Life cycle environmental impacts of biogas production and utilisation substituting for grid electricity, natural gas grid and transport fuels.

In this study, life cycle analysis (LCA) has been applied to evaluate the environmental impacts of biogas production and utilisation substituting for grid electricity, natural gas grid and transport fuels, with a focus on Greenhouse Gas (GHG) emissions. The results demonstrate significant reductions in greenhouse gas emissions for the biogas as a fuel scenario due to the displacement of fossil petrol and diesel fuels (scenario 3), with savings of between 524 and 477 kg of CO2 equivalent (per MWh of energy provided by the fuels). The utilisation of biogas for electricity generation saves around 300 kg of CO2 equivalent per MWh of electricity injected into the grid (scenario 1), while Scenario 2, the upgrading of biogas to biomethane and its injection into the gas grid for heating saves 191 kg of CO2 equivalent (per MWh of energy generated by the biomethane). The results emphasise the benefits of using life cycle analysis to provide an evidence based for bioenergy policy. The limitations of the research are identified and recommendations made for future research priorities to further the use of LCA in the evaluation of bioenergy systems.

Life cycle environmental impacts of substituting food wastes for traditional anaerobic digestion feedstocks.

In this study, life cycle assessment has been used to evaluate life cycle environmental impacts of substituting traditional anaerobic digestion (AD) feedstocks with food wastes. The results have demonstrated the avoided GHG emissions from substituting traditional AD feedstocks with food waste (avoided GHG-eq emissions of 163.33 CO2-eq). Additionally, the analysis has included environmental benefits of avoided landfilling of food wastes and digestate use as a substitute for synthetic fertilisers. The analysis of the GHG mitigation benefits of resource management/circular economy policies, namely, the mandating of a ban on the landfilling of food wastes, has demonstrated the very substantial GHG emission reduction that can be achieved by these policy options - 2151.04 kg CO2 eq per MWh relative to UK Grid. In addition to the reduction in GHG emission, the utilization of food waste for AD instead of landfilling can manage the leakage of nutrients to water resources and eliminate eutrophication impacts which occur, typically as the result of field application. The results emphasise the benefits of using life-cycle thinking to underpin policy development and the implications for this are discussed with a particular focus on the analysis of policy development across the climate, renewable energy, resource management and bioeconomy nexus and recommendations made for future research priorities.

Development and application of a multiple linear regression model to consider the impact of weekly waste container capacity on the yield from kerbside recycling programmes in Scotland.

This article describes the development and application of a multiple linear regression model to identify how the key elements of waste and recycling infrastructure, namely container capacity and frequency of collection, affect the yield from municipal kerbside recycling programmes. The overall aim of the research was to gain an understanding of the factors affecting the yield from municipal kerbside recycling programmes in Scotland with an underlying objective to evaluate the efficacy of the model as a decision-support tool for informing the design of kerbside recycling programmes. The study isolates the principal kerbside collection service offered by all 32 councils across Scotland, eliminating those recycling programmes associated with flatted properties or multi-occupancies. The results of the regression analysis model have identified three principal factors which explain 80% of the variability in the average yield of the principal dry recyclate services: weekly residual waste capacity, number of materials collected and the weekly recycling capacity. The use of the model has been evaluated and recommendations made on ongoing methodological development and the use of the results in informing the design of kerbside recycling programmes. We hope that the research can provide insights for the further development of methods to optimise the design and operation of kerbside recycling programmes.