Biofuel also called as agrofuel and is derived from biomass and may be in solid, liquid or gaseous form. The use of waste biomass to generate energy can decrease waste management problems, pollution, greenhouse gaseous emissions and the use of fossil fuels. There is a huge potential for bioenergy obtained from waste to decrease the speed of global warming. As per a recent report, by the year 2020, 19 million tons of oil equivalents could be derived from biomass. Out of this, 46% is obtained from bio-wastes like farm waste, agricultural waste, municipal solid waste and other biodegradable waste streams.
The waste buried in landfill site undergoes anaerobic digestion and generates gases. The gases so produced are called landfill gases (LFG). These gases can be burned and looked up to as a source of renewable energy. The LFG comprises of almost 50% methane, which is the same gas found in natural gas. This LFG can be used to generate electricity for public consumption or can be burned for heat.
If LFG is not used properly, it would add to the atmosphere. Methane is a greenhouse gas. It has a global warming potential of 23 relative to carbon dioxide. Thus, one ton of methane results in the same greenhouse gas as 23 tons of carbon dioxide. The formula of the burning of methane is as follows - CH4 + 2O2 = CO2 + 2H20. Thus, there are two advantages of harvesting and burning LFG. Firstly, the global warming potential is decreased by a factor of 23. Secondly, energy is provided for heat and power.
It has been discovered by Thomas Rockmann and Frank Keppler that living plants also generate methane. This methane of living plants is ten to hundred times more than that generated by dead plants in an aerobic environment. However, this methane does not raise chances of global warming due to the incorporated carbon cycle.
A separate waste management strategy is anaerobic digestion. This decreases the amount of waste sent to landfill to generate methane or biogas. In anaerobic digestion, any sort of biomass can be utilized. This waste breaks down and gives rise to methane. This methane is harvested and burned to create heat, power or to run some automotive vehicles.
The statistics related to landfill power plants are as follows - a 3 MW landfill power plant can supply power to 1900 homes. Due to this, it is possible to avoid 6000 tons of methane per year from entering the atmosphere. 18,000 tons per year of carbon dioxide from fossil fuel replacement would be eliminated.
First generation biofuels are those that are prepared from animal fats, vegetable oil, starch and sugar by the use of conventional technology. The anaerobic digestion of organic materials by anaerobes gives rise to biogas. This biogas can be produced from biodegradable waste materials. Digestate is a solid byproduct that can be used as a fertilizer or a biofuel. The biogas comprises of methane and this can be obtained from anaerobic digesters or mechanical biological treatment systems. LFG is a lesser clean form of biogas. Thermal depolymerization of waste results in the extraction of methane and other oils in a manner similar to petroleum.