Jan 04, 2012— read in full
What is waste-to-energy?
- Each year the average family throws away 1.5 tons of rubbish. That's like throwing half an elephant onto a landfill site
- There are 13 waste-to-energy plants in the UK
Turning waste into energy sounds like something a magician might do but in fact engineers and scientist around the world are now able to make rubbish into electricity!
If you’ve ever sat around a campfire and roasted marshmallows on the flames you’ve experienced one of the theories behind waste-to-energy. When materials we can burn, like the logs on a campfire, are burnt they release heat which is a form of energy.
In the past there have been attempts to reduce the amount of household waste going to landfill by burning it. This would happen in an incinerator. Until recently, little or no attempt was made to sort waste, heat, or any of the nasty gases and chemicals that went out of the chimney. The heat that is created has many purposes. The most useful function is creating electricity using the heat.
There are also other ways of getting energy from waste, for example gasification and anaerobic digestion.
How does it work?
The waste-to-energy process is a very simple concept. However, getting the maximum energy from waste, with minimal damage to the environment is a complex problem to solve.
Nowadays it is possible to capture everything that used to go out of the chimney of an incinerator - both the nasty and useful things. These can now be captured and processed in waste-to-energy plants.
Waste-to-energy plants burn waste but the heat is captured instead of escaping up the chimney. The heat can be used to produce hot water to heat local houses, offices and factories or to produce steam to drive turbines that produce electricity.
Harmful gases that would normally leave via a chimney are captured and used to produce chemical feedstocks such as fertiliser. You can even turn the gases into diesel to power cars or fuel to power aircraft!
Another way of generating energy from waste is gasification. Gasification is a thermal process that heats the waste with little or no oxygen in order to produce a chemical reaction.
The waste does not burn, because it is not heated with oxygen. The chemical reaction produces synthetic gases.
These can be burned to turn a turbine, which spins a generator and creates electricity. Gasification is a much more efficient way of making electricity compared to burning waste, like incinerators used to.
A third method is anaerobic digestion. This is a biological process that breaks down living material into simpler materials, a bit like your stomach does! The product of this digestion is a bio-gas which is rich in methane gas.
The methane can then be burned in order to create heat to turn a turbine in order to generate electricity. Alternatively, the bio-gas can be refined to create fuel for cars.
All these processes mean that we can now use waste from households, industry and agriculture as a sustainable and renewable resource.