Livestock farming contributes significantly to methane emissions in Germany, a large part of which comes from manure and digestate. Methane is a significantly stronger greenhouse gas than carbon dioxide and is driving climate change particularly quickly. To date, effective countermeasures have often been complex and cost-intensive. A research project now shows that an additive based on calcium cyanamide can reduce emissions from manure storage facilities.
The manure from pigs or cattle is an ideal place for microorganisms: “In the manure storage, microorganisms usually have free rein,” explains Christiane Herrmann from the Leibniz Institute for Agricultural Engineering and Bioeconomy eV (ATB). “They metabolize the organic material and release climate-damaging gases such as methane.” In 2023, around a fifth of methane emissions from livestock farming in Germany were due to these processes. Common measures such as sealing manure storage facilities only help to a limited extent.
In the EMeRGE project, Herrman’s team and colleagues from Alzchem Trostberg GmbH investigated the question of whether these emissions could be reduced using additives. They tested how the addition of calcium cyanamide affects the activity of the microorganisms in the manure.
Up to 97 percent less methane from the manure storage
The result: The addition of calcium cyanamide actually reduced the climate-damaging emissions from the manure. “In the summer, we were able to reduce methane emissions from cattle and pig manure by up to 97 percent. This figure results from tests on a pilot scale, but was confirmed by us through realistic tests on a 1,000 liter scale,” reports Herrmann. There was also a significant decrease at lower temperatures in winter and for digestate. However, the effect here was somewhat weaker or more additive was necessary. Nitrous oxide emissions also fell significantly during storage of the manure. , but this effect was not evident after application to the field.
But what does this mean for the microorganisms themselves? The ATB microbiologists investigated this throughout the entire process – in the manure, in the digestate and after application to the field. This showed that the composition of the microbial community changes significantly, but its tasks remain the same. Other microorganisms take over the functions of the temporarily inactive species. This means that methane formation in the biogas plant as well as important nutrient cycles in the soil continue to function.
Manure can still be easily used for fertilizer and biogas
The calcium cyanamide even gives the manure an additional advantage as a fertilizer. The nitrogen contained in the manure is converted more slowly during storage and is therefore retained by the plants for longer. This means that more nutrients are available when spreading, reducing the need for mineral fertilizer, as the researchers explain. In regions with high levels of livestock farming, fertilizer costs can be reduced by up to 22 percent in this way. According to the team, the treated manure can also be easily used for biogas plants. The microorganisms are only temporarily slowed down and resume their work later. If the manure is stored for a sufficient period of time, it can even provide more methane in the biogas plant than untreated manure because the energy potential is retained during storage.
In the next step, the researchers want to transfer their results into climate models and greenhouse gas inventories. Companies could then see in black and white what contribution they are making to climate protection and how much they can reduce their emissions through such additives. Incentive systems are also conceivable that would make their use more financially attractive in the future.
Source: Leibniz Institute for Agricultural Engineering and Bioeconomy eV (ATB)