Alternative Fuels


Biofuels are fuels produced from biomass, such as plant matter, algae, and animal fats (recently living “bio” materials). Biological processes can also produce biofuels directly from molecules in the atmosphere.

There are several types of biofuel. Currently, most are blended with petroleum products and serve as additives or as blendstock. Eventually, we may transition to using only renewable fuels, completely replacing fossil-based fuel.

The following are a few types of biofuel:

  • Ethanol – Ethanol was one of the first biofuels to be widely used in the United States, dating back to Henry Ford’s early automobiles. Ethanol most recently replaced methyl tertiary butyl ether (MTBE), a carcinogenic substance that, until banned in many states, was used to provide octane to liquid transportation fuel. Ethanol also serves as an oxygenate, reducing harmful emissions of gasoline-powered vehicles, which is particularly useful in Environmental Protection Agency (EPA)-designated “nonattainment areas.”
    • The ethanol molecule used in fuel is the same one you find in beer, wine, and spirits. Ethanol made from corn is called moonshine when made for drinking. For fuel purposes, it is distilled to nearly 200 proof (99.6%) pure.
    • Currently, almost all of the gasoline fuel in the United States contains 10% ethanol.
    • Ethanol can be made from many substances. Most fuel ethanol in the United States comes from corn starch. A number of commercial-scale plants in the United States also produce ethanol from corn stover (stalks, leaves, and cobs). In Brazil, ethanol from sugar cane fuels cars, and some of that ethanol is shipped as fuel to California.
    • Other countries make fuel ethanol from cassava and other plants.
    • Research is underway using algae and cyanobacteria that produce ethanol directly.
    • ASTM D4806 Denatured fuel ethanol states the performance standards for fuel ethanol.
  • Biodiesel – Biodiesel is mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, usually made with a transesterification process. Soybean oil, other plant oils, waste grease, and used cooking oil can also be made into biodiesel. Biodiesel may be used in diesel fuel at blends up to 5% (B5) in the United States, just as any other additive. Commercial-use blends of amounts over 5% must be identified. B20 is a common blend; a number of vehicle manufacturers warrant new diesel vehicles to use B20. People may use much higher blends in transportation vehicles, older farm equipment, and other vehicles designed for high blends such as the new Renault trucks designed to use 100% biodiesel.
    • Heating oil containing up to 20% biodiesel is sold in the United States, although current ASTM specifications apply to 5% biodiesel into the No. 1 and No. 2 grades of ASTM D396; the ASTM specifications for B6–B20 heating oil will be published shortly.
    • Biodiesel blends are also sold for power generation via generator sets.
  • Renewable diesel – Renewable diesel refers to petrodiesel-like fuels derived from biological sources that are chemically not esters and thus are distinct from biodiesel. Renewable diesel is chemically the same as petrodiesel. The terms “renewable diesel” and “green diesel” have been distinguished based on the processing method to create the fuel with a petrodiesel-like chemical composition. “Renewable diesel” can refer to all diesel fuels derived from biomass that meet the standards of ASTM D975 and are not mono-alkyl esters.
  • Jet fuel – Jet fuel includes kerosene-type jet fuel and naphtha-type jet fuel with hydrocarbons in the jet fuel range (C8–C14).
    • Biofuels compatible with aviation include those made with a Fischer-Tropsch (FT) process (Fischer-Tropsch Synthesized Paraffanic Kerosenes) and those made with hydroprocessed esters and fatty acids (HEFA, also known as HRJ or Bio-SPK).
    • Other processes under evaluation by ASTM include the following:
      • Alcohol-to-Jet (ATJ)
      • Catalytic Conversion of Oil to Jet (CCOTJ)
      • Catalytic Conversion of Sugar to Jet (CCOSJ)
      • Catalytic Hydrothermolysis, Hydroprocessing to Jet (CH-HRJ)
      • Direct Fermentation of Sugar to Jet (DFSTJ)
      • Hydrotreated Depolymerized Cellulosic Jet (HDCJ)
      • Synthesized Ido-Paraffinic Fuel (DSHC) (SIP)
    • Once ASTM approves the process, regulatory bodies around the world will allow fuel that meets the specification to be used in commercial aircrafts. Military fuels may also have to meet military specifications. The U.S. Navy has requested up to 50% blends of FT and HEFA, which meet specifications for JP-5 aviation turbine fuel and F-76 naval distillate fuel.
  • Marine fuel – Fuels are being developed with mariner use in mind. Bio-based fuels have been developed to meet military specifications for F-76 naval distillate fuel. Fuel including bio-isobutanol has been tested for the boating and marine market. Diesel blends with biodiesel and renewable diesel have also been used in commercial and recreational markets. For more information, visit Advanced BioFuels USA.
  • Bio-based natural gas – Biogas captured from anaerobic digestion using organic material from landfills, wastewater treatment facilities, agricultural operations, or separated municipal solid waste (MSW) is eligible for renewable fuel credits if cleaned and used as a renewable replacement for compressed natural gas (CNG) or liquid natural gas (LNG) for use as a transportation fuel, or if it is used to produce electricity and the generated electricity is used to power an electric vehicle.
  • Methanol – Bio-based methanol can be used as a chemical intermediate or as a fuel; however, in the United States, the EPA has not yet approved a pathway that would enable it to generate renewable fuel credits.

