How much nitrogen is emitted at livestock farms?
Twenty-nine percent of nitrogen from livestock feed was converted by cattle into products such as meat, milk and eggs. The rest of the nitrogen disappears into the manure. There has been hardly any improvement in animals’ ability to process nitrogen since 2000.
Nutrients in livestock feed, such as nitrogen and phosphorus, are absorbed by cattle to a limited extent. This is referred to as use-efficiency. The nitrogen thus absorbed ends up in meat, milk or eggs. What animals do not absorb disappears largely with the manure in the soil or the air. In the early 1990s, nitrogen use-efficiency stood at 21 percent, and increased to 26 percent in the years 2000–2001. After that, use-efficiency improved only slightly.
Use-efficiency rose to 27 percent in 2004–2006, to 28 percent in 2007–2010 and to 29 percent in 2011. There has been no improvement since then.
|Cattle (meat and milk)||Pigs (meat)||Poultry (meat and eggs)||Other animals|
Not all animals convert nitrogen equally efficiently. Nitrogen use-efficiency was highest in poultry at 42 percent. In the case of pigs, use-efficiency is 39 percent and in beef cattle only 23 percent. Use-efficiency rates have improved very moderately since 2000. Beef cattle use-efficiency was still 19 percent in 2000; in pigs this was 35 percent and in poultry 41 percent.
Nitrogen use-efficiency depends on composition of feed
Cattle feed consists of concentrates and roughage. The amount of nitrogen in concentrates was 420 million tonnes in 2018, i.e. 3 percent less than a year earlier. Grass, hay and silage maize contained 274 million kg of nitrogen, basically as much as in 2017.
The supply of nitrogen to livestock farms depends on both the size of the herd and the ratio of concentrates to roughage. For example, a kilo of grass or a kilo of concentrates contains up to almost three times as much nitrogen as a kilo of silage maize. If less maize is harvested, due to a disappointing harvest or a smaller maize acreage, as was the case in 2018, and the animals are fed more concentrates and grass, the roughage will contain more nitrogen.
|Year||Concentrates for cattle||Concentrates for pigs||Concentrates for poultry||Concentrates for other animals||Roughage for cattle||Roughage for other animals|
Less nitrogen lost
According to the nutrient budget, 711 million kg of nitrogen were supplied to livestock farms in 2018. Of this, 207 million kg was converted into animal products. The unused nitrogen – 504 million kg or 71 percent of all nitrogen supplied – disappeared into plants (352 million kg), the soil, the air, outside agriculture or they were part of inventory movements. In 2000, this was still 549 million kg, or 74 percent of the used nitrogen. The decrease is partly due to the more efficient application of fertiliser in arable farming. In addition, less nitrogen volatilised from animal houses and manure storage. The fact that less nitrogen was volatilised is also the result of a stricter manure policy that prescribed use standards for nitrogen.
Nitrogen emissions under production ceilings
In 2019, nitrogen excretion in livestock manure was 490 million kg. This is 14 million kg below the established nitrogen ceiling of 504.4 million kg. Last year, nitrogen excretion at dairy farms amounted to 281 million kg, just under the output ceiling (281.8 million kg) for this sector. Nitrogen excretion in the pig farming sector came to 94 million kg in 2019. This is also well under the nitrogen output ceiling of 99.1 million kg. Last year, the Dutch poultry sector produced 54.5 million kg of nitrogen excretions, well below the output ceiling of 60.3 million kg.