Valorization of invasive water hyacinth through anaerobic digestion: A pathway to clean cooking fuel and environmental sustainability

Abstract

The rising cost of conventional energy sources has intensified the global search for clean and affordable energy alternatives. Water hyacinth (WH) has great potential as a renewable energy source due to its high growth rate and abundance in tropical regions. This study explores the social, economic, and environmental feasibility of utilizing water hyacinth for biogas production in rural India, with a dual objective of generating clean energy and organic fertilizer. A case study was conducted among 30 households in Goalpara village, West Bengal, an area moderately developed but severely affected by water hyacinth infestation. To evaluate the grassroot applicability of the proposed technology, a behavioural economics approach was adopted through a choice experiment assessing villagers' willingness to adopt biogas technology at a cost of INR 60 per month. This framework integrates technical assessment with social acceptability, providing a holistic perspective often missing in purely engineering-based studies. Biomethane potential was evaluated using Automatic Methane Potential Testing System (AMPTS) yielding methane approximately 148.6 ± 3.4 L/Kg-Volatile Solids for WH at an inoculum-to-substrate ratio of 2:1. The study also examined the availability of cow dung and the seasonal availability of water hyacinth to estimate sustainable biogas yield sufficient for replacing traditional firewood-based cooking. Results indicate that co-digestion of water hyacinth and cow dung could partially replace 33.7 tons of firewood annually, reducing an estimated 60.38 tons of CO₂- equivalent emissions while producing about 700 kg of dry fertilizer for the participating households. Although technically and socially viable, the high initial installation cost remains a key barrier to widespread adoption. Nevertheless, the community's demonstrated willingness to pay and interest in replacing traditional fuels suggest a favourable environment for biogas-based clean cooking systems. By addressing SDG6 & SDG7 and contributing to carbon neutrality, the study offers a holistic scalable pathway towards sustainable rural energy transition and carbon-neutral growth.