Improving the UK agricultural greenhouse gas emissions inventory [REF2021]

Description of impact

Overview
Bangor’s greenhouse gas (GHG) research has generated substantial impact on UK / international GHG policy and UK industry. The underpinning evidence provided by Bangor-led research has been synthesised with additional datasets to generate UK country-specific N2O emission factors (EFs) for different fertilisers, manures, and urine and dung deposited by grazing livestock (cattle and sheep), resulting in many of these new EFs being much lower than the Intergovernmental Panel on Climate Change (IPCC) default N2O EFs that the UK had previously been using [5.1]. This research led to key changes in the EF calculation informing the UK GHG inventory and IPCC policy guidelines.

UK agriculture greenhouse gas inventory
The impact of these new Bangor-generated EFs on the reported UK agriculture greenhouse gas inventory emission for the 2016 submission (activity data year 2013) under the Framework Convention on Climate Change [5.2], was a reduction by approximately 11.6% (i.e. from 49.2MtCO2e to 43.5MtCO2e). Since then, these new EFs have been used to generate a more sophisticated N2O emissions estimate that accounts for the influence of factors such as rainfall. This has resulted in a greater reduction in the inventory estimate, by approximately 18.5% (9.1MtCO2e) compared with default EF methodology. The largest contribution to this reduction has been the reduction in N2O emission estimates from soils, by approximately 30% (for 2013) [5.2]. Since the calculated methane (CH4) emissions from enteric and manure management sources have only been decreased by approximately 4.5%, Bangor-led research has further highlighted the high relative contribution of GHG emissions from ruminant CH4 [5.2] with implications for policy and industry to prioritise strategies to reduce this challenging source of emissions. Another significant impact of the research is that a lower total agriculture GHG emission means that a greater proportion of emissions can be offset by increases in carbon sequestration, improving the UK’s ability to reach the 2050 target of net zero carbon.

Through Bangor’s research, the introduction of the UK country-specific EF (for grazing livestock) has had the most impactful effect, with the InveN2Ory project data resulting in a 75% reduction in the IPCC default N2O EF for cattle, from 2% of applied/deposited N (lost as N2O-N) to 0.44% [5.2]. The result was a reduction in estimated total N2O emission from the excreta of grazing livestock from 15.62ktN2O/year to 4.21ktN2O/year, for the year 2013. These new data also contributed significantly to the 2019 Refinement of the 2006 IPCC Guidelines (see below).

International greenhouse gas inventories
Bangor’s research has influenced policy in many countries. Specifically, the InveN2Ory project team have been requested by international groups to advise on improving estimates in their National Agriculture Greenhouse Gas Emissions. The countries specifically requesting Bangor’s assistance in improving the N2O component of their inventories were:
• Chile (2016): Chadwick and the team trained 4 Chilean technicians and researchers, and 1 policy advisor in appropriate experimentation, inventory calculations, emission factors derivation, and greenhouse gas modelling, via the Newton Picarte, Institutional Skills Development project, Improving the Greenhouse Gas Inventory for Agriculture in Chile, between INIA (Instituto de Investigaciones Agropecuarias, Chile), Bangor University (Chadwick) and Rothamsted Research [5.3].
• Denmark: Chadwick is an invited expert advisor on a 3-year Danish Administration-for-Agriculture funded project (2019 to 2022) Developing national emission factors for nitrous oxide from nitrogen fertilisers and crop rotations (NATEF).

2019 IPCC Guidelines
International impact of the Bangor-led research was achieved via the 2019 Refinement of the 2006 IPCC Guidelines [5.4], which cites this research in its method modification for accounting for N2O emissions from urine and dung deposited by grazing livestock. The 2019 IPCC Guidelines used Bangor-led research evidence to support the case for disaggregating the combined grazing excretal N2O EF by separating N2O EFs for urine and dung. This resulted in a much-reduced EF (comprising 0.77% for urine and 0.13% for dung, which are close to the average reported by Bangor of 0.69% for urine and 0.19% for dung), compared with the combined N2O EF of 2% (for cattle) in the previous 2006 IPCC Guidelines. Moreover, data from the Bangor-led experimental research with real and artificial urine treatments were used by IPCC to confirm the use of artificial urine studies within the analysed dataset enabling an additional 63 observations (out of a total 326) to be included in the statistical analysis to derive the urine N2O EF [5.4].

Bangor’s research will impact on the annual Agriculture GHG inventories of all countries using the Tier 1 EF3PRP when submitting to the United Nations Framework Convention on Climate Change (via their compliance with the updated 2019 IPCC guidelines). Ultimately, all Carbon-Footprinting tools will also be modified to take account of the improved N2O EF resulting from Bangor-led research.

UK Livestock Industry
Impact on the Welsh Government (WG) and Welsh livestock industry has been via parallel engagement through knowledge exchange by the Bangor staff in this research group (Williams, Styles and Chadwick). Working with WG, Hybu Cig Cymru (Meat Promotion Wales) and the Agriculture and Horticulture Development Board, Bangor research co-identified and costed practical strategies for reducing GHG emissions from, and carbon sequestration within, Welsh farms via the Climate Smart Agriculture-Wales project [5.5]. Resulting impact was achieved by raising awareness of the potential levels of greenhouse gas mitigation across the meat and dairy sectors, and by co-producing a Welsh Government report reviewing the most appropriate Carbon-Footprinting tool to roll out across Welsh livestock farms [5.6] for future bench-marking.

