by Gerald Kutney (Lee Consulting/Biofuels Digest) ... From the time of the caveman until the early Industrial Revolution, biofuels – namely wood and the advanced biofuel of the day, charcoal – reigned supreme. Both fossil fuels and biofuels originate from biomass. The major difference between them is that fossil fuels are sequestered carbon, and biofuels are renewable carbon. Nowadays, the basic technologies to treat biomass for conversion into fuel (or energy) can be logically placed into four general categories:
- MECHANICAL: Traditional routes for woody debris are strictly mechanical treatments such as chipping or grinding the material. Greater densification takes place by pelletizing the biomass.
- THERMOCHEMICAL: Combustion converts biomass into energy, while pyrolysis technology converts biomass into fuel. The latter process not only yields greater energy density than mechanical treatment but the fuel properties are chemically and physically more similar to fossil fuels than the original biomass. A related process is gasification which produces syngas which is a platform technology for the production of a variety of liquid biofuels, through the Fischer-Tropsch (FT) process.
- CHEMICAL: A route for production of transportation fuels which includes biodiesel, FT, and some cellulosic ethanol processes.
- BIOCHEMICAL: A common route for production of fuel ethanol from sugar or starch fermentation, and the production of biogas (methane) under anaerobic conditions.