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An improved inventory of greenhouse gases from agriculture - AC0101

Description
The UK is required under the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC) to reduce its Greenhouse Gas (GHG) emissions by 8% relative to 1990 levels by 2008-2012 but has accepted a target of 12.5 % reduction under the EU Burden Sharing Agreement. In the UK, agriculture contributes approximately 70% of the nitrous oxide (N2O) and about 40% of the methane (CH4) emissions and this represents 4.5% and 3.2%, respectively, in terms of their contribution to UK-derived global warming potential. Therefore, UK agriculture has a significant role in helping to achieve the above targets under Kyoto.

In order to register and account effectively for reductions in annual GHG emissions the UK GHG inventory should be sensitive to sources making large contributions to total emissions and to those factors amenable to causing reductions in them. The current UK inventory uses the standard methodology of the Intergovernmental Panel on Climate Change (IPCC) (IPCC, 1997), which is generalised and simplified due to an intended initial wide scope of application. This involves applying IPCC default emission factors (EFs) to UK activity data and so, for example, all EFs used to calculate direct N2O emissions are the same (1.25% of N source value). Some countries such as New Zealand already use their own EFs (rather than the default values) and provided that all data are from published sources, country-specific EFs and methodologies are permitted under IPCC. However, this methodology may not provide adequate sensitivity to important sources, nor give sufficiently accurate quantification of emissions. In line with other European member States, the UK now needs to develop an improved inventory of GHG emissions.

The purpose of this project is to develop such an improved GHG inventory as part of a general framework enabling policy makers to readily investigate the effects of potential management change options, whether specifically for GHG mitigation or for other uses. Emission factor values derived from measurement of emissions from specific sources can be highly variable due to effects of weather patterns, measurement error, and variability in a given land management. High quality, long-term datasets from specific land-use/source combinations are required in order to provide sufficient statistical confidence in the source/emission relationships for assignment of robust EFs. DEFRA’s CC02 programme is providing this kind of information but analysis of it shows that more data are required to enable differentiation of EFs for the main land use sectors, managements within these and some specific high source situations. These data are obtainable through field experimentation and systems modelling.

Thus the general objective of this project is to revise existing EFs and derive new ones for N2O and CH4 emitted from farmed land and animals in the UK through experimental work and modelling. The results will provide a framework to enable the derivation of an improved UK GHG inventory and also the methodologies to enable investigation of potential mitigation options and other management changes by policy makers. These broad aims will be achieved through a concerted set of 4 workpackages involving modelling, field experimentation, literature and data analysis to formulate, through close dialogue with DEFRA, the progression of steps towards the improved inventory. The annual submission of GHG inventory to the UNFCCC will be carried on as usual, but the EFs will be changed when the results of this project prove that we can produce land management specific factors. The project will be conducted jointly by IGER and ADAS. Experimentation consists of using the automated chamber technique at experimental sites to measure gas fluxes from targeted sources over the year at a range of nitrogen inputs to the soil and to account for spatial effects of soil and climate. Modelling further develops and makes use of the IGER UK-DNDC model (N2O and CH4 emissions) and the ADAS NITCAT model (leaching from crop rotations).
Objective
Over all: To provide a framework to enable the derivation of an improved UK GHG inventory and also the methodologies to enable investigation of potential mitigation options and other management changes by policy makers. To begin to populate this framework with new ‘improved’ EFs.

The objectives and descriptions of each workpackage are as follows:

WP 1. Experimental determination of N2O emission factors for grazed grassland and arable.
To quantify through field measurements the N2O emissions from the different land use sectors and major managements within these, according to a range of fertiliser and manure N sources. To calculate new EFs based on these new and existing data.

