Cleantan: Environmentally-friendly tanning

Leather is a popular material - be it for the manufacture of shoes, bags or furniture. However, production, or, more precisely, the tanning process, is very inefficient. The chrome tanning agent used is only bound between 50 and 70 percent in the leather. On average, 40 percent ends up in wastewater and can only be recycled at great expense. Fraunhofer UMSICHT has therefore set itself the goal of completely avoiding excess chrome tanning agents and chromium-laden waste water in the tanning process. The sustainable and cost-effective tanning process CLEANTAN^® was developed within the framework of several projects funded by the BMBF.

Worldwide, about 22,000 km² of leather are produced annually – this corresponds to the area of the Saarland. Strong growth in the leather industry can be seen above all in Asia and South America. Tanneries are facing growing demands from leather product manufacturers. The latter demand a reduction in production costs and emissions in the leather manufacturing process. The pressure on tanneries to produce sustainable leather products is growing.

With CLEANTAN^®, Fraunhofer UMSICHT offers tanneries an emission-reduced and, at the same time, economical tanning technology. By using CLEANTAN^® technology, 40 percent of the chromium tanning agent and 100 percent of the wastewater are saved. At the same time, tanning can be carried out in one-fifth of the usual tanning time. The savings enable a considerable reduction in production costs and the CLEANTAN^® technology pays for itself within 2 years. In addition, there is the image boost to be expected due to the sustainability aspect of the tanning technology. CLEANTAN^® can become an important building block to keep and strengthen the leather producing companies in Germany and Europe.

The innovation lies in carrying out the tanning process under the influence of compressed carbon dioxide (CO₂) at a pressure of 30 bar. Chromium-contaminated wastewater is no longer produced, the tanning process is free of wastewater and the amount of tanning agent required is significantly reduced by 40 percent.

The CLEANTAN^® technology was developed up to a pre-industrial scale and is to be implemented on an industrial scale. With the transfer from the pilot plant to the pre-industrial scale, Fraunhofer UMSICHT realized a globally unique plant with a tanning drum volume of 1700 l. The system enables the tanning of hides with a mass of up to 500 kg and a leather surface area of over 100 m².

• EARTO European Innovation Award, First Prize, Brussels, Belgium, 2017
• Ferchau-Innovation Award, Hannover Trade Fair, Germany, 2013
• Innovation Award Cologne, Cologne, Germany, 2012
• San Jordi Award, Puerto Vallarta, Mexico, 2012