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Tannins to make cows on pasture more climate-friendly

We've heard it before, cows are agriculture's big climate sinners, but what if you could reduce methane emissions by making them graze on fields with tannin-rich plants? A researcher from the Department of Agroecology at Aarhus University has been awarded a prestigious Sapere Aude grant to investigate just that.

Carsten Stefan Malisch from the Department of Agroecology has received a prestigious Sapere Aude grant to investigate whether tannin-containing plants can reduce the climate footprint of cows. Photo: Claus Lillevang/Danmarks Frie Forskningsfond

Cows and other ruminants emit methane, a powerful greenhouse gas that affects the atmosphere 28 times more than CO2. Cows thus contribute to climate change. So, wouldn't it just be better if we stopped having cows and other ruminants in our farms altogether?

"Some people think so, but cows are actually important to our ecosystems as well as human nutrition. Ruminants are the only animals that can eat grass and other crops that we humans can't eat, and turn them into products that we can eat. This could be cheese, dairy products and meat," explains Assistant Professor Carsten Stefan Malisch from the Department of Agroecology at Aarhus University. He is one of a total of 41 talented research leaders who have received a grant for their pioneering research project from the Independent Research Fund Denmark under the Sapere Aude DFF Research Leader Programme.  

Tannin can make free-range cows more climate-friendly

Cows on pasture are the main focus of the new Sapere Aude project. And particularly multispecies grasslands play an important role in the project.

"You can have cows in a barn, feeding them, among other things, grain that could have been used as food for us humans. Cows on pasture, on the other hand, eat something that we humans cannot eat, and at the same time they create a value for the grasslands, as they remove significant amounts of carbon from the atmosphere and store it underground," says Carsten Stefan Malisch.

The problem is that cows emit more greenhouse gases into the atmosphere than grasslands can mitigate by storing carbon. That's why the new Sapere Aude research leader has chosen to focus on introducing tannin rich forages as salad burnet (Sanguisorba minor) and big trefoil (Lotus pedunculatus) in grasslands and as feed for cows.

"Tannins can interact with microbes in the soil and in the digestive system of cows. So, our expectation is that when cows eat these plants with the grass, the tannins will reduce methane production in the cows' digestive systems," he says, adding that the tannin plants have another very big advantage. They can also help increase carbon storage in the soil.

"In this way, our project can help to even out the difference between ruminant emissions of methane and soil carbon storage, so that we can contribute to a more climate-friendly and perhaps even climate-neutral milk production," says Carsten Stefan Malisch.

International team with him

Carsten Stefan Malisch won't be doing it all by himself, he has enlisted a strong international team of scientists to help him make the project a success.

"There are collaborators from Wageningen University, Turku University, ETH Zurich and Luke in Finland, as well as researchers from Aarhus University, of course," he says.

Just as the team is international, the various experiments will also be carried out in the different participating countries in order to get a more international perspective on the results.

"These results could be used in many more countries than Denmark, so it is important that we involve other research institutions. Another advantage is that the various partners have a great deal of knowledge about tannin-rich plants, experts in genetics, soil and biochemistry, which we can benefit from greatly," says Carsten Stefan Malisch.

Although the research is of international character, Carsten Stefan Malisch believes that it would not be possible to carry out the project without support from his own department at Aarhus University:

"I'm really happy to be doing this research at the Department of Agroecology. The institute is excellent at solving problems in agricultural systems at all scales, which is also shown by the department's research sections, which include "Agricultural Systems and Sustainability" and the newly established LandCraft Center. In my view, these research hubs are extremely important if we are to get the most out of small-scale research. The research here at the department helps to ensure that there will also be a practical value from the research, which will aim to make agricultural practices more climate-friendly. It is increasingly urgent that we make agriculture more climate friendly, and I believe that the Department of Agroecology is an invaluable resource for researchers like me who want to work closely with researchers from all disciplines to find synergies and ensure that we can promote the green transition in agriculture."

Circular approach to farming systems

The project fits perfectly into Carsten Stefan Malisch's research portfolio. It is especially circular farming systems that interest him, because in such systems you let the animals eat everything, we humans can't. It could be grass/hay, harvest residues or by-products, and then the animals will turn it into food we can eat, but also into fertiliser for the fields.

"Circular farming systems are more sustainable that way. The animals provide the nutrients for the fields so we don't have to fertilise with chemical fertilisers. And ruminants are particularly valuable because they can digest grass and fibre. In this way they help to minimise competition between food and feed. The only problem is that if we can't reduce their impact on the environment and climate, we can't reduce the climate impact of agriculture sufficiently," he says.

He adds that this is precisely why he is so pleased and proud to receive the Sapere Aude grant. It's not just a professional pat on the back, more importantly it's an opportunity to lay the foundations to ensure that in the future we can have systems where ruminants can continue to provide high quality and climate friendly products from circular systems with minimal food competition.

More information

Collaborators Carsten Stefan Malisch, Department of Agroecology, Aarhus University; Marica Engström, University of Turku; Wilbert Pellikaan, Wageningen University; Roland Kölliker, ETH Zurich and Bartosz Adamzyk, LUKE
Funding Sapere Aude – the Independent Research Fund Denmark - Research Leader Programme
Contact Assistant Professor Carsten Stefan Malisch, Department of Agroecology, Aarhus University. Tel: +45 93522566 or mail: cmalisch@agro.au.dk