Biodegradable Plastics: The Consumer Future?

Plastics are both a wonder-invention and a mounting liability in the industrialized world. Remarkable in their ability to do everything from preserve food to form break-proof containers, plastics have changed the way the world works since the 1950s. However, most plastics out there today are not biodegradable, meaning that once discarded, they stay as they are instead of decomposing into smaller parts. It is estimated that 90% of plastics ever produced by mankind still exist in the world today. As landfills start to burst at the seams, research has begun to intensify over the viability of organically-produced, biodegradable plastics.

Plastics are constructed of things called polymers, which are little more than chains of molecules. These chains give a structural integrity to the plastic, allowing it to be both durable and versatile without shearing or tearing under stress. Most plastics are produced synthetically from certain chemicals (usually petroleum products) in large plants. The aim of many scientists is to reduce our dependence on both these kinds of plastics and the materials used to make them. Petroleum comes from oil, and our dependence on plastics ties us even more intricately in with that finite and volatile resource.

So what are biodegradable plastics made from? One particular source for natural plastics is starch. Starch is a complex carbohydrate that naturally occurs in many plants. However, it does have limitations. The most important limiting factor with starch is that if it is processed directly into a plastic, it is very susceptible to moisture. If the starch contacts anything wet, it will start to deform and can lose its structural integrity quite easily. This makes readily-converted starch a poor substitute for many plastics that are constantly in contact with moist materials, from shampoo to lunchmeat. Its weakness as a stand-alone plastic can be remedied by converting starch to a new polymer through chemical means, but this poses problems too. A form of starch polymer plastic called PLA has been commercially available since the early 1990s, but since it is harder and more expensive to make than other commercial plastics, it has failed to catch on. In order for a biodegradable plastic to be a viable consumer alternative, it needs to be cheap for companies to produce and consumers to purchase.

Similarly, another kind of biodegradable plastic can be produced through bacteria. These special bacteria create bits of bioplastic called PHA in their cells. These bacteria can be cultured to produce the PHA or can be grafted onto plant crops in order to expedite the process. But PHA runs into the same problem as PLA. It costs a lot to manufacture, and thus most companies would be very reluctant to purchase it as packaging or materials for production. Other materials that show promise in the manufacture of biodegradable plastics include cellulose, collagen, and soy protein. Like the others, these natural materials have yet to be developed into a truly cheap, durable, and cost-effective plastic for mass-production.

Although biodegradable plastics are capable of decomposing, they cannot be thrown away in the same manner as other plastics in landfills. If biodegradable plastic is piled into landfills, it won't decompose. Why? Similar to how a banana peel cannot compost at the bottom of a ton of garbage, the bioplastic cannot decompose their either. The reason for this has to do with the kinds of decomposing bacteria that break down organic materials. Aerobic (air using) bacteria are the ones responsible for composting, which is why farmers regularly turn their compost in order to aerate it. Anaerobic bacteria attack materials that are in the presence of little to no air, slowing the decomposition process and releasing smelly bi-products. This is why compost heaps do not stink as much as landfills. So, even if biodegradable plastics become commonly used, their disposal will be another issue to be resolved if they are to be used to their full potential.

The object of current research with biodegradable plastics is to produce polymers that are flexible and durable, ones that will not fall apart when subjected to normal environmental and storage conditions. If these plastics can be constructed from renewable resources in a timely and cost-effective manner, they may just have a chance in the world market. Biodegradable plastics may very well be the material of the future, but if we want to reduce our dependence on synthetic plastics and landfills, collaborative efforts of significant research and development will need to occur.