Anaerobic digestion as a critical technology for advancing circularity in renewable energy production and Africa's circular bioeconomy

Many low and middle-income countries, including the majority of African nations, face persistent challenges related to energy deficits, poor biowaste management, environmental degradation, and food insecurity. Within the framework of the circular bioeconomy, anaerobic digestion has emerged as a promising technology offering solutions to these interconnected challenges through the conversion of organic waste into renewable energy and nutrient-rich biofertilisers. This review critically examines the role of anaerobic digestion in promoting circular approaches to bioenergy production and advancing the circular bioeconomy in Africa. A systematic literature review following the PRISMA 2020 framework analysed 137 studies published between 2010 and 2026. Findings indicate that Africa generates approximately 300 million tonnes of agricultural residues annually, with a biomethane potential estimated at 31.3 billion m 3 per year. Furthermore, the organic fraction of municipal solid waste could generate an estimated economic value of US$8 billion annually if effectively recovered and utilized. Although around 103,000 small-scale biogas plants had been installed across Sub-Saharan Africa by 2021, large-scale AD deployment remains limited. The review identifies key barriers to wider adoption, including high investment costs, limited technical expertise, inadequate infrastructure, weak policy support, and institutional constraints. Nevertheless, AD offers significant opportunities to reduce fossil fuel dependence, mitigate greenhouse gas emissions, improve waste management, enhance soil fertility through biofertilisers, and increase agricultural productivity. By integrating technological, environmental, economic, social, and governance perspectives, this review demonstrates that the contribution of anaerobic digestion to Africa's circular bioeconomy depends not only on technological deployment but also on context-specific financing, robust regulatory frameworks, stronger institutional capacity, and coordinated policies adapted to both centralised and decentralised digestion systems.