Evaluating And Comparing the Global Warming Potential From Black Soldier Fly Bioconversion of Faecal Matter, Pig Manure and Chicken Manure

Abstract

Global warming, climate change and water pollution have become pressing environmental concerns worldwide. By 2050, the world’s population is expected to grow from 7.8 billion in 2020 to 9.9 billion people, generating more waste. The improper disposal of the organic waste has profound impact on the water quality in Nairobi’s River since they end up in open drains and waterways leading to elevated levels of nutrient such as phosphorus, which promotes and degrade aquatic ecosystems. This waste also results in increased greenhouse gases (GHGs) emissions into the atmosphere. Currently, in Kenya, the organic waste management, including faecal matter (FM), pig manure (PM), and chicken manure (CM), poses a significant challenge in the context of water pollution, global warming and climate change. Hence, this problem pertains to the need for an efficient way and cost-effective technology to manage waste that ultimately reduces the global warming potential (GWP). This research aimed to assess the global warming potential of the black soldier fly’s bioconversion of faecal matter (FM), pig manure (PM) and chicken manure (CM). It adopted Black soldier fly larvae (BSFL, Hermetia illucens) technology, which is environmentally friendly as it mitigates the amount of greenhouse gases released in the atmosphere because of its quick bioconversion rate, good sustainability, and low cost-effectiveness. The set-up was in a greenhouse tunnel at the Department of Soil, Water and Environmental Engineering, Jomo Kenyatta University of Agriculture and Technology (JKUAT). The study used the MQ4 and MQ135 sensors to measure in real time the concentration of methane (CH4), carbon dioxide (CO2), Nitrous oxide (N2O), and ammonia (NH3) emitted during the bioconversion process. A comparison of the concentration of gas emissions from the bioconversion of the three substrates was studied. Finally, the Life Cycle Assessment (LCA) of BSFL during bioconversion of the FM, PM and CM was undertaken. The data was analyzed using R Studio 4.3.3 software for graphical visualization of GHGs concentrations and OpenLCA software for the LCA of the gases. The total GWP values were: as follows: 0.194 kg CO2-eq (CM), 0.072 kg CO2-eq (FM), 0.005 kg CO2-eq (PM), 0.011 kg CO2-eq (BSFCM), 0.006 kg CO2-eq (BSFFM) and 0.001kg CO2-eq (BSFPM). CM had the highest GWP, FM had a notable GWP while PM recorded the lowest GWP. BSFL bioconversion process can be used to manage organic waste from the environment while at the same time mitigating the GHGs emissions. The study suggests that large-scale adoption of BSFL as a climate smart waste management solution can be promoted by developing supporting policies and regulatory frameworks. Additionally, various governments should provide incentives to enhance awareness campaigns and training programs to educate waste producers, farmers and industries to effectively contribute to the advancement of the circular economy.