Is it possible for a plastic bag to be environmentally friendly?

In 2007, concerns over the sustainability of polyethylene plastic bags gained traction. These bags, commonly used in grocery stores globally, are lightweight, crinkly, and even recyclable. The real issue lies in the fact that very few individuals bother to recycle them. In the U.S., a mere 1 percent of the 100 billion polyethylene bags consumed annually are recycled [source: CSM]. Around the world, these bags end up on beaches, get tangled in plants, and pose a serious threat to wildlife. Additionally, when exposed to sunlight, polyethylene bags take approximately 1,000 years to decompose [source: American Green Bag]. If they end up in landfills, they may never break down due to the absence of sunlight amidst the trash pile.

To tackle the growing issue of polyethylene bag waste, several cities and countries have introduced hefty fees for using them. In 2008, San Francisco became the first major U.S. city to outlaw plastic bags in its grocery stores and pharmacies, following the lead of countries like India, South Africa, and Rwanda. However, the problem extends beyond grocery bags; plastic bags in general are harmful to the environment.

In addition to taking centuries to break down, plastic is made from petroleum, a non-renewable resource. The same crude oil that eventually powers vehicles is also used to produce plastic. With the prospect of reaching peak oil — the point at which global oil supplies begin to decline — petroleum will become more valuable as a crucial energy source for the future, and we’ll need it for powering the world far more than for manufacturing plastic bags.

Due to the harmful environmental impact and unsustainable nature of plastic, some manufacturers are searching for better raw material sources for plastic production. One company has successfully created a plastic that is not only sustainable but can also be composted. The key ingredient? Corn. This is particularly fitting since one of their major clients is a corn chip manufacturer.

Make a Green Plastic Bag, Save the Earth

At first glance, it seems like a straightforward solution: create a biodegradable plastic bag to help save the environment. However, it's more complicated than it appears. Large corporations rely on plastic to prevent product damage during shipping, preserve food freshness, and produce durable goods. Despite the potential of biodegradable plastics, petroleum-based plastic, which has been in use since the early 20th century, remains irreplaceable for many applications.

Despite the widespread use and reliability of plastic, some manufacturers are still determined to develop a durable yet sustainable product. The leader in this effort is Natureworks, a Minnesota-based company that produces plastic from a biopolymer called polylactic acid (PLA), derived from corn. This corn-based plastic, known as Ingeo, uses corn starches that decompose much faster than traditional petroleum-based plastics. The process is natural enough that PLA items can be composted alongside other organic materials such as leaves and grass clippings.

To create PLA, starch is extracted from cornmeal, yielding a simple starch known as dextrose. Dextrose, a type of glucose, is a simple sugar produced by plants during photosynthesis. Once the active ingredient in corn starch is isolated, the dextrose undergoes a fermentation process similar to beer-making. Instead of alcohol, however, the dextrose is transformed into lactic acid—the same substance that causes muscle cramps when you work out without staying properly hydrated. Heat is then applied to the lactic acid polymers, causing them to link together into a long chain that becomes the raw material for many corn plastic products.

What differentiates corn plastic from petroleum-based plastic is the fact that the process used to make it can be reversed when the plastic ends up in a compost heap. Fungi and bacteria present in the soil begin breaking down PLA into its fundamental components. Under ideal aerobic (oxygen-rich) conditions, with heat and moisture, PLA composts just like other organic matter. The microorganisms in the compost digest the corn plastic, converting it into humus, a nutrient-rich, soil-like substance that nourishes plants. The end products are carbon dioxide and water.

Some corn plastics decompose more easily than others. When SunChips partnered with Ingeo biopolymers to produce PLA bags in 2010, the company tested the bags' compostability. They found that, in optimal compost conditions—such as those in professionally-managed commercial or municipal composting facilities—the SunChips bags made from PLA broke down into humus. Even better, the bags also composted in a home compost pile that was well-maintained with moisture, air, and a steady temperature of at least 131 degrees Fahrenheit (55 degrees Celsius). The process took between 12 and 16 weeks [source: Sun Chip].

If you're enjoying SunChips in 2010, reconsider throwing the empty bag in the trash. By then, you'll be able to compost it. Hopefully, more companies will soon follow suit.