Sustainable use of organic resources for bioenergy, food and water provision in rural Sub-Saharan Africa

This paper reviews use of organic resources in rural Sub-Saharan Africa (SSA), impacts on household energy, and interactions with provision of food and water. Wood, charcoal and dung supply over 70% of household energy in SSA, but with improvements in energy technologies, crop-residues and human excreta could also contribute. Improving cookstoves is not enough to make woodfuel use sustainable, reducing deforestation due to woodfuel demand by only 41-50%. Further reductions of 21% are achieved by using crop-residues and 23% by anaerobic digestion of cattle manure. Taken together, these measures could reduce deforestation due to woodfuel demand by 70-100%. Burning crop-residues loses a large proportion of nitrogen needed for crop production, which could be partially counteracted by applying biochar from pyrolysis cookstoves to improve retention of soil nitrogen. Better nutrient recycling would be achieved by composting, but this precludes energy provision. Both energy and efficient nutrient recycling are provided by anaerobic digestion, but carbon sequestration is reduced compared to composting or pyrolysis. Nevertheless, a wider range of waste materials may be recycled in the closed digester system, so pyrolysis of dry crop-residues together with anaerobic digestion of wet wastes is likely to provide the best solution for both food and energy. However, anaerobic digestion may demand more water than pyrolysis and, if soil carbon is reduced, may also increase the need for irrigation. Therefore, in water limited areas, biogas digesters should only be installed if integrated with water harvesting systems. Governments can encourage adoption of sustainable technologies by providing subsidies to cover fixed costs, facilitating credit and complementary infrastructure investments, and improving standardisation and quality control in cookstove and digester markets. Implementation work should involve communities and households, giving women a role in decision-making to ensure community investment in water access.