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From crab shells to raw materials


From crab shells to raw materials

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Crab is a culinary delicacy most of which ends up in the bin. In this edition of Futuris we look at the uses can we find for the hundreds of thousands of tons of crab shells thrown away by European consumers every year.

In a lab in Bavaria scientists are trying to chemically transform crab shells into a high performance biopolymer. This European research project, Chibio, turns the waste into a raw material and energy source. The first step is to extract the substance chitin from the shells. After cellulose, chitin is the most abundant biopolymer on earth.

“Shrimps, crabs, crustaceans, a large proportion of their body weight contains chitin,” says Prof. Dr Volker Sieber a biochemist at Fraunhofer IGB’s Chibio Project.

“Chitin is a polysaccharide, a polymer, which is composed of sugar molecules. Sugar molecules can be chemically or biotechnologically engineered to produce different molecules.”

Crab shells contain other non renewable biological substances. Used to produce biogas, they become a viable energy source. Meanwhile, biochemists from Munich have developped optimized yeast strains to convert the chitin through fermentation into fatty oils. The process which takes between 5 and 7 days.

“Once we’ve chosen the different yeast strains by fluorescence testing, we will intensify them in a fermentator to help produce enough oils for further experiments,” says Dr. Daniel Garbe, a biochemist at Munich University of Technology .

“These oils will be given to our partners in the industry to be processed. The oils we get by this procedure look like these samples.”

The oils are sent to a partner company in northern Germany. Dr Matthias Ullrich a chemist with Evonik Industries explains the process: “At this facility, we process the natural oil obtained from crab shells, a reaction takes place under high pressure and we obtain the raw material for our plastics.”

The oil is transformed into a pure chemical, the raw material for the production of plastic. The next step is what is called polymerisation. The high performance biopolymer is produced in a reactor at temperatures of up to 300°C. It’s then chopped into granulates.

“We use this reactor, which can be thought of as a pressure cooker, and we fill it with raw materials,” says Dr Ulrich. “This raw material is what we transformed from the natural oil into a pure chemical by catalysis. After the reaction we obtain this high performance plastic as we see it here, which is cooled in water.”

The biopolylmer is then molded into sample pieces for quality control; they are thoroughly tested.

From simple crab shells and a complex chemical process we finally end up with a high performance product, a raw material for the future, according to Dr. Joachim Leluschko an engineer with Evonik Industries: “What is interesting with biopolymers is that we don’t use any plants that are also used as a food source. We have a number of projects where we use organic wastes. Waste that would otherwise be destroyed, we can use it as natural raw material to make plastics in the future.”

This new raw material could be used in plastic products in the very near future.

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