In a review published in the journal Processes, authors Elena Olivera-Begué, Daniel González, and Antoni Sánchez examine how biochar serves as a critical tool for mitigating atmospheric emissions. The research team analyzed numerous studies to understand how biochar interacts with composting waste. Their work focuses on the urgent need to reduce gases like ammonia, methane, and nitrous oxide, which are naturally released during the decomposition of organic materials. While composting is a vital part of the circular economy, its large-scale implementation is often hindered by these gaseous emissions and the odors they produce.

The effectiveness of biochar comes from its unique physical and chemical properties, such as high 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 a large internal surface area. These features allow it to act like a sponge, trapping ammonia and volatile organic compounds before they can escape into the atmosphere. In many cases, adding biochar at a ratio of about 10 percent of the dry waste mass led to significant improvements. For example, studies on poultry and cattle manure composting showed ammonia reductions ranging from 30 to 89 percent depending on the specific conditions. This trapping effect not only cleans the air but also keeps valuable nitrogen in the final compost, making it a better fertilizer for sustainable agriculture.

Beyond odor control, biochar plays a sophisticated role in reducing greenhouse gas emissions by changing the environment for microscopic life. Methane, a potent greenhouse gas, is often produced in dead zones within compost piles where oxygen is scarce. Because biochar is highly porous, its addition improves the overall airflow and oxygen transport throughout the mixture. This increased oxygen limits the activity of methane-producing bacteria. The researchers found that greenhouse gas emissions can be reduced by half under most conditions, although the specific outcome depends heavily on factors like the temperature and acidity of the pile.

One of the biggest challenges identified in the review is the need for more consistent testing at a larger scale. Most current research has been done in small laboratory settings, which may not perfectly mimic the high temperatures and pressure found in professional composting facilities. The authors emphasize that standardizing how much biochar is used, ideally measured by dry weight, is essential for making this technology a reliable commercial standard. Despite these research gaps, the existing data strongly suggests that biochar is a cost-effective and environmentally friendly way to improve waste treatment.

The move toward using biochar in composting represents a major step toward a truly circular economy. It allows for the valorization of forestry and agricultural leftovers into a product that makes other waste treatment processes cleaner and more efficient. By reducing the need for expensive chemical air filters and enhancing the value of the final compost, biochar provides both economic and environmental benefits. As researchers continue to refine the optimal recipes for different types of waste, biochar is set to become an indispensable part of modern, sustainable waste management.

Source: Olivera-Begué, E., González, D., & Sánchez, A. (2025). A critical review of the role of biochar in mitigating atmospheric emissions during the composting of organic waste. Processes, 14(1), 71.