In a recent study published in the journal BiomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More Conversion and Biorefinery, lead researcher Aleksandra Petrovič and her team explored how the vegetable oil industry might contribute to a cleaner planet. The researchers focused on hemp oil cake, a carbon-rich byproduct left over after pressing hemp seeds for oil. By subjecting this waste material to a process called hydrothermal carbonization, they created hydrochar. To make this substance better at catching pollutants, the team tested various modification methods, including the use of common “green” modifiers like alcoholic and wine vinegar. Their goal was to find a sustainable way to remove synthetic dyes from water, which is a major environmental challenge for industries like textiles and medicine.

The findings reveal that the way the hemp waste is treated significantly impacts its ability to clean water. When the researchers modified the hydrochar with potassium hydroxide, the material’s surface area exploded from a mere 1.6 square meters per gram to over 582 square meters per gram. This massive increase in surface area created more “docking stations” for dye molecules to cling to. While potassium hydroxide produced the most powerful results, the use of natural vinegars also showed impressive potential. These green modifiers introduced specific acidic groups to the material’s surface, helping it grab onto dye molecules through electrical attraction and chemical bonding. This suggests that even mild, environmentally friendly household items can turn waste into a functional tool for environmental protection.

The performance of these new materials was tested against two common industrial dyes: methylene blue and bromocresol green. The results were particularly striking for the blue dye. The best-performing material removed the dye almost entirely in less than ten minutes, eventually reaching a capacity of 640.15 milligrams of dye for every gram of adsorbent. The researchers found that the materials were most effective in specific water conditions, with blue dye removal working best in slightly alkaline water and green dye removal preferring more acidic environments. This flexibility is important because real-world wastewater often has varying chemical levels depending on the industrial process it came from.

Beyond just cleaning the water, the study highlights the safety and sustainability of using agricultural residues. Analysis showed that the materials did not contain or release toxic heavy metals, making them safe for large-scale water treatment applications. By using hemp cake and cheese whey as the starting ingredients, the process supports a circular economy where waste from food and oil production is reused rather than discarded. The team also noted that these hemp-based cleaners are comparable to, and in some cases better than, other high-tech or expensive materials used in modern water treatment. This research opens the door for more affordable and eco-friendly ways to ensure that industrial progress does not come at the cost of our global water supply.

Source: Petrovič, A., Završki, P., Paljevac, M., Vohl, S., Čuček, L., & Simonič, M. (2026). Conversion of waste from the vegetable oil industry into efficient adsorbents for dye removal: thermo-chemical modification of hydrochar with green modifiers, adsorption kinetics and mechanisms. Biomass Conversion and Biorefinery, 16(19), 1-22.