How certain are greenhouse gas reductions from bioenergy? Life cycle assessment and uncertainty analysis of a forest residues-to-electricity supply chain.

How certain are greenhouse gas reductions from bioenergy? Life cycle assessment and uncertainty analysis of a forest residues-to-electricity supply chainIn existing climate change and energy policies bioenergy is considered as a valid greenhouse gas (GHG) reducing option and to contribute to the sustainability of the energy system. Up to date research presents different outcomes about environmental and climate change impacts of bioenergy. This is not only due to heterogeneous pathways of producing and converting biomass or indirect impacts but also because of uncertainties within bioenergy supply chains and evaluation methods. The here presented work examines a forest residues-to-electricity supply chain. It focuses on uncertainties arising from different points in the supply chain related to GHG emissions and associated with evaluating these emissions and impacts. Even though uncertainties from bioenergy supply chains cannot be eliminated, this will support the evaluation of their significance to the overall GHG reduction potential of bioenergy systems and their contribution to emission reduction targets.Bioenergy will play an important role in reaching national and international climate change targets. By 2020 about 10% of the EU’s primary energy requirements could be supplied by biomass. However, bioenergy is linked to a number of challenges, which have to be considered, e.g. real emission reductions, environmental impacts, sustainability, land use and land use change or food security. If the application of bioenergy is implemented and supported from a climate change and sustainability perspective, bioenergy systems must deliver real emission reductions and be sustainable to justify their utilisation. There are standards for evaluating GHG emissions but the results depend on assumptions at many points along the supply chain, with some attached to significant uncertainty. The purpose of the work is therefore to evaluate these uncertainties and the significance for the potential of bioenergy to reduce GHG emissions and fulfil sustainability criteria.For this, the research focuses on uncertainties arising from processes in bioenergy supply chains related to GHG emissions and associated with evaluating these. Taking a forest residues-to-electricity supply chain as an example, the main sources of uncertainty are examined and their emissions and environmental impacts evaluated. This is done with a whole systems approach, including direct and indirect impacts as well as sustainability. Life cycle impacts are assessed through life cycle assessment, with sensitivity and uncertainty analysis conducted for parameters representing the greatest uncertainty. Up to date research has generated very different results regarding the benefits and impacts of bioenergy. This is due to the broad variability in feedstocks, different application and conversion methods, uncertainties in supply chain processes or variability in models and methods to evaluate emissions and impacts. Looking not just at single points but examine the whole supply chain and indirect impacts will allow to draw a holistic picture of emissions and related uncertainties. The improved understanding of bioenergy impacts and identification of real GHG reduction potential will support energy and climate change policy development. The research is still in progress, but preliminary findings identified carbon sequestration and carbon stocks, emissions from soils, production management, temporal and spatial aspects, regional and meteorological variations, land use change, indirect impacts and measuring black carbon emission from combustion as main sources of uncertainty. While these relate to natural variability and data uncertainty, there are also uncertainties arising from scenarios and regarding the evaluation of GHG balances. The scenario uncertainties are based on choices of the evaluation methods and the scoping of the bioenergy system.Uncertainty in GHG emissions from bioenergy supply chains cannot be eliminated, but their better characterisation will support evaluation of their significance to the overall GHG reduction potential of bioenergy systems and their possible contribution to emission reduction targets. This will also support policy development by improving the understanding of bioenergy impacts and avoid unintentional outcomes from energy and climate change policies.