Advanced Biohydrocarbons

Quick Facts

• Advanced biohydrocarbons – as defined in this fact sheet – are derived from lignocellulosic biomass (e.g., trees, grasses, wastes, and agricultural or forest residues) or algae and do not compete with the production of feed or food crops.
• Depending on technology advancement and capital investment in biorefineries, some estimates have advanced biohydrocarbons displacing as much as 30 percent of the amount of petroleum consumed in the United States by 2050.[1]

Background

Advanced biohydrocarbons are similar to conventional hydrocarbon fuels such as gasoline or diesel but are produced from biomass feedstocks, such as woody biomass or algae, through a variety of biological and chemical processes. Advanced biohydrocarbons are considered a ‘drop-in’ fuel; in other words, their use does not require significant modifications to existing fuel distribution infrastructure or vehicle engine modifications (for gasoline or diesel powered vehicles), unlike ethanol as it is used today. Similarly, the energy content of advanced biohydrocarbons is equivalent to that of their petroleum-based counterparts (i.e., gasoline and diesel).

Description

Manufacturers can produce advanced biohydrocarbons by four primary pathways:

• Fermentation: In this case, manufacturers pre-treat the biomass with heat, enzymes, or acids to make the cellulose easier to break down into simple sugars using a chemical reaction called hydrolysis. The sugars from the biomass are subsequently fermented using genetically engineered microorganisms. This process is similar to the one used to produce corn or sugarcane ethanol (see Climate Techbook: Ethanol [1]). However, these microorganisms are engineered to break down the biomass to produce hydrocarbons rather than alcohols. This is an important distinction in the genetic modification of the microorganisms because alcohol formation generally would create a poisonous environment, thereby reducing the efficacy of the catalyst. With the modified microorganisms, however, hydrocarbons immediately form an organic layer separate from the microorganisms.
• Gasification: In this pathway, solid woody biomass is leftuntreatedand then converted at very high temperatures into a combination of carbon monoxide (CO) and hydrogen (H₂), a mixture termed syngas. Syngas is the starting material for catalytic chemical reactions, such as Fischer-Tropsch synthesis, which convert the syngas into a liquid fuel.
• Pyrolysis: Similar to gasification, untreated woody biomass is heated quickly at high temperatures, but in the absence of oxygen. The high heating leads to the breakdown of the complex structure of the lignin to produce an intermediate bio-oil. Typically, this bio-oil is subsequently refined to a liquid fuel via a catalytic reaction called hydrotreating.
• Algal conversion: There are currently three main pathways to produce a fuel from algae: 1) algae is genetically engineered to secrete bio-oils efficiently; 2) a bio-oil extract from algae is chemically treated to produce a bio-oil; or 3) algae cultures are converted in their entirety via pyrolysis (see above). In any case, the algae can be genetically modified to thrive in otherwise harsh conditions (e.g., high salinity or nonpotable water). In all cases, the bio-oil product derived from algae is subsequently upgraded via hydrotreating and becomes a liquid fuel similar to diesel or gasoline.

Figure 1: Production Pathways for Advanced Biohydrocarbon Fuels

[2]

This figure illustrates a) chemical (black), b) biological (green), and c) thermal (red) production pathways for advanced biohydrocarbons derived from i) woody biomass and ii) algae. The production of gasoline or diesel equivalents is dependent on the technology and pathway. Note that while jet fuel can also be produced, it is not discussed further in this summary.

• Biological and Chemical Catalysts: In each of these four pathways, liquid biofuels are formed as the result of biological and chemical catalysis. Catalysis is a process in which a material (the catalyst) is added to a reactive environment to increase the rate of reaction without being consumed by the reaction.[2] As shown in Figure 1, most of these pathways are processes that are characterized as chemical catalysis. Chemical catalysts have a number of advantages over biological catalysts. The advantages of chemical catalysts include: broader range of reaction conditions, lower residence time (i.e., faster reactions), potential for lower cost fuel production, and the elimination of a sterilization step. However, compared to biological catalysis, chemical catalysis, as it relates to the complex structures of the compounds that make up biomass, is a relatively new field. Developing these processes is a challenge.

