Biogas Production from Anaerobic Co-Digestion of Leather Shavings, Cow Dung, Sawdust and Food Waste

The tannery industry faces a serious challenge in managing solid waste sustainably. The most hazardous form of solid waste is chromium-tanned solid waste, mainly consisting of leather shavings with high chromium content. This study utilized laboratory-scale reactors to develop a suitable technology for producing biogas from leather shavings while ensuring safe disposal. Tannery waste, specifically leather shavings, has a low carbon-to-nitrogen ratio (C/N) of 3.01 and an acidic pH of 4.51 ± 0.42, challenging for anaerobic digestion. The research focused on the anaerobic co-digestion (i.e. AcoD) of leather shavings (LS) with cow dung (CD), sawdust (SD), and food waste (FW), optimizing the process across a range of C/N ratios and pH levels to maximize biogas yield. The results indicated that a reactor with a 1:1:1 ratio of LS:CD:FW achieved the best performance in terms of cumulative biogas production (5895.2 ml/kg solid feed), methane content (53.63%), total organic carbon (TOC) reduction (47.55%), volatile solids (VS) reduction (51.99%), and chemical oxygen demand (COD) removal efficiency (53.8%) when operated with a residence time of 40 days. This AcoD process not only produce biogas but also offers an alternative for reducing landfill use and minimizing the environmental risks associated with tannery waste disposal.