Rewetting peatlands plus biochar could turn major carbon sources into climate solutions

A new study shows that combining water management with biochar application could transform drained agricultural peatlands from greenhouse gas emitters into powerful carbon sinks, offering a promising pathway for climate change mitigation.

Peatlands store vast amounts of carbon accumulated over thousands of years. However, when drained for agriculture, these soils release large quantities of greenhouse gases, including carbon dioxide and methane. Scientists have long sought practical ways to reverse this process, but restoring peatlands often comes with trade-offs, particularly increased methane emissions.

Now, researchers have demonstrated that pairing rewetting strategies with biochar amendments can overcome this challenge.

“Our findings show that biochar can fundamentally shift peat soils from emitting greenhouse gases to actively removing them from the atmosphere,” said the study’s lead author. “This provides a realistic and scalable option for climate mitigation in agricultural landscapes.”

In the study, scientists conducted a year-long experiment using peat soil cores under controlled conditions. They tested different water table levels along with a range of organic amendments, including biochar, plant residues, biosolids, and paper waste. They also examined the effect of adding iron sulfate, a compound that can influence microbial processes in soils.

The results were striking. Raising the water table alone reduced carbon dioxide emissions by limiting decomposition, but it also increased methane emissions due to oxygen-poor conditions. This trade-off meant that rewetting by itself did not significantly reduce overall greenhouse gas emissions.

Biochar, however, changed the picture dramatically.

Derived from plant biomass through pyrolysis, biochar is a stable, carbon-rich material. When added to rewetted peat soils, it not only contributed additional carbon but also suppressed emissions of both carbon dioxide and methane. Compared to untreated soils, biochar reduced methane emissions by up to four times and significantly lowered carbon losses.

The study found that biochar-amended soils achieved the strongest net carbon gains among all treatments tested. Over one year, biochar additions resulted in much lower carbon losses compared to other organic materials, which tended to decompose quickly and release greenhouse gases.

In contrast, more labile materials such as straw, biosolids, and paper waste increased emissions, particularly methane. These materials provided easily available carbon for microbes, accelerating decomposition and offsetting any potential climate benefits.

The researchers also discovered that adding iron sulfate further enhanced the performance of biochar. This combination reduced methane emissions even more by providing alternative pathways for microbial metabolism, limiting methane production in waterlogged soils.

Overall, the most effective treatment, combining biochar, high water levels, and iron sulfate, produced a strong net removal of greenhouse gases. The climate benefit was substantially greater than that of rewetting alone and compared favorably with other land-based carbon mitigation strategies.

The study highlights an important insight: not all organic amendments are beneficial for climate mitigation in peat soils. The type and stability of carbon inputs play a critical role in determining whether soils act as carbon sources or sinks.

While the researchers note that long-term effects and life-cycle emissions of biochar production were not fully assessed, the findings provide strong evidence that biochar-based strategies could play a key role in achieving net zero targets.

Peatlands cover only a small fraction of the Earth’s surface but store more carbon than all the world’s forests combined. Protecting and restoring these ecosystems is increasingly recognized as essential for climate action.

This study suggests that with the right management approach, degraded peatlands could not only stop emitting carbon but actively help remove it from the atmosphere.

“Our work shows that it is possible to overcome the traditional trade-off between carbon storage and methane emissions,” the authors said. “With biochar, peatlands can become a win-win solution for climate and agriculture.”

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Journal Reference: Jeewani, P.H., Brown, R.W., Rhymes, J.M. et al. Greenhouse gas removal in agricultural peatland via raised water levels and soil amendment. Biochar 7, 39 (2025).     

https://doi.org/10.1007/s42773-024-00422-2   

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About Biochar

Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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