Bacteria could reduce N2O emissions from soil

BY Bárbara Pinho

Researchers have added nitrogen-hungry bacteria to farm soils, aiming to reduce greenhouse gas emissions.

When applied to soil samples from southern Norway, the nitrous oxide-consuming bacterium Cloacibacterium sp. CB-01 helped reduce N₂O emissions by up to 95%, depending on soil type, according to a recent study (Nature, DOI: 10.1038/s41586-024-07464-3). Extrapolating these results to the European level, the scientists estimate that the bacteria could help to significantly reduce anthropogenic emissions across the continent.

Agricultural soils contribute significantly to global warming by emitting N₂O, a potent greenhouse gas with a global warming potential 273 times that of carbon dioxide over a 100-year time scale. The researchers in Norway and Austria studied CB-01, a N₂O-respiring bacterium that doesn’t appear to carry antibiotic resistance genes into the soil or have any pathogenic potential.

The researchers cultured CB-01 bacteria in digestate from a wastewater treatment plant, which was already intended to be used as organic fertiliser. They applied digestate with and without CB-01 to four different types of soil collected from agricultural fields in southern Norway and measured nitrous oxide emissions after application.

They found a reduction in emissions of between 52 and 95% depending on the soil type, with CB-01 having a significantly greater effect on neutral pH soils than on two more acidic soils. The researchers also tested the digestate in field plots but found that emissions weren’t significantly reduced. They hypothesised that the fact CB-01 was more stable in the bucket trials soils could explain the large difference in results.

‘The variability in effectiveness based on soil conditions and mixed results regarding bacterial survivability indicate that further investigation is necessary,’ says Gabriele Mongiano, from the Council for Agricultural Research and Economics, in Italy, who wasn’t involved in the study.

He adds that special care must be taken regarding the effect of applying external bacterial strains on the indigenous soil microbiota but believes that the bacteria may one day play a role in reducing emissions. ‘With these factors addressed, it is not unrealistic to anticipate that farmers could one day apply CB-01 enriched fertilisers to their fields as a viable method.’