Cellulosic biorefineries-unleashing lignin opportunities

Increasing concerns on global climate change and energy security coupled with diminishing fossil fuel resources have spurred a renaissance of interest in the development of alternative forms of fuel and materials from renewable resources. Lignocellulosic biomass is a renewable resource, which can be converted to liquid transportation fuels as well as used as a platform to produce bio-based materials. Conversion of biomass to biofuels by biological conversion processes results in the production of a lignin-rich solid residue, only a fraction of which is necessary as a heat source for the pretreatment and ethanol distillation processes. This review provides an overview of lignin chemistry and the changes observed after biomass pretreatment. Recent advances in lignin modification pathways such as fragmentation/hydroprocessing and thermal depolymerization for green gasoline and diesel are discussed.