The effect of microbiological pretreatment on pyrolysis process of sunflower husk

In this study, two different microbial pretreatments (fungal and fungal-bacterial consortia) of sunflower seed husks were used to assess their impact on pyrolysis performance and the resulting biochar parameters. Both treatments reduced the activation energy of the pyrolysis process and shortened the temperature range of pyrolysis, making the process easier to initiate and sustain. Moreover, they enhanced the yield of fractions with compounds containing low (C₁-C₁₀) and medium (C₁₁-C₂₀) number of carbon atoms at 400 and 500 °C. However, fungal-pretreatment and pyrolysis at 500 °C proved to be a more effective approach for obtaining those compounds than fungal-bacterial pretreatment and pyrolysis at 600 °C. The FTIR analysis of biochar indicated that fungal-treatment followed by pyrolysis at 500 °C led to the shift of compounds containing methyl- and methylene-groups into gaseous or liquid pyrolysis products. Additionally, fungal-bacterial treatment slightly reduced the temperature at which biomass degradation occurred. Both pretreatments improved biochar quality by modifying its morphological properties (increasing the specific surface area of biochar obtained at 400 °C) and chemical composition (reducing nitrogen and sulphur content).