Cow Toilet urinatie zij aanzicht

Cow toilet can significantly reduce nitrogen emissions from dairy barn

Hanskamp Agrotech's CowToilet can significantly reduce nitrogen emissions from the dairy barn, according to research by Wageningen Livestock Research. After one year of measurement, emissions of total nitrogen, ammonia, nitrous oxide, and nitrogen gas, including estimated losses during urine storage, were 38%, 33%, 18%, and 43% lower, respectively, compared to a reference barn.

16-11-2023 | 15

A detailed nitrogen balance drawn up over one year showed that 9.2% of the cows' nitrogen excretion from the barn was lost. Accompanying emission measurements show that 4.1% was lost as ammonia (6.8 kg ammonia cow-1 year-1) and 0.14% as nitrous oxide. It follows that the rest of the loss, 4.9%, must have been due to nitrification-denitrification in the manure cellar under the floor, and was lost as non-reactive nitrogen gas (N2).

Reduction of nitrogen emissions

When comparing the barn with the CowToilet to a reference barn without the CowToilet, emissions per nitrogen form for total nitrogen, ammonia, nitrous oxide, and nitrogen gas were on average 41%, 39%, 18%, and 43% lower, respectively. These results are somewhat biased because the urine collected was immediately discharged from the barn and therefore did not contribute to the emissions from the barn, whereas the reference did. Including an estimate for this emission, under low-emission storage, nitrogen emissions were 38%, 33%, 18%, and 43% lower, respectively.

Collection of urine

The results of this study show that significant reductions in nitrogen emissions from the dairy barn can be achieved with emission-reducing systems over long periods. "It is mainly the urea in urine that is responsible for nitrogen emission from the dairy shed and from the land. Collecting part of the urine, as with the CowToilet, can therefore significantly reduce nitrogen emissions," says researcher Herman de Boer. "We measured both the total nitrogen loss and the composition of this loss, over a one-year period, linked to the amount of urine collected, and compared it to a reference barn. This makes the CowToilet the most extensively validated emission-reducing system today."

Possible improvement

During the measurement year, an average of 10.1 litres of urine per cow per day was collected, 35% of the estimated urine production of the cows. The reduction in nitrogen emissions was therefore somewhat larger for total nitrogen loss (-38%) than the proportion of urine collected, and somewhat smaller for ammonia emissions (-33%). By making adjustments to the CowToilet, the amount of urine collected could potentially be further increased, reducing emissions further.

Comparison with other barn systems

The CowToilet was one of barn systems in a study on the effects of source separation in the dairy barn on emissions and manure quality, within the public-private project 'Manure separation in dairy barns'. It was funded by ZuivelNL and the Ministry of Agriculture, Nature and Food Quality. The research on barn systems was conducted in 2020/2021 in the Environmental Measurement Barn at pilot facility Dairy Campus in Leeuwarden, under conditions representative of a regular slatted floor dairy barn.

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