Taken from the wonderful world of http://www.instructables.com
Sahas Chitlange, aging 14, from India. here is my homemade cheap and easy to build mini Biogas plant. It burns for approx. 20-30 mins on a bunsen burner. you can add anything from your kitchen waste ( Except Onion peels and eggshells). In 12 hours the Gas is ready for use. It is very easy and cost effective to build (only 2-3 dollars) and gives many useful products.
Biogas at home- Cheap and Easy by Chitlange Sahas
the end products of this system are:
1) Methane : (Can be used as a fuel)
2) Slurry : (the spent slurry is excellent manure)
The main components of this system are:
1) Inlet pipe
2) digester tank
3) gas holder tank
4) slurry outlet pipe
5) gas outlet pipe
You will have to choose a correct size container which will act as a digester tank. My one is 50 litres tank. I got it from scrap.
Make holes in the tank for Inlet and outlet. For this I took a old iron rod and heated it to make holes. CAUTION: rod is really very hot.
Or use core-drill bit with e-drill.
Step 3: Fix the inlet and outlet pipes
Glue the Inlet pipe and the Outlet pipe with any water proof adhesive.
Step 4: Making the Gas holder Tank
I took a paint bucket of 20 lts for making a gas holder tank. This tank holds the gas produced. The tank is overturned and fixed with a valve used for plumbing purposes.
Step 5: Time to mix the cow dung !
Mix the cow dung in proportion of 50/50. add 50% water and make a fine slurry. Now put the slurry in the digester tank.
Step 6: Almost finished!
Put the gas holder tank overturned in the digester tank after adding the slurry . REMEMBER: open the valve while putting the gas holder tank. the mini plant takes 10-15 days for the first time to get output. For the first time, the gas in the tank wont burn as it contains Carbon Dioxide gas, if fortunately it burns then good or wait for the second time. You can detect how much gas is there in this system, the gas holder tank will rises up as the gas is produced.