Browsing by Author "Johnston, Christopher"
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Item Are stakeholders ready to transform phosphorus use in food systems? A transdisciplinary study in a livestock intensive system.(Elsevier, 2022-02-12) Martin-Ortega, Julia; Rothwell, Shane A.; Anderson, Aine; Okumah, Murat; Lyon, Christopher; Sherry, Erin; Johnston, Christopher; Withers, Paul J.A.; Doody, DonnachaFood systems worldwide are vulnerable to Phosphorus (P) supply disruptions and price fluctuations. Current P use is also highly inefficient, generating large surpluses and pollution. Global food security and aquatic ecosystems are in jeopardy if transformative action is not taken. This paper pivots from earlier (predominantly conceptual) work to develop and analyse a P transdisciplinary scenario process, assessing stakeholders potential for transformative thinking in P use in the food system. Northern Ireland, a highly livestock-intensive system, was used as case study for illustrating such process. The stakeholder engagement takes a normative stance in that it sets the explicit premise that the food system needs to be transformed and asks stakeholders to engage in a dialogue on how that transformation can be achieved. A Substance Flow Analysis of P flows and stocks was employed to construct visions for alternative futures and stimulate stakeholder discussions on system responses. These were analysed for their transformative potential using a triple-loop social learning framework. For the most part, stakeholder responses remained transitional or incremental, rather than being fundamentally transformative. The process did unveil some deeper levers that could be acted upon to move the system further along the spectrum of transformational change (e.g. changes in food markets, creation of new P markets, destocking, new types of land production and radical land use changes), providing clues of what an aspirational system could look like. Replicated and adapted elsewhere, this process can serve as diagnostics of current stakeholders thinking and potential, as well as for the identification of those deeper levers, opening up avenues to work upon for global scale transformation.Item Effect of anaerobic digestate fuel pellet production on Enterobacteriaceae and Salmonella persistence(Wiley, 2022-07-07) Cathcart, Ashley; Smyth, Beatrice M.; Forbes, Christina; Lyons, Gary; Murray, Simon T.; Rooney, David; Johnston, ChristopherProduction of digestate pellets for fuel has been identified as a promising circular economy approach to provide renewable energy and additional income to farms, while at the same time presenting the potential to divert raw digestate from nutrient-saturated land and reduce the risk to water quality. Although previous research has investigated the feasibility of pellet production, there has been little focus on the bio-safety aspects of the system. Little is currently known about the persistence of bacteria present in the digestate and the potential impacts on human health for those handling this product. The aim of the present research was to determine the effect that each step in the pellet production process has on bacteria numbers: anaerobic digestion, mechanical separation, solid drying, and pelletisation. Enterobacteriaceae enumeration by colony count method was used to quantify bacteria, and the presence of Salmonella at each stage was determined. The Enterobacteriaceae count reduced with each stage, and the final pelletisation step reduced bacteria numbers to below detectable levels (<10 colony forming units/g). Salmonella was only detected in the starting slurry and absent from digestate onwards. Storage of the pellets under winter and simulated summer conditions showed no reactivation of Enterobacteriaceae over time. The pelletisation process produces a digestate product with Enterobacteriaceae counts below the maximum threshold (PAS110 specification) for transport off the source farm, but care must still be taken when handling digestate pellets as complete sterilisation has not been confirmed.Item The effect of biochar and acid activated biochar on ammonia emissions during manure storage(Elsevier, 2022-12-05) Baral, Khagendra; McIlroy, John; Lyons, Gary A.; Johnston, ChristopherAnimal manure contains valuable plant nutrients which need to be stored until field application. A significant proportion of slurry nitrogen is volatilized in the form of ammonia (NH3) during storage. This impacts human health, biodiversity, air and water quality and thus urgent action is needed to reduce NH3 emissions. In this experiment, we evaluated the NH3 emission mitigation potential of biochars derived from miscanthus (MB) and solid separated anaerobic digestate (DB), and orthophosphoric acid activated MB (AMB) and DB (ADB) as well as lightweight expanded clay aggregate (LECA) during four months of liquid manure storage. A slurry without amendment was included as a control (Ctrl). Acid activated and non-activated biochars were applied on top of the slurry maintaining a 7 mm thick surface layer, while LECA was applied in a 2 cm thick layer. NH3 emissions were measured by