Scientists are experimenting with producing fuel from “next generation” feedstocks – inexpensive, non-edible biomass (such as agricultural residue, waste from the wood products industry, and switchgrass and other grasses) that can be converted into a diesel replacement. These materials are mostly cellulosic.
While it is a fairly simple process to convert vegetable oil or animal fat into biodiesel, the conversion of cellulosic feedstocks to fuel is more complicated and more expensive. To produce a hydrocarbon fuel, the biomass is generally first converted into a synthetic gas using high heat. Then, the gas can be converted into a liquid diesel fuel.
The fuel resulting from these new technologies is technically not “biodiesel,” which is defined, according to the ASTM specifications, as “mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats.” Instead, these fuels from cellulosic feedstocks are termed “renewable diesel.” This term also includes fuels produced from vegetable oils and animal fats using conventional petroleum refining techniques.
For more information, see Renewable Diesel Technology, a white paper published in 2007 by the Washington State Department of Agriculture.
