New method could reduce agricultural greenhouse gas emissions


Forsker viser fram bakterieprøver på laboratoriet
Forskerne ønsker å bruke bakterier til å redusere klimagassutlipp fra landbruket. Photo: Tonje Halvorsen Walde

Norwegian researchers aim to use soil bacteria to cut greenhouse gas emissions from food production. Their research is now published in Nature.

Nitrogen fertilization leads to emissions of the greenhouse gas nitrous oxide (N2O) from agricultural soils, accounting for a significant portion of agriculture's total greenhouse gas emissions. It has been a prevailing belief that these nitrous oxide emissions are inevitable.

Now, researchers at NMBU have found a way to reduce these emissions. They have identified bacteria that can "consume" nitrous oxide as it forms in the soil, preventing the gas from escaping into the atmosphere. The researchers believe that this method alone has the potential to reduce European nitrous oxide emissions from agriculture by a third.

The research is also attracting interest outside of Norway. On May 29, 2024, it was published in Nature, one of the world's most respected scientific journals.

A Breakthrough

Lars Bakken is a professor at NMBU and led the study.

"This is a pleasant recognition that we have truly achieved something. Publishing in Nature shows that we have made a breakthrough in our efforts to reduce N2O emissions to the atmosphere, and that the knowledge base for our solution is solid," says Bakken.

In the peer review of the study at Nature, one of the external experts writes:

" The authors have conducted outstanding fundamental research on bacterial N2O-reduction, and they transitioned these findings to an important real-world application. This is an important contribution with transformative character and a biotechnology to curb N2O emissions has far-reaching implications."

“The study now published in Nature shows how important it is for us as a society to invest in fundamental research. The results are based on research that started almost 20 years ago and now we are beginning to see the potential it has to help solve important societal challenges. It is an incredible recognition to be published in Nature, and I am very proud that our researchers here at NMBU are taking such a clear role in these important issues," says Sigrid Gåseidnes, dean of the Faculty of Chemistry, Biotechnology and Food Science at NMBU.

Forfatterne av artikkelen på laboratoriet
Authors of the Nature-study. From the left: Lars Bakken, Lars Molstad, Elisabeth Gautefall Hiis, Kjell Rune Jonassen and Kristine Røsdal. (Not in the picture: Silas H. W. Vick and Wilfried Winiwarter) Photo: Tonje Lindrup Robertsen

The Nitrous Oxide Problem

Plants need a lot of nitrogen to grow. A productive agriculture, therefore, requires an abundant supply of nitrogenous fertilizer. This was a bottleneck in agriculture until Fritz Haber developed technology for industrial production of nitrogen fertilizer from atmospheric nitrogen. This technology has contributed to the world's food production keeping pace with population growth for 120 years.

However, there are microorganisms in the soil that produce the greenhouse gas nitrous oxide (N2O), and fertilization stimulates this production. This greenhouse gas has 300 times stronger effect than CO2, and N2O emissions from agricultural land currently account for about a third of agriculture's total greenhouse gas emissions.

Agriculture has thus become the most important contributor to nitrous oxide in the atmosphere.

Because it is the bacteria in the soil that regulate nitrous oxide emissions, it has proven very difficult to reduce these emissions. Soil bacteria are difficult to control.

Bacteria Can Do the Job

Researchers at NMBU have been conducting basic research for over 20 years on how microorganisms in the soil convert nitrogen. They have, among other things, thoroughly studied what happens when the microbes do not have access to enough oxygen, a condition called hypoxia.

When we fertilize (and when it rains), some parts of the soil become hypoxic. Since the microbes then do not have access to oxygen, they are forced to find other ways to get energy. Many microbes can use nitrate instead of oxygen, and through a process called denitrification, they convert the nitrate into other gases. One of these is nitrous oxide, and in this way, the microorganisms contribute to greenhouse gas emissions.

The researchers have found out a lot about how this process is regulated, and they have developed a unique way to study denitrification. They use, among other things, robotic solutions both in the laboratory and in the field, and have developed a special robot that can make real-time measurements of nitrous oxide emissions from the soil.

The solution to reduce nitrous oxide emissions is to use a special type of bacteria that lacks the ability to produce nitrous oxide but can reduce nitrous oxide to harmless nitrogen gas (N2).

"If we grow these microbes in organic waste used as fertilizer, we can reduce nitrous oxide emissions. This could mean a solution to the problem of nitrous oxide emissions from agriculture," says Lars Bakken.

"But it was not easy to find the right bacterium. It must be able to grow quickly in organic waste, function well in soil, and live long enough to reduce N2O emissions through an entire growing season. It was also a challenge to go from testing this in the laboratory to trying it out in nature, and to ensure that it actually reduced nitrous oxide emissions in the field.

Read more about the method and experiments in this case: New method can reduce nitrous oxide emissions from agriculture by 95 percent.

Potential for All of Europe

The research team is now working to find more bacteria that consume nitrous oxide and to test these in different types of organic waste used as fertilizer worldwide.

