Enhancing Methane Production from Physiochemically Pretreated Rice Straw via Thermal Steaming and Hydrothermal Treatment under Anaerobic Mesophilic Conditions

This study assessed a new method to boost methane yield, recover nutrients from sludge, and improve the environmental impact of managing rice straw (RS) instead of burning it. Biomethane production from rice straw (RS) is effectively achieved using thermal steaming and co-digestion with cow manure and sewage sludge, enhancing methane yields by 36-50% compared to single digestion methods. Methane yields were 140.4 ± 10.6, 118.7 ± 6.2, and 118.1 ± 3.3 mL − CH_4/g VS_added respectively for thermal steaming, hydrothermal, and untreated methods, with methane making up about 64 − 67% of total biogas. The digestate from thermal steaming was rich in macronutrients like nitrogen, phosphorus, and potassium, making it a promising biofertilizer. Microbial profiling showed diverse bacterial phyla and archaeal changes; thermal steaming enriched Methanobacterium and Bathyarchaeia, linked to higher methane output, while hydrothermal and untreated methods favored Methanosaeta and Methanosarcina. These results position thermal steaming with co-digestion as a strong and beneficial biogas production and sustainable approach, optimizing methane yield, nutrient recovery, and environmental performance.