Nitrogen from pig production can be vaporised into air in the form of ammonia. In Denmark, we have been focusing on this problem, and since 1985, the industry has succeeded in reducing the environmental impact per kg slaughter pig by 50 per cent.
Nitrogen (or "N" which is the chemical symbol for "Nitrogen") is an important nutrient for plants and forms a part in amino acids which serve as the building stones for proteins.
In relation to pig production, nitrogen is vaporised in the form of ammonia from pig houses and manure pits into air where it may for example affect the nature.
There is heavy emphasis on reducing the emission of ammonia into the air and pig production has therefore reduced the nitrogen emission per slaughter pig from 4.4 kg N in 1992 to 2.8 kg in 2012. In overall terms, the ammonia emission from pigs has fallen by 39% since 1990. In the same period, the production of pork has increased by 51%.
The development of breeding work and pig feed plays a major role for the reduction of ammonia
Some of the most significant factors behind the reduction of ammonia emissions from pigs are improvements of the agricultural sector’s breeding work and feed optimisation. Moreover, a change in the spreading of manure where the manure is either spread through hoses or is ploughed in has also contributed to reducing ammonia emissions.
When manure is spread, nitrogen is fed into the field thereby fertilising the crops. Depending on the amount of nitrogen spread onto the fields, the vegetation of the plants, the way the manure is spread, the weather etc., some of the nitrogen can be carried away into lakes and waterways.
For nitrogen, the environmental impact per produced kg slaughter pig has fallen to approx. 50 per cent of the level in 1985. Among other things, this has occurred through optimisation of the feed for the pigs, the breeding work and improved handling of the manure. Furthermore, more strict rules have been enforced for how much nitrogen you can release into the fields, for example through the so-called harmony criteria.