Bangor’s research [3.b, 3.6] informed the WG’s multidisciplinary approach to the agriculture sector’s contribution to the challenge of meeting Wales’ national Carbon Budgets. Reflecting the close integration with this policy process, Williams was asked by WG to present this approach to the UK Climate Change Commission (the independent statutory advisory body for UK and devolved governments), which received positive feedback from the Commission. This culminated in Bangor’s invitation to contribute to Hybu Cig Cymru’s “Sustainability roadmap” for the red meat sector in Wales, outlining which strategies need to be implemented so that GHG emission-reduction targets are met by the Welsh livestock sector for the period 2020 to 2050.

Impact Summary for the General Public

Bangor University’s greenhouse gas (GHG) research has impacted policy and industry through generation of new country-specific nitrous oxide (N2O) emission factors. Policy: Bangor’s evidence has significantly lowered calculated N2O contributions in the UK’s Agriculture GHG Inventory (since submission year 2016), and informed changes to GHG guidelines at the international level (via inclusion in the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories). Industry: Bangor research highlighted that enteric methane represents a greater proportion of the UK’s total Agriculture GHG Inventory than previously thought and worked with red meat / dairy sectors in Wales to enable co-identification of practical GHG emission mitigation practices.

Description of the underpinning research

Professor Dave Chadwick co-ordinated the Defra and Devolved Administrations-funded consortium research project [3.a] (GBP6,689,724) to more accurately quantify the nitrous oxide (N2O) component of the UK agriculture greenhouse gas (GHG) inventory. Collaborators included Aberdeen University, Agricultural Development and Advisory Service (ADAS), Rothamsted Research, Scotland's Rural College (SRUC), Centre for Ecology and Hydrology (CEH) and the University of East Anglia. This InveN2Ory project (Defra code AC0116) took place during 2010 to 2016 (led from Bangor since 2012). It produced data to underpin the generation of new country-specific N2O emission factors (EFs) for nitrogen fertilisers, manures, urine and faeces deposited by grazing livestock, for use in the revised inventory. Aberystwyth University co-ordinated a sister project to improve the ruminant methane (CH4) emission factors, whilst ADAS (UK’s largest independent agricultural and environmental consultancy) led a project to synthesise the data and generate the new agriculture inventory model. Together, these three projects made up the UK GHGPlatform.

The InveN2Ory research project comprised 37 field experiments throughout the UK, using replicated plots to determine N2O EFs from nitrogen fertiliser (including different fertiliser types, specifically urea and ammonium nitrate), different manure types, plus dung and urine deposited by grazing livestock, that better reflect the soils, climates and nitrogen management of the UK. The effects of season of application/deposition and methods of manure application on N2O EFs were assessed. Chadwick et al. also tested several N2O mitigation methods, e.g. use of the nitrification inhibitor, dicyandiamide (DCD), and splitting fertiliser doses into more frequent smaller amounts (to improve N use by the crop) [3.1]. In partnership with the five research groups involved in the field measurements, Chadwick developed a common sampling protocol for the chamber methods for measuring N2O fluxes [3.2], thereby contributing to the Nitrous Oxide Chamber Methodology Guidelines, which are the internationally agreed reference guidelines for measuring N2O emissions using chamber methodologies. Chadwick recently contributed to a revision of this guideline document, specifically the Chapter on ‘Sources of variability of N2O fluxes’, subsequently published in a series of research papers in Journal of Environmental Quality in 2020 [3.3].These guidelines are key to producing improved quality of N2O flux measurement data worldwide and better inter-comparability amongst international studies that are vital to improved understanding of the key factors controlling N2O EFs from different nitrogen sources.

Many of the individual site experiments have been published, but importantly several papers have synthesised the N2O EFs from the different N sources [3.1, 3.4, 3.5]. The revised N2O EFs from the project were combined with several additional datasets, and the new N2O EFs for fertiliser to arable soil (EF1), urine to grassland (EF3PRP), manure to arable and grassland (EF1), and ‘Pasture, Range and Paddock’ (EF3PRP) for excreta deposited by grazing livestock, were all significantly less than the IPCC default values for N applications (EF1).

Bangor researchers (Dr Prysor Williams, Dr David Styles and Chadwick) have coordinated collaborative research activities and knowledge exchange with the livestock industry in Wales. The research co-identified suitable Carbon-Footprinting tools for benchmarking individual farms, and ranking the practicalities and costs of bundles of mitigation options to reduce net GHG emissions. These are critical to enable Welsh Government and the livestock sector to better track and reach GHG emission reduction targets (via the Welsh Government-funded Climate Smart Agriculture Wales project, led by Aberystwyth University in partnership with Bangor) [3.b, 3.6]. Styles is an expert in Carbon Footprinting and Life Cycle Assessment for land use.

Impact status	Ongoing
Impact date	2017 → 2020
Category of impact	Policy and Public Services