The sustainability of short rotation coppice willow as riparian buffer strips on Irish dairy farms

Abstract

The use of renewable energy crops, planted as riparian buffer strips, is seen as one method to help increase the sustainability of agriculture. This thesis focusses on the crop short rotation coppice willow, which is fast growing, has high nutrient retention rates, requires little maintenance and can be harvested regularly without the need to replant. The aims of the system are to reduce agricultural run-off, reduce the climate impact of agriculture and provide a source of renewable energy. In this thesis the impact of implementing short rotation coppice willow riparian buffer strips into intensive dairy farm settings on the island of Ireland was considered for the first time. This was to assess the impact it would have on the food-energy-water nexus using a novel framework, the climate impact of the farm and the economic impact. On a typical Irish dairy farm, the implementation of a short rotation coppice willow riparian buffer strip could reduce total nitrogen and phosphorus leachate by 14% and 9% respectively. Total CO2eq emissions could be reduced by 16.5% if energy from the willow displaces fossil fuels, while the impact on milk production is minimal, thus relieving strain on the entire food-energy-water nexus. By implementing the willow system, the time-dependent climate impact of an Irish dairy farm could also be reduced by 9.33% with only 3.68% of the land used for willow cultivation, over a 101-year study period. Furthermore, the system was found to have an average yearly net present value of £497 ha-1 of willow buffer. Assuming 5% land usage, a drop in value of £28 ha-1 yr-1 was found when implemented in an Irish dairy setting. However, on a per litre of milk basis a farm employing willow coppice riparian buffer strips outperformed a typical dairy farm both environmentally and economically. An established short rotation coppice willow riparian buffer strip was also considered for the first time, using life cycle assessment to determine the global warming potential, energy ratio, eutrophication potential and acidification potential of the 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 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. Finally, the impact of a region-wide uptake for Northern Ireland was assessed. Key results showed that the widespread implementation of SRC willow riparian buffer strips in the region could result in a 2.75% reduction in total greenhouse gas emissions, 8% of the region’s heat demand being met or 8.7% of the region’s electricity demand, and 2,452 Mg N yr-1 and 416 Mg P yr-1 permanently prevented from polluting local water bodies.

Thesis is embargoed until 31 December 2024.

Date of Award	Dec 2022
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	INTERREG VA Programme (European Union) & The Bryden Centre
Supervisor	Beatrice Smyth (Supervisor), Aoife Foley (Supervisor), Simon Murray (Supervisor), Christopher R. Johnston (Supervisor) & Gary Lyons (Supervisor)