Biofuels Regulation

The Renewable Fuel Standard (RFS) is a federal mandate requiring companies that blend transportation fuels for commercial sales to incorporate biofuel into their products. Companies demonstrate their biofuel use through Renewable Identification Numbers (RINs) and an electronic system established with the EPA. The RFS allows new biofuels to be approved for use, especially fuels that reduce greenhouse gas emissions by 50% or more compared to 2005 petroleum fuel.


  • There is one biodiesel facility located in Hagerstown, and blending facilities are located in Baltimore City.
  • A few biofuel companies have launched in Maryland, such as Fiberite (developing ethanol from MSW).
  • TRI also draws on MSW or other waste materials to produce jet fuel.
  • HY-TEK Bio is developing an algae technology in partnership with the University of Maryland to develop biofuel and other high-value by-products.
  • Atlantic Biomass, Inc., develops enzymes for conversion of biomass to constituent sugars that can be used as building blocks for fuel, biochemicals, or other bioproducts in partnership with Hood College in Frederick.

Other Fuels

Compressed Natural Gas and Liquefied Natural Gas

A natural gas vehicle (NGV) is an alternate fuel vehicle that uses CNG or LNG as a cleaner alternative to other fossil fuels. NGVs should not be confused with vehicles powered by propane autogas (also known as liquefied petroleum gas [LPG]), which has a fundamentally different composition. Worldwide, there were 14.8 million NGVs in 2011. In 2009, there were 114,270 CNG vehicles (mostly buses) and 3,176 LNG vehicles in the United States. Maryland has nine CNG-filling stations, and two are open to the public.

Existing gasoline-powered vehicles may be converted to run on CNG or LNG, either in dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas) operation. An increasing number of vehicles worldwide are being manufactured to run on CNG. Until recently, the Honda Civic GX was the only NGV commercially available in the U.S. market; however, Ford, General Motors, and Ram Trucks now have bi-fuel offerings in their vehicle lineups.

Despite their advantages, NGVs face several limitations, including fuel storage and a lack of available infrastructure for delivery and distribution at fueling stations.

Propane Autogas

Propane autogas is an alternative vehicle fuel that reduces some harmful emissions compared to other fuels, costs on average $1.50 less per gallon than gasoline, and is almost entirely domestically produced. Autogas vehicles achieve 90% of the range of gasoline vehicles. Autogas vehicles can be produced by original equipment manufacturers, and gasoline vehicles can be converted to run on bi-fuel (either gasoline or LPG). Autogas is the third most used vehicle fuel in the world, with 18 million autogas vehicles on the road globally.

Autogas vehicles are ideal for light- to medium-duty, high-mileage fleets. Autogas fueling station installation costs are much lower than for natural gas fueling stations (on-site infrastructure is often installed at little or no cost to autogas fleets), and installation does not require integration with pipeline infrastructure.

Autogas Versus Natural Gas 

  • Autogas incremental vehicle and fueling infrastructure costs are significantly less than those for natural gas (CNG or LNG); fifteen autogas stations can be built for the cost of one CNG station.
  • Autogas distribution is not dependent on building new pipelines.

Nonattainment area info for mid-Atlantic: