Energy From Bio Waste

Using waste biomass to produce energy can reduce the use of fossil fuels, reduce greenhouse gas emissions and reduce pollution and waste management problems. A recent publication by the European Union highlighted the potential for waste-derived bioenergy to contribute to the reduction of global warming. The report concluded that 19 million tons of oil equivalent is available from biomass by 2020, 46% from bio-wastes: municipal solid waste (MSW), agricultural residues, farm waste and other biodegradable waste streams.

Landfill sites generate gases as the waste buried in them undergoes anaerobic digestion. These gases are known collectively as landfill gas (LFG). This is considered a source of renewable energy, even though landfill disposal is often non-sustainable. Landfill gas can be burned either directly for heat or to generate electricity for public consumption. Landfill gas contains approximately 50% methane, the gas found in natural gas.

If landfill gas is not harvested, it escapes into the atmosphere: this is undesirable because methane is a greenhouse gas with much more global warming potential than carbon dioxide. Over a time span of 100 years, one ton of methane produces the same greenhouse gas (GHG) effect as 23 tons of CO2. When methane burns, it produces carbon dioxide in the ratio 1:1 -- CH4 + 2O2 = CO2 + 2H2O. So, by harvesting and burning landfill gas, its global warming potential is reduced a factor of 23, in addition to providing energy for heat and power.

It was recently discovered that living plants also produce methane. The amount is 10 to 100 times greater than that produced by dead plants in an aerobic environment but does not increase global warming because of the carbon cycle.

Anaerobic digestion can be used as a waste management strategy to reduce the amount of waste sent to landfill and generate methane, or biogas. Any form of biomass can be used in anaerobic digestion and will break down to produce methane, which can be harvested and burned to generate heat, power or to power certain automotive vehicles.

A current project for a 1.6 MW landfill power plant is projected to provide power for 880 homes. It is estimated that this will eliminate 3,187 tons of methane and directly eliminate 8.756 tons of carbon dioxide release per year. This is the same as removing 12,576 cars from the road, or planting 15,606 trees, or not using 359 rail cars of coal per year.

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