Slow Pyrolysis of Quercus cerris Cork: Characterization of Biochars and Pyrolysis Volatiles

Waste cork granules of Quercus cerris bark were subjected to isothermal and non-isothermal slow pyrolysis. The heat of the reaction, as well as the yields and properties of biochar, bio-oil, and pyrolysis gas were investigated by thermogravimetric analysis, FT-IR, CHN elemental analysis, higher heating value (HHV) determinations, scanning electron microscopy (SEM), and gas chromatography (GC). The slow pyrolysis was carried out in a semi-batch reactor using an isothermal or a non-isothermal dynamic approach. The results demonstrated that isothermal or non-isothermal slow pyrolysis of cork is a slightly exothermic reaction that produces biochars. The elemental analysis results indicated that non-isothermally produced chars have similar fuel properties compared to isothermally produced chars. The FT-IR results showed that cork suberin undergoes a higher degree of degradation in isothermal chars and aromatization begins in the char structure. Bio-oils are also produced and they consist of C-5-C-12 hydrocarbons with C-8 carbon compounds making up the main fraction. Lighter components, mainly C-1-C-2 hydrocarbons are collected in the gas phase. The overall results indicate a possible reduced-cost route for the production of cork-based biochars by using non-isothermal slow pyrolysis.

Automated summary

The waste cork granules of Quercus cerris bark underwent isothermal and non-isothermal slow pyrolysis. The reaction heat, as well as the properties and yields of biochar, bio-oil, and pyrolysis gas were investigated. The results showed that both isothermal and non-isothermal slow pyrolysis of cork produced biochars, with non-isothermally produced chars having similar fuel properties to isothermally produced chars. Furthermore, the FT-IR results demonstrated a higher degree of degradation in isothermal chars and the beginning of aromatization in the char structure. These findings suggest the potential for cost-effective production of cork-based biochars using non-isothermal slow pyrolysis.