Tannin is a natural extract, known since antiquity, but at the centre of attention in recent years. Like all extracts, it must undergo an extraction process to be used. This term calls to mind laboratories and scientists, mathematical calculations and the latest generation computers.
However, nothing could be further from the truth: tannin extraction is carried out naturally and sustainably. In fact, it is very similar to an infusion, like when you prepare a nice, hot cup of tea. Of course, scientific progress has led to innovations in the field of industrial tannin extraction throughout history, but the principle has remained the same: wood immersed in hot water to slowly release the tannin.
In chemistry, extraction involves “drawing” a substance out of a source (in this case, wood) and isolating it from other substances. This is generally done using an extracting agent that is often chemical in nature. However, no chemical reagent is needed to extract tannin, hot water and nothing else. Extraction is not the only method for obtaining tannin: for example, Tara pods are so rich in tannin that they simply need to be grinded.
The process has been perfected over time to optimise yield, improve the energy efficiency and safeguard the responsible use of resources. The richest sources of tannin in the industrial world are chestnut and Quebracho wood, Tara pods, Aleppo oak and Chinese sumac.
The tannins are derived from forests managed in accordance with the very strict local regulations governing sustainable cutting and use. In Italy, tannin is extracted primarily from the chestnut and the Aleppo oak.
In Italy, wood cutting of chestnuts is subject to authorisation and is controlled and performed in accordance with local forestry legislation.
Cutting must not compromise the equilibrium of the natural habitat and the conservation of animal species. Its aim must not be to create new areas for agricultural use.
Furthermore, the wood must not come from “illegal cutting” (in breach of applicable national and regional laws) or from landfills, industrial sites or areas along high-traffic roads and/or motorways.
The chestnut tannin extraction process
The chestnut trunks are stacked and kept outdoors in the open air before undergoing successive treatments.
They are then chipped, which makes them easier to handle and ready for infusion in hot water. This increases the surface area of the wood in contact with the water and encourages the release of tannin.
Next comes extraction. The chestnut chips are poured into autoclaves filled with boiling water at 100°C. When the wood chips come in contact with the hot water, they begin to release tannin, just like a tea bag in a teapot. This process is completely natural because it uses only water and does not require the addition of any chemical additive.
A dark and thick liquid is obtained, which then undergoes various purification processes before the tannin is ready to be sold. First, the solution is cooled to room temperature to precipitate any impurities present in the plant matter.
The liquid tannin is ready to be used as it is. However, to facilitate storage, packaging and shipping, it is spray dried to turn it in powder form.
The chestnut tannin obtained in this way has a dark brown colour, reminiscent of instant barley coffee powder.
The water, which is so precious to the environment, is not wasted. On the contrary, tannin extraction can be considered sustainable because the steam formed during processing is not dispersed, but recovered through condensation and reintroduced in the production cycle.
Wood residues from tannin extraction can be used to generate heat and electricity in biomass power stations, or can be transformed through extrusion into 100% natural pellets for domestic and industrial wood stoves.