The use of solar-heated biogas digester for treating agricultural wastes: a review

Abstract

Globally, accumulation of agricultural wastes has reached critical proportions. To avoid depletion of natural resources, minimise risk to human health, reduce environmental loads, and maintain ecological balance, these agricultural wastes must be managed in a sustainable manner. Agricultural wastes are currently treated and managed in the following ways: used as animal feed, for mulching, composting, fertiliser, direct combustion, and pyrolysis. However, these wastes can further be treated and converted into biogas for domestic and industrial purposes. About ninety scholarly works from Google Scholar, African Journal of Agriculture Research (AJAR) and other Scopus-Indexed Academic databases were reviewed showed limited information on the use of single-stage solar-heated biogas digester for the treatment of agricultural wastes for both energy generation and hygienised organic fertiliser production. This review focuses on using anaerobic digestion process for converting agricultural wastes to biogas by employing a single-stage solar-heated biogas digester (SSSHBD). The digester to be used will depend on solar energy, which is largely untapped especially in sub-Saharan African countries, for its operation at a thermophilic condition. Sustainable renewable energy (biogas) and pathogen-free nutrient-rich digestate produced could be useful to farmers. The biogas produced could be converted to electricity using a combined heat and power generator. Appropriate policy should be made on the adoption and use of solar-heated biogas digester for treating agricultural wastes as it has enormous potentials for sustainable environment.