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That's a wrap! Corn yields a natural solution for sustainable food packaging.

By combining the best of large-scale industrial biotechnology with chemical processing, Cargill Dow LLC is providing food companies the opportunity to offer the complete package with its 100 percent corn-based food packaging material. This new material is known as NatureWorks[TM] PLA. The technology used to create it allows abundant, annually renewable resources such as ordinary field corn to replace finite ones, such as petroleum. The technology is being used in food packaging, fibres, and many other applications.

Natural packaging gives food fresh appeal

NatureWorks PLA is changing the way shoppers think about food packaging by offering all the convenience of traditional plastic packaging while helping reduce environmental impact.

"NatureWorks PLA packaging looks, acts, and feels like the packaging we are accustomed to buying, but with the important difference of sustainability," says Lisa Owen, global business leader for rigid packaging with Cargill Dow LLC. "This holds a special emotional appeal for consumers, especially among those already interested in natural or organic foods."

Owen sees the most immediate potential for NatureWorks PLA in rigid food containers such as berry packs, clamshells, drinking cups, and film applications like food wrap and container lids. Nature-based packaging offers great point-of-sale differentiation for fresh foods like produce, and deli and bakery items. Several leading grocery retailers in North America and Europe are currently using NatureWorks PLA to draw customer attention to their fresh food offerings. Natural foods retailer Wild Oats Natural Marketplace is using clear containers made from NatureWorks PLA in its deli and salad bar sections. Italian hypermarket chain IPER sells a broad range of foods packaged in NatureWorks PLA, including produce, fresh pasta and salads, and deli meats and cheeses. IPER also uses paper bread bags with NatureWorks PLA film windows.

With its favourable environmental qualities, NatureWorks PLA is also finding a fit with organics, as a way to extend these foods' all-natural appeal to the entire product offering. Biorigin S.p.A., Italy's leading organic pasta manufacturer, is packaging its fresh organic pasta specialties in containers and film from NatureWorks PLA. Pennsylvania candy company JoEl Inc. is also wrapping each piece of its new College Farm organic hard candies in clear film of NatureWorks PLA.

In addition to food packaging, NatureWorks PLA can be used for other plastic packaging items, ranging from floral wrap to disposable service ware and cutlery.

Bringing NatureWorks PLA to market

Cargill Dow's proprietary process for creating PLA is based on the fermentation, distillation, and polymerization of a simple plant sugar, corn dextrose. The company essentially harvests the carbon stored in the sugars and makes a polymer with similar characteristics to traditional thermoplastics.

The potential to make plastics from plant sugars was first discovered it in the 1920s by Wallace Corothers, the scientist who invented nylon. But it was only recently that a commercially viable method was developed to produce polymers with the cost and performance necessary to compete with traditional fibres and packaging materials. The breakthrough was the use of fermentation as a cost-effective way to produce PLA on a large-scale basis.

To produce PLA, the carbohydrates in corn are enzymatically hydrolyzed to sugar and then fermented to lactic acid. Lactic acid is polymerized through a condensation reaction to low molecular weight PLA, which is then depolymerized to form lactide, the cyclic dimer of lactic acid. High molecular weight linear PLA is produced by ring-opening polymerization.

Lactic acid exists as d and l stero-isomers. The lactide dimers exist as three forms: D lactide (a dimer of two d-lactic acid units), L lactide (a dimer of two l-lactic acid units) and meso lactide (a dimer of one l- and one d- lactic acid units.) The d-lactic acid content is controlled to adjust the polymer properties. Most notably, the d-lactic acid content affects the crystallinity potential and the melting point.

Cargill Dow operates a global-scale facility capable of producing more than 140,000 metric tons (300 million pounds) of NatureWorks PLA per year. The manufacturing plant requires 40,000 bushels of field corn per day and is making commercial-grade resin that is being shipped around the world for use in a wide range of consumer goods.

