Techno-economic analysis of a mini biogas electricity plant (MBEP) for a typical farm in the Zimbabwean off-grid areas

Abstract

Abstract In response to declining electricity production in Zimbabwe, the energy regulator engaged various stakeholders to work together to solve the energy shortage problem. Biomass waste, abundant in the country, can contribute to electricity generation for consumption and export to the grid. Compared to other renewable energy resources such as wind and solar, biomass has lower investment and per unit operational costs, making it more affordable. Although farmers in the remote off-grid areas produce large amounts of waste, which can be used for biogas production via anaerobic digestion (AD), the farmers are still ‘energy-poor’. There is insufficient information to enable farmers to make informed decisions on AD technology uptake. This study conducted a techno-economic assessment for a mini biogas electric plant (MBEP) for a typical farm in Zimbabwe’s off-grid areas. The sustainably available biomass for biogas production was determined, followed by quantifying the biogas produced, sizing and selecting the digester type, and sizing the generator. The MBEP produces 435,350.7 kWh of heat and electrical energy from 452 t of biowaste. The first biodigester-type option, the garage-shaped, has a negative net present value ( $$NPV$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>NPV</mml:mi> </mml:mrow> </mml:math> ) of − US$416.4. The Carmatec biodigester, the most popular AD technology in the country, has a positive $$NPV$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>NPV</mml:mi> </mml:mrow> </mml:math> (US$216,447.7), but its economics needs improvement. Adopting AD technology allows farmers to mitigate environmental pollution and improve soil fertility by converting organic waste into biogas and biofertilisers and promoting sustainable agricultural practices. Research was recommended to investigate supportive policies, incentives, and regulatory frameworks to promote the widespread adoption of AD technology in agricultural settings.