Biogas
- Produced by the process of anaerobic digestion of organic material by anaerobes from biodegradable waste materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields.
- The solid byproduct, digestate, can be used as a biofuel or a fertilizer.
- Biogas can be recovered from mechanical biological treatment waste processing systems.
Syngas
- Produced by partial combustion of biomass and is a combination of carbon monoxide, hydrogen and other hydrocarbons.
- Syngas may be burned directly in internal combustion engines, turbines or high-temperature fuel cells.
Ethanol
- Produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest), or cellulose (which is more difficult) and is the most common biofuel worldwide.
- The ethanol production methods used are enzyme digestion (to release sugars from stored starches), fermentation of the sugars, distillation and drying.
Biodiesel
- Biodiesel is the most common biofuel in Europe and produced from oils or fats using transesterification and is a liquid similar in composition to fossil/mineral diesel.
- Chemically, it consists mostly of fatty acid methyl (or ethyl) esters (FAMEs).
- Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, Pongamia pinnata and algae.
- Biodiesel can be used in any diesel engine when mixed with mineral diesel.