Updated July 6, 2014
Transportation around the world continues as it has for the past 100 years, dependent on petroleum in its many forms to function–as gasoline, diesel or jet fuel. The latest word from the U.S. Energy Information Administration is that even in 2040 the government expects 93.23 percent of light-duty vehicle fuels to be gasoline (down 6.1 percent from in market share from 2012). During that same period diesel will increase to 3.23 percent of the market, E85 take 2.82 percent of the market and electricity will take .28 percent (all three of those will make huge market share gains, but starting from a very small base). The rest of the market will be filled by propane, natural gas and hydrogen, according to EIA report. The resulting CO2 is one of the major contributors to global warming so many efforts around the world are looking for ways to reduce the carbon content of fuels with biofuels being the leading contenders to move the needle. Leading the way worldwide is the Low Carbon Fuel Standard of California, which measures the carbon content of fuels and their alternatives, assigning values for comparison. New alternatives are being developed and new fuels making their way to market slowly.
Diesel engines are the standard for heavy vehicles, such as trucks and buses. Biodiesel is a blend of petroleum diesel and biofuel from sources such as soy, waste vegetable oils or animal fats. Blends of 5, 10, and 20% biodiesel are popular because they run in many current diesel engines. The federal government has been promoting the use of B20, so look for wider use of B20 in heavy-duty vehicles, but watch out for restrictions from some light-duty manufacturers about any blends higher than B5. The latest word from California Air Resources Board’s testing showed FAME biodiesel increasing NOx, which may limit its application in that state.
- Nature Conservancy
- National Biodiesel Board
- USMC Camp Pendleton
- Portland Oregon Fleet of 84
- WVO Designs – Waste Vegetable Oil As A Fuel
Renewable diesel is produced from non-petroleum renewable resources but is not a mono-alkyl ester like biodiesel. Renewable diesel consists solely of hydrocarbons and thus is a drop-in fuel that can be used at various blend rates. There are several different chemical approaches to producing renewable diesel. One is based on hydrotreating vegetable oils or animal fats, a process already in use as part of petroleum refining. A second method involves synthesis of hydrocarbons through enzymatic reactions. A third method involves partially combusting a biomass source to produce carbon monoxide and hydrogen (syngas) and utilizing the Fischer-Tropsch reaction to produce complex hydrocarbons. Compared to biodiesel, renewable diesel uses similar feedstocks but has different processing methods and can include chemically different components. (Thanks to the California Air Resources Board website for some of the details above.)
When you drive a car, there is most likely an ethanol blend in your fuel tank. Ethanol is a fuel from a plant source that is normally mixed with gasoline. All U.S. gasoline vehicles can run on a blend of up to 10% ethanol (E10). Ethanol has the potential to reduce U.S. dependency on foreign oil. We are growing our own fuel. Ethanol—a form of alcohol—is the predominant biofuel in use today. The United States and Brazil together produce about 90 percent of global fuel ethanol. Brazil has used ethanol to reduce its dependency on gasoline by 40% and has the auto industry producing vehicles that can run on blends of up to E99 as well as gasoline. In the U.S., the vast majority of ethanol is processed from corn although a major effort is being made to move to cellulosic ethanol that will reduce the carbon intensity of the biofuel. In the real world vehicles running on E85 will discover that the less energy-dense fuel will deliver reduced fuel economy.
- Ethanol Statistics
- Dedicated U.S. Energy Crops Could Replace 30% of Gasoline
- Time Magazine Front Cover Story
- Nature Conservancy
- From Wood and Waste not Food and Haste
- Khosla Ventures Papers and Presentations
- Ethanol, Energy, Greenhouse Gas Paper – Science
- Letter to Science by Michael Wang
BP is spending millions running TV ads about fuel from sugar beets. BP and Dupont is looking for the type of funding assistance that is given to ethanol. They are also looking for millions of customers. Butanol has a much higher energy content than ethanol. Butanol can most likely be blended with gasoline in higher percentages than ethanol and run in non-flexfuel engines. Butanol may get transported in the same pipelines as gasoline.
- Butanol Facts and Links (PES Wiki)
- Dupont and BP Biobutanol Fact Sheet
Di-Methyl Ether (DME)
DME can be derived from many sources, including renewable materials (biomass, waste and agricultural products) and fossil fuels (natural gas and coal). It is currently being tested as a transportation fuel in California in a project based in the San Joaquin Valley involving Volvo Group and Oberon Fuels. They believe the fuel can provide reduced greenhouse gas emissions, reduced PM and NOx emissions, and be a replacement for diesel fuel.