New approach can reduce laughing gas emissions from agriculture by up to 95%

Norwegian scientists have isolated a soil bacterium that eats laughing gas. With a new technique developed at the Norwegian University of Life Sciences, the bacteria can help us reduce greenhouse gas emissions from food production.

Laughing gas is often called “the forgotten greenhouse gas”. However, it is the third most important greenhouse gas after CO2 and methane. It warms the earth around 300 times more than CO2 and damages the ozone layer. Most of the emissions come from agriculture, from the production and use of fertilizer.

Researchers at the Norwegian University of Life Sciences (NMBU) have now found a new way of reducing these emissions using special bacteria in the soil that can eat the laughing gas. Fresh figures from a field study show very promising results. The bacteria reduced N2O emissions from the soil by between 40 and 95 per cent.

“We find these results incredibly exciting. The new method could provide us with a powerful new tool in the fight against global warming,” says Elisabeth Gautefall Hiis, a PhD-student on the project at NMBU.

Urgent need for new solutions

Nitrogen-based fertilizers are used for crop cultivation worldwide. These fertilizers are crucial for our ability to produce enough food for the global population.

There are many bacteria in the soil that absorb nitrogen. Unfortunately, these bacteria also produce the greenhouse gas nitrous oxide, also called laughing gas, when they ‘eat’ the nitrogen, causing the gas to leak from the soil. The more we fertilize with nitrogen, the more of this greenhouse gas seeps into the atmosphere. This happens whether we use chemically produced artificial fertilizers or organic livestock manure.

The amount of laughing gas in the atmosphere has been stable for thousands of years, but in the last 200 years, the quantity has increased significantly – in line with the growing global population and our increased food production, hence the addition of more artificial fertilizers. There is little to suggest that this trend will reverse.

“There is a real need for new solutions,” says Hiis. “We have a major challenge because we need to maintain global food production while reducing N2O emissions.”

One-armed bandit to the rescue

The solution may lie among the same bacteria that produce laughing gas in the soil. In addition to the bacteria that create the gas, there are also some that can consume it and convert it into harmless nitrogen gas. However, finding the right bacteria is not easy.

“Soil is a very complex matter to work with,” says Hiis. In just one teaspoon of soil, there are billions of bacteria. The task of finding the right ones has been laborious and time-consuming.

“Some of the bacteria we initially looked at can both eat and produce nitrous oxide. That made it complicated. One bacterium, for example, would eat nitrous oxide in the laboratory, but once it was in the soil, it had little effect.”

The bacteria they finally chose to use in field trials is called Cloacibacterium sp. CB-01.

“We call it a one-armed bandit,” says Hiis. “It simply does not have the gene to produce nitrous oxide, it can only eat it.”

Developed a unique robot

After identifying the right bacteria, the NMBU researchers have been cultivating these in the lab and testing them out in the soil. They have a dedicated research area at a field called Kjerringjordet, just outside of the campus in Ås, Norway, where they can examine how effective the bacteria are in various types of soil.

They can then measure the greenhouse gas emissions from the individual soil samples. This is done using a specially developed robot that can measure greenhouse gas emissions directly from the soil.

Quantity matters

To reduce nitrous oxide emissions from the soil, large amounts of nitrous oxide-eating bacteria need to be introduced. This would be very complicated and costly if the bacteria were to be cultivated conventionally. The solution NMBU researchers came up with is to let them grow in organic waste, before using this as fertilizer and soil conditioner.

Astounded by the results

In the summer of 2021, the researchers conducted a major field trial at Kjerringjordet fields. They set up two rows of large pots with soil. In half of the pots, the soil was mixed with the new super-fertilizer containing nitrous oxide-eating bacteria. In the other half of the pots, the soil received the same type of fertilizer, but without the special bacteria.

• Read more
• (Nature, 2024; doi: 10.1038/s41586-024-07464-3)
• “New method could reduce agricultural greenhouse gas emissions”

Source

NMBU / Norwegian University of Life Sciences 2024 | By Tonje Lindrup Robertsen