Biohydrogen production from rice straw: Effect of combinative pretreatment, modelling assessment and energy balance consideration

Biohydrogen production from agro waste biomass through combinative pretreatments is an emerging cost effective, alternative energy technology. The present study aimed to ascertain the extent to which the combinative dispersion thermochemical disintegration (DTCD) enhances the cost effective and energy efficient biohydrogen production from rice straw. The efficiency of the combinative pretreatment was evaluated in terms of degree of disintegration and biohydrogen generation. The optimal conditions for combinative pre-treatments are pH 10, temperature 80 degrees C, rpm 12000 and disintegration time 30 mins. A higher degree of disintegration of about 20.9% was achieved through DTCD pretreatment when compared to dispersion thermal disintegration (DTD) (13.2%) and disperser disintegration (DD) (9.5%). The specific energy spent to achieve maximal degree of disintegration for the three pretreatments were in the following order: DD (1469 kJ/kg Rice Straw) > DTD (1044 kJ/kg Rice Straw) > DTCD (742 kJ/kg Rice Straw). Hence, a considerable amount of energy could be saved through this combinative pretreatment. First order kinetic model (exponential rise to maximum) of biohydrogen production is helpful in deriving the two parameters of uncertainty: substrate biodegradability and hydrolysis rate constant. These two parameters evaluate the maximal biohydrogen yield potential of rice straw through combinative pretreatments. As expected, a higher biohydrogen yield of about (129 mL/g COD) was observed in DTCD when compared to DTD (81 mL/g COD) DD (58 mL/g COD) and Control (8 mL/g COD). To gain insights into the feasibility of implementing the pretreatment at large scale, scalable studies are essential in terms of energy balance and cost. A higher positive net energy of about 0.39621 kWh/kg rice straw was achieved for DTCD when compared to others. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.