How Compostable Plastic is Made
The new type of compostable plastic is called polylactic acid or polylactide. Produced by NatureWorks LLC under the name of IngeoTM, polylactide is a bioplastic film derived from corn. No genetically modified plant material is necessary for its production, and the amount of field corn used in the manufacture of Ingeo constitutes less than 1/20 of one percent of the world's yearly corn crop, which does not have a negative impact on the price or supply of food crops. For each pound of Ingeo produced, 2.2 pounds of corn are used.
The manufacturing process involves cooking the corn, grinding it to isolate the starch, and converting the starch to sugar. The material is then fermented by microorganisms, which convert the sugar into lactic acid. The lactic acid molecules are linked together into long chains to create the polylactide polymer. The polymer, called NatureWorks PLA, is formed into pellets that are used for a variety of products.
At present, Ingeo is made from corn, but any source of sugar can serve as raw material, including wheat, sugar beets or sugar cane. The company's website states that in the future, Ingeo will be producing non-food crops.