photoacoustic analyzer. In comparison to Ctrl, acid activated biochar decreased (p < 0.05) NH3 emissions during the slurry storage. Activated biochar reduced the emissions by 37–51% within the first month of slurry storage and achieved a 25–28% emissions reduction efficiency throughout the four month period due to the reduction in emission mitigation efficiency as the storage period progressed. LECA reduced NH3 emissions by 21% during storage. Losses of NH3 as a percentage of total ammoniacal N were 29–31% for activated biochars, 35–39% for non-activated biochars and 33% for LECA. In conclusion, acid activated biochars and LECA could be good floating-covers to mitigate NH3 emissions during manure storage, but activated biochars may have better mitigation potential than LECA.Item Effect of two vs. three year harvest intervals on yields of Short Rotation Coppice (SRC) willow(Elsevier, 2021-11-24) Johnston, Christopher; Walsh, Linda R.E.; McCracken, Alistair R.Five genotypes of Short Rotation Coppice (SRC) willow: ‘Beagle’ ((S. viminalis ‘L810203’ x viminalis ‘L81102’) x ‘Astrid’ x male parent unknown), ‘Olof’ (S. viminalis ‘Bowles Hybrid’) x ((S. schwerinii ‘L79069’) x ((S. viminalis ‘L78195’ x viminalis ‘L78101’) ‘Orm’) ‘Bjorn’). ‘Ashton Stott’ (S.viminalis ‘Bowles Hybrid’) x S.dasyclados ‘Korso’, ‘Tora’ (S. schwerinii ‘L79069’) x ((S. viminalis ‘L78195’ x viminalis ‘L78101’) ‘Orm’), and ‘Torhild’ ((S. schwerinii ‘79,069’) x ((S. viminalis) x S. viminalis ‘L78195’ x viminalis ‘L78101’)) ‘Orm’) ‘Tora’) x ((S.viminalis ‘L78195’ x viminalis ‘L78101’) ‘Orm’) were grown in large mono-plots or within plots of intimate mixtures. Over a seven year period half of the plots were harvested on a two-year harvest cycle (three harvests) and the rest on a three-year harvest cycle (two harvests). At the end of this 7 year trial period there were no significant differences between total dry weights or stool survival, irrespective of harvest interval. With the realisation of the importance of this finding for more regular crop management practices, the experiment was continued for a further six years allowing for a further round of two and three year harvests. Results suggest that there ultimately are yield penalties, although these may be minimised by careful and appropriate clonal selection.Item Evaluating the impacts of SRC willows on phosphorus export from a temperate grassland micro-catchment(Elsevier, 2024-02-27) Adams, Russell; Johnston, Christopher; Environmental ProtectionWillows (Salix SPP.) are increasingly being grown as a source of biomass which can be harnessed for energy production at a commercial scale as one example of a Short Rotation Coppice (SRC) crop. What is less widely understood is the role of the plants in reducing nutrient loads when planted as a nature-based solution to mitigate diffuse pollution from agricultural lands. Strategically planted woodland and forest can play a major role in Nature Based Solutions (NBS) approaches. SRC willows were planted in a 22-ha grassland micro-catchment located on a research farm in Northern Ireland, which is regularly grazed by cattle and sheep. The micro-catchment comprises a small ditch with upstream and downstream monitoring points where a pair of autosamplers were used to collect water samples for nutrient analysis. It was possible to reconstruct a timeseries of hourly discharge in the ungauged micro-catchment using the SHETRAN hydrological model. Subsequently, the modelled flows were used to estimate daily phosphorus (P) loads at both upstream and downstream monitoring points from the measured P concentrations. The nearly four years (June 2018–April 2022) of monitoring data allowed P loads to be calculated for pre-planting, juvenile trees and mature trees phases. A baseline scenario was run without any changes to the model; this evaluated the changes in P loads from the catchment. A further Post-Willows scenario “P–W” modified some model parameters and evapotranspiration to represent the land use change due to the willow plantation. The results from the baseline were evaluated and showed that (i) there was a statistically significant reduction in particulate P (PP) and total P (TP) concentrations at the outlet of the micro-catchment; (ii) a statistically significant reduction in PP and TP loads, indicating that the willows were reducing PP export (losses) probably by trapping fine sediment in the ditch. Results from the P–W scenario showed a smaller than expected decrease in discharge from the model results. The overall export of TP from the micro-catchment could be further decreased by additional planting of SRC willows, but the export of soluble forms of P did not decrease by a significant amount post-planting which is a recommendation for further study in mitigation programmes. The use of SRC willows in riparian buffer strips (RBS) which are a common form of NBS, has shown promising results in terms of trapping particulate forms of P. The layout of the RBS should also be carefully designed in terms of maximising the buffer strip width, here the areas planted was optimised to make best use of unproductive farmland. If the RBS can be designed to maximise the interception of runoff flowing downhill from agricultural fields then the removal rate should be even higher.Item Evaluating the opportunity for utilising anaerobic digestion and pyrolysis of livestock manure and grass silage to decarbonise gas infrastructure : A Northern Ireland case study.