Environmental Benefit / Emission Reduction Potential

The environmental benefits of advanced biohydrocarbons are significant. For instance, they have the potential to overcome obstacles related to the use of ethanol: land use changes; transportation and distribution of finished fuel; impacts on other agricultural commodities; and the need for vehicle modification.

The primary feedstocks for advanced biohydrocarbons are woody biomass (primarily food and agricultural waste) and algae — neither of which have the same land requirements as biofuels derived from traditional food or feed crops (such as corn or sugarcane). While there will inevitably be some pressure on agricultural lands and forestry resources, the impacts are less than first generation biofuels.

The development of heterogeneous chemical catalysts,[3] used in combination with biological catalysts to produce advanced biohydrocarbons, has the potential to improve biofuel production efficiency and reduce costs. Furthermore, advanced biohydrocarbon fuels are chemically equivalent to the fuels derived from petroleum, which may make it possible to link biorefining processes to existing petroleum refineries. This has the potential to reduce the environmental impact of construction of new refineries and distribution networks (e.g., pipelines), and other fueling infrastructure.

Advanced biohydrocarbons have the potential to reduce significantly the amount of water used in feedstock production and in fuel processing compared to the crops for “first generation” biofuels and the processing using dilute sugar solutions for ethanol production.[4]

The greenhouse gas emissions reduction potential of advanced biohydrocarbons is significant. However, there are no reliable estimates of the GHG emissions (reported as grams per megajoule, g/MJ) of advanced biohydrocarbons because there are no commercial scale processes that can be used to develop the appropriate energy balance equations.

The Department of Energy (DOE) has estimated that the availability of domestic biomass streams, with “relatively modest changes in land use and agricultural and forest practices,” could yield advanced biohydrocarbons at a volume equivalent to approximately 30 percent of petroleum used in the United States by 2050.[5] The oil yield of algal-based diesels is predicted to be as much as an order of magnitude higher than other biodiesel crops. Assuming a lower limit for the oil yield of algal-based biodiesel (30 percent by weight), only 2.5 percent of existing U.S. cropping area would be required to displace 50 percent of petroleum based diesel use in the United States.[6]

Cost

The current cost of large-scale production of advanced biohydrocarbons is unknown, as only bench-scale production has been conducted thus far. As such, only estimates of cost are available at this time.

There are four primary factors that determine the cost of the finished product: the feedstock, chemical processing (e.g., pyrolysis), refining and finishing the crude product, and the transportation and distribution of finished fuel.

Feedstock: The cost of woody biomass feedstocks is dependent on a number of factors including, but not limited to: crop yield, land availability, harvesting, storage and handling, and transportation costs.[7] Huber estimates a cost of $34 to $70 per dry ton, or $5 to $15 per barrel of oil energy equivalent.[8] This is generally consistent with the BRDI review of the literature. They report costs for a number of advanced biofuel feedstock types, including agricultural residues (e.g., corn stover), forest biomass, urban woody wastes and secondary mill residues, herbaceous energy crops (e.g., switchgrass), and short rotation woody crops.

Catalyst: The long-term potential of advanced biohydrocarbons is linked to the ability of producers to produce liquid fuels using cost-effective catalysts. Looking at existing catalytic processes, the DOE has a projected cost of cellulase enzymes for the production of ethanol between $0.30–0.50 per gallon of ethanol.[9] In contrast, the chemical catalysts in the petroleum industry are estimated to cost about $0.01 per gallon of gasoline.[10]

Refining and Upgrading: Estimates for refining and upgrading the bio-oil produced from pyrolysis or hydrolysis suggest that these steps account for about 33–39 percent of the capital costs of producing the finished product.[11] The range varies due to the variable amount of refining and upgrading required based on the pathway.

Transportation: The cost of transporting biomass feedstocks can increase production costs considerably. The savings derived from economies of scale at centralized facilities are often offset by the increased transportation costs of the raw material(s). Developing a distribution system that is built on local and distributed production facilities rather than large centralized facilities will help reduce transportation costs.

In terms of net production, various start-up companies have claimed that they anticipate that in the long term, advanced biohydrocarbons will be competitive with conventional petroleum products at oil prices of about $40–60 per barrel.[12]

Current Status

Advanced biohydrocarbons are currently in the development and demonstration stage. A variety of processes have been demonstrated using bench-scale reactors to produce liquid fuels and liquid fuel components (e.g., aromatic compounds). Most estimates suggest that commercial scale production of advanced biohydrocarbons will begin within the next five to ten years.

