Boosting Farm Energy production through Waste to Energy Conversion. A case study using Piggery Waste and Charcoal Dust.
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Uganda is an energy-deprived country with limited access to electricity making farmers with a high-energy demand resort to alternative sources of energy like solar and biogas. Biogas is the more environmentally friendly solution and substrate for the biogas production is abundant. This is due to the heavy reliance of Uganda on livestock farming due to demand from the rapidly growing population. The decomposition of waste from this practice is the main source of methane emissions, which have a higher global warming potential than carbondioxide. Therefore a need to curb these emissions. The aim of this work was to investigate how piggery farm energy biogas production could be boosted through the use of charcoal dust as an additional carbon source. Specifically, the study would; (i) characterise the piggery waste and charcoal dust, (ii) assess the performance of an existsing on-farm biodigester, and (iii) optimize the biodester performance using charcoal dust. Focus was put on the potential benefits of utilizing charcoal as an additive in the biogas production process. This would promote on-farm renewable energy generation, waste management and reduction of greenhouse gas emissions. Piggery waste samples and inoculum were collected from a local piggery farm with a biodigester dome used for on-farm biogas production in Njeru Municipality, Buikwe District. Bio-methanation Potential (BMP) tests were done with 0.5% and 2% charcoal dust treatments with inoculum to substrate ratios of 1:1 and 2:1. Addition of charcoal dust significantly increased biogas production from the piggery waste with a p value of less than 0.05 for both treatments The charcoal used had an ash content of 61.92±0.28%, C:N ratio of 30:1 and moisture content of 14.46±0.43% . The piggery waste had a C:N ratio of 13:1,63.96±0.62%VS 36.48%, TOC 2.45%, TN and pH of 7.72. Methane production was 68.25±1.95, 74.85 ± 4.95 and 154.6 ± 14.8 mlCH4/gVS from the farm biodigester (0%), 0.5% and 2% charcoal treatments, respectively. The C:N ratio improved from 15:1 in the original piggery waste to 20:1 and 25:1in the 0.5% and 2% charcoal treatments, respectively. These results indicate that addition of charcoal promotes the anaerobic digestion process by providing a suitable carbon source which increases the C:N ratio to the optimum level. Extrapolation of the laboratory results to full-scale performance and comparing with measured performance parameters of the digester indicated that addition of 2% charcoal could boost the daily digester biogas yield by 33%. Farms with onsite biodigesters could therefore explore the possibilities of boosting their biogas production through addition of charcoal dust to the biodigester substrates at the indicated levels. Further research and experimentation is, however, recommended to establish the whether charcoal dust treatments above 2% would create a further positive impact.