I think there are three levels of biogas industry.

1. Biogas for small farms, of the sort I have described about the two projects I had in Kenya and Nigeria.

I think there needs to be a manufacture of suitable small devices, of the sort pioneered by the Tunnel Company in the 1960s. I am not aware of whether anyone has designed and is manufacturing such a device.

There is also the problem of how to finance such a project. Small farmers would benefit by not having to buy fuel for cooking and some small activities such as baking, pottery and so on (see the WaterHyacinthProject). How could a small farmer pay for such a device? If he had an activity that produced saleable goods he could generate enough money to pay for the devices, either by rent or by hire purchase (borrowing the cost first and then repaying it with interest).

2.A larger size of biogas apparatus to be used at a commercial farm of the sort used by Tim Hutchinson at his mixed farm and coffee plantation in Kenya in the 1960s and 70s. This can replace money for most farm fuel uses, except for tractors and vehicles. Hutchinson used the gas for cooking, refrigerators in the farm house. He also powered an electric generator for all electric needs on the farm. A line of gas worked a water pump to bring water from a dam below the house.

This sort of biogas system needs a good investment. The general farm accounts will benefit by lower energy costs. In addition the other output of the biogas plant will benefit the farm by avoiding the need to buy fertiliser and sometimes sprays. Thus if there is a bank loan the increased productivity of the farm and the lower input costs will make it possible to repay the loan.

3. Industrial size biogas.
This will be used when there are large amounts of input that can be made into gas. This needs the sort of apparatus I have suggested for the Water Hyacinth project. A good example is the slaughterhouse installation in Sweden where enough biogas is produced to run a small train (Diesel Multiple Unit rail car, modified to use gas instead of Diesel).

This size of installation will make its money from selling gas, or electricity sold to the Grid (if there is one) and above all to sell various kinds of fertiliser products.

It may also be possible to sell carbon dioxide separated from the biogas, to be used in an agricultural Tunnel to increase the growth of plants.