Thermo-decompositional Analysis of Sawdust Blends of Invasive Alien Plants

This study examined the effect of blending two invasive wood species of distinct physical and chemical properties, maximum char yields and rates of decomposition, on their thermal behaviour towards sustainable production of energy. To evaluate their potential use for production of briquettes/pellets, an examination of the dynamic thermogravimetry of sawdust blends of bugweed, a low density, fast-growing fibrous invasive shrub with eucalyptus wood was conducted. Individual blends in ratios of 50:50 (BUG50), 30:70 (BUG30) and 70:30 (BUG70) were tested under a pyrolysis condition and also in oxidized atmosphere to examine their combustion behaviours at a constant heating rate. Results were compared to individual results of 100% bugweed sawdust (BUG100) and 100% eucalyptus sawdust (BUG0) as control. The pyrolysis test on the blended samples reveal an increase in maximum char mass yield of up to 17% from that observed in BUG100. Meanwhile, amongst all blends, BUG70 exhibited the least maximum char yield of 34.9% and the highest ash residue of 4.3%. The high ash residue in BUG70 was believed to distort its char combustion. The lowest maximum peak rate of volatilization achieved amongst all blends was 6.6%/min by BUG50 and that of the char decomposition was as low as 2%/min for BUG30. Remarkably, the peak and final decomposition temperatures of all three blends occurred at higher temperatures than those of BUG100, in the pyrolysis test. Results of their combustion tests conducted, reveal thermograms with profiles similar to those observed during the pyrolysis tests. However, there was a general decrease in the peak and final combustion temperatures from those observed during the pyrolysis test of the samples. BUG30 exhibited good char combustion stability across a wide temperature range and at higher combustion temperatures than BUG50 and BUG70. No significant differences were observed in the heating values of all samples tested.