Energy from Waste
A lot of waste we produce is disposed of in landfill sites. When this waste decomposes over time, a lot of methane is given off. If left to accumulate in the atmosphere, this methane can contribute to global warming. However, it can be utilised to generate electricity by burning it. Although this releases carbon dioxide into the air, it is not as strong a greenhouse gas as methane.
It has been estimated that 6 to 8 tonnes per cubic metre of methane gas are produced from landfill gas extraction each year. This method was first utilised to power boilers and furnaces in close proximity to the landfill sites. However, present schemes use the gas to power engines and generate electricity. Landfill gas currently provides approximately 250 megawatts (MW or million watts) of electricity in the UK, about 21% of all electricity produced by renewable sources. This figure set to increase further in the coming years.
Energy can be derived from waste besides the burning of methane. Firstly, when waste is incinerated in large amounts, heat energy can be recovered and used for heating schemes in factories, hospitals and other large-scale complexes. Secondly, waste-derived fuel can be burnt in many conventional boilers and larger combustion units. Unfortunately the fuel is not as energy-rich as coal, and is therefore not always economically viable for companies to utilise. Incentives are often required to encourage firms to use this type of fuel.