• Energy Research

Scotland is committed to meeting a net-zero target for greenhouse gas (GHG) emissions by 2045 (Climate Change (Emissions Reduction Targets) (Scotland) Act 2019)). Agriculture and the land use sector can help in two ways: by changing practices to reduce GHG emissions and by storing carbon in the soil and plants. In 2018 agriculture and related land use was responsible for 23% of total Scottish emissions. The Climate Change Plan (CCP) is a key policy tool which is now being revised to help Scotland meet the new net-zero target. Policy development is informed by the Scottish ‘TIMES model’. This model pulls together emission, mitigation and mitigation cost data from all sectors to help understand the strategic choices required to decarbonise an economy. To ensure the model uses the most recent data for agriculture, our research updated estimates of the mitigation potential and the cost-effectiveness of a selection of agricultural mitigation options. It took into account the significant recent improvements in UK agricultural GHG inventory reporting (Smart Inventory). The aim was to estimate the average mitigation potential of different measures, along with costs per unit (e.g. hectare or animal), and total maximum applicability on-farm.

AbstractThis study summarizes a large diverse dataset of methane (CH4) fluxes measured from agricultural sites across the British Isles. A total of 53,976 manual static chamber measurements from 27 different sites were investigated to determine the magnitude of CH4 fluxes from a variety of agricultural fields across the UK and Ireland. Our study shows that contrary to some studies, agricultural soils (both arable and grassland) are small net emitters of CH4 rather than sinks. Mean fluxes measured from arable and grassland sites (excluding fertiliser and tillage events) were 0.11 ± 0.06 and 0.19 ± 0.09 nmol m−2 s−1, respectively, and were not found to be significantly different (Welch t‐test, p = 0.17). Using the values reported in this study, we estimate that an annual emission of 0.16 and 0.09 Mt of CO2‐eq is expected from arable and grassland agricultural soils in the UK and Ireland (comparable to 0.3 and 0.7% of the current annual CH4 emission inventories, respectively). Where CH4 uptake occurs in soils, it is negligible compared to expected emissions of the application of animal manures and tillage events, which were both found to significantly increase CH4 emissions in the immediate few days to months after events. Our study highlights that there are significant differences in CH4 uptake and emissions between sites, and that these differences are partially the result of the moisture content of the soil (i.e., the aerobic status of the soil). We expect uptake of CH4 to be more prevalent in drier soils where volumetric water content does not exceed 35% and emissions to be exponentially greater where agricultural fields become waterlogged.Highlights This study investigated 53,976 CH4 flux measurements from 27 sites across the UK Our study shows both arable and grassland soils are small net emitters of CH4 We estimate annual CH4 emissions of 0.16 Mt of CO2‐eq from agricultural soils in the UK We estimate annual CH4 emissions of 0.09 Mt of CO2‐eq from agricultural soils in Ireland

In this study, we present the first long-term N2O eddy covariance dataset measured from a working farm. The eddy covariance method was used over a four year period to measure fluxes of the greenhouse gas nitrous oxide (N2O) from an intensively managed grazed grassland, to which regular applications of ammonium nitrate or urea fertilisers were spread, for two years each at the field site. The mean emission factors (EFs) reported for ammonium nitrate and urea fertiliser applications in this study over a period of 30 days after fertilisation, were 0.90 and 1.73% of the nitrogen applied, respectively, with EFs of individual events ranging between 0.13 and 5.71%. Our study accurately quantifies emission factors for multiple events and showing unambiguously that large-scale variability is real. EFs do indeed vary from one fertiliser event to another, even at the same site with the same fertiliser type under similar environmental conditions. This makes distinguishing EFs between different fertiliser types for the purposes of developing emission mitigation policy very difficult.

Biomass is an important energy resource for producing bioenergy and growing the global economy whilst minimising greenhouse gas emissions. Many countries, like Australia have a huge amount of biomass with the potential for bioenergy, but non-edible feedstock resources are significantly under-exploited. Hence it is essential to map the availability of these feedstocks to identify the most appropriate bioenergy solution for each region and develop supply chains for biorefineries. Using Australia as a case study,we present the spatial availability and opportunities for second and third generation feedstocks. Considerations included current land use, the presence of existing biomass industries and climatic conditions. Detailed information on the regional availability of biomass was collected from government statistics, technical reports and energy assessments as well as from academic literature. Second generation biofuels have the largest opportunity in New South Wales, Queensland and Victoria (NSW, QLD and VIC) and the regions with the highest potential for microalgae are Western Australia and Northern Territory (WA, NT), based on land use opportunity cost and climate. The approach can be used in other countries with a similar climate. More research is needed to overcome key technical and economic hurdles.