David Styles

Cattle feed or bioenergy? Consequential life cycle assessment of biogas feedstock options on dairy farms.

On‐farm anaerobic digestion (AD) of wastes and crops can potentially avoid greenhouse gas (GHG) emissions, but incurs extensive environmental effects via carbon and nitrogen cycles and substitution of multiple processes within and outside farm system boundaries. Farm models were combined with consequential life cycle assessment (CLCA) to assess plausible biogas and miscanthus heating pellet scenarios on dairy farms. On the large dairy farm, the introduction of slurry‐only AD led to reductions in global warming potential (GWP) and resource depletion burdens of 14% and 67%, respectively, but eutrophication and acidification burden increases of 9% and 10%, respectively, assuming open tank digestate storage. Marginal GWP burdens per Mg dry matter (DM) feedstock codigested with slurry ranged from –637 kg CO2e for food waste to +509 kg CO2e for maize. Codigestion of grass and maize led to increased imports of concentrate feed to the farm, negating the GWP benefits of grid electricity substitution. Attributing grass‐to‐arable land use change (LUC) to marginal wheat feed production led to net GWP burdens exceeding 900 kg CO2e Mg−1 maize DM codigested. Converting the medium‐sized dairy farm to a beef‐plus‐AD farm led to a minor reduction in GWP when grass‐to‐arable LUC was excluded, but a 38% GWP increase when such LUC was attributed to marginal maize and wheat feed required for intensive compensatory milk production. If marginal animal feed is derived from soybeans cultivated on recently converted cropland in South America, the net GWP burden increases to 4099 kg CO2e Mg−1 maize DM codigested – equivalent to 55 Mg CO2e yr−1 per hectare used for AD‐maize cultivation. We conclude that AD of slurry and food waste on dairy farms is an effective GHG mitigation option, but that the quantity of codigested crops should be strictly limited to avoid potentially large international carbon leakage via animal feed displacement.

Environmental balance of the UK biogas sector: An evaluation by consequential life cycle assessment

Anaerobic digestion (AD) is expanding rapidly in the UK. Previous life cycle assessment (LCA) studies have highlighted the sensitivity of environmental outcomes to feedstock type, fugitive emissions, biomethane use, energy conversion efficiency and digestate management. We combined statistics on current and planned AD deployment with operational data from a survey of biogas plant operators to evaluate the environmental balance of the UK biogas sector for the years 2014 and 2017. Consequential LCA was applied to account for all major environmental credits and burdens incurred, including: (i) substitution of composting, incineration, sewer disposal, field decomposition and animal feeding of wastes; (ii) indirect land use change (ILUC) incurred by the cultivation of crops used for biogas production and to compensate for bakery and brewery wastes diverted from animal feed. In 2014, the UK biogas sector reduced greenhouse gas (GHG) emissions by 551-755Gg CO2e excluding ILUC, or 238-755Gg CO2e including ILUC uncertainty. Fossil energy depletion was reduced by 8.9-10.8PJe, but eutrophication and acidification burdens were increased by 1.8-3.4Gg PO4e and 8.1-14.6Gg SO2e, respectively. Food waste and manure feedstocks dominate GHG abatement, largely through substitution of in-vessel composting and manure storage, whilst food waste and crop feedstocks dominate fossil energy credit, primarily through substitution of natural gas power generation. Biogas expansion is projected to increase environmental credits and loadings by a factor of 2.4 by 2017. If all AD bioelectricity replaced coal generation, or if 90% of biomethane replaced transport diesel or grid natural gas, GHG abatement would increase by 131%, 38% and 20%, respectively. Policies to encourage digestion of food waste and manures could maximize GHG abatement, avoiding the risk of carbon leakage associated with use of crops and wastes otherwise used to feed livestock. Covering digestate stores could largely mitigate net eutrophication and acidification burdens.

