Improving paddy straw digestibility and biogas production through different chemical-microwave pretreatments

Biofuel and Bioenergy generation from paddy straw offers a great potential as an alternative to fossil-fuels. Association of holocellulose with the protective structures such as lignin and silica adversely affects the conversion of paddy straw into the desired product. In this context, paddy straw was pretreated with different concentrations (0–10%) of various chemicals viz. NH₃, Na₂SO₃, Na₂CO₃ and NaOH by soaking for 48h and by irradiating with microwave (720W, 180°C) for 60 min. Chemicalmicrowave pretreatment was found to be better than the chemical-alone pretreatment. Amongst the various chemical pretreatments, 4% Na₂CO₃ -microwave and 4% NaOH-microwave was found to greatly enhance the paddy straw digestibility and biogas production where 44.3% and 65.6% increase in cellulose, 15.0% and 68.3% decrease in lignin, and 84.5% and 92.5% decrease in silica was observed resulting in 54.4% and 60.9% increase in biogas production, respectively.