Natural gas provides almost a third of the energy used by U.S. industry. It is used for on-site electricity generation (fueling boilers and turbines); for process heat to melt glass, process food, preheat metals, and dry various products; and for combined heat and power (CHP) systems. Natural gas is also used as a material input itself—as a feedstock—to make products such as fertilizers, chemicals, and plastics in processes that do no emit greenhouse gases.
Even as the manufacturing sector expands, replacing lower-efficiency boilers and deploying CHP systems can reduce emission intensity while using more natural gas.
Analysis by the Massachusetts Institute of Technology found that replacing older natural gas boilers with high-efficiency or super-high-efficiency units would decrease CO2 emissions by 4,500 to 9,000 tons or more per year per boiler.
Residential and commercial buildings
Electricity use has been growing more rapidly in buildings due to the proliferation of electronic devices, while natural gas use has remained flat and generally confined to space heating, water heating, cooking, and clothes drying. However, natural gas appliances can often be more efficient on a full-fuel-cycle basis than similar appliances that use electricity, propane, or oil. The source-to-site efficiency of natural gas, averages 92 percent; that is, 92 percent of the energy contained in extracted natural gas is useful energy that can directly fuel appliances, as compared to about 30 percent efficiency for electric appliances.
Natural gas may also increase the overall efficiency of consumer energy when used for electricity generation on site through fuel cells and microturbines.
Natural gas-powered fuel cells use natural gas and air to create electricity and heat through an electrochemical process rather than combustion. Fuel cell technology has been around for decades, but has not been widely deployed due to concerns about cost and durability.
Microturbines are small combustion turbines approximately the size of a refrigerator with individual unit outputs of up to 500 kilowatts (kW). They can be fueled by natural gas, hydrogen, propane, or diesel. Like fuel cells, microturbines can achieve much higher energy efficiencies, because the electricity and waste heat generated can be used on site.
Transportation accounts for about 27 percent of U.S. greenhouse gas emissions, and energy use in the sector is dominated by oil. Only 3 percent of vehicles on the road in the United States are fueled by natural gas. Of these, the majority are buses and trucks running on compressed natural gas (CNG) or liquefied natural gas (LNG). CNG and LNG can reduce greenhouse gas emissions as compared gasoline and diesel, and they are energy-dense fuels that can be used in heavy-duty engines where electrification may not yet be economically viable. Limited availability of fueling infrastructure is one of the hurdles to deploying more natural gas trucks.