In a recent review published in 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, Sara Mrhari Derdag and Naaila Ouazzani explore the significant advancements in sustainable biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More production from waste, highlighting its multifaceted applications in renewable energy generation and environmental remediation. Biochar, a carbon-rich material produced from the thermal degradation of biomass, offers a promising solution for waste valorization and addressing pressing environmental challenges, including water pollution and soil degradation.

While pristine biochar demonstrates considerable potential, its effectiveness can be limited by factors such as low surface area and a scarcity of active sites. To overcome these limitations, researchers have developed various modification techniques. Chemical modifications, for instance, involve treating biochar with acids, bases, or metals to introduce new functional groups and enhance its properties. Acid treatments can increase surface acidity and 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, improving the adsorption of heavy metals through complexation and ion exchange. For example, treating biochar with a 1:1 solution of nitric acid and sulfuric acid significantly increases carboxyl functional groups, enhancing cadmium adsorption. Similarly, base modifications can augment surface area and hydrophobicity, while metal and oxide modifications, such as with potassium permanganate or zirconium oxychloride octahydrate, can introduce oxygen-containing functional groups and increase specific surface area for enhanced adsorption. These chemical enhancements have led to remarkable pollutant removal efficiencies, with some modified biochars achieving up to 98.97% removal of sulfamethoxazole.

Physical activation methods, including heating biochar in the presence of carbon dioxide or steam, induce pores and increase the specific surface area and micropore creation. Steam activation, for instance, can boost the cation exchange capacity of biochar and enhance its sorption capabilities by 55% compared to conventional biochar. Ball milling is another physical technique that reduces particle size to ultrafine dimensions, increasing both external and internal surface areas and improving sorption capacity by 6.47 times.

Biological modifications, an emerging and feasible technique, involve using bacterial conversion or anaerobic digestion from pre-treated biomass feedstocks. Biochar derived from both 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 and anaerobic digestion exhibits enhanced hydrophobicity, cation exchange capacity (CEC), anion exchange capacity (AEC), surface area, and a more negative surface charge. Studies have shown that anaerobic digestion can augment biochar’s adsorption capacity for phosphates and heavy metals, positioning it as a viable option for environmental pollutant remediation. For example, biochar combined with phosphate-solubilizing bacteria effectively removed lead from organic mediums with removal percentages of 24.11% and 60.85%.

These modified biochars are being applied across various sectors. In water and wastewater treatment, biochar’s enhanced porosity and surface chemistry enable efficient removal of nutrients, heavy metals, and organic compounds. Studies have shown biochar’s capacity to adsorb up to 398 mg/g of phosphate and 128.3 mg/L of ammonium from swine effluents. For heavy metal removal, biochar prepared at 700°C demonstrated superior performance, especially for arsenic, compared to biochar prepared at 300°C, attributed to increased specific surface area and surface aromaticity. Magnetic biochar composites, incorporating iron, have shown improved adsorption capacities for heavy metals like copper, cadmium, lead, and zinc, with some achieving up to 358.7 mg/g adsorption capacity for lead.

Beyond remediation, biochar is also critical for renewable energy generation. It serves as an effective electrode material in microbial fuel cells (MFCs), transforming chemical energy into electrical energy using microorganisms as catalysts. Biochar-based electrodes, often derived from agricultural and forestry residues, are significantly more cost-effective than commercial alternatives, with material costs as low as 0.03 to 0.08 USD g⁻¹. MFCs using biochar electrodes have demonstrated notable power outputs, with one example reaching up to 6 W m⁻³, alongside significant reductions in chemical oxygen demand (95%), ammonia (73%), and phosphorus (88%) in wastewater treatment.

Biochar also plays a role in producing biohydrogen, particularly in anaerobic digestion and water splitting processes. Pine dust-derived biochar enhanced methane yield by 10.0% and hydrogen yield by 31.0% in anaerobic digestion of liquid carbohydrates. Furthermore, calcium lignosulfonate-derived biochar augmented hydrogen production by 50.9%. In water splitting, biochar nanocomposites from watermelon peels have shown superior hydrogen evolution reaction efficiency compared to platinum/carbon electrocatalysts.

The versatility of biochar, stemming from optimized production processes and targeted modifications, positions it as a key component in circular economy strategies and climate change mitigation. While lab-scale studies have shown promising results, further research and field-scale trials are essential to standardize production protocols and fully realize biochar’s long-term performance and widespread applicability in diverse environments.

Source: Masud, M. A. A., Samaraweera, H., Mondol, M. M. H., Septian, A., Kumar, R., & Terry, L. G. (2025). Iron biochar synergy in aquatic systems through surface functionalities electron transfer and reactive species dynamics. npj Clean Water, 8(1), 46.