The UK's forest resource and its potential as a sustainable feedstock for bioenergy

The solutions for mitigating climate change are diverse, ranging from innovative technological advancements to national and international policy mechanisms, aimed at behavioural changes. Although rudimentary, the use of wood biomass in energy generation – as an important short- to mid-term transitional fuel – has continued to grow, forming a key component of global mitigation strategies. This is particularly apparent in the UK, which relies upon large volumes of imported wood pellets to supplement home-grown feedstocks. As the UK’s forest resource is relatively small – when compared to the rest of Europe – the governments recently proposed afforestation schemes should prove beneficial; however, before initiating any major tree planting scheme, it is important to first fully understand the existing resource. This interdisciplinary research – exemplifying the diverse nature of forestry – has investigated the UK’s current forest feedstocks, focusing on samples sourced from different tree sections of UK-grown oak, birch, Scots pine and Sitka spruce. Their fundamental characteristics have been analysed, including the completion of Proximate, Ultimate and Lignocellulosic analysis, and the determination of their calorific values. Utilising these results – alongside data collated from extensive literature sources – the statistically significant differences that exist between wood feedstocks have been defined, inferring relationships that link their elemental, chemical and structural components. Consequently, the known heterogeneity of wood – and how this differs between species and tree sections – has been demonstrated, specific to UK-grown wood species. These differences can have both negative and positive impacts upon woodfuel quality and the forest environment, particularly in relation to the blending of residues and stump wood with stem wood. In the case of UK-grown birch and Sitka spruce this could increase the volume and energy content of the produced woodfuel, however it will also result in a more reactive fuel, containing increased contents of nitrogen and potassium. An investigation into the costs of felling and extracting wood from UK forests – incorporating geospatial analysis of the UK’s existing feedstocks – suggests it is currently economically viable to increase the supply of woodfuel from the nation’s forests. This could produce an estimated 2,645 TJ yr¯¹ of additional energy, specifically for domestic use in rural locations, situated close to the UK’s forest resource. Although the continued expansion of the UK’s woodfuel market is viable, it is important that the profitable production of fuel is balanced with the continued protection of our forest environments.