Most recently, the DOE’s ARPA-E awarded seven projects (out of 37) a total of $37.2 million (out of $151 million) in areas related to advanced biohydrocarbons as part of their solicitation for Transformational Energy Research Projects.[13]

The DOE awarded $78 million for the development of ‘drop-in’ renewable hydrocarbon biofuels such as advanced biohydrocarbons and associated fueling infrastructure.[14]

Within the past year alone, five major oil companies – BP,[15] Chevron,[16] ExxonMobil,[17] Royal Dutch Shell,[18] and Total[19] – announced joint ventures with biofuel companies to work on the development of advanced biohydrocarbons.

Obstacles to Further Development or Deployment

Currently, there are no low-cost technologies to convert the large fraction of energy in biomass or the bio-oils derived from algae into liquid fuels efficiently. Production costs must be reduced considerably, and the production volumes necessary for widespread use still need to be demonstrated. The lower limit benchmark for commercial scale processing of biomass is about 150,000 metric tons per year.[20]

Ultimately, the optimization of advanced biohydrocarbon production processes is an essential step to allow biorefineries to produce up to commercial volumes. These barriers exist in processes such as selective thermal processing, liquid-phase catalytic processing of sugars and bio-oils, and catalytic conversion of bio-gas.

• Selective thermal processing via pyrolysis
  • The production of bio-oil using fast pyrolysis results in a product that is high in oxygen content. This bio-oil is not compatible with the existing fueling infrastructure, so the oxygen needs to be removed, typically via hydrotreatment or hydrocracking. This process can be expensive and requires large quantities of hydrogen.
  • Another concern is that bio-oils tend to be acidic and can cause corrosion in standard refinery units. Furthermore, they are toxic and require careful handling.
• Liquid-phase catalytic processing of sugars and bio-oils
  • There is a need to increase our understanding of the intermediate processes during liquid-phase catalytic processes, namely the composition of the intermediate components, to help researchers tailor the finished product.
  • Catalyst development for biohydrocarbon production is difficult because of the aqueous (i.e., water-based) environment. The catalysts developed in the petroleum and petrochemical refining industries are unstable under aqueous conditions as they operate in the gas phase or in organic solvents.
  • There are also limitations related to the stability of the catalyst. For instance, a catalyst that works on bench scale may break down when applied to biomass feeds because of the various impurities present in the feedstock.
• Catalytic conversion of bio-gas
  • Cost-effective production of bio-gas is challenging because the quantity of biomass required for commercial production is either not readily accessible or is currently being used for other purposes. Currently, gasification is done on a small scale (10,000-20,000 barrels per day of oil equivalent) at the local level which increases the costs of fuel distribution.
  • The clean-up of bio-gas is an important step to streamline the processing of advanced biohydrocarbons. Bio-gas can contain impurities due to the various biomass feedstocks used in its production, which may require the development of feedstock-dependent catalysts.
  • In addition to the conversion to bio-gas and the clean-up, the final step of conversion of bio-gas to liquid fuel requires considerable advancement in areas including the Fischer-Tropsch Synthesis, reactor technologies, and the integration of catalysts and reactors.

Policy Options to Help Promote Advanced Biohydrocarbon Fuels

Federal, state, county, and local governments support advanced biohydrocarbons in a variety of ways. Although current policies are aimed at alcohol transportation fuels, recent debate over the potential environmental and societal impacts of using feed and food crops for energy production has bolstered interest in biofuels produced from non-food feedstocks. Current support for advanced biohydrocarbons generally falls into three categories: 1) policies that mandate levels of use of biofuels, 2) policies that offer subsidies or tax credits for fuel production and/or use, and 3) and research initiatives.

Mandates

• The Energy Independence and Security Act (EISA) of 2007 established a Renewable Fuel Standard that requires the production of 100 million gallons of cellulosic biofuel in 2010 and increasing over time to 16 billion gallons of cellulosic fuel in 2022.
• The Low Carbon Fuel Standard in California requires a 10 percent reduction in the carbon intensity of transportation fuels sold in California by 2020. In order to meet these requirements, one of the strategies that can be pursued is the introduction of advanced biohydrocarbons. The credit towards the LCFS is ultimately a function of the volume sold and the reduction in lifecycle emissions of the fuel as compared to the baseline fuel, i.e. gasoline or diesel.

