Energy Recovery from Rice Straw through Hydrothermal Pretreatment and Subsequent Biomethane Production

Rice straw is an abundant agricultural waste in Asia. Anaerobic digestion (AD) as an environmentally friendly process for bioenergy recovery is expected to solve the environmental issues brought about by open burning of rice straw. In order to test the feasibility and scalability of hydrothermal treatment (HTT) on rice straw for subsequent methane production from pretreated straw, this study attempted two peak HTT temperatures (150 and 210 °C, i.e. HTT150 and HTT210, respectively) for holding 0–30 min to pretreat rice straw which was then used for mesophilic methane fermentation. Thereafter energy balance and energy recovery were analyzed on HTT and subsequent AD of rice straw. Results show that HTT150 exhibited a positive effect on subsequent methane production, achieving the highest methane yield of 134 mL (STP) for per gram of added volatile solid (VSadded) of rice straw after being hydrothermally pretreated at 150 °C for 20 min. The maximum specific methane production rate (μ), around 17–40% higher th...