Turning lavender waste into a high-performance sensor for safer ethylene glycol detection

A new study has shown that agricultural waste from lavender straw can be transformed into a highly sensitive biochar-based sensor for detecting ethylene glycol, a widely used but potentially toxic chemical found in products such as antifreeze and industrial solvents.

Published in Biochar, the study reports a green and controllable strategy for engineering the tiny pores and surface defects of biochar derived from lavender straw nanocellulose. By carefully adjusting the hydrolysis time during material preparation, the research team created a sensor material that can detect ethylene glycol at room temperature with high sensitivity, a low detection limit, and long-term stability.

“Our work shows that agricultural residues can be more than waste. With precise structural design, they can become advanced functional materials for public safety and environmental monitoring,” said corresponding author Professor Zhaofeng Wu of Xinjiang University. “The key was learning how hydrolysis time controls the internal structure of the biochar.”

Ethylene glycol is commonly used in antifreeze, polyester production, and other industrial processes. However, exposure to ethylene glycol can pose health risks, including effects on the central nervous system and damage to multiple organs. Fast and reliable detection is therefore important for workplace safety, automotive maintenance, industrial inspection, and environmental monitoring.

The team selected lavender straw, an underused agricultural residue from Xinjiang, as the starting material. Lavender straw has a loose fibrous structure and naturally contains calcium, making it suitable for producing biochar with useful sensing properties. The researchers first extracted nanocellulose from the straw using an oxalic acid and acetic acid hydrolysis process, then converted it into biochar through carbonization.

The most important finding was that hydrolysis time acted as a structural “control knob.” When the treatment time was too short, the nanocellulose did not fully separate, limiting pore formation. When the treatment was too long, the structure became damaged and compacted. A moderate hydrolysis time of 3 hours produced the best material, named CLN-3.

CLN-3 formed an open mesoporous network with a specific surface area of 46.36 m² g⁻¹ and abundant oxygen-related surface sites. These features helped ethylene glycol molecules enter the material, interact with the surface, and trigger a strong electrical response.

In testing, the CLN-3 sensor showed an exceptional response of 17,576.67% toward ethylene glycol at room temperature, with a low detection limit of 0.36 ppm. It also maintained stable operation over 40 days and showed repeatable performance over multiple sensing cycles. Compared with many conventional ethylene glycol sensors that require elevated operating temperatures, this room-temperature performance could help reduce energy use and support portable or on-site detection devices.

To better understand why the material performed so well, the researchers combined experimental testing with density functional theory calculations. The calculations showed that naturally present calcium in the lavender-derived biochar enhanced the adsorption of ethylene glycol, increasing adsorption energy from −0.13674 eV to −0.39508 eV when calcium doping and pre-adsorbed oxygen worked together. This stronger interaction promoted charge transfer at the sensor surface, improving the sensing signal.

“The synergy between pores, oxygen vacancies, and natural calcium doping gives the biochar its strong sensing ability,” said corresponding author Hua Zhuo. “This provides a practical design principle for developing low-cost sensors from biomass resources.”

The researchers also demonstrated the sensor’s potential for antifreeze detection in laboratory tests. While further calibration and field validation are still needed for complex real-world environments, the study offers a promising route toward sustainable, low-cost, and sensitive detection technologies.

By converting lavender straw into a functional sensing material, the work highlights a broader opportunity: agricultural byproducts can serve as valuable building blocks for next-generation environmental and safety monitoring devices.

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Journal Reference: Gong, Y., Liang, C., Sun, Q. et al. Hydrolysis time-controlled pore and defect engineering in nanocellulose-derived biochar for enhanced ethylene glycol sensing. Biochar 8, 110 (2026).   

https://doi.org/10.1007/s42773-026-00624-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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