Where recycling uses more resources (materials and energy) than making goods from scratch, it makes more sense to deal with the waste in a different way, for example to burn it and recover some of its intrinsic energy recovery which can replace energy produced from fossil fuels. This applies to items such as food-contaminated light weight packaging such as the wrapper round meat or cheese. To transport, sort and clean it to enable it to be recycled would take more energy and resources than the recycled material would yield.
Recovering energy from unrecycled waste is preferable to landfilling it, according to the government’s waste hierarchy.
There are a number of ways of recovering energy from waste. The most basic one is collection of the landfill gas which is given off as wastes degrade in landfills. After hydro power, landfill gas is the second largest contributor to renewable energy in the UK (contributing 23% in 2004).
Another method is to separate the combustible parts of the waste (such as paper, food and plastics) and make them into a solid fuel. Biodegradable waste (such as food ) can also be treated by anaerobic digestion to produce a biogas. This is the same process which is used to process sewage sludge.
The most widely used method of recovering energy from waste (EfW), and the one most people mean when they use the term, is the combustion (or incineration) of waste to recover the heat which is released. This heat can be used to provide steam or hot water to nearby industry or housing, or to generate electricity for the National Grid. Sometimes it is used for both, which is known as Combined Heat and Power (CHP).