The goal is to find a wide range of bacteria that can function in different types of soil and with various fertilizer mixtures. In the Nature article, they write that this method alone has the potential to reduce European nitrous oxide emissions from agriculture by up to a third.

In March 2024, they started a new research project to take the biotechnological solutions further. The project is supported by the Research Council and industrial partners are VEAS, Yara, and N2Applied.

The Way Forward

The research team has big plans for the future.

"We will make the technology more robust by finding more bacterial strains, and above all measure the effect on N2O emissions under varying conditions. Scaling up from field experiments to agriculture will be a major challenge. We will also develop technology that makes it possible to create fertilizers that contain N2O-eating bacteria. This can become a major product internationally," says Lars Bakken.

He says that going forward they will recruit more researchers and continue to find new bacteria that can be suitable for a wide range of organic waste.
"We will intensify the work to make it possible to use the technology in practical agriculture. It is not trivial," he says.

"We will also create a new generation of field robots for measuring nitrous oxide. We will do this together with the mechatronics company ADIGO, which is a pioneer company for the robotization of agriculture, and which made our first field robot 15 years ago. It is still the only one of its kind in the world, but old, tired, and a bit cumbersome.

He emphasizes that the need for new and better field robots is urgent.

"We need them to document the effect of our measures against N2O emissions under realistic agronomic conditions. We are now looking for fresh money for developing the new generation of field robots. To serve our own research, but we expect international interest, and thus a market.

Bakken believes there are two things that must be in place before the technology can be used by all farmers in Europe:

"First and foremost, we need to find practical solutions, and then we must be able to document that it actually reduces N2O emissions under realistic agronomic conditions. Such documentation is incredibly important: the prerequisite for our technology to be used is that the authorities establish incentives (stick or carrot) that ensure profitability for the farmer. The authorities will not introduce such incentives until they know that it works; understandably so."

Professor Lars Bakken i arbeid på laboratoriet
NMBU-professor Lars Bakken. Photo: Alexander Benjaminsen

About the Nature-paper

The article "Unlocking bacterial potential to reduce farmland N2O emissions" was published in Nature on May 29, 2024.

Also, see Nature News and Views: Nitrogen-hungry bacteria added to farm soil curb greenhouse-gas emissions


From NMBUs Faculty for Chemistry, Biotechnology and Food Science: Lars R Bakken, Elisabeth Gautefall Hiis, Silas H. W. Vick, Lars Molstad, Kristine Røsdal

From VEAS WWTP, Slemmestad: Kjell Rune Jonassen

From International Institute for Applied Systems Analysis in Austria and Institute of Environmental Engineering ved University of Zielona Góra in Poland: Wilfried Winiwarter

Nitrous oxide/laughing gas

  • Nitrous oxide is considered the third most important greenhouse gas, after CO2 and methane.
  • Nitrous oxide has the chemical formula N₂O and its chemical name is dinitrogen oxide.
  • In Norway, most of the man-made nitrous oxide emissions come from the use and production of fertiliser.
  • Both nitrogenous mineral fertiliser (artificial fertiliser) and animal manure lead to emissions of nitrous oxide.
  • In 2020, 77 percent of nitrous oxide emissions came from the use of fertiliser and other sources in agriculture, while 10 percent came from industrial production of mineral fertiliser. This is shown by figures from Statistics Norway (SSB).

About the research group NMBU Nitrogen Group

  • Researchers in the NMBU Nitrogen Group (NMBUNG) have been conducting strategic basic research on microbial nitrogen turnover for 20 years.
  • This is to understand the ecology and physiology of microbes, and especially how they cope with hypoxia, i.e., lack of oxygen. The regulatory response to hypoxia plays a key role in N2O emissions from soil: Every time it rains, and every time we add organic fertiliser, parts of the soil volume become hypoxic, forcing the bacteria to find a substitute for oxygen. Many bacteria can use nitrate (NO3-) as a substitute for oxygen, reducing it step by step to N2 via N2O. This is called denitrification. Through research on the genetic and regulatory basis of denitrification, NMBUNG has established an important knowledge base.
  • The research group has also developed a unique experimental platform, with robotic solutions for both the laboratory and for measuring N2O emissions in field experiments. Both are important prerequisites for the group's finding a possible solution to agriculture's N2O problem.
  • The researchers have found a denitrifying bacterium that lacks the genes for producing N2O and is therefore a net "sink" for N2O: Such an N2O-respiring bacterium (NRB) cannot produce N2O, but can "consume" N2O produced by other bacteria. NRB is cultivated in organic waste, which is then used as fertiliser, thus reducing N2O emissions.
  • It has taken a long time to find a suitable NRB: it must be able to grow to about one billion per g in the organic waste, be active in soil, and above all, survive long enough to reduce N2O emissions throughout an entire growing season.
  • Another challenge has been to "scale up" from laboratory to field experiments, and especially to document robust reduction of N2O emissions in the field.

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