Thermochemical Liquefaction

Whereas nature converts biomass into fossil fuels by applying heat and pressure over millions of years, thermochemical liquefaction can convert a liquid slurry of organic material into hydrocarbon oils and products  to produce fuel in a matter of minutes. Water, injected into a feedstock slurry under pressures of up to 200 atmospheres and temperatures near 350 degrees Celcius, facilitates a chemical reaction that increases the hydrogen to carbon ratio, thereby improving hydrocarbon yields (Zhang et al. 1999). Direct liquefaction, or thermal depolymerization, has been successful in producing a liquid oil while the newer indirect liquefaction has had success producing syngas, ethanol, and methanol (PETC 1985).

Changing World Technologies has a process in which their feedstock, mainly turkey grease and oil, is pulped and heated under pressure to initiate the chemical reactions. First stage oils are removed and the heat is increased to produce a light hydrocarbon and char. The technology is roughly producing 500 barrels of bio-derived oil daily and has an energy efficiency of 85 percent measured by the energy of combustible products that leave the Carthage, Missouri plant divided by the total energy input.

Much more research and technological testing is needed to make this process work more efficiently with woody biomass, but the future is promising (BROKEN-LINKDuncan and White 2002).