to include nuclear power in California’s renewable portfolio standard (RPS). That standard requires utilities to produce a certain amount of electricity from renewable sources like wind, solar, geothermal and hydropower. Including nuclear would have helped it compete economically with other low-carbon energy.
New York’s path
That’s exactly the path being taken in New York, which gets a third of its in-state electricity from nuclear power. To preserve the low-carbon benefits of its economically troubled upstate reactors and ensure its electricity mix becomes increasingly clean – with no backsliding – New York’s Public Service Commission has approved a clean energy standard (CES), which is essentially an RPS that includes nuclear.
New York’s CES mandate, which will take effect in 2017, is a novel approach that incorporates best practices from other states. It’s designed to incentivize new renewables deployment while also preserving existing clean electricity generation.
New York’s CES has three tiers, each with its own supply-demand dynamics. Tier 1 will incentivize new renewable development. Tier 2 is designed to provide sufficient revenue for existing renewable electricity supply. Tier 3 is designed to properly value the emission-free power from the state’s at-risk nuclear power plants.
Nuclear plant operators have long sought to correct what they perceive as a market failure to compensate nuclear power for its low-carbon benefits. If the at-risk reactors were replaced by an equivalent amount of fossil generation, emissions would increase by 14 million metric tons – increasing the state’s carbon dioxide emissions nearly 10 percent.
New York’s plan isn’t without controversy. There’s concern that it’s too costly. However, an associated cost study by the PSC found that the state could “meet its clean energy targets with less than a 1 percent impact on electricity bills.”
Most U.S. states have a renewable portfolio standard or alternative energy standard. Only Ohio allows new nuclear to qualify. Only New York has provisions for existing nuclear power plants.
Illinois is working to expand its RPS to include nuclear into a low-carbon portfolio standard, similar to New York’s CES, but efforts have stalled in the state legislature. Exelon has announced plans to close two nuclear power plants in the state in 2017 and 2018, which could lead to an additional 13 million metric tons of carbon dioxide emissions for the state.
Across the U.S., nine reactors are scheduled to close by 2025, which could increase carbon emissions by about 32 million metric tons, or 1.7 percent of the current total U.S. carbon emissions from the power sector.
New York’s approach to reducing its emissions is a practical, well-considered model that many other states could be following (Arguably, a national price on carbon would be more efficient, though more challenging to enact.)
New York’s four upstate reactors provide significant environmental and economic benefits. From a climate perspective, it doesn’t make sense to prematurely close these facilities when, in the short- and medium-term, they cannot realistically be replaced by alternative zero-emission power sources. Keeping these reactors operational also buys us additional time to address energy storage and transmission challenges to support more renewable generation.
With reasonable policies in place to support the existing U.S. reactor fleet, it will be easier for the U.S. to reduce its emissions and achieve its climate goals.
Rooftop solar panels in central India.
Photo courtesy Coshipi via Flickr
A bold initiative to vastly expand solar energy in developing countries recently reached two major milestones toward its ultimate goal of mobilizing $1 trillion in solar investments by 2030.
In late June, the World Bank Group signed an agreement establishing it as a financial partner of the International Solar Alliance, providing more than $1 billion in support. The Bank Group will develop a roadmap and work with other multilateral development banks and financial institutions to mobilize financing for development and deployment of affordable solar energy.
The news follows the June 7 joint announcement between India and the United States to launch an initiative through the Alliance focusing on off-grid solar energy.
The International Solar Alliance was announced at the Paris climate conference in December by Indian Prime Minister Narendra Modi and French President François Hollande. It was one of many new initiatives involving business, civil society, and public-private partnerships launched in Paris.
The alliance will comprise 121 countries located between the Tropic of Capricorn and the Tropic of Cancer that typically have 300 or more days of sunshine a year. Companies involved in the project include Areva, HSBC France and Tata Steel.
According to the Renewable Energy Policy Network for the 21st Century (REN21), global solar capacity experienced record growth in 2015, with the annual market for new capacity up 25 percent over 2014. More than 50 gigawatts were added, bringing the total global capacity to about 227 gigawatts. That’s about 10 percent of the total amount of electricity the U.S. produced in 2015.
In developing and emerging economies, affordable financing is a challenge. The alliance will work to expand solar power primarily in countries that are resource-rich but energy-poor by mobilizing public finance from richer states to deliver universal energy access. Strategies include lowering financing costs, developing common standards, encouraging knowledge sharing and facilitating R&D collaborations.
President Hollande laid the foundation stone of the International Solar Alliance at the National Institute of Solar Energy in Gurgaon, Haryana in January, marking the first time India has hosted the headquarters of an international agency. The Indian government is investing an initial $30 million to set up the headquarters. The French Development Agency has earmarked over 300 million euros for the next five years to finance the alliance’s first batch of projects.
The solar alliance complements India’s own ambitious solar energy goals, which include a 2030 target of 40 percent of electric power capacity from non-fossil fuel energy sources as part of its intended nationally determined contribution to the Paris Agreement. India also plans to develop 100GW of solar power by 2022, a 30-fold increase in installed capacity.
The growing support for the solar alliance is evidence of rising political momentum around the world to act on climate change and transition to a low-carbon economy. Look for a third major milestone in September, when the Alliance meets for its inaugural Founding Conference in Delhi.
