Why liquid manure should make beef steak more expensive

Nitrogen pollution from meat production
Why liquid manure should make beef steak more expensive



by Sandra Wiebe *

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In some discussions, buffalo lovers are under pressure to justify themselves. Not only animal welfare is mentioned as an argument against meat consumption, but also the climate-damaging methane emissions from meat production. And as if that were not enough, researchers from KIT have now calculated how much environmental pollution that nitrogen from liquid manure causes is – and how much extra money actually has to be paid for meat to compensate.

In Germany, liquid manure is generally applied to arable land or grassland without pre-treatment. The nitrogen released in the process has a negative impact on the environment.

(Photo: Markus Breig, KIT)

Karlsruhe – Large amounts of nitrogen fertilizer and animal feed are used in agriculture. A significant part of the nitrogen used ends up unused in the environment, for example through leaching of nitrate from agricultural soil or through ammonia emissions from factory agriculture. Spreading liquid fertilizers releases nitrogen compounds such as ammonia and nitrous oxide into the atmosphere, which are harmful to the climate. In addition, groundwater is contaminated with nitrate via the liquid phase. “Meat production is known to have a very negative effect on the global nitrogen balance,” says Prantik Samanta of the Engler-Bunte Institute – Water Chemistry and Water Technology of KIT. However, when calculating the nitrogen footprint, it has not yet become clear how much of it is due to the amount of liquid manure produced in meat production.

“At the same time, these amounts of nitrogen mean a huge loss of resources. Recovering nitrogen is very energy-intensive, ”explains Samanta. Together with colleagues, the PhD student and first author of the study has now investigated how much nitrogen is polluted via liquid manure in beef, pork and poultry production and is lost as a raw material. In addition, they calculated how much energy was to be used to process the manure and recover nitrogen. This could again be made available as fertilizer.

Aquatic plants are important for stabilizing the clear water condition in shallow lakes.  (Photo: Solvin Zankl)

Nitrogen loss in various animal species and countries

In their calculations, the KIT researchers found that the nitrogen loss per. kilos of meat can be calculated directly using a virtual nitrogen factor, or abbreviated VNF. “The ratio between the total nitrogen intake and the corresponding nitrogen loss per kilogram of meat produced is linear,” explains Samanta. VNF relates the nitrogen loss to the nitrogen content of the meat. The largest loss is reflected in the liquid manure to be disposed of or treated.

The results show that beef production has the greatest impact on the nitrogen footprint in most parts of the world. The nitrogen loss is three and eight times higher, respectively, than with manure from pork and poultry meat production. The researchers attribute this to the cattle’s high feed requirements and high basal metabolism. They tend to attribute the loss of nitrogen in pig and poultry meat production to poor housing conditions rather than to feed and animal digestion.

In their studies, the researchers also found more countries compared.Japan releases the largest amount of nitrogen in relation to the meat consumed, followed by Australiasays lead author Samanta. “This is also due to a change in value when countries export or import feed and meat on a larger scale. As a result, the amount of liquid fertilizer to be treated per kilograms of meat, also the highest in Japan. ” USA and Europe bottom.

Meat must be up to 1.50 euros more expensive per kilo

Researchers have also calculated how much energy is required to minimize the amount of nitrogen released into the environment as much as possible. “In the production of one kilo of beef, there are 140 grams of ammonium nitrogen left in the cattle manure,” Samanta gives an example. “To recover this, we need seven kilowatt hours of energy. By comparison, Germans consume an average of about 29 kilowatt hours of electricity per week.” When treating one kilo of pig and poultry manure, the energy requirement drops significantly to less than three and 0.8 kilowatt hours, respectively.

“Our results clearly show how high the energy consumption for manure treatment would be to reduce the total nitrogen footprint in livestock farming,” says the KIT researcher. At present, this energy requirement is not taken into account in pricing: “If it were included, the price of meat would have to increase by 0.20 to 1.50 euros per kilogram, depending on the type of meat.”

Original release: Prantik Samanta, Harald Horn and Florencia Saravia: Impact of livestock farming on nitrogen pollution and the corresponding energy requirement for zero liquid emissions. MDPI Water 2022, 14 (8), 1278; DOI: 10.3390 / w14081278

* S. Wiebe, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe

(ID: 48459556)

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