Exploitation of Cocoa Pod husks for rural electricity production : towards a sustainable cocoa value chain in Uganda

Abstract

Although access to electricity power supply is critical to national development, utility companies in Uganda either lack the financial capacity to expand their grids to isolated rural areas or choose not to do so due to low return on investment. Mini grid using biomass would be an effective solution to providing power to remote/rural households. This study evaluated the resource and technology feasible for generating electrical energy from cocoa pod husks (an agricultural residue/waste) generated in Uganda. The use of agricultural waste for energy generation is the most suitable for the rural population in Uganda because of the availability of the raw material for its production (renewable and clean) and the lack of competition of use. The inability to convert these solid wastes into useful products culminates into environmentally related challenges (such as land fill, global warming, and floods), pests and diseases. The amount of CPH generated in Uganda was estimated. The physio-chemical analysis showed that the proportion of the Cocoa Pod Husks (CPHs) in the fresh pod was about 74%. This value was close to the one reported in literature. The analysis of dry matter content of the CPH was found to have an average of 19% and an average energy of 17.5 MJ/kg at 14% moisture which comparable to bagasse, 18.2 MJ/kg at 14% moisture Mbugua, M, et al., (2014) (See Appendix I). On this basis, the results showed that the energy of 11.93 MWh of energy can be produced each year from CPHs in Uganda. This study therefore, showed that the CPHs is an important energy source. There is an increasing trend in cocoa and CPHs production in Uganda per year, hence, the electricity production from CPHs is sustainable and can be up scaled. The electricity generation technologies and economics have also been assessed to come up with the optimum option for CPHs conversion and electricity commercialization in Uganda. In doing so, the solid waste can be reduced, the income can be improved, the environment is conserved and the energy is produced. The electricity generation potential from CPHs in Uganda was found to increase annually up to 2.97 MW in 2018 from approximately 19092 tones of dry CPHs. The analysis in this study identified direct combustion as the suitable technology to be used because of its low cost and due the fact that the process is mature with a technology readiness level (TRL) of 9, the costs, input and outputs are fully known. The technology is already in application with bagasse in Uganda and CPH can also be co-fired with bagasse. The efficiency of about 30% is comparable with those of pyrolysis and gasification. The capacity of power plant was estimated to be 1.604 MW. The unit of electricity would therefore cost 0.077 USD/kWh, which is close to the national target of 0.04 USD/kWh compared to the current average electricity market price of (UGX 780) ≈ 0.22USD per unit in Uganda. From the results of this study, it has been envisioned xii that converting ‘cocoa waste’ into commercial products (i.e. electricity and others) would lead to sustainable value chain of cocoa production.