Enhancing Hydrogen Production from Bioenergy Crops via Photoreforming

Photoreforming perennial bioenergy crops (willow, Miscanthus, and poplar) has the potential to produce 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 values 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 multicomponent mixtures resulted in higher rH₂, whereas lignin reduced the 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 values 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, rH₂ was positively correlated with the interaction between water and the biomass, as assessed by NMR relaxation 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 maximize H₂ yields while minimizing land area requirements.