(Elsevier, 2022-07-04) Mehta, Neha; Anderson, Aine; Johnston, Christopher; Rooney, David W.The need to mitigate climate change and improve energy security has led to an increasing interest in the utilisation of renewable gas to decarbonise natural gas use. Northern Ireland serves as an interesting case study to evaluate how biomethane from manure and silage material can displace natural gas. This is because of high agricultural intensity, the low penetration of gas relative to the wider UK and the modern pipeline infrastructure. This study included spatial mapping of biomethane yield and life cycle assessment for processing scenarios. The results demonstrated that current manure management i.e., storage and application of manure to grassland, results in 344 kg CO2 equivalent/person of greenhouse gases and 9.7 kg/person of ammonia being emitted. In a second scenario where collected manure and underutilised grass silage is routed to anaerobic digestion, the estimated net energy produced is 6124 GWh, with −464 kg CO2 equivalent/person. A third scenario, combining anaerobic digestion and pyrolysis, also produces 6124 GWh and 200 kilo tonnes of biochar (retaining 64% of manure phosphorus), −563 kg CO2 equivalent/person. This research evaluates the opportunity for biomethane while acknowledging that a comprehensive approach which balances energy potentials and nutrient management is required for sustainable biomethane based decarbonisation.Item Identification of high-value bioactive constituents in Northern European willow varieties: S.X. Dasyclados, Endeavour, Cheviot, Tora, Resolution, S. Purpurea, Terranova, endurance(Elsevier, 2022-09-05) Hijazi, Ayman; Pisano, Italo; Leahy, J.J.; Kwapinski, Witold; Johnston, Christopher; Prendergast, JohnWillow trees have maintained their place in medicine for many years as they are herbal source of various cures. Willow varieties are considered to contain a wide range of anti-inflammatory and anti-bacterial species such as salicylates and flavonoids. The current work is centred on the presence of high bioactive pharmaceutical constituents other than salicin such as flavan-3-ol catechin, salicortin, and other complex compounds, which contribute to the total medical value of willow extracts. To evaluate the distribution of these bioactives, bark, and wood fractions of 8 different willow varieties (S.X. Dasyclados, Endeavour, Cheviot, Tora, Resolution, S. Purpurea, Terranova, Endurance) were extracted using dispersive solid phase extraction and then analysed using LC-MS comprising a quadrupole time-of-flight spectrometer. Indeed, various high value constituents such as salicortin, catechin, triandrin, acacetin-5-O-xyloside, picein, apigenin-7-O-glucoside, vitexin-2-rhamnoside, luteolin-7-glucoside, catechin gallate, and kaempferol as well as giberellic and 5-methoxysalicylic acid were detected in bark and wood fractions of the willow varieties 80:20 ethanol/water extracts.Item An Inventory of Good Management Practices for Nutrients Reduction, Recycling and Recovery from Agricultural Runoff in Northern Periphery and Arctic (NPA) region(MDPI, 2022-07-04) Drizo, Aleksandra; Johnston, Christopher; Gudmundsson, JonThe excess loading of nutrients generated by agricultural activities is a leading cause of water quality impairment across the globe. Various management practices have been developed and widely implemented as conservation management strategies to combat water pollution originating from agricultural activities. In the last ten years, there has also been a widespread recognition of the need for nutrient harvesting from wastewaters and resource recovery. In Europe’s Northern Periphery and Arctic (NPA) areas, the expertise in water and runoff management is sporadic and needs to be improved. Therefore, the objective of this research was to perform a comprehensive review of the state of the art of Good Agricultural Practices (GAPs) for the NPA region. A set of questionnaires was distributed to project partners combined with a comprehensive literature review of GAPs focusing on those relevant and/or implemented in the NPA region. Twenty-four GAPs were included in the inventory. This review reveals that there is a large level of uncertainty, inconsistency, and a gap in the knowledge regarding the effectiveness of GAPs in nutrient reduction (NRE), their potential for nutrient recycling and recovery (NRR), and their operation and maintenance requirements (OMR) and costs. Although the contribution of GAPs to water quality improvement could not be quantified, this inventory provides a comprehensive and first-of-its-kind guide on available measures and practices to assist regional and local authorities and communities in the NAP region. A recommendation for incorporating and retrofitting phosphorus retaining media (PRMs) in some of the