Recycling economy: New separation technique saves costs

Press release / April 01, 1998

Germany was the first country to enact a recycling (the so-called "closed loop economy") law in 1996: Instead of disposing waste it ensures the recycling or reprocessing of waste materials with the aim of saving natural resources. Fraunhofer IGB has developed a process for combined waste water purification and acid recycling. This not only protects the environment but also reduces costs.

Germany was the first country to enact a recycling (the so-called "closed loop economy") law in 1996: Instead of disposing waste it ensures the recycling or reprocessing of waste materials with the aim of saving natural resources. This not only protects the environment but also reduces costs.

One way of economizing in closed loops are production- or process-integrated recycling techniques. Thus, innovative methods may not only result in purification of waste water - thereby saving disposal expenses - but even in production of high-value substances. The Fraunhofer Institute for Interfacial Engineering and Biotechnology develops methods which combine purification of (e.g. waste) water with the production of high-value substances.

Such a process is the combined purification of dairy waste water and production of lactic acid. Specific high-performance lactic acid bacteria transform the lactose contained in whey to lactic acid. Lactate is separated from the fermentation broth by filtration processes and purified as free acid by electrodialysis using bipolar membranes. This lactic acid can be used as intermediate in chemical industry for example for the production of biodegradable plastics based on polylactides. The process has been tested in laboratory and pilot plant scale. Calculations of the Fraunhofer researchers show that this integrated bioprocess promises to be ecomic in technical scale: From 100,000 tons of whey about 4,200 tons of lactic acid can be produced at a price of approximately 1.20 DM per kilogram. The current market price for lactic acid is 2.50 DM.

A plant for electrodialysis with bipolar membranes has been presented at this year's Hannover Trade Fair. The process does not only facilitate the separation of lactic acid from fermentation broths but can also be applied in food technology, for example for the production of fruit acids from juices. The process is made possible by combining product separation with the electrodialytically forced water dissociation resulting in the transformation of ion salts into the relevant free acids or bases. Furthermore, the electrodialysis process can be transferred to other applications: Acids from old batteries can be reconditioned, and the chelating agent EDTA can be recycled e.g. from galvanic copper baths. These recycling processes do not only save chemicals but costs as well. And by recycling economy the environment benefits, too.