From Science and
From Science and Research HMF from chicory salad waste 800,000 tonnes: That’s how much waste in the form of chicory roots is generated during the production of chicory salad in Europe per year. Currently, after harvesting the chicory salad, the roots are disposed of in composting or biogas plants. What a waste, thought two researchers of the University of Hohenheim, Germany. Because these roots can be used to generate hydroxymethylfurfural (HMF), a basic material in the future plastics industry. The biennial chicory plant only spends the first five months on the fields. In mid-October the leaves are mulched and the roots are harvested, stored in a cool place, and then brought to special growing rooms. Only there will the new buds, the future chicory salad, sprout. Fig. 1: 30 % of the chicory plant can be used for making HMF (Source: Wikipedia/Rasbak) But in contrast to the food production, at the University of Hohenheim the focus lies primarily on the non-edible root. “The root makes out approximately 30 % of the plant (cf. fig.1). The stored carbohydrates are not fully used for the formation of the buds and valuable reserve substances remain. However, the roots can only be used once for chicory growing and have to be thrown away after the buds are harvested”, explains agricultural biologist Dr. Judit Pfenning. Polyamides, polyester, or plastic bottles Prof. Andrea Kruse, of the Institute for Agricultural Engineering at Univ. Hohenheim explains what they do: “On the rack in figure 2 you can see pencil-sized stainless steel tube reactors. These are filled with chopped chicory roots and water. After adding diluted acid into the ultra-stable pressure container, it is heated up to a temperature of 200 °C.” This results in a watery product which is then processed in further proprietary steps to produce unpurified hydroxymethylfurfural (HMF) in the form of yellow-brown crystalline powder. This is a precursor to form furandicarboxylic acid (FDCA), identified by the US Department of Energy (DoE) as one of the 12 most important platform chemicals. FDCA serves as a raw material for polyamides (e. g. for nylon stockings), for polyesters, polyurethanes or – more concrete – to make PEF (polyethylene furanoate). PEF can for example be used for the production of bottles, as a biobased alternative to PET. Chicory-made HMF as part of bioeconomy As part of a previous research project Kruse already found a way to extract the basic chemical HMF from fructose. However, she is of the opinion that chicory roots as a source are more elegant. After all: “Fructose 40 bioplastics MAGAZINE [02/16] Vol. 11
From Science and Research is edible. There are better uses for it than extracting HMF.” This is not the case for chicory roots. “Until now, they were waste.” The challenge: storage and quality of the roots The project poses a challenge: “The root is only of interest for the industry if we can guarantee permanent quality,” explains Prof. Kruse. To this end, the technical chemist cooperates with the plant scientist Judit Pfenning from the Department of General Crop Farming. “In general, the conditions are very good,” explains Pfenning, “because the consumer who wants to eat the chicory also has very high and consistent quality expectations. That is why only roots of very high quality are transferred from the fields into the commercial growing rooms operating with water-forcing techniques.” Another research aspect: How the roots can be stored without going bad. The problem is that chicory is a seasonal business. However, suppliers of the chemical industry want permanent deliveries in order to be able to constantly use their plants. “This project can only be carried out through interdisciplinary cooperation,” emphasize the scientists. One the one hand the project includes quality control, growing trials, and storage experiments, and on the other hand laboratory experiments and conversion technology. MT www.uni-hohenheim.de Fig. 2: Chicory waste can be used as a source for different plastics, e. g. nylon or PEF for bottles (Photo: Univ. Hohenheim) Fig. 3: Chicory is harvested from special growing rooms. (Source: Wikipedia/slick) bioplastics MAGAZINE [02/16] Vol. 11 41