Initially, Cargill Dow is using sugars derived from corn. While the process doesn't distinguish between plant sugars, an abundant, cost-effective raw material is required to be economically viable. Today, corn is one of the best sources. In the future, NatureWorks PLA will likely be made using other sources of cellulosic biomass, such as the stalks and leaves, as feedstock. Harnessing these plant parts as the raw material would essentially allow farmers to create a new revenue stream for their crops--one for the grain, and one for the waste.

"What Cargill Dow is doing is taking a renewable, abundant crop (corn) and using it as the raw material for a range of consumer goods. This process is a step-change in environmental stewardship," Owen says.

The fact that NatureWorks PLA fits all disposal options differentiates the polymer from competitive materials is. It is fully compostable in industrial facilities, where it breaks down like other matter derived from plants. With the proper infrastructure, products made of NatureWorks PLA can be recycled back to a monomer and into polymers.

Performance without sacrifice

While environmentally sound products are highly desired by consumers, performance is the ante for even being considered. What makes NatureWorks PLA such an attractive option is that it offers performance that is on par with existing packaging materials, such as cellophane or oriented plypropylene. Some of the inherent physical properties that the resin provides include high gloss, superior clarity, superb twist retention, excellent optics, strong deadfold, heat-seal ability, and flavour and aroma barrier.

"NatureWorks PLA offers a more sustainable future," says Owen. "It satisfies consumers' needs to feel good about the entire product they purchase, not just the food. Consumers want to do their part in protecting the environment, and purchasing fresh food packaged in NatureWorks PLA gives them a way to contribute directly."
How NatureWorks[TM] PLA is Made ... and Unmade

Annually Renewable Resource A renewable resource such as corn is
(Unrefined dextrose) milled to separate starch from the
 raw material. Unrefined dextrose is
 processed from the starch. Future
 technology enhancements may eliminate
 the milling step and allow for utili-
 zation of even more abundant agricul-
 tural by-products.

Fermentation Cargill Dow turns dextrose into lactic
(Lactic acid) acid using a fermentation process
 similar to that used by beer and wine
 producers. This is the same lactic
 acid that's used as a food additive
 and is found in muscle tissue in the
 human body.

Intermediate Production Through a special condensation proce-
(Lactide) ss, a cyclic intermediate dimer, ref-
 erred to as a lactide, is formed.

Polymer Production This monomer lactide is purified
(Polylactides) through vacuum distillation. Ring-
 opening polymerization of the lactide
 is accomplished with a solvent-free
 melt process.

Polymer Production This monomer lactide is purified
(Polylactides) through vacuum distillation. Ring-
 opening polymerization of the lactide
 is accomplished with a solvent-free
 melt process.

Polymer Modification A wide range of products that vary in
for Customers. molecular weight and crystallinity can
 be produced, allowing Cargill Dow to
 modify PLA for a large number of

How it's Unmade NatureWorks PLA fits all disposal
 systems. It is compostable. Products
 made of NatureWorks PLA can be recyc-
 led back to a monomer and into poly-
 mers. It is inert in a landfill, pro-
 ducing no leachate or toxins. At the
 end of its lifecycle, a product made
 from NatureWorks PLA can be broken
 down into its simplest parts so that
 no sign of it remains.

Reduced Fossil Resource Use Because NatureWorks PLA is derived
 from annually renewable resources, it
 uses 20 to 50 percent less fossil
 resources than comparable petroleum-
 based plastics.

Reduced C[O.sub.2] Emissions Because NatureWorks PLA recycles the
 earth's carbon, it potentially reduces
 the carbon dioxide in the atmosphere.
 Carbon dioxide is removed from the
 atmosphere when growing the feed stock
 crop and is returned to the earth when
 NatureWorks PLA degrades.

NatureWorks, the NatureWorks logo and the EcoPLA design are trademarks of Cargill Dow LLC.
COPYRIGHT 2004 Chemical Institute of Canada
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2004 Gale, Cengage Learning. All rights reserved.

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Title Annotation:NatureWorks PLA
Publication:Canadian Chemical News
Article Type:Cover Story
Geographic Code:1USA
Date:Jan 1, 2004
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