Turning sugarcane waste into a tool for managing barium pollution in flooded soils

A study published in Biochar shows that biochar made from sugarcane straw could help scientists manage barium contamination in flooded soils, but its effectiveness depends strongly on how hot the biomass is heated during production.

Barium is a naturally occurring element that can become a concern when human activities increase its concentration in soils and waters. It is widely used in industries such as oil and gas drilling, where barite, a barium sulfate mineral, is commonly added to drilling muds. Although barite is usually considered relatively stable under oxygen-rich conditions, flooded and oxygen-poor environments can change the chemistry of soils and promote barite dissolution, releasing more bioavailable barium into the environment.

To better understand how biochar might influence this process, researchers tested sugarcane straw biochar produced at three pyrolysis temperatures: 350 °C, 550 °C, and 750 °C. The team added these biochars to soils artificially contaminated with barite and kept the soils flooded for 365 days, simulating wetland-like conditions. They then measured soil pH, redox potential, dissolved barium, and the forms of barium remaining in the soil.

“Our findings show that biochar is not a one-size-fits-all solution,” said corresponding author Jussara Borges Regitano. “The temperature used to produce biochar changes its chemistry, and that chemistry can either limit barium release or make barium more available for assisted remediation strategies such as phytoremediation.”

The study found that high-temperature biochar, especially the material produced at 750 °C, had higher carbon content, more ash, and a much larger surface area than low-temperature biochar. It also released far less dissolved organic carbon. When added to flooded soil, this high-temperature biochar raised the soil pH but did not strongly lower the redox potential, meaning it did not promote the reducing conditions that can drive barite dissolution. As a result, BC750 helped limit barium mobility risk compared with the untreated control.

In contrast, the biochar produced at 350 °C released much more dissolved organic carbon. This carbon can fuel microbial processes that make flooded soils more reducing. Under these conditions, barite dissolution increased by about 23 percent. The released barium was not mainly found in the water, but instead shifted into more labile soil fractions, meaning forms that may be more accessible for plant uptake or further remediation.

This difference points to two possible uses for sugarcane straw biochar. High-temperature biochar may be useful when the goal is to keep barium locked in place and reduce mobility in flooded soils. Low-temperature biochar, on the other hand, may be useful in assisted remediation programs designed to make barium more available for removal by plants.

The work is especially relevant for countries with large sugarcane industries and regions where wetlands or flooded soils may be affected by oil-related activities. Brazil, the world’s largest sugarcane producer, generates large amounts of sugarcane straw, a residue that can be converted into value-added biochar.

The authors note that this was an initial controlled experiment using barite-spiked soil. Future studies should test biochar-based strategies at contaminated field sites, examine long-term stability under changing environmental conditions, and evaluate possible effects on soil microbial communities.

Still, the message is clear: how biochar is made matters. By tuning pyrolysis temperature, agricultural waste such as sugarcane straw could become a more targeted tool for managing barium risks in flooded environments.

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Journal Reference: Viana, D.G., Soares, M.B., Alleoni, L.R.F. et al. Sugarcane straw biochar: effects of pyrolysis temperature on barite dissolution and Ba availability under flooded conditions. Biochar 6, 83 (2024).   

https://doi.org/10.1007/s42773-024-00371-w   

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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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