The smell of rotten eggs or a freshly struck match is more than just unpleasant; it is the signature of sulfur-containing gaseous pollutants. When fossil fuels are burned for energy, industries like power plants and refineries release toxic gases like hydrogen sulfide sulfur dioxide , and carbon oxysulfide . These pollutants are a primary driver of acid rain, and they contribute to severe respiratory illnesses, water contamination, and ecosystem damage. A new review by Omojola Awogbemi and Dawood A. Desai, published in Engineering Reports, synthesizes the advancements in a sustainable solution to this problem: turning common waste into a high-tech pollution filter.

The proposed solution is biochar, however, there is a catch: in its raw form, biochar is not a very effective filter for sulfur gases. Its surface area is relatively small, and it lacks the specific chemical properties needed to grab and hold onto sulfur molecules. The research shows the key is not just using biochar, but modifying it.

This modification process is called “functionalization”. As the review details, functionalization enhances the biochar’s microstructure, porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More, and surface chemistry, essentially creating millions of tiny, specialized “active sites” that act like magnets for sulfur pollutants. Scientists can functionalize biochar using several methods. Chemical techniques involve treating the biochar with acids, bases, or impregnating it with metal oxides, such as iron or copper, which have a strong affinity for sulfur. Physical methods use thermal treatments, microwave irradiation, or ball milling (a high-energy grinding process) to change the biochar’s structure. Advanced techniques like plasma treatment or “heteroatom doping” (inserting elements like nitrogen into the carbon structure) can further tailor the material for specific pollutants.

The results of this functionalization are striking. The review aggregates data from numerous studies showing massive quantitative leaps in performance. For H2S, the highly toxic “sewer gas,” one study found that modifying biochar from pomelo peels with copper boosted its adsorption capacity from 12.1 mg/g to 358.3 mg/g. This represents an increase of over 2,800%. For SO2 , a primary component of acid rain, impregnating rice straw biochar with magnesium oxide (MgO) increased its adsorption capacity from 11.1 mg/g to 194.6 mg/g—a more than 16-fold improvement^16161616. In other cases, such as using metal-oxide-modified biochar from gulfweed, researchers achieved 99.5% removal of COS.

The future of this technology, as the authors highlight, lies in precision and optimization, driven by Artificial Intelligence (AI). Instead of relying on lengthy trial-and-error, machine learning algorithms can analyze vast datasets to predict how different feedstocks, 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 temperatures, and functionalization methods will impact the final biochar’s performance. This AI-driven approach can rapidly design the most effective and economical biochar for capturing a specific pollutant, accelerating the technology’s path from the lab to large-scale industrial use. The review makes it clear that functionalized biochar is a powerful and efficient technology, offering a sustainable way to turn our waste into a critical tool for mitigating pollution and safeguarding public health

Source: Awogbemi, O., & Desai, D. A. (2025). Advancements in Biochar Functionalization for Sustainable Adsorption of Sulfur-Containing Gaseous Pollutants. Engineering Reports, 7, e70440. https://doi.org/10.1002/eng2.70440