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Kilama et al. Energy, Sustainability and Society (2019) 9:22 Energy, Sustainability https://doi.org/10.1186/s13705-019-0205-4 and Society ORIGINAL ARTICLE Open Access Quantification and characterization of cocoa pod husks for electricity generation in Uganda George Kilama1,2, Peter O. Lating1, Joseph Byaruhanga1 and Saphina Biira3* Abstract Background: Due to limited coverage, the electricity power supply in Uganda is an obstacle to the country’s economic development. Utility firms in Uganda either lack the financial capacity to expand their grids to isolated rural areas or choose not to do so due to the low return on investment. Therefore, connecting households to mini- grids represents an effective solution to providing power to remote/rural areas. This study evaluates the resource and technology of generating electrical energy from cocoa pod husks (CPHs), an agricultural residue/waste, generated in Uganda. The use of agricultural waste for energy generation is the most suitable option for the rural population in Uganda because of the availability of a raw material (biomass) for its production, which is pollution- free (renewable and clean) and does not have competition for use. The inability to convert these solid wastes into useful products culminates into environmental related challenges, such as landfilling, climate change, pests, and diseases. Therefore, the aim of this study is to quantify the amount of generated CPHs and evaluate its potential for electricity generation in Uganda. Subsequently, we have been looking into the potential of CPHs as a feedstock for a thermochemical conversion process and the feasibility of a direct combustion technology. Results: The amount of CPHs generated in Uganda has been estimated. The physiochemical analysis has shown that the proportion of CPHs in the fresh pods is about 74%, which is nearly the same as in other studies. The dry matter content of CPHs has been found to be on an average of 19%, whereas ash content, moisture content, and the gross caloric value have been recorded to be 12.3%, 12.58%, and 17.5%, respectively. It seems therefore likely that 41.7 GJ of energy might be produced each year from CPHs in Uganda. Conclusion: This study has demonstrated that the CPHs are an important energy source. As there is an increasing trend in cocoa and CPH production in Uganda per year, the electricity production based on CPHs is sustainable and can be upgraded. The use of CPHs for energy conversion is therefore feasible, cost-efficient, and a solution to some environmental challenges. Keywords: Cocoa pod husks, Electricity generation, Biomass, Uganda Background of access to electrification with 90% of the population Energy is an essential need for mankind and the driving depending on biomass (in the form of firewood and force for the development of all sectors. Electricity re- charcoal), which leads to deforestation, climate change, mains a critical aspect for Uganda with regard to the and loss of biodiversity [2, 3]. growth capacity and socio-economic transformation of Due to increased national energy demand, diminishing its fast growing population. Currently, about 10% of fuel reserves in the world (leading to increasing fuel Uganda’s population have access to electricity [1]. costs), enhanced environmental concerns, depleting Uganda still ranks among the lowest in Africa in terms hydropower plant sites, and waste management chal- lenges [4], the need to find alternative renewable energy sources is indispensable. It is important to note that * Correspondence: [email protected] 3Department of Physics, Busitema University, Tororo, Uganda hydroelectricity power generation is facing the challenge Full list of author information is available at the end of the article of sinking water levels in lakes and a depletion of the © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Kilama et al. Energy, Sustainability and Society (2019) 9:22 Page 2 of 11 available sites due to the continuously rising power the most feasible thermochemical treatment for the ener- demand. In this case, renewable energy technologies getic valorization of CPHs. might help countries to meet their policy goals for se- This study is aimed at ascertaining the quantity of cure, reliable, and affordable energy and expand elec- CPHs produced in Uganda and the feasibility of pro- tricitysupplyamongthepopulationtopromoteits ducing electricity from CPHs generated after harvest- development. Up-to-date and reliable information on ing the cocoa pods. To achieve this, the potential of the costs and performance of renewable energy tech- CPHs as a feedstock for a thermochemical conver- nologies might be able to assist governments in ren- sion process using direct combustion was evaluated. dering decisions on the choice of renewable energy The feasibility of a direct