Consequential life cycle assessment of biogas, biofuel and biomass energy options within an arable crop rotation

Feed in tariffs (FiTs) and renewable heat incentives (RHIs) are driving a rapid expansion in anaerobic digestion (AD) coupled with combined heat and power (CHP) plants in the UK. Farm models were combined with consequential life cycle assessment (CLCA) to assess the net environmental balance of representative biogas, biofuel and biomass scenarios on a large arable farm, capturing crop rotation and digestate nutrient cycling effects. All bioenergy options led to avoided fossil resource depletion. Global warming potential (GWP) balances ranged from −1732 kg CO2e Mg−1 dry matter (DM) for pig slurry AD feedstock after accounting for avoided slurry storage to +2251 kg CO2e Mg−1 DM for oilseed rape biodiesel feedstock after attributing indirect land use change (iLUC) to displaced food production. Maize monoculture for AD led to net GWP increases via iLUC, but optimized integration of maize into an arable rotation resulted in negligible food crop displacement and iLUC. However, even under best‐case assumptions such as full use of heat output from AD‐CHP, crop–biogas achieved low GWP reductions per hectare compared with Miscanthus heating pellets under default estimates of iLUC. Ecosystem services (ES) assessment highlighted soil and water quality risks for maize cultivation. All bioenergy crop options led to net increases in eutrophication after displaced food production was accounted for. The environmental balance of AD is sensitive to design and management factors such as digestate storage and application techniques, which are not well regulated in the UK. Currently, FiT payments are not dependent on compliance with sustainability criteria. We conclude that CLCA and ES effects should be integrated into sustainability criteria for FiTs and RHIs, to direct public money towards resource‐efficient renewable energy options that achieve genuine climate protection without degrading soil, air or water quality.

A proposed framework for determining the environmental impact of replacing agricultural grassland with Miscanthus in Ireland

Energy crops offer an opportunity to substantially increase bioenergy resources which can replace rapidly depleting fossil fuel reserves and mitigate the effect of climate change. Energy crops are typically established within traditional agricultural systems such as tillage land or grassland. Associated land use conversion has environmental implications. The aim of this paper is to propose a framework to examine how such environmental implications can be assessed, based on (a) a Strategic Environmental Assessment (SEA) approach which considers potential impacts at different stages of a plan across a wide range of environmental receptors and (b) a literature review. The example we used was that of Miscanthus replacing grassland farming. This scenario is particularly relevant to Ireland, where over 90% of the agricultural land is permanent pasture, but is also applicable to grassland conversion throughout Europe and the United States. Two consecutive phases of land‐use change were identified for assessment, each with a distinct set of environmental impacts. The first was a transition phase, lasting from initial livestock clearance and grassland ploughing until the Miscanthus crop became established (2–3 years). The second phase was the mature crop phase, lasting up to 25 years. Miscanthus cultivation was more likely to impact negatively on the environment during the transition phase than the mature phase, primarily due to abrupt disturbance and the time required for a new equilibrium to establish. However, a literature review of the impact on the environmental receptors revealed that replacing Irish agricultural grassland with Miscanthus had the potential to improve biodiversity, water, air and soil quality, and climatic factors once the crop became established and reached maturity. In order to confirm these findings an appropriate monitoring programme involving objectives and indicators associated with each environmental receptor would need to be developed.

Assessing the impact of within crop heterogeneity (‘patchiness’) in young Miscanthus × giganteus fields on economic feasibility and soil carbon sequestration

In Ireland, Miscanthus × giganteus has the potential to become a major feedstock for bioenergy production. However, under current climatic conditions, Ireland is situated on the margin of the geographical range where Miscanthus production is economically feasible. It is therefore important to optimize the yield and other ecosystem services such as carbon sequestration delivered by the crop. A survey of commercial Miscanthus fields showed a large number of areas with no Miscanthus crop cover. These patches can potentially lead to reduced crop yields and soil carbon sequestration and have a significant negative impact on the economic viability of the crop. The aim of this research is to assess patchiness on a field scale and to analyse the impacts on crop yield and soil carbon sequestration. Analysis of aerial photography images was carried out on six commercial Miscanthus plantations in south east Ireland. The analysis showed an average of 372.5 patches per hectare, covering an average of 13.7% of the field area. Using net present value models and a financial balance approach it was shown that patchiness has a significant impact on payback time for initial investments and might reduce gross margins by more than 50%. Total and Miscanthus‐derived soil organic carbon was measured in open patches and adjacent plots of high crop density showing significantly lower Miscanthus‐derived carbon stocks in open patches compared to high crop‐density patches (0.47Mg C ha−1 ± 0.42 SD and 0.91Mg C ha−1 ± 0.55 SD). Using geographic information system (GIS) it was shown that on a field scale Miscanthus‐derived carbon stocks were reduced by 7.38% ± 7.25 SD. However, total soil organic carbon stocks were not significantly different between open patches and high crop density plots indicating no impact on the overall carbon sequestration on a field scale over 3–4 years since establishment for these Miscanthus sites.

