After several false dawns, the market for biopolymers began to take off about two years ago in applications such as food packaging, agricultural mulch film, fast food tableware and nappies (ENDS Report 315, pp 29-32 ).
Much of the growth is led by Cargill Dow, which brought on stream a 140,000 tonnes per year polylactic acid (PLA) plant in Nebraska last year. The company is focusing on two applications for its NatureWorks plastic: fibrefill for soft bedding products and - a more traditional testing ground - packaging.
However, the material is now being used in Japan to manufacture parts for consumer electronic goods.
Sony launched a Walkman model last autumn which uses NatureWorks in more than 90% of the casing by weight. Conventional PLA lacks the physical properties needed for durable consumer goods. However, working with Cargill Dow's licensee, Mitsubishi Plastics, Sony says that it has improved the polymer's durability, mouldability and heat and shock resistance so that it can be used for equipment casings.
Around the same time, Fujitsu announced that NatureWorks would be used for some of the components in a laptop computer model. It claimed this to be the first time that bioplastic would be used in this application. The company expects to use it in the product's entire housing by 2004/05.
Under Japan's revised recycling law, introduced in 2001, companies must recover, recycle or compost their products and components, reduce material inputs and increase product lives in order to reduce the amount of waste generated. This has stimulated closed-loop recycling, with Fujitsu, for example, now beginning to use recycled ABS plastic from computer housings in new laptop housings.
Composting of plastics may also receive a major boost in Japan from the "GreenPla" logo for products made from biodegradable plastics. The logo was launched two years ago by Japan's Biodegradable Plastics Society. In 2001, NatureWorks film wrap for Sony computer disks became the first product to bear the logo.
The prospect of waste plastics actually being consigned for composting remain low. "It is rare that such products are composted at end-of-life," said Asako Nagai of Sony corporate environmental affairs. "However, vegetable-based products give more options for environmentally sound disposal than current plastics." As well as composting, material recycling of bio-PLA is technically feasible.
In Japan, products made with biodegradable plastics are marketed as having a number of environmental advantages. One is that, unlike PVC, they are chlorine-free and therefore, says Fujitsu, "eliminate emissions of dioxins and other harmful chemicals if incinerated."
Secondly, says Fujitsu, it takes less energy to produce NatureWorks than conventional plastics - a claim backed by Cargill Dow's life-cycle assessments (LCAs) (ENDS Report 300, pp 19-21 ). Thirdly, plant-based plastics are a renewable resource and can help reduce dependence on finite petroleum resources.
Both Sony and Fujitsu also point out that NatureWorks can decompose to carbon dioxide, water and inorganic substances. But while Sony says this occurs "through a process induced by microorganisms or enzymes in composters", Fujitsu unwisely claims that the same process occurs if the product ends up in a landfill. In fact, in the anaerobic conditions of a landfill, such materials will decompose to produce the powerful greenhouse gas methane.
Fujitsu omits to mention this - even though its environmental report says that the company "designs products with the prevention of global warming in mind" and LCA is part of the design process.
Sony admitted that it did not take methane emissions from landfill into account in its LCAs of such products. "Methane generation during [sic] vegetable-based plastic in landfill is not well researched because of difficulties in setting reliable parameters," said Mr Nagai.