Bioenergy for climate change mitigation: scale and sustainability

Many global climate change mitigation pathways presented in IPCC assessment reports rely heavily on the deployment of bioenergy, often used in conjunction with carbon capture and storage. We review the literature on bioenergy use for climate change mitigation, including studies that use top-down integrated assessment models or bottom-up modelling, and studies that do not rely on modelling. We summarise the state of knowledge concerning potential co-benefits and adverse side-effects of bioenergy systems and discuss limitations of modelling studies used to analyse consequences of bioenergy expansion. The implications of bioenergy supply on mitigation and other sustainability criteria are context dependent and influenced by feedstock, management regime, climatic region, scale of deployment and the counterfactual land use and
energy system. Depending on previous land use, widespread deployment of monoculture plantations may contribute to mitigation but can cause negative impacts across a range of other sustainability criteria. Strategic integration of new biomass supply systems into existing agriculture and forest landscapes may result in less mitigation but can contribute positively to other sustainability objectives. There is considerable variation in evaluations of how sustainability challenges evolve as the scale of bioenergy deployment increases, due to limitations of existing models, and uncertainty over the future context with respect to the many variables that influence alternative uses of biomass and land. Reducing the risks of large-scale deployment of bioenergy in mitigation portfolios requires integrative policies, coordinated institutions and improved governance mechanisms to enable co-benefits and minimize adverse side-effects. Further, strong efforts are needed to improve efficiency and management for both energy and non-energy uses of land and biomass in addition to ongoing efforts to decarbonise the energy mix, so as to constrain the biomass demand growth that will likely arise as countries phase out fossil fuels.