Importance of pyrolysis temperature and pressure in the concentration of polycyclic aromatic hydrocarbons in wood waste-derived biochars

Biochar addition to soil can lead potential environmental risks due its content of polycyclic aromatic hydrocarbons (PAHs). Until now, previous research focused on assessing the influence pyrolysis peak temperature and feedstock formation evolution PAHs. Nevertheless, effects other important process parameters —such as pressure, gas residence time, type carrier gas— have not been comprehensively explored. To fill this gap, a 2-level full factorial design experiments was conducted assess above-mentioned behavior an untreated wood waste well properties resulting biochars, including their PAHs contents. Results showed that highest production reached at lower temperatures, whereas increase in led substantial reduction final content. An increased pressure also resulted marked decrease PAHs, probably consequence higher flow rates used under pressurized conditions, which could inhibit generation by condensation polymerization. The outstanding results obtained from phytotoxicity assessment for three plant species (barley, watercress, basil) suggest were major responsible observed short-term phytotoxic since considerable part compounds biochar be removed simple water washing step.