Life Cycle Greenhouse Gas Emissions of Water Hyacinth-Derived Biochar for Fuel and Soil Amendment Applications: Japanese Model Applied to Ethiopian Context

This study assesses life cycle greenhouse gas (GHG) emissions from water hyacinth (Pontederia crassipes; WH) biochar production and its subsequent use as fuel or soil amendment in Ethiopia. Overgrowth of WH in Lake Tana has created ecological and socioeconomic challenges, while the country continues to rely heavily on biomass fuels and imported chemical fertilizers. To address these issues, three scenarios were evaluated using a functional unit of 1 kg of dried WH: (Case 1) current practice of abandonment and decomposition; (Case 2) WH-derived biochar (WHB) used as household fuel; and (Case 3) WHB applied as a soil amendment. Experimental data from pyrolysis of WH and acacia, combined with background life cycle inventory data, were used to quantify GHG emissions across each value chain. Japanese WH and WHB were used for life cycle GHG evaluation and applied to Ethiopian social contexts due to biological resources restrictions. The results showed that Case 3 provided the greatest reduction in net GHG emissions due to long-term carbon sequestration in soil. Case 2 also reduced emissions through substitution of acacia charcoal by use of WHB for household fuel, though to a lesser extent. Sensitivity analyses highlighted the influence of transport distance and biochar yield on overall performance. These findings demonstrated the environmental advantages of integrating WHB into Ethiopia’s energy and agricultural systems, supporting sustainable biomass management and climate mitigation strategies.