Design Optimisation of a Combined Heat and Power Supply Bio-Reactor: A Case of Koala Park Abattoir, Harare

Abstract

This article proposes a dynamic design methodology for optimising biomethane yield  for applications in combined heat and power system for an identified urban abattoir. A discrete number of substrates were examined to obtain the physiochemical characteristics of each feedstock available at Koala Abattoir, located in urban Harare. Biochemical methane potential of each substrate was obtained through manipulating Chem-Hashimoto kinetic equations as applied in anacrobic digestionn. Specific methane yielding equations at different volatile solid (VS) content for each discrete feedstock, thermal and electrical conversion efficiency equations and manipulated economic analysis equations  were integrated into the Excel spreadsheet model. The proposed system can generate 1564 MWh of electrical energy and 2138 MWh of thermal energy per year. Economic performance  metrics gave an IRR of 38.99%, an NPV of $887 298 and a pay-back period of 3.10 years. The system has a LCOE of $0.06/kWh with the potential to avert 1722 tons of GHG per year. It was postulated that when optimally integrated, the model can be successfully applied in assessing the viability of integrating any  bio-reactor in a CHIP system.