Synergistic effects of blending seafood wastes as Co-pyrolysis feedstock on syngas production and biochar properties

[Display omitted] •Synergistic effects of blending chitin and oyster shell as co-pyrolysis feedstock.•CO2-assisted co-pyrolysis increased syngas production and enhanced biochar property.•Biochar produced in CO2 condition showed strong pH buffering capacity.•Cu(II) adsorption capacity was 2.5 time greater for CO2 biochar than N2 biochar. Common seafood wastes, chitin and oyster shell, were co-pyrolyzed in different atmospheric conditions of N2 and CO2 to investigate the effects of blending the two wastes on syngas production and adsorption capability of the produced biochar in Cu(II) adsorption. The gas analyses indicated that amendment of oyster shell to chitin pyrolysis substantially enhanced production of H2 and CO as compared to using chitin as a sole feedstock. The enhanced syngas production was deemed to arise from the catalytic effect of calcite (CaCO3) contained in oyster shell that expedited thermal decomposition of chitin. The syngas production was more pronounced in N2 condition than in CO2 condition. The biochar samples produced from co-pyrolysis in both atmospheric conditions had different mineralogical composition and surface characteristics. The biochar produced under CO2 condition showed strong pH buffering capacity to maintain the pH increase within neutral range. The maximum adsorption capacity of CO2 biochar was 2.5 times (∼1,000 mg g−1) higher than N2 biochar (∼400 mg g−1), which was attributed to the abundance of calcite particles that served as major reactive sites of ion exchange reaction with Cu(II). In overall, this study offers an effective strategic way to maximize syngas production and produce biochar with specific functionality.