There are types of biodegradable plastics and it is important to distinguish between them; their costs and uses are very different. The two main types are oxo-biodegradable and hydro-biodegradable. Oxo-biodegradable plastics are “good” biodegradable plastic. When purchasing what you believe to be biodegradable, be sure the product is made from Oxo-biodegradable plastic.

In both cases degradation begins with a chemical process followed by a biological process. Both types emit CO2 as they degrade, but hydro-biodegradable can also emit methane. Both types are compostable, but only oxo-biodegradable can be economically recycled. Hydro-biodegradable is much more expensive than oxo-biodegradable.

OXO-BIODEGRADABLE PLASTIC - This new technology produces plastic which degrades by a process of OXO-degradation. The technology is based on a very small amount of pro-degradant additive being added into the manufacturing process, which changes the behavior of the plastic. Degradation begins when the programmed service life is over and the product is no longer required. This “life” of the plastic product is determined at the time of manufacture by the additive formula and can be as little as a few months or as much as a few years.

There is little or no additional cost involved in products made with this technology, which can be made with the same machinery and workforce as conventional plastic products.

The plastic bottles or bags fragment, and will be consumed by bacteria and fungi after the additive has reduced the molecular structure to a level which permits living micro-organisms access to the carbon and hydrogen. So, it is “biodegradable.” This plastic biodegrades to nothing more than CO2, water, and humus, and it does not leave fragments of petro-polymers in the soil.

Oxo-biodegradable polymers do not contain PCBs, nor do they emit methane or nitrous oxide.

HYDRO-BIODEGRADABLE PLASTICS - Some plastics in this category have high starch content and it is sometimes said that this justifies the claim that they are made from renewable resources. However, many of them contain up to 50% of synthetic plastic derived from oil, and others are entirely based on oil-derived intermediates.

Hydro-biodegradable plastics are not genuinely “renewable” because the process of making them is a significant user of fossil-fuel energy and a producer of greenhouse gases.

A disproportionate amount of land would be required to produce sufficient raw material to replace conventional plastic products, along with a huge amount of water.

Plastics made from crops, are up to 400% more expensive, they are not strong enough for use in high-speed machinery, and they emit methane in landfills.

Oxo-bio plastics degrade in the upper layers of a landfill, but they are completely inert deeper in the landfill in the absence of oxygen.

Paper bags use 300% more energy to produce. They are also bulky and heavy to store and are not strong enough, especially when wet. They also emit methane in a landfill.

So before your company decides to eliminate plastic, be sure you know your options and understand the different types of biodegradable plastics.