Research

Crop residues as a potential renewable energy source for Malawi's cement industry

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Abstract

Crop residues have been undervalued as a source of renewable energy to displace coal in the national energy mix for greenhouse emission reduction in Malawi. Switching to crop residues as an alternative energy source for energy-intensive industries such as cement manufacturing is hampered by uncertainties in crop residue availability, cost and quality. In this study, future demand for energy and availability of crop residues was assessed, based on data at the sub-national level. Detailed energy potentials from crop residues were computed for eight agricultural divisions. The results showed that the projected total energy demands in 2020, 2025 and 2030 were approximately 177 810 TJ, 184 210 TJ and 194 096 TJ respectively. The highest supply potentials were found to be in the central and southern regions of Malawi, coinciding with the locations of the two clinker plants. Crop residues could meet 45-57% of the national total energy demand. The demand from the cement industry is only 0.8% of the estimated biomass energy potential. At an annual production of 600 000 t of clinker and 20% biomass co-firing with coal, 18 562 t of coal consumption would be avoided and 46 128 t of carbon dioxide emission reduction achieved per year. For sustainability, holistic planning and implementation would be necessary to ensure the needs of various users of crop residues are met. Furthermore, there would be a need to address social, economic and environmental barriers of the crop residue-based biomass energy supply chain. Future research should focus on local residue-to-product ratios and their calorific values.