Life cycle assessment of a short-rotation coppice willow riparian buffer strip for farm nutrient mitigation and renewable energy production

As agricultural activity intensifies across Europe there is growing concern over water quality. Agricultural run-off is a leading cause of freshwater degradation. Simultaneously there is a continually increasing drive to promote renewable energy and reduce greenhouse gas emissions. Willow coppice planted as a riparian buffer has been suggested as a solution to help mitigate these problems. However, there is limited research into the use of such a system and several key knowledge gaps remain, such as, the energy ratio of the system is not known, and a fully harvested site has yet to be analysed in the literature. The aim of this research is to fill these knowledge gaps to help inform agri-environmental policy. To do this a life cycle assessment was carried out on an established willow buffer system, considering the global warming potential, eutrophication potential, acidification potential and cumulative energy demand impact categories, alongside the calculation of the energy ratio. To our knowledge it is the first site to be fully harvested and for which a full life cycle assessment has been carried out. The willow was combusted to fuel a district heating system. Key results showed emissions of 4.66 kg CO2eq GJheatout−1 and 0.01 kg SO2eq GJheatout−1, both of which are significant reductions compared to an oil heating system (95% reductions for both impact categories). The system also resulted in the permanent nutrient removal of 55.36 kg PO43−eq ha−1 yr−1 and had an energy ratio of 17.4, which could rise to 64 depending on the harvest method.