However, biomass also has several challenges which include high<br>moisture and oxygen content, low energy density, hydrophilic nature,<br>and highly variable composition and properties. These issues lead to<br>operational concerns during thermal conversion of biomass, such as<br>high-energy demand for grinding and pelletisation, poor ignition<br>properties, low combustion temperature, inefficient combustion, fume<br>and flue gas production (Vassilev et al., 2015). . Furthermore, hydrophilic properties bring up some problems related to the storage and<br>energy density of the biomass. A solid fuel with hydrophilic properties<br>is unstable and likely to deteriorate biologically (Yang et al., 2015).<br>Considering these challenges, biomass needs to be pretreated to improve its characteristics and thereby, efficient utilisation during the<br>thermal conversion. In the literature, several pretreatment processes<br>have been proposed, and torrefaction is among them (Kambo and<br>Dutta, 2014; Wigley et al., 2016; Xin et al., 2019; Xu et al., 2018). . In<br>recent years, torrefaction has received significant attention from both,<br>researchers and industries because of its potential to improve the biomass properties to a level comparable with coal.<br><br>Torrefaction is a biomass pretreatment process, which is mainly<br>intended to improve the fuel characteristics of the biomass by altering<br>the physicochemical properties of biomass and finally improve its applicability in thermal conversion process (Chen et al., 2015). In general,<br>the torrefaction process is carried out in the temperature range of<br>200–300 °C at slow heating rates, i.e. < 50 °C /min mainly in an inert<br>environment.
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