Farmers Weekly 12 January 2000
Making plastic from maize, once a pipedream, is now a growing business in the US. Brendan James looks at what could be an important new use for the crop
THERE would seem to be little connection between farmers of the American Mid-West and petrochemical plastics factories burning precious reserves of fossil fuel. But what if their vast, rolling fields of corn had granules of plastic forming in the stalks and leaves?

For farmers   like   Brian Peterson, a Western Iowa corn grower, this is a far from academic question. Mr Peterson farms near Mondamin in Harrison County, 30 miles from the wet milling plant of agricultural giant Cargill. It is also the site of Cargill Dow's $300m (£200m) plastic manufacturing facility that will be taking l000t of maize a day by the end of 2001.
"This is something farmers have been waiting for," says Kevin Swanson, chairman of the Nebraska Corn Board. "It represents a new market and a variety of new, high-tech products."
The effects will not, however, be limite to American corn growers. Cargill Dow is developing the technology to use annually renewable agricultural waste and other crops such as wheat, and sugar beet. It has also announced plans to open a similar facility in Europe within the next two years.
What type of plastic is it?
Cargill Dow, a 50/50 joint venture between Cargill Inc and the Dow Chemical Co, owns the most successful process. Currently Cargill Dow is manufacturing 6000- 8000t/yr of corn-derived plastics (PLA) at its plant near Minneapolis, but construction has started on a new $300m (£200m) 140,000t/yr plant in Blair, Nebraska. This will begin production by the end of 2001 and produce NatureWorks PLA, a polylactide polymer for worldwide sale.
"PLA is not just one plastic it's a whole range that matches petroleum-based plastics on cost and performance," says Randy Howard, president of Cargill Dow. "It competes   head-on   with   nylon, polypropylene, polyethylene, polystyrene, and cellophane, as well as natural materials such as wool, cotton, and paper. Also, NatureWorks PLA is fully biodegradable when composted, and because the raw materials come from renewable sources it reduces consumption of fossil fuels by 30-50%.
Is this a new process?

PLA is the result of only 15 years research started by Cargill Inc and is reckoned to be a big achievement for a specialist grain trader with fermentation  and  distillation expertise. However, as an agricultural firm, Cargill had taken it as far as it could by 1997. The company needed an associate with access to chemical markets and polymerisation capabilities, and Dow Chemicals was the ideal partner.
PLA production starts with the fermentation of corn sugar which turns it into lactic acid. Condensation is then used to turn the lactic acid into short-chain polylactic acid which is turned into lactic by the vacuum distillation process. The final stage, called ring-opening polymerisation, then creates the final product.
What will it be used for?

By January 2000 two firms, Fibre Innovations Technology  and Unifi, were already producing fibres and yarns from Nature-Works PLA. They are now developing new products with industry brand leaders such as Woolmark and several well-known sports wear companies.
Cargill Dow believes that it is the application advantages of PLA, rather than its environmental benefits, that will let it compete with conventional plastics. It is apparently soft and wrinkle resistant and when used in clothing drapes well. Used in carpeting, it has low flamability and excellent UV stability. In packaging, it offers outstanding gloss, a good printing surfface and resistance to moisture and grease.
Importantly, Cargill Dow's long term vision for PLA takes the process even further. "We may eventually go all the way from taking in local corn supplies to producing finished goods in the same location," says Gruber. "It is also conceivable that we could set up the whole  process as a closed loop, in which we bring in the biomass, extract the sugar, and burn the rest as fuel to reduce dependency on imported hydrocarbons.
A new agricultural industry?

Clearly, harvesting the carbon which plants remove from the air to produce plastics from natural plant sugars is no longer just a vision. It is something that Cargill Dow and their closest rivals Du Pont already do on a global scale.
Cargill Dow uses maize that is not genetically modified, while Du Pont and several others use GM plants. One experimental process actually produces plastic granules in leaves and stalks within the plant itself, converting plant sugars to polymers during growth. Many researchers see this as the most efficient, and most elegant, way to make plastics from renewable resources. Developed first by ICI, then Monsanto, it was used to manufacture packaging for niche markets in the nineties but lack of funds and opposition by environmental groups has halted development.

Who else is involved?

Though commercially some way behind Cargill Dow, Du Pont has recently announced its intention to market a plant-derived polymer under the brand name Sorona. The technology involves inserting four genes taken from various species of bacteria and yeast into industrial strains of E Coli.
Unlike PLA, Sorona in its commercial form is not biodegradable.It is, however, recyclable, easily dyed, and stain resistant. It can also be stretched up to 15% while retaining its original shape and can be used in polyurethane and synthetic leather when mixed with other acids.
Du Pont began commercial production of Sorona in October 2000. Initial production will be 12,000t a year with the ability to expand to 50,000t a year. Manufacturing agreements are also in place with Du Pont's Dacron polyester businesses in Europe, the US, Korea, and Japan.