3 November 2008

Natural tannins from wine waste

Cheap and safe alternative to wood based tannins for the leather industries

Europe’s leather industries have traditionally used tannin agents sourced from high nature value deciduous woods, but an innovative Spanish EU project in the LIFE programm has successfully demonstrated alternative natural tannin compounds produced from wine grape seed waste.

Scientists from Spain’s Leather Research Centre were aware that producing traditional tree-based tannins involved large amounts of energy and the powder-based end products also created health and safety concerns in tanneries. The LIFE Environment project “Saving of forest exploitation for obtaining of tanning extracts through valorisation of wine waste” (LIFE04 ENV/ES/000237) was proposed to address these concerns and identify an effective, cheaper, safer alternative.

Woodland conservation also formed an important objective of the GRAPE TANNINS LIFE project that paid particular attention to improving the conservation status of species such as quebracho, mimosa, and chestnut, all of which are felled to provide tannin agents for the leather industry.

Research was undertaken by the LIFE team to first establish and test potential tannin content from different types of wine waste. Results from the investigations confirmed that natural tannins could be extracted from wine wastes, which allowed the LIFE project to begin developing a prototype technology for collecting and concentrating grape tannin extract. The prototype proved successful and generated energy savings by producing tannins in a liquid form. This was shown to be more cost efficient than producing powder based tannins, which required large amounts of heat to vaporise timber fluids.

The resulting grape seed tannins were tested during preliminary trials at two separate tanneries that participated in the pioneering project. The effectiveness of different types of grape tannin was assessed by the LIFE project team. One grape tannin was applied to tan cow hides that would be used to produce leather for shoe soles and another was tested to determine its ability to tan sheepskin, to be used to produce lining leather.

Leather obtained from the trials was analysed using standard physio-chemical techniques and compared against conventional tannery processes. Outcomes were positive and demonstrated that the leather produced using grape tannin extracts at industrial scale provided better “light fastness” than tannins sourced from hardwoods. Colours were considered appropriate and economic studies showed that the alternative tannins could be produced for 450 Euros/tonne, which is competitive with prices for conventional commercial tannins.

Further environmental studies concluded that 2,625 tonnes of tannin from grape extracts could be produced each year by recycling 22,830 tonnes of grape seed waste. These figures were then converted to show that substituting timber tannins with this amount of grape tannin extract could save the felling of some 551,250 quebracho, mimosa, and chestnut trees.

Additional environmental benefits included:

  • reducing the energy requirements in tanning production,
  • reusing and valorising agricultural waste products,
  • establishing a sustainable production technique for leather tannins and
  • reducing tanneries logistic costs by using locally available vegetable extracts and avoiding overseas sources of timber tannins.

The Leather Research Centre staff was highly satisfied with the LIFE project results which also delivered the desired health and safety benefits, since the new liquid tannins avoided risks from dust formation in tannery work places.

LIFE is the EU’s financial instrument supporting environmental and nature conservation projects throughout the EU, as well as in some candidate, acceding and neighbouring countries. Since 1992, LIFE has co-financed some 2,750 projects, contributing approximately €1.35 billion to the protection of the environment.

Further information

Source: LIFE, 2008-10-30.

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