Mr.E.G.Matthews,
I recently had a look at the model of a
biogas digester that you have come up with.
This particuar design realy caught my eye
because it looks very easy to construct and appears to
be really cheap.I live in Uganda,a poor country,so you
can understand why this design appeals to me.
I am currently studying my final in mechanical
engineering at makerere university in Uganda.I have
chosen to do something on biogas digesters as my final
year project.The project includes construction of the
digester.
The purpose of my mail is to request further
information about different models of biogas
digesters, and in particular your design.Please give
me information about the nature of loading and how to
protect the oil drums from rust and corrosion.
My regards,
Lematia philip

lephilipe@yahoo.com

 Thanks for your reply. The paper was aimed at people like you so I am glad you found it interesting.

I made that device in Nigeria when I was teaching there in a secondary school. There was a shortage of cooking gas and very poor electricity. It so happened that I found exactly the right combination of oil drums and tar barrels so that one fit inside the other.

I had previously made biogas in Kenya (1972-74, in Musingu, near Kakamega) with apparatus I purchased from a commercial producer - a farmer near Kericho. Of course he has retired now but possibly his business still goes on. He was at the Tunnel Company.

The last address I had is:

Tunnel Company
Private Bag
Koru
Kenya

How did I load it? It was very simple. I used to empty out a bucket full of material from the bottom, leaving a space in the tank. Then I used to get an ordinary bucket, half fill it with dry chicken manure, then fill it with water and stir it, and then pour it into the top of the tank.

As I explain in the paper this is not entirely satisfactory as some undigested material comes out but it worked quite well and the used material did not seem to harm my vegetables. Fresh chicken manure is bad for vegetables, but digested material makes them grow well.

On protection from corrosion.

I didn't protect them. But I only wanted them for a few years. The inside probably didn't corrode much while it was in use, as there was no oxygen inside.

I think I should have covered both inside and out in a good quality paint.

Note some proposals for Uganda

E.G.Matthews

 I have seen here in Costa Rica, they used an iron scruff (the one used to
clean dishes or pots) placed somewhere in the gas conduct. This produced
the H2S to oxidized the iron. It has to be changed periodically, but seems
to work fine.

The gas was produced with a modified chinese type biodegestor fed with hog
manure.

Jorge Montero
Costa Rica.

I think that is what is called "Steel Wool" in Britain. The method is described in several books. The H2S combines with the iron in the steel wool and forms a solid sulphide.

In my experience the H2S is not a problem if large amounts of the gas are coming from the vegetation digesters. The worst is when the main source is chicken manure. Gas from vegetation can be used to dilute the gas from animal manure.

E.G.Matthews