Combating climate change through the use of biochar - Preliminary results on the effects of biochar application on different forest soils

The application of biochar (a stable carbon-rich material produced by pyrolysis under oxygen-limited conditions) in forests can simultaneously contribute to improving soil water-retention capacity and mitigating climate change. In forest soils, biochar’s fine pore structure and large specific surface area may have beneficial effects on soil structure: it can increase porosity, enhance the aggregation of soil particles, and provide more “micro-storage” sites for water. This may be particularly important in coarser-textured soils that dry out rapidly, where biochar can help a portion of precipitation remain longer in the root zone, thereby reducing drought stress and improving the survival prospects of natural regeneration and seedlings. Beyond water, biochar may also support nutrient retention: in certain cases, it can reduce nutrient leaching and create more favorable microhabitats for soil biota, which can indirectly enhance the stability of the soil water–nutrient balance.

From a climate-mitigation perspective, the key benefit of biochar is that it can “lock” part of the plant-derived carbon into a more persistent form in the soil: instead of quickly returning to the atmosphere as carbon dioxide, it can contribute to increasing soil carbon stocks over longer time scales. In addition, if biochar is produced from local biomass residues and applied in a well-considered manner, it can become part of a circular economy approach and support forest climate adaptation (for example, by improving resilience during drier periods). In our studies, the optimal dose determined in laboratory germination-inhibition tests and pot experiments is being applied to three forest sites with different soil types. Even from our measurements so far, it has become evident that the effect strongly depends on the biochar feedstock and production conditions, the soil type, and the application method and rate. Therefore, in forest settings, small-scale pilot trials and monitoring are especially justified to ensure that water-management benefits are actually realized.

The research was supported by the INTERREG AT-HU 2021-2027 CS4Region "A green and resilient border region" project.