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n. Fuel such as methane produced from renewable biological resources such as plant biomass and treated municipal and industrial waste.

n. Any fuel that is obtained from a renewable biological resource, especially from biomass

"In general, the term biofuel is associated with only a few select chemical compounds, especially ethanol (used exclusively as a gasoline replacement in spark-ignition engines) and very large methyl esters in biodiesel (used as a diesel fuel replacement in diesel engines)."

corn-based    ethanol    biodiesel    billion-a-year    small-scale