Anaerobic Co-Digestion of Rice Straw and Dairy Manure for Biogas Production and Digestate Valorization

Abstract

The effective management of agricultural residues and livestock waste has become increasingly important for sustainable energy generation and environmental protection. The present study investigates the anaerobic co-digestion of rice straw and dairy manure for enhanced biogas production and digestate valorization under controlled operational conditions. The research focuses on evaluating the influence of substrate mixing ratio, hydraulic retention time, organic loading rate, temperature, and pH on methane yield, process stability, and nutrient recovery efficiency. Experimental analysis demonstrates that the co-digestion of lignocellulosic rice straw with nutrient-rich dairy manure significantly improves microbial activity, carbon-to-nitrogen balance, and substrate biodegradability compared with mono-digestion systems. Results indicate that optimized feedstock combinations enhance biogas generation, methane concentration, and volatile solids reduction while reducing process inhibition associated with ammonia accumulation and acidification. The study further reveals that pretreatment and proper mixing conditions contribute to improved hydrolysis and fermentation performance, thereby accelerating organic matter degradation and energy recovery. Comparative assessment with conventional anaerobic digestion methods confirms that co-digestion technology offers superior operational stability, improved renewable energy output, and efficient waste utilization. In addition, the digestate produced after anaerobic treatment exhibited substantial nutrient content and potential application as an organic soil amendment, supporting circular economy and sustainable agricultural practices.