Bioplastic from Corn

By Michael Caduto

Summer is finally here. With widespread vaccination against COVID-19, Vermont and many other states are opening up to larger social and familial gatherings. You may soon find yourself choosing foods from a delicious spread at a friend’s potluck or sampling exotic dishes at an ethnic foods street fest, when you notice that the writing on your plastic cup, plate or utensil says, “Made from Corn: Certified Compostable.” But the item looks and feels like ordinary plastic, so how could it be compostable? Most likely, there is also some fine print on the plastic that says, “In Industrial Facilities.”

Welcome to the world of corn-based bioplastic—an alternative to the ubiquitous and environmentally disastrous petroleum-based plastics. Since plastic production skyrocketed following World War II, over 9 billion tons have been produced. More than 200,000 barrels of oil are now required to manufacture the plastic products consumed by residents of the United States alone every day.

Plastic comprises over one quarter of the volume of trash in our landfills. The remainder ends up in the environment where it persists for half a millennium while harmful compounds leach into soils and aquatic ecosystems. More than 165 million tons of plastic have been dumped into our oceans.

Along comes bioplastic. Corn is the raw material for making polylactic acid (PLA)—the basic material for producing a biodegradable plastic that is used to manufacture a wide range of consumer products, from cups and films to food containers, drinking straws and garbage bags. During the production process, cornstarch is converted into dextrose, which is then fermented into lactic acid. Lactide molecules are joined to form polylactic acid.

Manufacturing PLA requires 65 percent less energy and produces just 32 percent of the volume of greenhouse gases versus manufacturing plastic engineered from petroleum. And PLA bioplastic contains no toxic compounds. But there is a downside: Many PLA products begin to melt when they reach about 114°F. Most brewed coffee, however, is served at about 200°F. Many heat-resistant cups that use PLA tend to be laminates of several different materials, which present challenges to incorporating them into into the conventional recycling stream. Some products, such as cup lids and cutlery, are made from heat-resistant CPLA (crystallized PLA) that can withstand temperatures of almost 200°F. So consider the temperature of the food and drink you’ll be serving before buying PLA products.

While producing PLA is more Earth-friendly than petroleum-based plastics, there are always environmental costs when it comes to consuming resources—including issues that arise with products that are designed to be used just once before entering the waste stream. It is estimated that over 3.4 million acres of food-producing cropland will be needed to meet the growing worldwide demand for corn-based bioplastics. There are other environmental issues to consider when raising any crop on an industrial scale, including energy use, carbon emissions, water consumption and contamination from pesticides and herbicides. Most PLA is sourced from corn grown with genetically modified seed.

And PLA will not decompose in your backyard compost bin. An industrial composting facility is required in order to fully decompose PLA plastics, where the plastic is brought up to at least 140 degrees for 47 to 90 days. Only 113 industrial composting plants of this kind exist in the U.S. As a result, a lot of PLA plastic ends up in landfills, or inadvertently mixed in with recyclable petroleum-based plastics (PET), contaminating the conventional plastics recycling stream. It is also estimated that a PLA plastic bottle, if not composted correctly, could last as long as a PET bottle in a landfill or in the natural environment.

Ham Gillett—Program/Outreach Coordinator for the Greater Upper Valley Solid Waste Management District and Outreach Coordinator for the Southern Windsor/Windham Counties Solid Waste Management District—recommends: “Read the fine print on the packaging. It will often say, ​‘This product is only compostable in a commercial composting facility.’ ​Compostable ware contaminates recyclables because it can’t be recycled. Even regular plastic utensils can’t be recycled. It should all go in the trash. At the very least, ask your hauler or local recycling facility what they accept. When in doubt, throw it out.”

In our single-use obsessed world where just 9 percent of discarded plastic gets recycled. If a workable recycling system and processing is eventually developed, PLA could take a step toward cutting down on carbon emissions and reducing the huge volume of long-lived plastics that we dispose of, along with their litany of environmental impacts.

Bioplastics aside, in the long run nothing is more Earth-friendly than those old standbys that are still the best alternatives to any forms of plastic, including real silverware and dishes, as well as reusable bags, drinking straws and food containers.

Picnic backpacks are relatively inexpensive and make it easy and enjoyable to eliminate the use of disposable plastic utensils, paper cups, plates, etc. And you don’t have to keep purchasing items that you use once and throw away. (Photo: Marie L. Caduto)


  • Do not throw PLA bioplastic items into the recycle bin, along with PET plastics. PLA plastics contaminate the conventional recycling stream, forcing large volumes of normally recyclable plastics to be discarded.
  • Ham Gillett recommends: Buy To Go Ware and other Earth-friendly utensils ( or buy re-usable ware, available in some local stores and on line. Better yet, go to a thrift store or yard sale and purchase some plates, bowls, cups, and utensils. Use them and wash them.


Learn more about our Vermont Standard articles.