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

David Livingstone,Beatrice M Smyth,Gary Lyons,Aoife M Foley,Simon T Murray,Chris Johnston

doi:10.1016/j.rser.2022.112154

Abstract

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.

Highlights

To meet increasing global demand, the agricultural sector has seen continual growth across the European Union (EU) over the past three decades [1]
The study considered the impact of the system from its cultivation to its termination along with the use of heat produced in a district heating (DH) system but did not consider the end use efficiency of the heating appliances used
Through the removal of excess nutrients from the agricultural system, the use of an short rotation coppice (SRC) willow riparian buffer strip can play an important role in protecting local ecosystems and water bodies

Summary

Introduction

To meet increasing global demand, the agricultural sector has seen continual growth across the European Union (EU) over the past three decades [1]. As of 2018, on average only 40% of surface water bodies across the EU were achieving ‘Good or Better’ ecological status, as defined by the Water Framework Directive (WFD) [2]. Agricultural activities are one of the main contributors to the degradation of surface water bodies due to nutrient run-off, which often results from the excess use of fertiliser (synthetic or organic) [2]. These nutrients can damage aquatic ecosystems through the process of eutro phication, which can cause widespread disruption to the entire ecosystem and leading to oxygen deficient ‘dead zones’ [4].

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