Gross, et al (2024) Long-term 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 and soil organic carbon stability – evidence from long-term field experiments in Germany. EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9944, https://doi.org/10.5194/egusphere-egu24-9944.

Biochar, known for its aromatic structure and resistance to microbial decomposition, has been hailed for its potential to enhance soil organic carbon (SOC) sequestration. However, the long-term impact of biochar on SOC under actual field conditions remains underexplored. To address this, researchers conducted a detailed study at two long-term field sites in Germany, which have utilized industrial biochar for nine and eleven years respectively.

The first site, characterized by sandy, nutrient-poor soil in northern Germany, experienced a rapid increase in SOC stocks shortly after biochar application (40 Mg ha-1), with a notable rise to 61 Mg ha-1. However, the gain diminished significantly over four years, settling to a modest 7 Mg ha-1 increase compared to control plots after nine years. In contrast, the loamy soil of the southern German site responded differently to biochar amendments (31.5 Mg ha-1). Here, an increase of 38 Mg ha-1 in SOC stocks was observed and notably remained stable over eleven years, reinforcing the potential of biochar in SOC sequestration.

The analysis of black carbon as a marker for biochar stability showed variable results. In northern Germany, black carbon levels initially rose but later dropped near to original levels, suggesting a loss of biochar material over time. Meanwhile, the southern site displayed considerable variability in black carbon stocks, possibly indicating challenges in maintaining biochar stability long-term.

The findings highlight that while biochar can enhance SOC sequestration, its effectiveness is highly dependent on soil type, biochar quality, and environmental conditions. The observed dissipation in biochar at both sites raises important questions about the mechanisms involved—whether through particle movement or microbial breakdown—and the overall reliability of biochar as a carbon sequestration strategy. Further research is crucial to optimize biochar use and ensure its efficacy in carbon management.