Assessment of the Bioenergy Potential of Cassava Peels in Togo: Biogas and Hydrogen Production and Life Cycle Assessment

Abstract

Energy insecurity and environmental degradation remain significant challenges for development in West Africa. Togo illustrates these issues through rapid population growth, urbanization, and a heavy reliance on imported fossil fuels. Cassava farming, vital for rural livelihoods and food security, produces substantial peel waste during processing. This underused biomass is often discarded or burned, worsening land and water pollution. Turning this waste into renewable energy could reduce environmental damage, cut fossil fuel use, and help Togo meet its climate goals. This study investigates how cassava peels can serve as a renewable energy source through anaerobic digestion to generate biogas, followed by hydrogen production via steam methane reforming (SMR). The research encompasses physicochemical analysis of cassava peels, biochemical methane potential (BMP) testing with various substrate-to-inoculum ratios (1:3, 1:2, 1:1, and 2:1), simulation of the SMR process using Aspen Plus for hydrogen production, and a life cycle assessment (LCA) to evaluate environmental impacts. Cassava peels showed a high volatile solids content (91.03%) and a carbon-to-nitrogen ratio of 88.9, indicating that co-digestion could enhance efficiency. BMP tests achieved a maximum methane yield of 469.5 mL CH₄/g VS at a 1:2 ratio. Aspen Plus simulations demonstrated effective methane conversion to hydrogen, with a mole flow rate of approximately 1.19 kmol/h, corresponding to a mass flow of 2.41 kg/h of high-purity hydrogen (~99.99%) after purification. The hydrogen yield from the Aspen Plus simulation was 0.10 kg/Nm³, which is lower than the values reported by S. Phan et al. [1] and D. Singh et al. [2] who found yields ranging from 0.15 to 0.20 kg/Nm³ under similar conditions in an experimental simulation, but closely matches the experimental production range of 0.13-0.16 kg/Nm³ from Ayodele et al. [3]. The life cycle assessment was performed from gate to gate, using 1 m³ of biogas produced and 1 kg of hydrogen as the functional unit. It evaluated five impact categories, including climate change, acidification, particulate matter, photochemical ozone formation, and eutrophication, using the OpenLCA software. Results indicate that producing biogas and hydrogen from cassava peels significantly reduces greenhouse gas emissions, fossil energy use, and overall environmental impact compared to conventional fossil-based methods.