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Is there any simple design to construct the bio digester to produce gas for fuel, heat and electricity?

Ahana Shrestha
Practical Action
related country: United Kingdom of Great Britain and Northern Ireland

I am designing a digester for 100 acre farm in the UK where I want to use grass and dung to produce gas for fuel, heat and electricity. I appreciate that there are high-tech systems available on the market but my aim is to Keep It Simple.

The impression I get is that many failed systems are simply because of the wrong ingredients or the wrong quantities.

At present my only questions are,

  1. Are poultry, pig, horse and chicken dung as efficient as cow dung on a per litre basis?

  2. Using freshly mown/chopped grass, at what proportions would you recommend with water, dung & grass?

  3. Would it be advisable to create a pre-mix (cocktail) basis of grass, water and dung?

2 Answers


Hi Ahana, I am afraid for solid manure and grass there is only one possibility to keep it simple - batch dry fermentation. That means no water mixing, but percolation of bacteria water. There are very simple systems for self construction, but the bigger the more complex they get in any system as you have to keep to the health and safety rules. In case you want more input also in regards to a ready made system in small scale just to produce gas for cooking, which we actually have developped and sell, please come back to me under Kind regards Michael Köttner

  1. Poultry, pig and chicken dungs are nitrogen richer than cow and horse dungs. Thus, they are more efficient. 2. Fresh grass has rich nitrogen. The right proportion of carbon and nitrogen is about 30:1. If you use fresh grass, you'll use less manure as the nitrogen source. The water is supposed to submerge the grass. 3. It is advisable that the raw materials are added to the digester batch by batch. Don't dump all of them in the digester. I am Sam Shan from China. I can recommend some portable biogas digesters to you. My email:
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2018-06-18 11:50:09
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Last updated:
Jun 18 '18