Thermal valorization and elemental composition of industrial tannin extracts

Due to their natural origin and broad availability, industrial tannin extracts are extending their application field from the classical, and still principal, application in tannery, to oenology, pharmacy, adhesives and material science. Despite the growing interest, not much is known about the thermal valorization of these biomolecules. In this article we present the thermal properties of the eight most common commercial tannin extracts and their elemental chemical composition to shed light on the end-life of the bio-materials based on these polyphenols. Results have shown that hydrolysable tannins can be managed similarly to wood, while condensed tannins have higher heating values but also generally higher chlorine content. Sumac and gambier leaf extracts registered contained heating values and significant amounts of ashes rich in calcium and sulfur. The high chlorine content observed for the extracts of mimosa (Acacia Mearnsii) does not hinder the combustion of its derived products which can still be thermally valorized. Mimosa tannin-based materials can also be added up to 2% to wood pellets and briquettes without significantly affecting the overall quality of the biofuels according to the in-force standards.