Existing taxes and subsidies

• Registered cellulosic biofuel providers are eligible to receive a tax incentive up to $1.01 per gallon of biofuel that is sold and used by the purchaser in the purchaser's trade or business to produce a cellulosic biofuel mixture; sold and used by the purchaser as a fuel in a trade or business; sold at retail for use as a motor vehicle fuel; used by the producer in a trade or business to produce a cellulosic biofuel mixture; or used by the producer as a fuel in a trade or business.[21] Biodiesel blenders can claim a tax credit of $1 per gallon. Note that only blenders that have produced and sold or used the qualified biodiesel mixture as a fuel in their trade or business are eligible for the tax credit.[22]

Other tax and subsidy policies that may be considered:

• Promote additional tax incentives for processes and biorefineries that use biomass feedstocks from non-food sources.
• Support distribution and transportation infrastructure, including tax incentives to attract the required capital investments.

Research initiatives

• Promotion of public-private partnerships for interdisciplinary research for the entire supply chain of advanced biohydrocarbons. For example, the recent DOE awards for $78 million of funding for advanced biofuels research are matched by $19 million in private and non-federal cost share funds.
• Support for research on non-food feedstock production in areas such as increased crop yields.
• Continued and focused support for the research and demonstration of conversion technologies in biohydrocarbon processing. The National Advanced Biofuels Consortia, led by NREL, received about $34 million of the recent DOE award for research to develop “infrastructure compatible, biomass-based hydrocarbon fuels.”
• Continued and increased support of bench- and pilot-scale research into the production of advanced biohydrocarbons.

Related Business Environmental Leadership Council (BELC) Company Activities

• BP [3]
• The Dow Chemical Company [4]
• DuPont [5]
• Royal Dutch/Shell [6]
• Weyerhaueser [7]

Related C2ES Resources

Agriculture's Role in Greenhouse Gas Mitigation [8], 2006

Biofuels for Transportation: A Climate Perspective [9], 2008

Climate TechBook: Biofuels Overview [10], 2009

Climate TechBook: Biodiesel [11], 2009

Climate TechBook: Cellulosic Ethanol [12], 2009

Climate TechBook: Ethanol [1], 2009

MAP: State Mandates and Incentives Promoting Biofuels [13]

Further Reading / Additional Resources

Biomass as a feedstock for a bioenergy and bioproducts industry: The technical feasibility of a billion-ton annual supply [14].

Biomass Energy Data Book [15], 2008.

Breaking the Chemical and Engineering Barriers to Lignocellulosic Biofuels: Next Generation Hydrocarbon Biorefineries [16].

Green Car Congress, Bio-Hydrocarbons [17].

National Biofuels Action Plan [18], October 2008, Biomass Research and Development Board

Biomass Research & Development Initiative [19].

Biomass Research and Development Initiative (BRDi), “The Economics of Biomass Feedstocks in the United States, A Review of the Literature [20],” 2008.

Chisti, Y. (2007). Biodiesel from microalgae. Palmerston North: Biotechnology Advances.

Hubert, GW, et al. “Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysis, and Engineering.” Chemical Reviews, 2006, 106, pp. 4044-4098.

Perlack R., L. Wright, A. Turhollow, R. Graham, B Stokes, and D. Erbach, Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, USDA/DOE, DOE/GO-102005-2135, ORNL/TM-2005/66, April 2005.

Regalbuto, J. “Cellulosic Biofuels – Got Gasoline?” Science, Vol 325, 5492, pp. 822-824, August 2009.

NSF. “Breaking the Chemical and Engineering Barriers to Lignocellulosic Biofuels: Next Generation Hydrocarbon Biorefineries”. Ed. George W. Huber, 2008, 180 p.

Green Car Congress, “Terrabon to Open New Demonstration Facility Next Week for Biomass to Renewable Gasoline Technology [21],” October 2008.

Wu, M.; Mintz, M.; and Wang, M. Water Consumption in the Production of Ethanol and Petroleum Gasoline,” Env Mngmt, 44, 981-997, 2009.