Agricultural potential and safety assessment of biochar obtained from river biomass

Biochar, a carbon-rich residue produced by controlled biomass decomposition in oxygen-deprived conditions, like pyrolysis or gasification, has gained attention as a soil enhancer for improving fertility and sequestering carbon. In this study, we analyzed a biochar produced from woody and herbaceous biomasses resulting from river cleaning operations. The potential impacts of biochar on fauna and flora were evaluated through tests on two soil invertebrates (Folsomia candida and Eisenia fetida/E. andrei) and several agricultural plant species. Toxicological assessments included the Ames test using Salmonella typhimurium; the Comet Assay, conducted on Cucumis sativus, Cichorium endivia, Lactuca sativa, Lepidium sativum, Sorghum saccharatum; and the MTS assay, performed on various human cell lines. Results showed that biochar did not negatively impact the collembolans or earthworms' survival, even at high concentrations. However, reproductive capacity declined significantly at concentrations above 2%. In plant assays, higher concentrations generally inhibited growth, while lower concentrations (1% to 2%) commonly used in agriculture promoted root elongation and, in some cases, increased germination rates. No harmful effects were detected in Ames test or in the cytotoxicity assay on human cell lines. Biochar did not negatively affect plant species survival or cause DNA damage, making it suitable as an agricultural soil conditioner.