Testing food for pesticides or heavy metals is a messy, but essential, job. Before a sample can be analyzed, it must be “cleaned up” to remove all the fats, proteins, and sugars that interfere with the results. This cleanup step, often referred to as sample preparation, is one of the most resource-intensive parts of analytical chemistry, frequently relying on synthetic, petroleum-based materials and harsh solvents. In the push for “green” chemistry, scientists are turning to an unlikely hero: biochar. In a comprehensive review published in Talanta, researchers Carla Iglesias-Martín, Ana M. Ares, José Bernal, and Adrián Fuente-Ballesteros investigate the application of biochar as a sustainable tool for food analysis. They categorize the wide world of biochar based on its origin, revealing what works, what doesn’t, and where the “green” label falls short.

Biochar is the perfect poster child for a circular economy. It takes low-value agro-industrial waste (think fruit peels, nut shells, and straw) and turns it into a high-value analytical tool through a heating process called pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More. With the UN reporting over a billion tons of food wasted in 2022, there is no shortage of raw material. This review found that the use of biochar in food analysis is a growing field, with researchers applying it to a wide range of samples. Drinking water (32%) and fruits & vegetables (30%) are the most common matrices studied. The biochar is typically used in solid-phase extraction (SPE) or its magnetic variant (MSPE), which together account for nearly 40% of applications, acting like a tiny, specialized sponge to trap contaminants.

A major pillar of “green” chemistry is reusability, and here the review’s findings are stark. The ability to reuse a sorbent is critical to its cost-effectiveness and environmental footprint. The researchers found a massive range in performance depending on the biochar’s source. The champions of sustainability were bamboo and corncob biochars, which researchers reported could be reused up to 100 times without a significant drop in performance. Biochars from cotton fibers (90 cycles) and glucose (80 cycles) also proved highly durable. At the other end of the spectrum, biochars made from peanut shells and shungite (a mineral) could only be reused 4 times. This finding is crucial: not all biochars are created equal, and choosing a feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More like bamboo over peanut shells can make the method 25 times greener.

However, the review uncovers a significant contradiction in this “green” field: the solvent problem. A green sorbent is useless if you need a hazardous chemical to remove the trapped contaminants. The review found that acetonitrile is the most commonly used desorption solvent, accounting for 36% of the methods studied. According to the CHEM21 solvent guide, acetonitrile is classified as “problematic”. Even worse, 10% of studies used “hazardous” dichloromethane, and 3% used “highly hazardous” hexane. This reliance on toxic solvents contradicts the core principles of Green Analytical Chemistry, thereby undermining the environmental benefits of using biochar in the first place.

The review’s feedstock-oriented approach also revealed that fruit waste is the most popular source material, used in 33% of all studies. This category, which includes banana peels, pomelo peels, and coconut husks, has been tested on a range of products, from fruit juice and tomato paste to breast milk. While promising, the field faces significant hurdles. A key challenge is the lack of reproducibility; biochar’s properties can vary wildly based on the pyrolysis conditionsThe conditions under which pyrolysis takes place, such as temperature, heating rate, and residence time, can significantly affect the properties of the biochar produced.   More, making results difficult to replicate. Furthermore, most research has focused on simple liquid samples. Complex, high-fat matrices, such as dairy, oils, and meats, remain a largely unexplored frontier. Finally, biochar sorbents have no official regulatory acceptance, which will be impossible to achieve without standardized production methods. Biochar is a powerful and versatile green tool. Still, this review makes it clear that the field must solve its solvent problem and standardize its materials to fulfill its sustainable promise truly.

Source: Iglesias-Martín, C., Ares, A. M., Bernal, J., & Fuente-Ballesteros, A. (2026). Natural-derived sorbents: Application of biochar materials as green extractive approach in food analysis. Talanta, 297, 128608.