The effect of attached growth media on biogas production.

Abstract

Household energy is increasingly becoming a scarce resource in developing countries. In these countries, cooking accounts for about 90% of all household energy consumption. Motivated by the need to meet the ever-increasing energy demand and sustainability consciousness, many Governments have promoted renewable energy technologies such as biogas. However, further development of biogas technology in Uganda is constrained by insufficient gas production due to the failure to drain the effluent in time from, incomplete breakdown of substrates in the biodigesters, Washout of bacterial during release of effluent, accumulation of the substrate in the biodigester. This paper presents the findings of a research that was carried out to determine the effect of attached growth media on biogas yield. The substrates for the experiment in an anaerobic laboratory digester are cow dung and pig dung in a ratio of 1:1, the attached growth medias are macadamia walnut shells and eucalyptus sawdust. The experimental set-ups were sub-divided into three groups of digesters. Each group was made up of five digesters seeded with attached growth media of the wood, from digester A-E (Macadamia walnut shells) and F-J (Eucalyptus sawdust) in the following percentages: 33%, 27%, 20%, and 11%. And digesters K-O (Mixture of walnut shells and eucalyptus sawdust each digester seeded with 100g of attached growth medias) in the ratios of 0:1, 1:3, 1:1, 3:1, 1:0 respectively. The attached growth media materials in different percentages were added and mixed thoroughly and the methane in biogas produced was recorded at a regular interval of 3 days for a hydraulic retention time of 30 days. The volume of methane in biogas produced ranged from 22.0ml to 345.9ml. In all the experiments, the methane in biogas yield was decreasing with a decrease in percentage of attached growth media materials seeded in the bio digester. Digester E which was seeded with the highest mass(100g) of macadamia walnut shells has the largest methane yield of 56.4 ml/ day while digester A and F which were not seeded with any attached growth media had the least yield of 25.8ml/day and 25.8ml/day methane gas respectively Keywords: Biogas, Biodigester, Attached growth media, methane, ratio.