Comparing physical and chemical pretreatments, biological
methods are slower but less energy-consuming and with better
environmental footprint [227]. Fungal pretreatment of lignocellulose prior to pyrolysis has been proved to improve the
efficiency of the pyrolysis performance. White-rot fungus has been
selected to pretreat the natural lignocellulose as it could selectively decompose the refractory lignin component during pyrolysis
[228,229]. Yang et al. [230] employed three different species of
white-rot fungus (Pleurotus ostreatus BP2, Echinodontium taxodii
2538, and Irpex lacteus CD2) to biopretreat corn stover and then
studied its thermal characteristics during pyrolysis in a TGA
instrument. Results showed that this biopretreatment could
effectively lower the pyrolysis temperature by 1–35 °C and
decrease the emission of toxic SO
x through reduction of the sulphur content in the feedstock by 30–45%. Yu et al. [227] investigated fast pyrolysis of corn stover pretreated by white-rot fungus I.
lacteus CD2 in the presence of ZSM-5 zeolite, and observed 10%
improvement in valuable aromatics product yields and 20%
reduction in deposition of undesired coke on catalysts.
Microbial consortium has been generally used to pretreat lignocellulosic biomass to enhance the biogas production. It employs
certain microbes selected from the natural environment which
mainly degrade the cellulose and hemicellulose components [174].
The process lasts for several hours to several days with the ability
of increasing the methane yield by 25% to nearly 100% [174].
Enzymes have been proposed as a pre-treatment for hydrolysis
of lignin prior to its pyrolysis in order to enhance production of
aromatic phenols and hydrocarbons [231]. The produced chars
also appeared to be highly porous with vesicles.