A review article in the journal Agricultural Engineering by Wang Xiuqing and colleagues explores the preparation, modification, and application of 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 as a renewable and environmentally friendly material. The authors highlight its potential for pollution control, soil improvement, and sustainable agriculture due to its excellent adsorption capacity, well-developed pore structure, and chemical stability. The review details three primary methods for biochar preparation: 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, gasificationGasification is a high-temperature, thermochemical process that converts carbon-based materials into a gaseous fuel called syngas and solid by-products. It takes place in an oxygen-deficient environment at temperatures typically above 750°C. Unlike combustion, which fully burns material to produce heat and carbon dioxide (CO2​), gasification More, and hydrothermal carbonization. Pyrolysis is the most widely used method, involving heating organic materials in an oxygen-deficient environment.

Key parameters like temperature, heating rate, and reaction time directly influence the biochar’s properties. For example, a higher pyrolysis temperature increases the carbonization degree, leading to greater specific surface area 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. One study found that biochar prepared from buckwheat straw at 700∘C with a heating rate of 12.5∘C/min showed excellent physicochemical properties. Gasification, which involves partial oxidation at high temperatures, yields biochar with a higher carbon content and more developed pores, making it suitable for applications requiring high electrical conductivity. In contrast, hydrothermal carbonization operates at lower temperatures ( 180−300∘C) and high pressure in a water medium, producing biochar rich in oxygen-containing functional groups that are beneficial for adsorbing heavy metals and organic pollutants.

The modification of biochar is crucial for optimizing its performance. Chemical modification using agents like acids, bases, or metal oxides can increase surface functional groups and improve adsorption efficiency. For instance, a study on modified corn straw biochar found that chemical treatment significantly improved its adsorption of phenol, achieving a removal rate of up to 99.5% under optimal conditions. Another study showed that biochar modified with FeSO4 achieved a high Cr(VI) adsorption rate of 97%. Biochar made from sulfate-reducing sludge demonstrated a significant Cr(VI) adsorption capacity of 8.22 mg/g compared to regular biochar. Similarly, a study on modified sludge biochar found it could improve iodine adsorption to an impressive 516.68 mg/g.

Beyond pollution control, biochar plays a vital role in soil improvement and agricultural sustainability. Its ability to improve soil structure and nutrient retention can significantly increase crop yields. The review notes that in wastewater treatment, biochar can effectively remove inorganic pollutants like nitrogen and phosphorus , with removal rates ranging from 70.5% to 92.3%. When combined with microorganisms, this efficiency can increase .

Despite these successes, the review highlights several challenges, including the high cost of large-scale production, the need for further research on long-term environmental impacts, and the stability of modified biochar in practical applications. Future research should focus on developing low-carbon, efficient preparation processes and exploring multifunctional modification strategies to fully realize biochar’s potential.

Source: Wang, X., Wang, Y., Wang, W., & Li, Y. (2025). Research progress on biochar preparation, modification and applications. Agricultural Engineering, 15(8), 58-67.