Pig farming: Less ammonia emissions from the stable
Even simple measures such as cooling the manure or reducing its surface area have proven effects: the emission of harmful gases, especially ammonia, from fattening pig stalls can be reduced. This is an interim result from the University of Hohenheim in Stuttgart in the joint project “Reducing emissions from livestock farming”, EmiMin for short. With a good 2 million euros in federal funding, the sub-project at the University of Hohenheim is a research heavyweight.
Excessive production of ammonia and climate-impacting gases such as methane, carbon dioxide and nitrous oxide from livestock farming can put a strain on people, animals and the environment. But even with relatively simple measures, these can be reduced under normal husbandry conditions, according to an interim result in the joint project “Emission Reduction for Farm Animal Husbandry” (EmiMin).
Prof. Dr. Eva Gallmann, agricultural engineer at the University of Hohenheim, and her team are researching how structural and technical measures available on the market, in particular ammonia emissions, can be reduced in fattening pig stalls. The researchers' focus is on cooling the manure and reducing the size of the manure channel, also in combination with other measures, for example feeding.
They test both procedures for their effectiveness at two locations. In each case, a stable compartment with a built-in reduction measure is compared with a reference compartment without a reduction measure. “Initial results show that both methods not only reduce emissions, but also improve the stable climate,” says Prof. Dr. Gallmann. “Sophisticated animal husbandry technology ensures good air in the stable. This is good for animal health and well-being – and good for the environment.”
The main problem is ammonia
Closed, thermally insulated fattening pig houses with fully slatted floors in particular have a higher emission potential for ammonia. “There, the manure is usually stored below the slatted floor throughout the entire fattening period. This large surface area, together with the long storage period and the large storage quantity as well as the comparatively high temperatures in the stable, promote the emission of ammonia,” explains Lilly Wokel, doctoral student in the field of process engineering of animal husbandry systems at the University of Hohenheim.
That's why the researchers are particularly interested in the possibilities of cooling manure and reducing the size of the manure channel in closed fattening pig houses, where the exchange with the ambient air takes place via fans. They primarily rely on conversion solutions for existing stables. “According to our measurements in a direct comparison of the stable compartments with and without reduction technology, there is a reduction potential of between 10 and 60 percent for ammonia,” says Prof. Dr. Gallmann. “In detail, of course, this also depends heavily on the time of year and the fattening phase and fluctuates over the course of the year.”
Manure cooling reduces emissions
The temperature of the slurry has a major influence on the formation of harmful gases: “By lowering the slurry temperature to below 15 °C, the chemical-biological processes occurring in the slurry can be reduced, which contributes to a significant reduction in emissions,” explains Lilly Wokel .
One way to reduce the temperature in the slurry is through cooling pipes, which are concreted into the bottom of the slurry channel when the stable is built. In existing stables, cooling fins are used that float in the manure in the manure channel. “They are easy to retrofit and have a positive effect on the stable climate,” says the scientist.
Cooled water circulates through the ribs in a closed circuit and absorbs the heat from the manure. This is released again via a heat pump and can be used in other areas of the stable, for example as heating for lying areas or in rearing piglets. In this way, the energy required for cooling can be partially compensated.
Reduction of the slurry channel by installing slurry trays
A slightly larger structural change requires the installation of a partial slatted system in combination with a reduction in the size of the manure surface. The animals' pens are divided into different functional areas. With differently designed lying, eating and defecating areas, the animals are encouraged to only urinate and defecate in a small area that is equipped with gaps.
“Pigs usually place their defecation area away from the resting area and, if they have the opportunity, also away from the feeding area,” says Prof. Dr. Gallmann. “If I assign these functions accordingly and provide enough space for each function, then they do this on their own.” Clean bays can also reduce the size of the dirty or emitting surface and reduce the formation of harmful gases.
There are V-shaped trays under the slatted areas, which have a smaller surface area than a conventional manure channel. If these tubs are emptied as often as possible, not only is the surface area further reduced, but the amount of manure stored in the stable is also significantly reduced.
Relevant reduction potential on ammonia emissions
Both measures examined have a relevant potential to reduce ammonia emissions. “But we also see that the general conditions play a big role,” explains Lilly Wokel: “A lot depends on the structural conditions, for example how well the liquid manure can drain away or whether solid material might build up on the cooling fins. But how often cleaning is carried out and how the behavior of the animals in the stable can be controlled also plays a role.”
Next, the data from the optimization phase is evaluated. The researchers examined whether the combination with other feeding measures or the addition of acid whey to the manure enables a further reduction in emissions, especially for the stable compartments without structural and technical measures. “Ultimately, we also have to offer practical solutions that can be implemented quickly and comparatively cheaply in a first step.”
BACKGROUND: Project to reduce emissions from livestock farming (EmiMin)
EmiMin launched on July 1, 2018 and is designed to run for five years. In addition to the University of Hohenheim, the alliance partners are the Board of Trustees for Technology and Construction in Agriculture. V. (KTBL), which is also in charge of the project, the Christian Albrechts University of Kiel, the University of Bonn, the Leibniz Institute for Agricultural Engineering and Bioeconomy eV (ATB) and the ZB MED - Information Center for Life Sciences in Cologne. The EmiMin project was funded using funds from the federal government's special purpose assets at the Agricultural Pension Bank on behalf of the Federal Ministry of Food and Agriculture (BMEL). The project is being funded with a total of around 9 million euros, of which a good 2 million euros will go to the University of Hohenheim.
