Investigating the use of biogas as fuel for generators

Abstract

Biogas is a sustainable and clean alternative energy source to fossil fuels. Majority of biogas generation units use animal wastes as feed material. In Uganda, the production of biogas has been adopted by large scale industries like Nile breweries and NWSC setting up large biogas digesters. It’s widely produced on a small scale on farms, schools and some households where it’s used for mostly cooking purposes. Biogas has potential to be used as fuel to run generators. This study investigates the usage of biogas as an alternative fuel to run generators. Its primary focus is on small size petrol generators. To use biogas as fuel for generators its methane content must be increased by filtering it to remove water vapor, carbon dioxide and hydrogen sulphide which is corrosive to internal engine parts. Modifications to the inlet fuel system of generator need to be done to ensure an A/F ratio of about 1:15, modification of compression ratio for generator engine to the range of 15-20 and adjustment of ignition timing. This study establishes that whereas it’s possible to use biogas to run SI engines, the undertaking is not to be taken lightly as it requires a high level of technical expertise. Also the cost implication of setting up purification and scrubbing mechanisms makes it unfavorable for subsistence and small business enterprises who are the intended target users for which this the study was carried out. It also details why small sized SI petrol engines may not run steadily on biogas while being used in rural Ugandan villages and recommends that further research be done to enable usage of biogas with larger CI diesel generators being favored for our Ugandan setting