Evidence on the environmental impacts of farm land abandonment in high altitude/mountain regions: a systematic map

BackgroundMany ecosystems have developed in the presence of agriculture and cessation of management resulting from land abandonment can have significant ecological impacts. Around 56 percent of the utilised agricultural area of the European Union is classified as ‘less-favourable areas’ and much of this is mountainous. The small-scale and extensively managed farmlands that are common in mountain areas are particularly vulnerable to marginalisation and abandonment. We conducted the first systematic global mapping of evidence to inform stakeholders and policy makers of the potential impacts of farm land abandonment in mountain areas.MethodsEvidence was collated from a range of academic literature databases and grey literature sources. Identified articles (8,489) were screened for relevance at title, abstract and full text using predefined inclusion criteria set out in a published protocol. Relevant studies (165 across 189 articles) were then mapped using predefined coding and critically appraised for internal validity (i.e. susceptibility to bias).ResultsMapping identified a number of interesting themes in the evidence base: the majority of research was undertaken in arable and mixed farming systems; large evidence bases were found in China, Spain and Italy; studies were mostly observational with spatial/successional comparators; biodiversity, soil and vegetation were most frequently studied. Several knowledge gaps were identified: including outcomes (socioeconomics and environmental hazards), regions (key mountain ranges including the Himalaya), and specific outcome-region groups (e.g. vegetation and soil measures in the UK). Several deficiencies in methodology were identified across studies: a lack of replication; non-random sample selection; lack of methodological detail (including details of spatial scale, replication, and sample selection).DiscussionSystematic mapping has produced a searchable database of studies relating to high altitude farmland abandonment. The map identifies a number of potential areas for fruitful future synthesis, for example research on biodiversity, soil and vegetation in the Loess Hilly Plateau in China, and soil research in Spain. Such synthesis would be rapid given the effort expended here in identifying and screening relevant articles. It also points to several areas that were under-represented in the literature, such as natural hazards (avalanche, fire and flood risk), that would potentially benefit from increased primary research.

Current and Future Environmental Balance of Small-Scale Run-of- River Hydropower

Globally, the hydropower (HP) sector has significant potential to increase its capacity by 2050. This study quantifies the energy and resource demands of small-scale HP projects and presents methods to reduce associated environmental impacts based on potential growth in the sector. The environmental burdens of three (50-650 kW) run-of-river HP projects were calculated using life cycle assessment (LCA). The global warming potential (GWP) for the projects to generate electricity ranged from 5.5-8.9 g CO2 eq/kWh, compared with 403 g CO2 eq/kWh for UK marginal grid electricity. A sensitivity analysis accounted for alternative manufacturing processes, transportation, ecodesign considerations, and extended project lifespan. These findings were extrapolated for technically viable HP sites in Europe, with the potential to generate 7.35 TWh and offset over 2.96 Mt of CO2 from grid electricity per annum. Incorporation of ecodesign could provide resource savings for these HP projects: avoiding 800 000 tonnes of concrete, 10 000 tonnes of steel, and 65 million vehicle miles. Small additional material and energy contributions can double a HP system lifespan, providing 39-47% reductions for all environmental impact categories. In a world of finite resources, this paper highlights the importance of HP as a resource-efficient, renewable energy system.

