Techno-economic analysis of a biogas driven poly-generation system for postharvest loss reduction in a Sub-Saharan African rural community

Sub-Saharan African region currently suffers from the lack of clean energy and heavy postharvest loss. Hence, a biogas driven combined cooling, heating and power generation system that harmonises power generation with food drying and cold storage is studied in the context of current renewable energy policies of the Nigerian government. Wastes from a community cattle market are assessed for biogas generation that is subsequently used to power a 72 kW internal combustion engine. Heat is recovered from the engine to drive a cabinet dryer, an absorption chiller and maintain anaerobic digestion process. The model is developed in Aspen Plus and the results are used to evaluate the economic viability of the system. The electricity and tri-generation efficiencies are 25.7% and 74.5%, respectively. Results also suggest that energy demand of 407 farmers can be met including drying of 12,190 kg of cassava, 3,985 kg of maize and cold-storage of 6,080 kg of tomato per farmer every year. At $0.05·kWh⁻¹ of electricity, the discounted payback period varies between 2.5 and 4.7 years depending on agricultural product processed. Levelised cost of energy and profitability index are also sensitive to both interest rate and plant's availability which become uneconomical above 9% and below 80%, respectively.