GAPs, and/or the implementation of passive filtration systems and trenches filled with PRMs to intercept surface and subsurface farm flows, would result in the enhancement of both NRE and NRRItem Phosphorus stocks and flows in an intensive livestock dominated food system(Elsevier, 2020-07-31) Rothwell, S.A.; Doody, Donnacha; Johnston, Christopher; Forber, K.J.; Cencic, O.; Rechberger, H.Current use and management of phosphorus (P) in our food systems is considered unsustainable and considerable improvements in the efficiency of P use are required to mitigate the environmental impact of poor P stewardship. The inherent low P use efficiency of food production from animals means food systems dominated by livestock agriculture can pose unique challenges for improving P management. This paper presents the results of a substance flow analysis for P in the Northern Ireland (NI) food system for the year 2017 as a case study for examining P stewardship in a livestock dominated agricultural system. Imported livestock feed was by far the largest flow of P into the NI food system in 2017 (11,700 t ± 1300 t) and P from livestock excreta the largest internal flow of P (20,400 ± 1900t). The P contained in livestock slurries and manures alone that were returned to agricultural land exceeded total crop and grass P requirement by 20% and were the largest contributor to an annual excess soil P accumulation of 8.5 ± 1.4 kg ha−1. This current livestock driven P surplus also limits the opportunities for P circularity and reuse from other sectors within the food system, e.g. wastewater biosolids and products from food processing waste. Management of livestock P demand (livestock numbers, feed P content) or technological advancements that facilitate the processing and subsequent export of slurries and manures are therefore needed.Item Production pathways for profitability and valuing ecosystem services for willow coppice in intensive agricultural applications(Elsevier, 2023-01-20) Livingstone, David; Smyth, Beatrice M.; Sherry, Erin; Murray, Simon T.,; Foley, Aoife M.; Lyons, Gary A.; Johnston, ChristopherIncreasing agricultural sustainability is a key challenge facing the globe today. Energy crops, planted as riparian buffers are one way to support this, simultaneously mitigating water quality degradation and climate change. However, the economics of implementing such riparian buffer systems is under researched. Hence this work conducted a bottom-up economic analysis of willow coppice riparian buffers on a Northern Irish dairy farm, which is indicative of agricultural intensification across Europe. This work includes an economic assessment of a willow coppice riparian buffer strip, using harvested yield data from an established willow buffer site for the first time. It also considered the impact of harvesting technology on the economic performance of a willow coppice riparian buffer strip for the first time. The analysis considered three willow production pathways: 1) direct chip harvesting, 2) full-stem harvesting, and 3) a scenario with a guaranteed purchasing contract for fresh chip. Economic performance was considered using net present value over a 25-year plantation lifetime. The full-stem scenario provided the highest economic return over its lifetime with an average yearly net present value of £497 ha−1 (in £ sterling). This system was then considered for integration into a typical dairy farm, assuming 5 % land usage and including government grants for establishing riparian zones. The result was a drop in value of £28 ha−1 yr−1 compared to a dairy-only scenario; however, per litre of milk the farm employing willow coppice riparian buffer strips outperformed a typical dairy farm both environmentally and economically. Further analysis considered a novel approach that included payments for ecosystem services in the economic analysis. This analysis found that the implementation of government payments for ecosystem services (nutrient removal) increased the economic return of the willow coppice riparian buffer system by £400 ha−1 yr−1, resulting in minimal impact on the return from dairy land.Item Reducing the time-dependent climate impact of intensive agriculture with strategically positioned short rotation coppice willow(Elsevier, 2023-07-27) Livingstone, David; Smyth, Beatrice M.; Cassidy, Rachel; Murray, Simon T.; Lyons, Gary; Foley, Aoife M.; Johnston, ChristopherIn this study the implementation of a short rotation coppice willow system, planted as a riparian buffer in an intensive agricultural setting, to intercept and reduce nutrient losses, was investigated. The aim of the work was to assess how such a system could reduce the overall climate impact of an intensive agricultural setting. A life cycle assessment was carried out for a combined Irish dairy farm and willow buffer system considering the impact category, climate impact. The climate impact was considering using the time-dependent climate impact metric, with the results given in terms of the impact on the global surface temperature. The results were compared to an Irish dairy farm in which no willow was planted. Such a system has not previously