During the 2006-2007 season, N2O emissions will be measured on grazed grassland operating at a range of N inputs and at sites with contrasting soil types and climatic regimes. The objective is to obtain accurate values for annual N2O emissions from grazed land with which to add to existing data. The combined dataset provides the basis for deriving a statistically significant regression of annual N2O emission on N input for fertiliser and/or manures. From this the EF for ‘grazed grassland’ will be calculated and added to the list of new Smart EFs incorporated within the framework derived under WP3.
During the 2007-2008 season both arable and grassland systems will be measured and during the 2008-2009 only arable will be evaluated.

Specific time bound objectives:

1. To setup 3 grassland sampling sites in Devon, Wales and North Yorkshire with a range of N –use levels each, climatic conditions and soil type combinations typical of UK grazing land.
2. To measure N2O emissions from the experimental grassland sites on a temporal ‘event’ basis throughout the year dependent upon additions of fertiliser and manure, grazing management and incidence of rainfall (2 years).
3. To use the results to extract an emission factor for N2O from inorganic N input for grazed grassland and to improve the significance of the statistics.
4. To setup 3 arable sampling sites in Devon, Cambridshire and Nottinghamshire with a range of N –use levels each, climatic conditions and soil type combinations typical of UK arable land.
5. To measure N2O emissions from the experimental arable sites on a temporal ‘event’ basis throughout the year dependent upon additions of fertiliser and manure, cultivation management and incidence of rainfall (2 years).
6. To use the results to extract an emission factor for N2O from inorganic N input for arable land and to improve the significance of the statistics.


WP 2. Experimental determination of N2O and CH4 emissions from “unmanaged” areas of intensive grassland systems
To quantify through field measurements N2O and CH4 emissions from specific, hitherto neglected, but potentially large sources of the intensive grassland system. To calculate new EFs for manure ‘seepage’ areas, poached areas around gateways and water troughs, on-farm wetland areas and beneath silage bales. This work will begin with measurements on beef and sheep farms which will supplement earlier analogous measurements made on 2 dairy farms under CCO268.

Specific Time bound objectives:

1. To quantify N2O and CH4 emissions from the major influencing sources of unmanaged components from a number of livestock farms, including beef, with contrasting management to generate representative data.
2. To quantify the area of the major ‘unmanaged’ sources on farms.
3. To calculate the importance of these areas as a source of emissions in relation to all other farm sources.
4. To use the information from 1-5 to aid the identification and definition of potential mitigation options for their reduction and consider how changes in farm practice, management, or farm layout may reduce N2O emissions from unmanaged components of farms.


WP 3. Model evaluation of N2O emissions factors from different sources in UK agriculture.
To provide the frame work for an improved inventory of GHG from UK farm land and animals, through the provision of new sets of EFs obtained by the use and development of models, analysis of existing data and those new data obtained from WPs 1 and 2 above.

Specific time bound objectives

1. To modify the UK-DNDC model, incorporating all necessary scientific advances and to run the model to provide a range of EFs for N2O supplementary to those obtained through experiment (WPs 1 and 2) and from existing data, both for ‘status quo’ and some mitigation options scenarios.
2. To modify the NITCAT model and perform runs to quantify FracLEACH for soil, crop and climate combinations.
3. To develop a user-friendly transparent framework for the new improved inventory and compare estimates of emissions made with the improved inventory with those calculated using default IPCC methodology.

WP 4. Annual update and reporting of the GHG inventory for the UK from agriculture
To Update the UK GHG inventory on an annual basis according to IPCC guidelines and submitting it in the required format to DEFRA and AEAT (Netcen) according to schedule.

Specific time bound objectives

1. Revise and update the inventories of N2O and CH4 emissions from UK agriculture for the years 2005, 2006 and 2007.
Provide forward and backward projections of N2O and CH4 emissions from UK agriculture for the years 1990-2020.

Time-Scale and Cost
From: 2006

To: 2009

Cost: £1,049,948
Contractor / Funded Organisations
Institute of Grassland and Environment Research (IGER), North Wyke Research
Keywords
Air Pollution              
Ammonia              
Environmental Protection              
Pollution              
Sustainable Farming and Food              
Fields of Study
Agriculture and Climate Change