Polycyclic aromatic hydrocarbons in biochar originated from pyrolysis of aseptic packages (Tetra Pak®)

Abstract

Determination of the total yield of polycyclic aromatic hydrocarbons (PAHs) and their derivatives in a Tetra Pak (R) biochar was the leading target of this study. It was also evaluated the toxicity of Tetra Pak (R) biochars originated from pyrolysis performed at different temperatures. The rela-tionship between the pyrolysis temperature and the yield of PAHs contained in Tetra Pak (R) biochars was also investigated. The material (Tetra Pak (R) packages, aseptic type) was decomposed in a laboratory pyrolysis reaction unit at different temperatures (400 degrees C, 500 degrees C, 600 degrees C, 700 degrees C). The concentrations of PAHs in Tetra Pak (R) biochars were determined using the method of py-rolysis gas chromatography combined with mass spectrometric detection. The toxicity of Tetra Pak (R) biochars was evaluated by Sinapis alba test and calculating of toxic equivalents.

The total PAHs concentration in Tetra Pak (R) biochars oscillated between 79.6 mg/kg and 173.0 mg/kg. The measured concentrations of 16 priority PAHs U.S. Environmental Protection Agency (US EPA) reached the range from 38.4 mg/kg to 73.7 mg/kg. The yields of methylated derivatives of Tetra Pak (R)-biochar-borne PAHs varied from 5.2 mg/kg to 77.1 mg/kg. A phytotoxicity index of Sinapis alba has shown that biochar produced at temperatures above 500 degrees C is more likely to have a stimulating effect, supported by the leaching of Ca after the thermal decomposition of calcite and water extractable organic carbon. The stimulating effect of the addition of Tetra Pak (R) biochar increases with the decreasing concentration of biochar-borne PAHs. Given the financial cost and the minimisation of environmental risk, the addition of biochar in the range of 5-10% can be recommended.