The emission from the agricultural sector includes emission of the greenhouse gases methane (CH₄) and nitrous oxide (N₂O) and the air pollutants ammonia (NH₃), particulate matter (PM), non-methane volatile organic compounds (NMVOC). Further, minor emissions of NO_x, CO₂, CO, SO₂, heavy metals, dioxin and PAH are included for field burning of agricultural residue. The main part of the agricultural emissions is related to the livestock production.

Air pollutants

The most important air pollutant from the agricultural sector is ammonia. Approximately 97 % of the national ammonia emission originates from the agricultural sector and the ammonia emission is decreased from 94 Gg NH₃-N in 1985 to 59 Gg NH₃-N in 2008, which corresponds to a 38 % reduction. The significant decrease of the ammonia emission is a consequence of an active national environmental policy in the last twenty years. A string of measures have been introduced by action plans to prevent loss of nitrogen from agriculture to the aquatic environment, for example the NPO Action Plan (1986), Plans for the Water Environment (1987, 1998, 2004), the Action Plan for Sustainable Agriculture (1991) and the Ammonia Action Plans (2001). These measures include e.g. improved utilisation of nitrogen in livestock manure, requirements with regard to storage and application of livestock manure, increased area with winter green fields to catch nitrogen, a maximum number of animals per hectare and maximum nitrogen application rates to agricultural crops. The result has brought about a decrease of emission per produced animal and a decreasing use of synthetic fertiliser, which all has reduced the overall ammonia emission significant (figure 1). 

In 2008, emission from animal manure contributes with approximately 85 % of the total ammonia emission from agriculture. The remaining emission originates from synthetic fertilisers contribute (7 %), growing crops (8 %) and less than 1 % are related to other sources as ammonia-treated straw, sewage sludge and industrial sludge applied to fields and from field burning of agricultural residue. 

Figure 1: Ammonia emissions in the agricultural sector, 1985 to 2008. Straw contains ammonia treated straw and field burning of agricultural residue. Click here for background data.

 
 
Most of the emission from animal manure originates from the production of cattle and swine, with 36% and 44%, respectively in 2008 (figure 3). It is noteworthy, that despite a considerably increase of the pork production from 15.1 million produced slaughter pigs in 1985 to 22.9 millions in 2008, the overall emission from swine has decreased by 34%. One of the most important reasons for this is the improvement in feed efficiency. 

Figure 2 Ammonia emission from animal manure distributed according to different livestock categories. Other includes horses, sheep, goats and deer. Click here for background data.
 

Emissions ceiling

The 1999 Gothenburg Protocol, under the UNECE Long-range Transboundary Air Pollution Convention, and the EU’s NEC Directive on national emission ceilings (2001/81/EC) commit Denmark to reduce ammonia emissions from all sectors to 69 Gg NH₃ by 2010 at the latest. It is important to point out, that the emission ceiling does not include the emission of ammonia from crops, themselves, or ammonia-treated straw. The ammonia emission in total excl. emission from ammonia treated straw growing crops are estimated to 67 Gg NH₃ in 2008

It is important to point of the difference between the ammonia emission given in nitrogen NH₃-N and given in total ammonia NH₃. The conversion factor are 17/14 corresponding to the difference in weight of mole.

Greenhouse gasses

The greenhouse gas emission of methane and nitrous oxide from the agricultural sector contributed in 2008 with 15 % of the total greenhouse gas emission.

The emission of greenhouse gases given in CO₂-equivalents has decreased from 14.2 Gg CO₂-equivalents in 1985 to 10.0 Gg CO₂-equivalents in 2008, which corresponds to a 29 % reduction. From 1990, which is the base year of the Kyoto protocol, the emission from the agricultural sector has decreased by 24 %. Nitrous oxide has the most powerful global warming potential and represents the largest contribution to the overall agricultural emission of greenhouse gases. In figure 3 below is shown the emission from 1985 to 2008 distributed on the main emission source categories.

Figure 3   Danish greenhouse gas emissions 1985 – 2008. Click here for background data.
 
 

Methane emission

The methane (CH₄) emission primarily originates from the livestock’s digestive processes, whereas a smaller part comes from animal manure and particularly the slurry. Biogas plants using animal slurry reduce the emission of methane and nitrous oxide and the reducing effect is included in the inventory. Field burning of agricultural residue also have to be mentioned as an emissions source, but contributes with less than 1 % of the total CH₄ agricultural emissions.

The emission from enteric fermentation has decreased mainly due to decrease in the number of cattle. Regarding emission from manure management an opposite development has taken place. Structural change in the agricultural sector and increased focus on animal welfare has led to a change towards greater use of slurry-based housing systems, which have a higher emission factor than systems with solid manure.

Nitrous oxide emission

The emission of nitrous oxide (N₂O) occurs in the chemical transformation of nitrogen and is therefore closely related to the nitrogen turnover. The major part of the emission 2008 occurs from from the nitrogen leaching and run-off (33 %), synthetic fertilisers (22 %) and animal manure applied on soil (18 %).

The reduction in total N₂O emission is strongly related to a significant fall in emissions from use of synthetic fertiliser and nitrogen leaching and run-off. This development is primarily a consequence of improvements in feed efficiency and utilisation of nitrogen in animal manure. This development has furthermore resulted in a significant decrease in the consumption of synthetic fertiliser.

Convention

Denmark has ratified the Kyoto Protocol under the United Nations Framework Convention on Climate Change (UNFCCC). Denmark has committed to reduce the emission of greenhouse gases, measured in CO₂-equivalents, by 21 % from the level in the base year of 1990 to the first commitment period 2008-2012. According to the latest emission inventory reported the total greenhouse gas emission is decreased by 7 % from 1990 to 2008.