All three measures help to reduce climate-impacting ammonia and greenhouse gas emissions. The amount of nutrients that are washed into deeper soil layers and into the groundwater by rain from arable soil fertilized with liquid manure or urine, known as nutrient leaching, can also be reduced with the cow toilet and slurry acidification. This has a positive impact on water quality in the agricultural landscape and protects biodiversity.
"Our results show that the combination of these measures has the potential to reduce a farm's greenhouse gas emissions by around 20% to 30%, while also reducing other environmental impacts, such as possible acidification or eutrophication of water and soil, i.e. an excess of nutrients in the environment," explains Méité. However, the study also showed that a farm using only one of the methods mentioned would have to be prepared for negative effects on its ecological footprint. This is because the combination of measures depends very much on the right management. "However, an increase in energy consumption must also be accepted when combining the measures. The sustainability effect is therefore particularly high if the measures are combined correctly and the farm uses renewable energy."
Red algae reduces methane formation in the digestive tract of cows
Methane, which is largely released during the digestion of ruminants, is a particularly potent greenhouse gas. Although it does not remain in the atmosphere for as long as CO2 , it is many times more effective on the climate than carbon dioxide. When the red algae Asparagopsis is fed to dairy cows, it helps to reduce methane production from digestion due to its high bromoform content. The first farms have been supplied with the algae in Australia since this year.
Cow toilets and slurry acidification protect the climate and groundwater
The cow toilet has only been on the market for a few years but is still little used in agriculture. It separates urine and excrement during excretion. The urine contains high amounts of ammonium nitrogen. This can be used in agriculture as a substitute for mineral fertilizers. The separation of urine primarily prevents the formation of ammonia in the barn. Slurry acidification, i.e. the addition of sulphuric acid to cow manure and urine, reduces ammonia and methane emissions when it is spread on the fields. Due to the lower ammonia formation, more nitrogen remains in the liquid manure, which means that a higher fertilizing effect can be achieved and less liquid manure needs to be spread. This in turn reduces the risk of nutrient leaching from the soil. This technology has been used in the Netherlands and Belgium for over 10 years but cannot be used in Germany without restrictions due to legal requirements and is therefore still not very widespread in this country.
Efficiency and interactions need to be investigated further
As the three measures have hardly been established in the EU to date or are still in the research and development phase, the authors argue that reliable statements on their climate impact on dairy farms are still lacking. However, such results are important to assess the reduction potential of the measures and, above all, to uncover possible negative effects on the environment.
To obtain the results, the research team used the life cycle assessment (LCA) method and assessed not only greenhouse gases but also the potential for eutrophication, i.e. the undesirable increase in nutrients in a body of water, acidification and energy consumption. In their study, the researchers modeled and compared the environmental impacts of the measures individually and in combination on two dairy farms, based on data from the federal states of Lower Saxony and Brandenburg.
Future research should test the efficiency of these measures under different agricultural conditions and assess their economic viability.
