Photo of a compressed natural gas truck

What emerging alternative fuels are under development or are already developed and available in the United States?

Clean Cities coordinators and stakeholders are familiar with the most commonly used alternative fuels, which have been covered over the last several months in the Question of the Month “key terms” series. However, there are also several emerging fuels that are currently under development or already in use in the United States. Like other alternatives, these fuels can increase energy security, reduce emissions, improve vehicle performance, and stimulate the U.S. economy. In addition, some are considered alternative fuels under the Energy Policy Act of 1992 and may qualify for federal and state incentives.

Below we have listed a few emerging alternative fuels, their characteristics, and their benefits:

  • Biobutanol (butyl alcohol):
    • Composition and production: Biobutanol is a 4-carbon alcohol that can be produced from the same feedstocks as ethanol, including corn, sugar beets, and other biomass wastes.
    • Use as a transportation fuel: Biobutanol can be blended with other fuels for use in conventional gasoline vehicles.
    • Benefits and more information: See the Alternative Fuels Data Center (AFDC) Biobutanol page.
  • Drop-In Biofuels:
    • Composition and production: Drop-in biofuels are hydrocarbon fuels that are substantially similar to petroleum-based gasoline, diesel, or jet fuels. They can be produced from various biomass feedstocks, such as crop residues, woody biomass, dedicated energy crops, vegetable oils, fats, greases or algae.
    • Use as a transportation fuel: Drop-in biofuels are in an early stage of development, with several commercial plants in the United States and abroad. The focus is aimed at eventually replacing gasoline, diesel, and jet fuel.
    • Benefits and more information: See the AFDC Drop-In Biofuels page.
  • Methanol:
    • Composition and production: Methanol, or wood alcohol, has similar chemical and physical fuel properties to ethanol. Methanol can be produced using various feedstocks, including carbon-based feedstocks, such as coal. However, natural gas is currently the most economical feedstock.
    • Use as a transportation fuel: In the 1990s, 100% methanol and 85% methanol/15% gasoline blends (M85) were used in compatible vehicles, similar to ethanol flexible fuel vehicles (FFVs) on the market today. The National Renewable Energy Laboratory is currently researching ways to use methanol for fuel cell vehicles.
    • Benefits and more information: See the AFDC Methanol page.
  • Renewable Natural Gas (Biomethane):
    • Composition and production:Renewable natural gas (RNG), also known as biomethane, is pipeline-quality gas that is fully interchangeable with fossil natural gas. RNG is essentially biogas (also known as swamp gas, landfill gas, or digester gas) that has been processed to purity standards. Biogas is typically composed of 50-80% methane, 20-50% carbon dioxide, and trace gases such as hydrogen, carbon monoxide, and nitrogen. It is produced by decomposing organic matter, such as sewage, animal byproducts, and agricultural, industrial, and municipal solid wastes.
    • Use as a transportation fuel: Renewable natural gas can be used in existing natural gas vehicles without modification.
    • Benefits and more information: See the AFDC Renewable Natural Gas page.
  • xTL Fuels (Fischer-Tropsch):
    • Composition and production: Synthetic liquid transportation fuels, otherwise known as xTL fuels, are produced through various conversion processes. These processes convert fuels from carbon-based feedstocks to yield various fuels, such as gasoline, diesel, ethanol, and methanol. In particular, the Fischer-Tropsch process produces liquid fuels from coal and natural gas. Coal can also be converted into liquids through liquefaction.
    • Use as a transportation fuel: Much like drop-in biofuels, xTL fuels can replace conventional petroleum diesel for use in vehicles without modifications to the engine or fueling infrastructure.
    • Benefits and more information: See the AFDC xTL Fuels page.
  • Dimethyl ether (DME):
    • Composition and production: DME is a non-toxic, colorless gas that can be easily liquefied to a biodegradable synthetic liquid fuel. It is produced from various feedstocks, such as natural gas, coal, biomass, or even carbon dioxide.
    • Use as a transportation fuel: DME can be used in conventional diesel engines and stored in similar vehicle storage tanks to those used for propane fuel.
    • Benefits and more information: See SAE International's presentation, DME from Natural Gas or Biomass: A Better Fuel Alternative.