Enhanced biogas production from water hyacinth and cow dung with wood and faecal sludge biochar

• Water hyacinth and cow dung are ideal for anaerobic digestion (AD) due to high organic matter and optimal C/N ratios. • Addition of 2 % faecal sludge (FS) biochar, significantly enhances methane yield. • Wood and FS biochar stabilizes anaerobic digestion. Water hyacinth (WH), known for its ecotoxicity and economic burden in tropical regions, can play an important role as a lignocellulosic biomass source for biogas production. Co-digesting WH with cow dung (CD) enhances biogas yield but poses challenges like process instability and excessive carbon dioxide production. To improve biogas yield from digestion of WH and CD, this study examined the impact of wood and faecal sludge biochar on the anaerobic co-digestion of CD and WH using a temperature of 37 °C for 40 days. In the controlled laboratory tests, cow dung alone produced the least methane (CH 4 ), but introducing 2 % wood and faecal sludge biochars significantly boosted CH 4 production by 76.8 % and 94.0 %, respectively. However, a 50 % CD-50 % WH mixture, the CH 4 increase was milder at 20 % and 37 %, respectively. Wood biochar had no significant effect while faecal sludge biochar made a statistically significant impact ( P < 0.05). These findings offer a sustainable solution, paving the way for cost-effective and eco-friendly biogas production in regions plagued by this invasive plant. The use of faecal sludge biochar, in particular, has substantial implications for optimizing anaerobic digestion processes and reducing their environmental footprint, thereby promoting a more sustainable approach to managing WH and addressing energy needs in tropical, eutrophic regions.