Environmental impacts of farm land abandonment in high altitude/mountain regions: a systematic map of the evidence

BackgroundEnvironmental impacts of farm land abandonment can be viewed as either an opportunity for ecological restoration to a state prior to agricultural establishment, or as the loss of an on-going process of land management and an associated threat to biodiversity. Whether land abandonment poses an ecological opportunity or threat depends upon the agricultural history and the presence of ecological systems that depend upon regular management for their existence. In Europe, many ecosystems have developed in the presence of agriculture and the loss of continued management resulting from land abandonment can have significant negative ecological impacts. Around 56 percent of the utilised agricultural area (UAA) of the EU is classified as ‘less-favourable areas’ and much of this is mountainous. The small-scale and extensively managed farmlands that are common in mountain areas are particularly vulnerable to marginalisation and abandonment. The work herein will form the first systematic synthesis of the evidence of impacts of farm land abandonment in mountain areas across the globe.MethodsThis review will take the form of two interrelated systematic maps, cataloguing the existing evidence across a wide range of variables such as setting, methodology, scale, measured outcomes etc. Mapping will be undertaken both at abstract-level at a coarse scale and at full text-level at a finer scale. Literature databases, organisational web sites, and search engines will be used to collate all of the available literature regarding the impacts of agricultural land abandonment. All studies investigating farmland abandonment in mountainous regions with an appropriate comparator and measuring an appropriate outcome will be included. Outcomes will be coded in a partly iterative process but will include; natural hazards (fire-/flood risk, land/mud slides), soil (fertility, erosion), water (chemistry, eutrophication, sediment load, hydrology), ecosystem functioning (biodiversity, abundance, invasive species presence), socio-economics (e.g. health, wellbeing, employment). The systematic map outputs will be in the form of searchable databases of relevant and obtainable (full text only) literature, coded by subject, methodology and study design, and internal validity.

Using a Strategic Environmental Assessment framework to quantify the environmental impact of bioenergy plans

Renewable energy and greenhouse gas (GHG) reduction targets are driving an acceleration in the use of bioenergy resources. The environmental impact of national and regional development plans must be assessed in compliance with the EU Strategic Environmental Assessment (SEA) Directive (2001/42/EC). Here, we quantify the environmental impact of an Irish Government bioenergy plan to replace 30% of peat used in three peat‐burning power stations, located within the midlands region, with biomass. Four plan alternatives for supplying biomass to the power plant were considered in this study: (1) importation of palm kernel shell from south‐east Asia, (2) importation of olive cake pellets from Spain and (3) growing either willow or (4) Miscanthus in the vicinity of the power stations. The impact of each alternative on each of the environmental receptors proposed in the SEA Directive was first quantified before the data were normalized on either an Irish, regional or global scale. Positive environmental impacts were very small compared to the negative environmental impacts for each of the plan alternatives considered. Comparison of normalized indicator values confirmed that the adverse environmental consequences of each plan alternative are concentrated at the location where the biomass is produced. The analysis showed that the adverse environmental consequences of biomass importation are substantially greater than those associated with the use of willow and Miscanthus grown on former grassland. The use of olive cake pellets had a greater adverse environmental effect compared to the use of peat whereas replacement of peat with either willow or Miscanthus feedstocks led to a substantial reduction in environmental pressure. The proposed assessment framework combines the scope of SEA with the quantitative benefits of life cycle assessment and can be used to evaluate the environmental consequences of bioenergy plans.

Best Environmental Management Practice in the Retail Trade Sector

Retailers have a large potential to reduce their environmental impacts and many are already implementing effective actions. This document describes what are the best practices implemented by frontrunner retailers in all aspects under their direct control or on which they have a considerable influence. They cover the energy performance of retailers, the sustainability of retail supply chains, transport and logistics, waste and other areas including engaging with consumers. The document also contains sector-specific environmental performance indicators and benchmarks of excellence. These can be used by retailers to monitor their environmental performance and to benchmark it against the performance of frontrunner retailers in each given specific area. Overall, this document aims at supporting all actors in the retail trade sector who intend to improve their environmental performance and seek for reliable and proven information on how best to do it.