combustion technology technologies (which are most appropriate for a par- was examined. CPH use for electricity, if adopted, ticular circumstance and place). In this study, we can contribute to the conservation of non-renewable examine the possibility of generating electricity from energy (mostly fossil resources) and provide an inde- CPHs in Uganda. pendent energy source. Improved electricity supply Cocoa (Theobroma cacao L.) is a major cash crop and distribution in rural areas might create employ- of the tropical world, including Uganda. The post- ment and enhance income in the communities. Since harvest processing of cocoa pods into cocoa beans the entire CPH can be used for electricity produc- generates a number of by-products that are usually tion, fire and soil erosion risks in the plantations is discarded as waste. If an appropriate technology is likely to be reduced. Apart from the cocoa beans, applied, these ‘wastes’ could in fact be processed into the development of other marketable cocoa products other cocoa products of economic importance [5]. such as the generation of electricity from CPHs Among these wastes are cocoa pod husks (CPHs) might encourage further growth of the crop and an which constitute about 81% of the cocoa fruit. At improvement in the cocoa value chain. Therefore, present in Uganda, CPHs are essentially waste prod- this study will support efforts towards the generation ucts that are left on plantation sites to decompose and application of technologies that will enhance the which leads to several environmental issues, such as transformation of Uganda’s rural electrification pro- pests and diseases. Most of the cocoa produced in gram by the use of biomass-based mini-grids. Uganda is exported. For example, by December 2015, Uganda exported 26,412 metric tons of dry cocoa Materials and methods beans, fetching total export earnings of about $72.536 Area of study million [6]. As already mentioned, CPHs constitute 81 In this study, fresh cocoa pods were obtained from se- to 90% of the fresh weight of the cocoa fruit which is lected cocoa gardens in the Bundibugyo District. Bundi- discarded as waste, meaning that only about 10 to bugyo District is located at the foot of Mt. Rwenzori in 19% by weight of the cocoa fruit is commercialized the western region of Uganda. The district is bordered [7]. Moreover, CPHs pose a waste disposal problem. by the Ntoroko District to the north, the Kabarole Dis- The continuous deposition of agricultural wastes (in- trict to the east and southeast and the Democratic Re- cluding CPHs) without transformation to other usable public of Congo to the west. The main administrative products has resulted in silting, blockage of water headquarter of the district is located at 0°49′60′′ N, drainage systems, flooding of rivers, and water pollu- 30°15′0′′ E at an elevation of about 890 m above sea tion [8]. This problem could be reduced if these level [16]. The map of Bundibugyo District is indicated wastes were processed into other products such as in Fig. 1. The Bundibugyo District was chosen because electric fuels, which is a pressing need for Uganda. more than 70% of the cocoa produced and exported Several studies have been conducted dealing with the from Uganda originates from that area [17, 18]. conversion of CPHs into useful products, such as pyrolysis oil [9], biochar [10], potash [11], and animals feeds [12]. Sample collection Only a few studies have quantified and examined CPHs as Ripe and ready to harvest cocoa pods were purchased a potential feedstock for energy generation with respect to from 17 randomly selected farmers from cocoa-growing the quantity of cocoa beans produced in a particular geo- areas of the Bundibugyo District. The farmers are de- graphical location. For example, Maleka [13] investigated noted A to Q in Table 1. Of these farmers, 16 provided the feasibility of converting CPHs into energy by direct 10 cocoa pods each, whereas 1 farmer provided 8 cocoa combustion, gasification, pyrolysis, anaerobic digestion, pods totaling 168 pods. These pods were all mixed to- and hydrothermal carbonization. Syamsiro et al. 2012 [14] gether. The reasoning for this was that exported cocoa studied the use of CPHs as a renewable energy source by beans are usually mixed together from several farmers. means of pelletization and carbonization into high-quality These pods were plucked from the cocoa plant on the solid fuels, whereas in 2015, Martínez et al. [15] assessed day of purchase. The pods were then maintained fresh Kilama et al. Energy, Sustainability and Society (2019) 9:22 Page 3 of 11 Fig. 1 Map of Bundibugyo [6, 26] until the moment of cracking (opening the pods). Prior Mp is the mass of the wet pods before they were opened to cracking of the pods and removal of the beans, the to remove the beans.

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