Biofuels

Environmental biotechnology covers cleaning up pollution (bioremediation), preventing it, monitoring it, and genetic engineering for the environment. Prevention includes making biofuels and biodegradable products.

Biofuels are fuels made from living things or biological waste. They are renewable: plants can be grown again. Fuels made from crops such as soybean, jatropha, pongamia, palm and algae are called agrofuels. The main kinds:

• Biodiesel is made from fats and oils by a reaction called trans-esterification. Compared with ordinary diesel, it has more hydrogen and oxygen and less carbon, so it burns more cleanly. It runs in ordinary diesel engines, pure or blended.
• Bioethanol (bioalcohol): sugars released from starch or cellulose (in wheat, corn, sugarcane, molasses) are fermented, then distilled and dried. Ethanol blended with petrol cuts the use of fossil fuel and the release of greenhouse gases. But it can make engines hard to start, and it oxidises aluminium and rusts steel. Algae could provide both bioethanol and biodiesel without using food crops, but this is not yet cost-effective.
• Biogas: mainly methane and CO₂, made when bacteria break down dung, human waste, crop residues and other waste without oxygen. It removes waste, provides manure and energy, and frees homes from smoky kitchens. India has about 49.3 lakh biogas plants under the National Biogas and Manure Management Programme. Used in vehicles, it corrodes engines.
• Biomass (solid biofuels): wood, sawdust, crop waste, dried manure, cow dung cakes, pellets. It is important for poorer households, but burning it releases harmful particles and chemicals called PAHs.