Technology: Italian firm first with 'truly biodegradable' plastic

日期:2019-02-28 04:06:06 作者:风芡嘧 阅读:

By DEBORA MACKENZIE in BRUSSELS FERRUZZI, a chemicals company in Italy, has invented what it claims is the world’s first truly biodegradable plastic. The firm publicised its discovery last month by giving away 750 thousand ‘Mickey Mouse’ watches made with the plastic. It has applied for a patent on the material, and expects to launch it next year. Amilcare Collina, the scientist in charge of the project, says that Ferruzzi’s plastic differs from the currently available ‘biodegradable’ plastic now used for disposable goods such as carrier bags. These are made from webs of polyethylene that have starch in the ‘gaps’. Microbes in soil degrade the starch, but not the polyethylene, so the bags are only partly biodegradable. Ferruzzi’s new plastic also contains starch, from maize, but in larger quantities. Whereas current ‘biodegradable’ plastics may contain up to 10 per cent starch, says Collina, Ferruzzi’s plastic contains between 10 and 50 per cent. Microbes degrade that part of the plastic to carbon dioxide and water. The rest of the plastic consists of compounds called ‘plasticisers’ – which reduce brittleness – and of straight chains of small hydrocarbon molecules, or polymers, derived from oil. A new feature of Ferruzzi’s plastic is that the oil-derived polymer is a relatively short molecule which dissolves in water. This makes it much more amenable to attack and digestion by microbes in soil than, for example, polyethylene, a long molecule which repels water. The rate of decay decreases as the amount of starch in the plastic decreases, but is still ‘a few times faster than conventional oil-derived plastic,’ says Collina. Tests are now under way to measure the time the plastic takes to decay in various environments, and to determine the degradation products formed by bacteria acting on the oil-based component. The other unique innovation, says Collina, is that Ferruzzi’s plastic is a true blend of polymers, referred to as an alloy. This means that chains of the starch polymer and the oil-derived polymer interweave to form a substance with new properties. Existing ‘biodegradable’ plastics are simply mixtures of substances, not alloys. The innovation has allowed Ferruzzi to raise substantially the amount of starch in the plastic. If the loading in existing ‘biodegradable’ plastics is raised to more than 10 per cent, the polythene ‘support’ is too weak to bind the starch – which dissolves in water on contact, making it impractical as a material for shopping bags. Ferruzzi’s plastics can have a loading of 20 per cent starch and still be strong enough for shopping bags. The development of the plastic is one of several projects in a ‘green chemistry’ programme that Ferruzzi launched, at a cost of 20 billion lire (Pounds sterling 10 million), in January. This year, the Italian government ruled that all non-biodegradable packaging material, including shopping bags, must be phased out over the next decade: and in the last few weeks, Sweden has outlawed packaging material made from non-biodegradable polyvinyl chloride. ‘Regulatory pressure from governments is a major factor in the time-frame in which we can develop alternatives to existing technology,’ says Collina. Another factor in promoting ‘green’ chemical products is the European Community, which allocates money to assist research such as Ferruzzi’s and to induce farmers to produce raw material for industry instead of surplus food. The Community has a programme, called Flair, to assist such research, although it accounts for a small proportion of the Community’s total research budget. Ferruzzi’s new biodegradable plastic costs more than existing plastics. Collina says the difference is less than twice as much. Scientists at Fertech, a research subsidiary of Ferruzzi, invented the plastics. ICI Biological Products based in Cleveland on Teesside is also developing a truly biodegradable plastic, one that engineers can fabricate directly into consumer products. Now, the company is experimenting with a pilot-scale plant to make the plastic, a product generated by the fermentation of Alcaligenes bacteria in glucose. However, the product, called polyhydroxybutyrate, is more expensive to make at present than commodity plastics, so large-scale commercial exploitation is some way off, says John Stageman,