By Nicholas Brown.
There are various ways to use rubbish to generate renewable energy. This idea is often called “waste-to-energy”, and it is a very old, but brilliant one.
What humans first used to provide lighting hundreds (or thousands) of years ago is now considered rubbish by today’s standards: twigs, pieces of wood, dried leaves, and any other combustible matter which we would normally throw away. These were ignited to produce luminous, warm fires.
Today, we have so much more combustible matter at our fingertips than ancient humans did, such as paper, cardboard, etc, and are gradually starting to put it to use.
One way to produce renewable using that rubbish is to burn it directly so that it generates heat, which can then boil water to produce steam. The steam would then drive an electricity-generating steam turbine. That heat can also directly heat buildings, or the resulting flames can provide inferior lighting (and a fire hazard to boot).
There are also more advanced methods…
The Modern Method (Anaerobic Digestion)
Anaerobic digestion enables us to produce and use biogas which contains methane, which is a highly energy-dense fuel (it contains 55.5 MJ or 15.4 kWh of energy per kg), to power gas-powered generators. [Source]. This is a fully renewable way to generate electricity without using any fossil-fuel backup, or any materials whatsoever from other countries.
It is environmentally friendly because methane is a relatively clean gas, and, the methane would otherwise have been released into the atmosphere if unused, causing more global warming, as methane is a potent greenhouse gas.
Putting a relatively clean gas like this to use, reducing coal requirements, is where one of its greatest environmental benefits is –Generating electricity cleanly. The other environmental benefit is that it uses waste which would have otherwise been placed in landfills to rot and potentially cause pollution.
How Anaerobic Digestion Works
Anaerobic digestion is the process of fermenting organic matter (such as manure, old food, and plant matter) in an oxygen-free environment. During this process, bacteria break down the matter and produce biogas.
Biogas is normally 60-70% methane, 30-40% carbon dioxide, and it contains traces of other gases. [Source]