Generating and Using Biogas is Easy. Some quick facts…
Keeping the Dream Alive
Since childhood, it has always been my long term goal to one day generate and use renewable energy for my lighting and heating needs. With diminishing fuel wood, increasing energy demands and for ethical reasons, I strongly feel that renewable energy is the way to go.
This aspiration was piqued at an early age when an ambitious biogas project was set up in my village. It however stalled after a few years, but my hopes and renewable energy dreams still live on…
Biogas digester on a farm
Biogas
Biogas is basically methane gas (around 60%), with carbon dioxide (around 40%) and a little hydrogen and hydrogen sulphide. It is made by the anaerobic breaking down of organic matter by bacteria, in the absence of oxygen.
We can make it ourselves from plant and animal wastes, and even human waste. It can be burnt to drive a generator, or on a smaller scale, for cooking or lighting gas lamps.
The equipment in which the organic matter breaks down anaerobically is called a digester, and there is also some sort of storage container for the gas produced.
So, Why Use Biogas?
- Biogas reduces CO2 emissions and resource use:
Biogas is a substitute for natural gas. CO2 from biogas is from recently-alive plant matter (even if it was fed to animals), it is part of a cycle – i.e. the plants for the next batch of biogas take in the CO2 given off by the previous batch. Using biogas also saves trees. - Biogas reduces methane emissions:
Animal manures release methane into the atmosphere. When methane is burnt it releases CO2, but methane is a more potent greenhouse gas than CO2, so it is a good idea to burn it rather than release it. - Biogas creates two renewable resources:
Sewage sludge and animal slurries usually end up as fertiliser anyway – so it’s better to obtain fuel from it first, and prevent runoff and methane emissions at the same time – and you still get fertiliser at the end of the process.
It’s the missing link for those wanting to switch from fossil fuels – many (green) people heat their homes with wood/charcoal and their water with solar, and get their electricity from wind and solar – but cooking is a problem; it’s too expensive with electricity, and LPG gas is expensive.
But gas is still the best, and now it can be done without gas bills. With biogas.
Where and How to Start
Biogas generation on a domestic scale
Batch digesters like the one above are feasible on the domestic scale.
A typical small family digester will be around one cubic metre. For cooking and lighting, you don’t need much; every kilogramme of biodegradable material will yield around 0.4 m³ (400l) of gas, and gas lights need around 100l per hour. 2 gas rings for a couple of hours a day will use between 1-2 m³, so if you have some livestock, plus kitchen and human waste, you can do this easily.
The length of time you leave the material in a batch digester depends on temperature. The average is around 1 month – so gauge how much material you will add each day, and multiply it by 30 to calculate the size of the digester. The waste input must be a slurry – so add water if it’s too solid. Try and keep the temperature over 30°C.
You can get more information on biogas at the University of Adelaide web site.
Let us learn, share and do the needful to meet our energy needs.
