## 3 Results
### Thermogravimetric Analysis  
Thermogravimetric analysis (TGA) was employed as a useful tool in studying the thermal degradation behavior of torrefied sewage sludge and sugarcane bagasse samples. Figure 2 presents the TGA plots of torrefied SS and BG blended at two different ratios of 50% SST to 50% BGT (M\({}_{\text{a200}}\), M\({}_{\text{a250}}\), M\({}_{\text{a300}}\) and M\({}_{\text{a350}}\)) and 75% SST to 25% BGT (M\({}_{\text{e200}}\), M\({}_{\text{e250}}\), M\({}_{\text{e300}}\), M\({}_{\text{a350}}\)). Note that the subscript 200-350 represents the torrefaction temperature for the samples. Figure 2: Thermogravimetric analysis (TGA) curves of torrefied sewage sludge and sugarcane bagasse blend. Figure 2 demonstrates the percentage weight loss of the samples as a function of temperature ranging from ambient to 900 \({}^{\circ}\)C at 20 \({}^{\circ}\)C/min heating rate. The thermal degradation profile of M\({}_{\text{a250}}\), M\({}_{\text{e250}}\) and M\({}_{\text{e350}}\) samples, as observed from Figure 2, can be divided into three stages differing from M\({}_{\text{a200}}\), M\({}_{\text{a300}}\), M\({}_{\text{a350}}\), M\({}_{\text{e200}}\) and M\({}_{\text{e300}}\) samples that showed a two-stage degradation. The first stage corresponds to the removal of moisture and some light volatiles, and this spanned from 30-150 \({}^{\circ}\)C for all the samples with a percentage weight loss of 5.01%. The low percentage of moisture recorded in all samples is due to the torrefaction process; the samples underwent during which some moisture was evaporated from the samples. This was consistent with an initial mass loss of 7% recorded at a temperature below 250 \({}^{\circ}\)C during the gasification, pyrolysis and combustion of SS in air + nitrogen, nitrogen and air, respectively [25]. Furthermore, the negligible mass loss of 0.6%, 0.8% and 1.2% corresponding to release of moisture reported for sewage sludge torrefied at 230 \({}^{\circ}\)C, 260 \({}^{\circ}\)C and 290 \({}^{\circ}\)C, respectively, differed from the present study [26]. This could be attributed to the difference in composition of the samples as well as torrefaction conditions. Notably, the second stage was characterized by devolatilization of cellulose, hemicellulose and lignin content of the sugarcane bagasse, as well as carbohydrate and lipids content of sewage sludge. Consequently, this resulted in the release of gases such as carbon monoxide (CO), hydrogen (H\({}_{2}\)), carbon dioxide (CO\({}_{2}\)) and methane (CH\({}_{4}\)) [27; 28]. Most notably, the percentage weight loss was very significant at the second stage (200-600 \({}^{\circ}\)C), with M\({}_{\text{a250}}\) and M\({}_{\text{e250}}\) recording the highest value of 76.31% and 69.98% respectively and M\({}_{\text{a350}}\) giving the least weight loss value of 30.26%. The principal decomposition (second) stage was initiated at a higher temperature (400 \({}^{\circ}\)C) for M\({}_{\text{a300}}\), M\({}_{\text{a350}}\) and M\({}_{\text{e300}}\), M\({}_{\text{e350}}\) samples compared to M\({}_{\text{a200}}\), M\({}_{\text{a250}}\), M\({}_{\text{e200}}\) and M\({}_{\text{e250}}\) samples that commenced at a lower temperature of about 300 \({}^{\circ}\)C. Similarly, in [PERSON] et al. [29] study, the thermal decomposition of digestate from biogas and sewage sludge principally started at 300 \({}^{\circ}\)C and 350 \({}^{\circ}\)C with an average weight loss of 63% and 50%, respectively. [PERSON] et al. [30] similarly recorded a temperature range of 360-500 \({}^{\circ}\)C for the second phase degradation of bio-oil from food waste and attributed it to the heterogeneous combustion of heavy compounds and oxygen. In addition, another study reported a lower temperature of 235 \({}^{\circ}\)C for the initiation of the main devolatilization phase for the sugarcane sample [31].