The sustainability of organic nutrient recycling in Northern Ireland

: a study of the constraints and opportunities associated with manure management and the potential for beyond the farm-gate strategies

Abstract

The production of food and energyin Northern Ireland harnesses the nitrogen, phosphorus, and carbon cycles, howeverthe intensification of livestock agriculture and the heavy reliance on fossilfuels has disrupted these cycles, leading to increased rates of nutrient loss,greenhouse gas emissions and the pollution of different ecosystems. This thesispresents an investigation into the current sustainability of organic nutrient recycling in Northern Ireland.Additionally, new steps of manure management weresimulated using geographic information system software and nutrient budgeting, witha key objective to evaluate the potential for beyond the farm-gatestrategies to rebalance nutrient cycles in Northern Ireland. Nitrogen and phosphorusmanure nutrient surpluses were found to exist on 14% and 30% of farms respectively,with high imbalances concentrated to the south of Northern Ireland. Nitrogenrealignment was achieved through recovering 20-45% of manure nitrogen withredistribution over 0.5-20 km. Redistribution and recycling of manure phosphorusat a council scale decreased the manure phosphorus surplus from 10.2kg/ha to4.9kg/ha, and uncovered the potential for full displacement of imported phosphorus.The simulation of large-scale anaerobic digestion recovered between 2.1-4.7 millionkg of phosphorus for redistribution and recycling from different manure feedstockscenarios, with estimated energy potentials representing 18-35% of the naturalgas heat distribution network demands for Northern Ireland. The research showsthat nutrient budgeting can direct and inform future beyond the farm-gatemanure management strategies to rebalance nitrogen, phosphorus and carboncycles, and that nutrient realignment can be achieved in tandem with renewablegas production. To deliver beyond the farm-gate manure management strategies, increaseduptake of nutrient recovery technologies and up-to-date soil data to informnutrient budgeting is required. 

Thesis is embargoed until 31 July 2026.