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No. 108: Danish emission inventories for agriculture

Mikkelsen, M.H., Albrektsen, R. & Gyldenkærne, S. 2013. Danish emission inventories for agriculture. Inventories 1985 – 2011. Aarhus University, DCE – Danish Centre for Environment and Energy, 142 pp. Scientific Report from DCE – Danish Centre for Environment and Energy No. 108 http://dce2.au.dk/pub/SR108.pdf

Summary

International conventions obligate Denmark to prepare annual emission inventories and document the methodologies used to calculate emissions. The responsibility for preparing the emission inventory for agriculture in Denmark is undertaken by DCE - Danish Centre for Environment and Energy, Aarhus University (AU). This report is an updated version of NERI Technical Report No. 810 published in 2011. The following chapters of the report include a detailed description of methods and data used to calculate the emissions.

The emissions from the agricultural sector include the greenhouse gases: methane (CH4) and nitrous oxide (N2O) as well as the air pollutants: ammonia (NH3), particulate matter (PM), non-methane volatile organic compounds (NMVOC) and other pollutants specifically related to the field burning of agricultural residues such as nitrogen oxides (NOx), carbon dioxide (CO2), carbon monoxide (CO), sulphur dioxide (SO2), heavy metals, dioxins, polycyclic aromatic hydrocarbons (PAHs), hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs).

The emission calculation is based on the Integrated Database model for Agricultural emissions (IDA). The model covers all aspects of the agricultural inputs and estimates both greenhouse gases and air pollutants. The largest contribution to agricultural emissions originates from livestock production and most of the input data are sourced from Statistics Denmark and from DCEA - Danish Centre for Food and Agriculture, Aarhus University. These data include the extent of the livestock production, land use, Danish standards for feed consumption and excretion. Furthermore, the estimation of nitrogen from leaching and runoff is based on data collected in connection with the Danish Action Plans for the Aquatic Environment. The emission inventory reflects the actual conditions for the Danish agricultural production. In cases where no Danish data are available, default values recommended by the Intergovernmental Panel on Climate Change (IPCC) and the European Monitoring and Evaluation Programme (EMEP) are used.

Approximately 96 % of the total NH3 emission originates from the agricultural sector as does approximately 17 % of total greenhouse gas emission.

The agricultural ammonia emission from 1985 to 2011 has decreased from 116 800 tonnes of ammonia NH3 to 71 300 tonnes NH3, corresponding to a reduction of approximately 39 %. Converted to ammonia nitrogen (NH3-N), the 2011 emission is estimated to 58 700 tonnes NH3-N. Most of this ammonia emission is related to livestock manure and mainly from the production of swine and cattle.

Regarding NH3 emission it has to be noted that the reported emission under the EU Directive - National Emissions Ceilings Directive (NECD) does not include emission from growing cops and ammonia treated straw. The NH3 emission from all sectors in Denmark reported under NECD in 2011 is thus estimated to 69 500 tonnes, where the agricultural sector contributes with 65 500 tonnes NH3.

The emission of greenhouse gases in 2011 is estimated at 9.7 million tonnes CO2 equivalents and is reduced from 13.4 million tonnes CO2 equivalents in 1985. Since 1990, which is the base year of the United Nations Framework Convention on Climate Change a reduction of 23 % is obtained.

The emission of CH4 is primarily related to cattle and swine production, which contributed 73 % and 22 %, respectively. The CH4 emission in 2011 is estimated to 198 gigagram (Gg), or given in CO2 equivalents as 4.2 million tonnes.

The emission of N2O primarily originates from transformation of nitrogen compounds in agricultural fields. The main sources are related to the use of livestock manure, synthetic fertiliser and nitrogen leaching and runoff. The emission of N2O in 2011 is estimated to 17.8 Gg, corresponding to 5.5 million tonnes CO2 equivalents.

Biogas plants that process animal slurry reduce the emission of CH4 and N2O. A methodology to estimate the emission reductions is not provided in the IPCC guidelines. The calculation of a lower emission from biogas treated slurry is based on the content of volatile solids and nitrogen. In 2011 approximately 6 % of all slurry was treated in biogas plants and the lower emission of greenhouse gases as a consequence of biogas treated slurry has resulted in a lower emission of 0.04 million tonnes CO2 equivalents, corresponding to 0,4%.

Improvements in feed efficiency, the utilisation of nitrogen in livestock manure and a significant decrease in the consumption of synthetic fertiliser are the most important explanations for the reduction of NH3. This development has furthermore resulted in a significant reduction of N2O emission, which is the main reason for a considerable decrease in the total greenhouse gas emission. There has been a reduction in CH4 emissions as a consequence of a decrease in the number of cattle. However, this trend is partially counteracted by changes in animal housing towards more slurry-based systems.