Characterization and ecotoxicological investigation of biochar produced via slow pyrolysis: Effect of feedstock composition and pyrolysis conditions

This study systematically investigated the biochar toxicity from the in vitro tests involving the use of human liver and lung cell lines, as well as in vivo tests using Drosophila melanogaster (fruit fly). Biochars used in this study were produced from vegetable waste, pine cone and their mixture (1:1 by weight) at two representative temperatures (200 and 500 °C). Two common toxicant groups in biochar, heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) contents, were detected for clarification of the relationship between their toxicity behaviors and biochar bulk characteristics. The results showed that (1) no HMs can be found in the biochar if HMs are absence in their feedstock (2) PAHs were formed during the pyrolysis no matter what type of biomss used, but the concentration is low that can be acceptable for soil legislative criteria (3) biochars had limited impact to the viability of flies, but inhibited the growth of the cells (4) the low leaching potential of HMs and PAHs (total 16 USEPA) in the studied biochars may not be the major reason which put the harm to the cell, more effort on the identification need to be done. This work can provide a new picture to the biochar researchers for better understanding of the two faces of biochar.