Back in 2005, the U.S. Energy Information Administration projected that, under current policies, U.S. energy-related carbon dioxide emissions would increase nearly 18 percent by 2015.
They did not.
In fact, emissions fell – by more than 12 percent. So we were off by 30 percent.
As Yogi Berra may have said: It's tough to make predictions, especially about the future. We didn’t know then the impact a variety of market and policy factors would have on our energy mix. And we don’t know now all of the factors that could help us meet, or exceed, our Paris Agreement pledge – to reduce our net emissions 26-28 percent below 2005 levels by 2025.
U.S. emissions have fallen over the last 10 years due to factors that include:
- Growth in renewable energy
- Level electricity demand
- Improved vehicle efficiency
- A shift in electricity generation from coal to natural gas.
An unanticipated abundance of cheap natural gas has transformed the U.S. electricity mix. Coal-fired generation has fallen from 50 to 33 percent of the mix, while less carbon-intensive, natural gas-fired generation has risen from 19 to 33 percent.
The last 10 years also included a major economic downturn, which in 2009 drove electricity sales below 2005 levels. Despite a return to positive economic growth in the following year that continues through today, electricity sales have remained flat. Declines in manufacturing; improvements in energy efficiency, including in buildings, lighting, and appliances; warmer winters; and increased use of on-site generation like rooftop solar panels are the likely drivers.
What will happen in the next 10 years?
Certainly, the electric power sector will continue to decarbonize. It is not unreasonable to assume that natural gas will play an even larger role, while coal will play a substantial albeit diminishing role in the electricity mix.
Here are some other factors that are hard to quantify now, but could affect how quickly we transition to a clean energy future:
More zero-emission electricity
Increased clean and renewable electricity production, spurred by the Environmental Protection Agency’s Clean Power Plan and congressional tax credit extensions for wind and solar, could reduce renewable power costs, which have already been dropping. In other words, economies of scale could lead to higher deployments and lower emissions than currently forecast.
Wind and solar generation have grown nearly twelve-fold since 2005, nearly eight times greater than what was expected back then. In the 2016 Annual Energy Outlook, wind and solar generation are projected to increase 2.5 times by 2025. Historical precedent would tend to suggest that this is a highly conservative estimate.
However, sustained low prices in wholesale power markets from low natural gas prices and a proliferation of renewable electricity sources could harm another zero-emission source: nuclear. In particular, we could see natural gas continue to replace zero-emission merchant nuclear plants, moving us in the wrong direction, unless remedies are implemented. Also, low wholesale prices would tend to discourage new renewable generation.
More zero-emission vehicles
Electric vehicles (EVs) make up less than 1 percent of new U.S. car sales. But as their prices drop and range expands, the adoption rate could accelerate over the next 10 years, spurring important reductions from what is now the largest emitting sector. In one sign of growing demand, more than 400,000 people have put down a deposit for a Tesla Model 3 EV that won’t even be on the market until 2018.
Advances in battery storage could drive the transformation of the transportation sector and would provide obvious benefits to the electric power sector as well.
Meanwhile, automakers are exploring alternative fuels: natural gas, hydrogen fuel cells, and biofuels. And more than a dozen states and nations have formed a Zero-Emission Vehicle (ZEV) Alliance to encourage ZEV infrastructure and adoption.
Action by cities, the magnitude of which is not easily captured by national macroeconomic models, could lead to greater than anticipated emission reductions. Starting with the groundbreaking Mayors Climate Protection Agreement in 2005, initiatives are evolving to connect cities with each other to exchange knowledge and achieve economies of scale for new technologies.
More cities are exploring ways to generate additional reductions by 2025. These include: more energy-efficient buildings; better tracking of electricity and water use, innovative financing for more efficient generation, appliances and equipment; and improved public transportation and promotion of electric vehicles.
Last, but not least, steps taken by companies beyond regulatory requirements could produce greater emission reductions than we can foresee. Companies are investing in clean energy projects, reducing emissions throughout the supply chain, establishing internal carbon pricing, and helping customers reduce their carbon footprint. More than 150 companies have signed the American Business Act on Climate Pledge.
C2ES and The U.S. Conference of Mayors are teaming up to encourage city and business leaders to work together to reduce greenhouse gas emissions. Imagine how effective we can be when we coordinate climate action.
A 2015 UNEP report suggests that beyond each countries’ individual commitments to the Paris Agreement, actions by sub-national actors across the globe can result in net additional contributions of 0.75 to 2 billion metric tons of carbon dioxide emissions in 2020.
The United States has significantly reduced its greenhouse gases over the past decade, and has put in place policies ensuring continued reductions in the years ahead. With so many resources and tools at our disposal, it is clear that we can meet or exceed our climate goal. The only uncertainty is how we will do it.
Event: Innovation to Power the Nation
Technology, policy, and business experts discuss how innovative technology and policy can help us reach our climate goals at Innovation to Power the Nation (and World): Reinventing Our Climate Future at 1 p.m. ET on Wednesday, June 29. Watch the livestream.
Speakers include Patent and Trademark Office Director Michelle K. Lee; C2ES President Bob Perciasepe; Dr. Kristina Johnson, CEO of Cube Hydro Partners; Nate Hurst, Chief Sustainability & Social Impact Officer at HP; and Dr. B. Jayant Baliga, inventor and director of the Power Semiconductor Research Center at North Carolina State University.