Pyrolysis Products as Soil Fertilizers: Screening of Potentially Hazardous Aromatic Compounds

Abstract

This study investigated the concentrations of polycyclic aromatic hydrocarbons (PAHs) in pyrogenic carbonaceous materials (PCM) produced from three waste materials during slow pyrolysis at 400 and 500°C. As feedstocks bone meal (BM), biogas slurry (BC) and chicken manure (CM) were used. As potentially problematic substances 1- and 2- methylnaphthalene were analysed as indicators for methylated hydrocarbons in pyrolysis products. The phytotoxic effect of soil amendments was evaluated by a standard cress germination test with Lepidium sativum L. The analysis showed higher concentrations of the sum of 16 US-EPA PAHs in samples produced at lower temperature and in samples produced from biogas slurry. Concentrations of 1- and 2-methylnaphthalene showed similar trends with concentrations in a range of 35-205% of the sum of 16 PAHs. Germination tests showed inhibition effects of products from biogas slurry when applied in concentrations of ≥ 10 % to standard substrate. Apparently pyrolysis of biogas slurry requires special attention to avoid accumulation of PAHs and methylated naphthalenes.

Keywords

• biochar
• PAHs
• methylated naphthalene
• phytotoxicity