Replacing Peat with Biochar: Can Adding Biochar to Peat Moss Reduce Carbon Dioxide Fluxes?

Replacing peat with biochar in nursery growing media could help offset carbon emissions and reduce environmental degradation caused by mining wetlands for peat. However, the effects of replacing peat with biochar on CO2 emissions are little known. In this study, we measured CO2 flux rates in growing media with varying proportions of biochar (0%, 25%, 50%, 75%, and 100% levels) as a replacement for peat. Overall, we found that higher biochar levels (≥75%) in growing media resulted in a reduction in CO2 fluxes compared to pure peat (0% biochar), approaching near-zero emissions. In contrast, lower biochar levels (≤25%) had little to no effect on CO2 fluxes. When the growing media was fertigated or irrigated, we observed a decrease in CO2 fluxes in mixes containing 25%, 50%, and 75% biochar, though this effect was absent in mixes that were pure peat or pure biochar, suggesting that irrigation and fertilization regimes could be strategized to enhance biochar’s carbon emission impacts. Our study offers insights into the development of sustainable growing media to reduce the carbon footprint of horticulture and forestry nursery production systems and may help balance productivity with environmental conservation.