Biochar as a Fuel: 2. Significant Differences in Fuel Quality and Ash Properties of Biochars from Various Biomass Components of Mallee Trees

This study shows the significant differences in the fuel quality and ash properties of biochars produced from the slow pyrolysis of various biomass components (leaf, wood, and bark). The objective is to identify which component is likely to cause problems in subsequent utilization processes if biochar produced from various components of mallee trees is used as a fuel. It is found that the pyrolysis of different biomass components produced biochars with distinct characteristics, largely because of the differences in the biological structure of these components. Leaf biochar showed the poorest grindability, possibly because of the presence of abundant tough oil glands in leaf. Even for the biochar prepared from the pyrolysis of leaf at 800 °C, the oil gland enclosures remained largely intact after grinding. Biochars produced from leaf, bark, and wood components also have significant differences in ash properties. Even with low ash content, wood biochars have low Si/K and Ca/K ratios, suggesting that these biochars may have a high slagging propensity, in comparison to bark and leaf biochars. It appears that, in the utilization of biochar prepared from mallee biomass, the grindability is likely to be limited by the leaf fraction while ash-related problems could be due to the wood and bark components