In a recent study published in Carbon Research, authors Lei Zhong et al. conducted a meta-analysis to investigate the impact 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 on nitrous oxide (N₂O) emissions from fertilized cropland soils. N₂O is a potent greenhouse gas, with approximately 300 times the global warming potential of CO₂. The widespread use of nitrogen fertilizers in agriculture contributes significantly to N₂O emissions. Biochar application has been proposed as a strategy to mitigate N₂O emissions and enhance soil fertility.  

The meta-analysis synthesized 550 observations from various studies to assess how biochar production conditions, properties, and application rates influence N₂O emissions, nitrification enzyme activity (NEA), denitrification enzyme activity (DEA), and related functional genes.  

The study found that biochar application generally reduces N₂O emissions. Specifically, a biochar application rate of 20 tons per hectare decreased N₂O emissions by 19%. Higher application rates (50+ tons per hectare) resulted in even greater reductions (48%). The reduction of N₂O emissions is primarily attributed to the modification of denitrification processes.  

Biochar properties and production conditions, such as feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More type and 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 temperature, also play a role in N₂O emission reduction. For instance, wheat straw biochar increased the abundance of genes related to N₂O emissions and denitrification enzyme activity, while higher pyrolysis temperatures (exceeding 450°C) decreased denitrification enzyme activity.  

The findings of this meta-analysis highlight the potential of biochar to mitigate N₂O emissions from fertilized cropland. Optimizing biochar application can be a valuable strategy in agricultural management to combat climate change.  

SOURCE: Zhong, L., Wang, P., Gu, Z. et al. Biochar reduces N₂O emission from fertilized cropland soils: a meta-analysis. Carbon Res. 4, 31 (2025)