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.