IntroductionWaste management has become an issue of growing global concern as urban populations continue to increase and consumption patterns change. The health and environmental implications associated with garbage disposal are mounting in urgency, particularly in developing countries like Nigeria. Anaerobic digestion of organic fraction of municipal solid waste (OFMSW) is of great importance in the management of solid waste and by application, it will considerably decrease the volume of waste that is being generated. On the other hand, as one of the driving forces of economic and social development, anaerobic digestion of OFMSW for the production of sustainable biofuel (such as biogas) as well as biofertilizer has become a growing world interest [1][2][3][4][5][6][7][8][9][10][11][12][13]. The initial concentration or solid content of the substrate in a bioreactor can significantly affect performance of the anaerobic digestion process [14][15][16][17][18][19]. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of total solids content (substrate concentration) on the behaviour of the microbial communities involved in anaerobic digestion of organic matter in wet and dry technology [18]. Low solid anaerobic digestion systems contain less than 10% total solid, medium solid anaerobic digestion systems contain around 15% to 20% total solid and high solid anaerobic digestion systems contain around 22% to 40% total solid of the substrate [10]. Ordinarily solid concentrations between 6% and 10% are said to be best suited for biogas production under wet anaerobic digestion condition [20][21][22]. As part of a pilot scale study, we conducted a laboratory-scaled anaerobic digestion of organic fraction of municipal solid waste (OFMSW) to determine the optimum substrate concentration required to maximize biogas yield under wet ambient condition. AbstractThe problem of pollution resulting improper management of municipal solid waste (MSW) in Nigeria needs to be eliminated by converting MSW to useful resources. In this study, we conducted lab-scale anaerobic digestion of OFMSW to optimize substrate concentration required to maximize biogas yield under wet ambient condition. After characterization, various concentrations of the substrate (OFMSW) ranging from 0% (wet process) to 45% (dry process) was subjected to One-Factor response design (using Design Expert version 9.0) as well as anaerobic digestion (using rumen juice as the source of microbial inoculum) inside one-stage 500 ml-capacity batch-type anaerobic digesters with useful volumes of 350 ml. Result showed that the highest and lowest volume of cumulative biogas production (596.4 ml and 107.6 ml) was recorded in the experimental set-up with 30% and 5% substrate respectively after 42days. However, the highest biogas yield (8.51 ml/gr. VS) was recorded in the experimental set-up with 5% substrate followed by the experimental set-up with 30% substrate (7.86 ml/gr. VS), while the lowest biogas yield (0.96 ml/gr. VS) was recor...