been investigated in this way and this was the first time-dependent climate impact assessment of a willow plantation planted on pastureland. Geographic information systems software, was used to map areas particularly susceptible to agricultural run-off and suitable for willow planting, using the land bank of the Agri-Food and Biosciences Institute research farm in Hillsborough, Northern Ireland, for the case study. The harvested willow was assumed to be combusted in a combined heat and power plant. By implementing the willow system the time-dependent climate impact of an Irish dairy farm could be reduced by 8% with only 3.7% of the land used for willow cultivation over a 101-year study period. The results also found an immediate reduction in climate impact following the implementation of the willow system. Total GHG emissions were reduced by 131 Mg CO2eq ha−1 over the study timeframe. The results can be more broadly applied to other agricultural sectors, such as arable farming where the climate impact savings of the willow system could be even higher.Item Review of two mechanical separation technologies for the sustainable management of agricultural phosphorus in nutrient-vulnerable zones(MDPI, 2021-04) Lyons, Gary A.; Cathcart, Ashley; Frost, J. Peter; Wills, Michael; Johnston, Christopher; Ramsey, Rachel; Smyth, BeatriceThis work reviews two mechanical separation technologies (screw press and decanting centrifuge) which could be used in the dairy, beef, pig and anaerobic digestion sectors in nutrient-vulnerable zones in order to improve the sustainability of manure and anaerobic digestate management by decreasing agricultural phosphorus loss and reducing environmental impact on water quality. Capital and operating costs, separation efficiency and throughput, and management and processing of separated fractions, including transport costs, environmental impacts and the biosecurity of separated solids for export, were considered. Of the two technologies reviewed, screw press separation is a more cost-effective option (5-fold cheaper per tonne of feedstock) when lower amounts of export of phosphorus off farm are acceptable. For farms and those with anaerobic digesters managing larger volumes of manure/digestate, screw press separation is possible. However if higher levels of phosphorus removal are required, the use of decanting centrifugation is a viable option. Centralised processing facilities could also make use of decanting centrifuge technology to act as processing hubs for local farms within a distance that makes it economical for transport of manure/treated manure to/from the processor (the maximum distance for economical transport of raw manure and separated solids is approximately 70 km and 84 km, respectively). Both separation technologies could be integrated into agricultural manure and digestate management systems in order to provide a more sustainable approach to managing agricultural phosphorus loss and its associated impact on water quality. Screw press and decanting centrifuge separation could reduce phosphorous loss to water bodies by 34% and from 30 to 93%, respectively.Item A review of Willow (Salix spp.) as an integrated biorefinery feedstock(Elsevier, 2022-10-22) Baker, Paul; Charlton, Adam; Johnston, Christopher; Leahy, James J.; Lindegaard, Kevin; Pisano, Italo; Prendergast, John; Preskett, Dave; Skinner, CampbellThroughout history, the genus Salix (willow) has been an incredibly useful temperate plant for humans, with widespread global distribution and species indigenous to all continents except Antarctica. Estimations of the number of species range from 450 to 520 worldwide, and there are still more natural hybrids and multi-hybrid combinations. Several biomass willow breeding programmes have been established across the globe. All of these attempt to produce fast-growing, high-yielding stems with a straight habit and minimal side branching that are highly adaptable to different sites and are also disease and pest resistant. Short rotation coppice (SRC) cultivation involves growing willow at close spacings with a stocking rate of around 15,000 per hectare with harvests every 2–4 years. The crop is mechanically harvested, typically using a forager, and material has recently been used for bioenergy applications. Trial plots have achieved yields of up to 20 odt/ha/yr, whilst well-tended commercial crops have yielded up to 14 odt/ha/yr. Global willow breeding programmes have produced a wide variety of commercial genotypes that have suitable properties for easy planting and harvesting and have the added benefit of elevated levels of bioactive compounds, including salicin, present in the bark, which can be used in medical and veterinary applications. These high-yielding willow varieties grow well in the wetter regions of the globe, including NW Europe, and afford multiple harvests before re-planting. Salix's versatility and adaptability and the SRC cultivation process make them an ideal candidate feedstock for use in an integrated biorefinery to produce a range of biobased materials, including pharmaceuticals, and biocomposites, fuels, energy and fertiliser.