Global interest grows in biodegradable polymers

Life-cycle assessments show that biodegradable polymers have a "significant" role to play in the UK's moves to a sustainable future, according to a report by the Government-funded National Non-Food Crops Centre.1 Meanwhile, global giants such as Procter & Gamble, Unilever and DuPont are making significant investments in pilot and commercial production facilities.

Biodegradable polymers made from crops such as maize or potatoes are increasingly being used in applications such as packaging and fibres as a "green" alternative to conventional, petrochemical-based plastics.

According to the new report, "several classes of biodegradable polymers...have a positive role to play in advancing [the] UK's move towards greater sustainability by reducing environmental impacts over their life cycles. This role is likely to become more significant in the future."

These conclusions echo the Government's recent strategy for non-food crops, which said that plant-based products and fuels offered significant economic and environmental benefits for the UK (ENDS Report 352 p 53 ).

Drawing on a review of over 40 LCAs and responses to a questionnaire sent to organisations involved with biodegradable polymers, the report highlights their environmental advantages over oil-based polymers - but glosses over areas where the picture is less clear cut.

Materials such as thermoplastic starch or polylactic acid (PLA) have "favourable eco-profiles for many applications due to their relatively low energy in manufacture, their carbon dioxide 'neutral' status for agriculture/forestry organic carbon content, and their end-of-life value in composting or energy recovery."

However, most biodegradable polymers are currently landfilled, breaking down to produce methane, a potent greenhouse gas (ENDS Report 315, pp 29-32 ). The report admits that LCAs which took account of landfill disposal showed oil-based polymers to have "equivalent or better eco-profiles".

Some producers of biodegradable polymers downplay the issue. "It's not an argument against biodegradable polymers," said Toby Matthews, chief executive of packaging manufacturer Potatopak. "It's an argument for the Government to build composting facilities."

However, while investment in composting plants and collection schemes for compostable household waste will increase as local authorities strive to meet the landfill diversion targets set by the EU landfill Directive, progress will be slow.

The report's bullish stance reflects the market reality of a growing number of biodegradable polymer manufacturers and predictions of rapid market expansion.

Cargill Dow, which has a PLA plant in Nebraska, plans to build two more over the next five years, increasing their capacity from 140,000 tonnes to 500,000 tonnes (ENDS Report 338, pp 33-34 ).

Speaking at a recent National Non-Food Crops Centre conference, John Oakley of packaging manufacturer Autobar Disposables said that Marks & Spencer and the Co-op were just "weeks away" from introducing PLA in a number of own-brand products ranging from yoghurt pots to sandwich packaging.

However, M&S still has concerns about PLA being made from genetically modified maize, as well as how well it dyes and irons when used in clothes. Although Cargill Dow does offer to use non-GM maize, it processes the material alongside GM maize and so cannot guarantee the polymer it supplies as GM-free (ENDS Report 338, pp 33-34 ).

The Co-op also denies that it is so close to introducing PLA into any product lines, although the material is being assessed as part of a current review of own-brand products. The Co-op is one of several retailers already using carrier bags made from degradable polymers, although these products are mostly petroleum-based at present (ENDS Report 332, pp 35-36 ).

Toothbrush manufacturer Wisdom is testing PLA in the hope of using it as a substitute for PVC, while carrier bag producer Europackaging, which supplies most of the major UK supermarkets, launched a range made from PLA in March.

In May, Dow's rival DuPont announced that its new joint venture with Tate & Lyle will build its first commercial-scale plant for making 1,3 propanediol (PDO) - a biodegradable material derived from maize - by March 2006 in Loudon, Tennessee. PDO will be used to make the polymer PTT for packaging, clothing and carpets (ENDS Report 346, pp 32-33 ).

Procter & Gamble has set up a joint venture with Japanese chemical firm Kaneka to produce a polyhydroxyalkanoate biopolymer, trading under the name Nodax H. The companies hope to build a 30,000-50,000 tonnes per year plant, but are a long way from deciding when and where it will be built. The polymer would be used to make fibres for medical clothes and flushable consumer products.

Unilever is also making moves into the biodegradable polymer market, looking to develop them for use in packaging and washing powder, according to Naheed Rehman of the firm's R&D division.

Toyota recently announced that it will start up a pilot plant in Japan this August to produce "bioplastics (PLA)" from sugar cane. If this is successful, a commercial scale plant will follow by 2007. The company currently makes some car mats out of "bioplastics", but hopes to make other office supplies and car parts. By 2020, it plans to produce 20 million tonnes of bioplastics, two-thirds of its estimate for the world market.

The National Non-Food Crops Centre is supported by the Departments for Environment, Food and Rural Affairs and Trade and Industry plus private-sector sponsorship. Its role in stimulating market development was highlighted in the Government's recent non-food crops strategy (ENDS Report 352, p 53 ). The new report, drawn up jointly by Imperial College and the NNFCC, was funded through the Government's Sustainable Technologies Initiative.