In an attempt to meet its ambitious climate change targets, the UK government has decided to incentivise the uptake of bioenergy. However, the full economic costs and environmental impacts of this decision have not yet been quantified at a national level. This is the topic of this research which evaluates the life cycle environmental and economic sustainability of different options for electricity and heat generation using biomass available in the UK, notably waste wood, agricultural residues and wastes, straw, municipal solid waste (MSW), food waste, and energy crops. These results are then used to evaluate the environmental impacts and costs for the whole bioenergy sector in the UK.The results suggest that the environmentally and economically most sustainable electricity generating options are, in descending order: manure/agricultural residue anaerobic digestion (AD) combined heat and power (CHP), Miscanthus co-firing with coal, and chicken litter gasification CHP. The most sustainable heat-generating systems are manure/agricultural residue ADC CHP, waste wood gasification CHP, and chicken litter gasification CHP. However, the use of these technologies is limited by the availability of their respective feedstocks.The research finds that there is currently 30.4 million odt of biomass produced annually in the UK which could be used for electricity and heat generation and that potentially 77.8 million odt could be produced if greater amounts of energy crops are grown. Dry biomass makes up the largest proportion of available biomass, which itself largely consists of wood wastes and energy crops. Dry biomass can therefore make the largest contribution of electricity or heat to potential bioenergy sectors. The electricity-generating biotechnologies identified as those which would make the most sustainable use of wood wastes and energy crops are biomass power plants and co-firing plants. Heat would be most sustainably generated from these feedstocks using biomass gasification CHPs and biomass boilers.According to the results, it is more sustainable to use the UK's current and potential biomass resources for generating electricity, rather than for producing heat. Electricity from biomass has higher potential for reducing the majority of environmental impacts compared to the current UK electricity grid. Despite this, some impacts are expected to increase, including eutrophication, terrestrial ecotoxicity, depletion of elements and acidification. Furthermore, the economic sustainability of most biomass options is often dependent on subsidies being available, mainly because of the high capital costs.It is recommended that the government look beyond climate change and consider full life cycle impacts when deciding which technologies to incentivise to avoid solving the one problem at the expense of others. It is also advised that subsidies be tied to the sustainability of the feedstock, incentivising the use of waste over energy crops (at least in the short term) and encouraging the displacement of coal and oil. Furthermore, the government should consider scaling the FIT and RHI subsidies smoothly with capacity and consider scaling ROC payments which are currently not linked to capacity at all. Improvements to the environmental sustainability of bioenergy could be gained by funding research into cleaning emissions from biomass combustion, enforcing strict regulation of ash disposal and digestate treatment, and encouraging the reuse and recycling of rare elements.
|Date of Award||1 Aug 2015|
- The University of Manchester
|Supervisor||Adisa Azapagic (Supervisor)|