Biochar shows promise for cleaning nitrate pollution from soil and water

Excessive use of fertilizers has fueled global food production, but it has also left behind a serious problem: nitrate pollution in soil and water. High nitrate levels threaten drinking water safety, aquatic ecosystems, and public health. Now, a new review published in Biochar highlights how biochar, a carbon-rich material made by heating plant or waste biomass, could provide an effective, low-cost, and sustainable solution.

The study, led by researchers from Auburn University and the USDA, examines how biochar can capture and reduce nitrate contamination in groundwater, agricultural soils, and wastewater. Unlike conventional methods such as reverse osmosis or ion exchange, biochar offers the advantage of being renewable, affordable, and adaptable to different environmental conditions.

“Biochar is more than a waste recycling product. Its unique porous structure and surface chemistry make it highly effective at removing nitrate from water and retaining it in soils,” said Rakesh Kumar, the study’s lead author. “This means we can improve water quality and crop productivity at the same time.”

The review highlights several ways biochar can be used in practice. When added to contaminated soils, biochar helps retain nitrate and reduces leaching into groundwater. In stormwater systems, it can work alongside filter materials to capture pollutants before they reach rivers and lakes. Biochar can also be integrated into constructed wetlands, where it boosts microbial activity and enhances natural nitrogen removal. In many cases, modified biochar materials, such as those infused with iron, achieved removal efficiencies above 80 to 90 percent.

The team also examined economic considerations. Treating nitrate pollution is often costly, with expenses for households and municipalities running into hundreds of dollars per year. Biochar, however, can be produced from locally available waste materials such as crop residues, forestry byproducts, and food waste. Cost–benefit analyses suggest that scaling up biochar use could reduce nitrate treatment costs, support sustainable agriculture, and deliver broader environmental benefits such as restoring aquatic ecosystems.

Nitrate pollution is not only an environmental issue but also a public health concern. Excess nitrate in drinking water has been linked to “blue baby syndrome,” certain cancers, and other health risks. By providing a safe and affordable way to manage nitrate, biochar could help protect vulnerable communities.

The review concludes that while laboratory and pilot-scale studies are promising, larger field trials and supportive policies will be essential. The authors recommend incentives such as subsidies and “polluter pays” principles to encourage widespread adoption.

“Biochar has the potential to be a game-changer in managing nitrate pollution,” said co-author Jasmeet Lamba. “But success will depend on strong partnerships among scientists, farmers, policymakers, and industry to bring these solutions from research into practice.”

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Journal Reference: Kumar, R., Rahman, A., Lamba, J. et al. Harnessing biochar for nitrate removal from contaminated soil and water environments: Economic implications, practical feasibility, and future perspectives. Biochar 7, 94 (2025). https://doi.org/10.1007/s42773-025-00486-8 

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About Biochar

Biochar 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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