GreenFuel Technologies Corporation developed a patented bioreactor system that uses
nontoxic photosynthetic algae to take in smokestacks flue gases and produce biofuels
such as biodiesel, biogas and a dry fuel comparable to coal.[23]
Syngas
Syngas is produced by the combined processes of pyrolysis, combustion, and gasification. Biofuel is converted into carbon monoxide and energy by pyrolysis. A limited supply of oxygen is introduced to support
combustion. Gasification converts further organic material to hydrogen and additional carbon monoxide.
The resulting gas mixture, syngas, is itself a fuel. Using the syngas is more efficient than direct combustion of the original biofuel; more of the energy contained in the fuel is extracted.
Syngas may be burned directly in internal combustion engines. The wood gas generator is a wood-fueled gasification reactor mounted on an internal combustion engine. Syngas can be used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process to produce a synthetic petroleum substitute. Gasification normally relies on
temperatures >700°C. Lower temperature gasification is desirable when co-producing biochar.
Solid biofuels
grown for fuel in the .
Examples of solid biofuels include wood, sawdust, grass cuttings,
domestic refuse, charcoal, agricultural waste, non-food energy crops (see picture), and dried manure.