Travelling home from a trip to Europe, I was concerned about unnecessary plastic packaging on several items - multiple layers around a magazine and still more encasing those tiny airplane earbuds. But when I looked more closely at the writing on the bags, it explained that the plastic was oxo-biodegradable. Unfamiliar with the term, I decided to find out more. After all, the name suggests that such packaging will break down eventually, unlike most plastics.

In fact, there is increasing interest in sustainable packaging. To this end, the Oxo-Biodegradable Plastics Institute was started in 2004, with the stated goal “to support and promote the acceptance and development of the global oxo-biodegradable plastics industry.” Many plastics are designed for a single use and then discarded, particularly with food wrapping, garbage bags, and diapers. Widespread use of such plastics has led to mountains of waste in landfills and waterways.

So how does oxo-biodegradable plastic work? The process involves polyolefins - conventional plastics like polystyrene, polypropylene, and polyethylene - treated with additives that promote their ability to be biodegraded. Typically, plastic polymers are so long that they cannot be broken down by normal processes. Water doesn’t penetrate these plastics and the molecules are too large for microorganisms to convert, resulting in the long-term problem of inert waste plastics.

With the addition of certain compounds, oxidation is accelerated. Oxygen combines with the plastic and results in fragmentation over 3-4 months. Once the larger molecules are broken into smaller chunks, the second step is biodegradation by microorganisms in soil, air, compost, or landfill. The final products are carbon dioxide and water. However, the process is slow enough that these plastics cannot be labelled as compostable. Typically, it may take up to two years to fully recycle through both stages.

The additives, typically transition metal (such as cobalt) salts, comply with food and safety guidelines, so there is no problem with direct food contact, no ecotoxicity, no heavy metals or harmful residues. The degradation process is initiated by UV light, heat, or mechanical stress. Break-down does not start until disposal, so that products still have reasonable storage potential.

Why is it so hard to get away from plastic wrapping? Old-fashioned paper bags, once common, are actually quite expensive and energy-intensive to produce. Not to mention the need to cut down trees to make them. They certainly don’t work with wet products, limiting their usefulness in many applications. Other alternative plastics, often derived from corn and other starchy sources, may be less robust and sensitive to heat, as well as being costly to make. On the other hand, bioplastics are more readily biodegraded, breaking down in a shorter time but releasing methane as a by-product.

Oxo-biodegradable plastics certainly offer an appealing alternative to conventional plastics. They eliminate the usual culprits involved in plastic degradation - methane, nitrous oxide, and organochlorines. It would be difficult to persuade most Western shoppers to buy unpackaged meat, pasta, and other products (typically sold in plastic). If oxo-biodegradable plastics are not in your local store, consider rinsing and reusing your produce bags. Pick up some of the reusable bags that seems to be everywhere. And don’t forget to take them when you shop!