Enhancing Hydrogen Production from Bioenergy Crops via Photoreforming

Photoreforming of perennial bioenergy crops (willow, miscanthus, and poplar) has the potential to generate H2 with reduced environmental impacts. To understand the compositional effects of the biomass on the average rate of H2 production over the first 30 min of reaction (rH2), the rH2 of model biomass component (i.e., cellulose, hemicellulose, and lignin) mixtures were compared with those from the raw biomass. The higher cellulose or hemicellulose content in multi-component mixtures resulted in higher rH2, whereas lignin reduced hydrogen production rate. However, with raw biomass, the ratio of biomass components alone did not determine the rH2 via photoreforming with rates of hydrogen production for different varieties of willow ranging between 1.9 µmol h−1 and 12.3 µmol h−1, 11.8 µmol h−1 for a poplar, and 6.8 µmol h−1 for a miscanthus biomass. In addition, comparable rH2 of raw poplar and its extracted cellulose via an IonoSolv treatment indicated the possibility of using raw biomass materials without delignification for generating H2 via photoreforming. Importantly, the rH2 was positively correlated with the interaction between water and the biomass, as assessed by NMR relaxometry via an examination of the T1/T2 ratio. A stronger water-biomass interaction resulted in a higher rH2. Genetic modification of biomass has been suggested as a putative way to improve the rH2 of biomass with an enhanced interaction with water. This research enhances the understanding of factors influencing H2 production from lignocellulosic biomass by photoreforming and supports the breeding and management of perennial biomass crops to maximise H2 yields while minimising land area requirements.