Effect of Solids Concentration on the Kinetic of Biogas Production from Goat Droppings

Abstract

This experiment was conducted at the Bioenergy laboratory of Groupe de Génies Congolais (GGC) at the Université Loyola du Congo in Kinshasa, D.R.Congo. The experiment started on May 23, 2019 and ended on July 17, 2019. The study focused on the relationship between solids concentration and the kinetic of anaerobic digestion of goat droppings in the methanation process. The feedstock consisted of goat droppings waste made into slurry of four solids concentration (SC); A=50%, B=38%, C=30% and D=25%. Each SC was repeated three times. Feedstocks were inserted in laboratory scale anaerobic digesters constructed from 5L plastic containers. The results revealed clearly that the time required for the production of biogas depends on SCs. The ratio D (1/3), i.g. 75% of water and 25% of biomass produced the biogas in 3 weeks (±22 days) and the ratio A (1/1), 50% of water and 50% of biomass, in 7 weeks and a few days (±53 days). The ratio C (1/2), 66.6% of water in the mixture, provided the biogas in ± 26 days (approximately 4 weeks) and finally, it took ±30 days (4 weeks and a few days) for ratio B to produce biogas rich in CH4 (<50%). The equation f(x)= 1.1x + 1 can be used to predict the approximative number of days to produce a biogas containing more than 50% of CH4. The average temperature inside the reactors was found to be 28.5 ± 0.8°C during the combustion testing process implying that the reactors designed at the GGC were operating in a mesophilic regime. Finally, the pH of the digestates obtained from reactors had an average of 9.0 ± 0.2.