## 3 Results and Discussion
### Analysis of Raw and Torrefied Wheat Straw
Based on TGA data, approximately 31-32% of the biomass remained as fixed carbon or biochar for both raw and 280 \({}^{\circ}\)C-torrefied wheat straw, while the remaining 70% was lost as volatilized compounds that began vaporizing at around 150 \({}^{\circ}\)C. Biochemical composition analysis has shown wheat straw to be composed of 18.8% lignin, 18.2% hemicellulose, 52.4% \(\alpha\)-cellulose, and 3.7% ash [42]. Hemicelluloses, celluloses, and lignin are known to decompose at 225-300 \({}^{\circ}\)C, 305-375 \({}^{\circ}\)C, and 250-300 \({}^{\circ}\)C [43]. In torrefaction, hemicellulose is considered to be the most reactive constituent and degrades via the removal and decomposition of various saccharides and branches in the hemicellulose. Cellulose, which is composed of a polymer of glucose with no branches, is thermally more stable and thermally decomposes at higher temperatures. Lignin, to a limited extent, will decompose to three products: a char solid, tars and volatiles/gases, the latter two contributing to the significant loss of mass upon torrefaction at higher temperatures. The plots of conversion vs. either the log (exponential factor) and activation energies for the Friedman method are depicted in Figure 3. Activation energy is a barrier to energy  
Figure 2: FTIR spectra for raw and 280 \({}^{\circ}\)C-torrefied wheat-straw particles. transfer between reacting molecules that must be overcome and is evidently a function of conversion, likely because of the different primary reactions occurred during thermogravimetric analysis. The Friedman-method average activation energy and exponential factor for all 0.05-incremented conversions between 0.05 and 0.90 for the raw wheat-straw was estimated as 199,398 J mole\({}^{-1}\) and 1.12 \(\times\) 10\({}^{18}\) min\({}^{-1}\), respectively. Those for the 280 \({}^{\circ}\)C-torrefied wheat-straw for conversions between 0.05 and 0.65 were estimated to be 233,406 J mol\({}^{-1}\) and 2.84 \(\times\) 10\({}^{28}\) min\({}^{-1}\), respectively. Knowledge of the kinetics of biomass thermochemical reactions during torrefaction is very important to estimate the yield of products, understand reaction mechanisms, and enhance selectivity, and design more efficient thermochemical reactors. Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) is a technique which thermally decomposes a sample's large high-molecular weight molecules (at >600 \({}^{\circ}\)C in the absence of O\({}_{2}\)) into smaller and more volatile low-molecular weight fragments that are then separated by gas chromatography in an inert atmosphere or a vacuum depending on their volatility. Higher volatile particles travel faster through the column than lower volatile particles. The volatile molecules are then ionized using an electric charge and then sent to an electromagnetic field that filters the ions based on their specific mass (mass divided by charge number) expressed in units of m/z, which an ion detector will count. A mass spectrum correspondingly depicts the ion abundance that is counted by a detector via measurement of the current of electrons generated when the ions strike the detector for each m/z as a function of retention time. Spectra from Py-GC MS of raw and 300 \({}^{\circ}\)C-torrefied wheat straw revealed a marked change in relative peak areas for various compounds (Figure 4). These primary peaks corresponded to various compounds whose retention times are presented in Table 1.  
Figure 3: Rate exponential factor (**a**) and activation energy (**b**) as function of conversion for raw and 280 \({}^{\circ}\)C-torrefied 40–60 mesh wheat-straw particles, as determined by the Friedman Method.