The latest report from the Intergovernmental Panel on Climate Change (IPCC) indicates a significant rise in greenhouse gas emissions, with atmospheric carbon dioxide (CO2​) concentrations reaching 422 parts per million (ppm) in 2024. This continuous increase poses a critical challenge to limiting global warming to less than 2°C. In response, scientists are exploring various strategies to reduce these emissions, with soil-based carbon sequestration emerging as a promising solution due to soil’s immense capacity to store CO2​—up to three to four times more than vegetation and 50 times more than air. A recent review in npj Materials Sustainability by Basanta Kumar Biswal and Rajasekhar Balasubramanian delves into one such solution: the use of biomass-derived 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 to enhance carbon sequestration in soil and mitigate climate change.

Biochar offers a nature-based approach to this challenge. Biochar with high stability and a high carbon-to-nitrogen (C/N) ratio is particularly effective at sequestering carbon in soil. The review highlights that the carbon sequestration potential of biochar in soil systems ranges from 0.7 to 1.8 gigatons of carbon equivalent per year (tCO2​−C(eq)​/year).

The characteristics of biochar, which are influenced by the type of 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 used and the temperature of the thermal process, play a crucial role in its effectiveness. For instance, biochar produced from plant biomass generally has a higher C/N ratio and greater carbon sequestration potential compared to biochar from other sources. The synthesis temperature is also a key factor; biochar made at higher temperatures (e.g., ≥600 °C) has higher 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 aromaticity, making it more stable and resistant to degradation. One study showed that biochar produced at 600 °C reduced CO2​ emissions by 15%, whereas biochar from a lower temperature (300 °C) increased emissions by 45%. Furthermore, chemically modified biochar, such as that treated with phosphoric acid and nanoscale zero-valent iron (nZVI), has been shown to be even more effective. One lab-scale test using nZVI-based biochar reduced CO2​ release from soil by 80.29-91.60%.

Biochar’s effectiveness is also dependent on soil conditions. Alkaline soils with a pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More greater than 7.5 and high porosity are more favorable for carbon sequestration. The review notes that biochar application can considerably increase soil organic carbon (SOC), with one global meta-analysis reporting an 84.3% increase in SOC and a 20.1% increase in microbial biomass carbon. Another study found that biochar amendment to soil enhanced crop yield by 10-42% and increased phosphorus availabilityPhosphorus is another essential nutrient for plant growth, but it can sometimes be locked up in the soil and unavailable to plants. Biochar can help release phosphorus from the soil and make it more accessible to plants, reducing the need for chemical fertilizers.   More by 4.6 times. In a field trial, rice grain yield increased by nearly 44% with the application of rice husk biochar.

Biochar influences soil microbial communities, which are critical for carbon cycling. The dominant bacterial communities enriched by biochar include Proteobacteria and Acidobacteria, while the fungal communities are dominated by Ascomycota. Biochar can suppress soil organic carbon mineralization—a process that releases CO2​—by limiting microbial access to organic substrates and inhibiting the activity of certain enzymes. A recent meta-analysis of short-term biochar applications found that cellulase activity decreased by 4.6%, leading to an 87.5% increase in soil carbon sequestration.

This comprehensive review highlights the immense potential of biochar as a sustainable material for carbon sequestration. Biochar produced from waste biomass is considered environmentally friendly and economically feasible for large-scale applications. However, the authors stress the need for more long-term, field-scale research to validate these findings and to standardize methodologies for carbon accounting, ensuring the effective implementation of biochar as a key climate change mitigation strategy.

SOURCE: Biswal, B. K., & Balasubramanian, R. (2025). Use of biomass-derived biochar as a sustainable material for carbon sequestration in soil: recent advancements and future perspectives. npj Materials Sustainability, 3(26).