Plastic bags are the subject of increasing public debate. Inherently resistant to biodegration, conventional plastics are expected to remain intact in landfill for decades or longer.
Jurisdictions around the world have used a variety of strategies to deal with the issue. Taiwan has banned the use of plastic bags; Ireland taxes them; California mandates the use of a fraction of recycled materials in their manufacture; Europe has mandated their exclusion from the organic refuse stream destined for composting; others consider the use of biodegradable technologies.
Oxo-biodegradable plastics offer a viable alternative that fits in this overall spectrum, as a relatively low-cost degradable product that safely returns to the environment in certain disposal situations via a scientifically well understood route.
Oxo-biodegradable plastics are conventional plastics, such as polyethylene, that are treated with an additive that accelerates the reaction of the plastic with oxygen in the atmosphere, breaking down the large polymer molecules. The smaller molecules are digestible by micro-organisms. This process of biodegradation is the same process by which naturally produced products such as leaves and grass return to the ecosystem.
The benefit of using degradable bags for waste destined for landfill is not only that the bag itself degrades into organic matter, but that it exposes any organic materials within the bag to oxygen in the landfill, thereby permitting more aerobic biodegration.
Any material that degrades aerobically produces carbon dioxide, a greenhouse gas that is over 20 times less harmful than methane. Methane is produced when the biodegration process occurs without the presence of oxygen, which is the case with conventional plastic bags. The only oxygen these organic materials are exposed to is the small amount that is sealed in the bag with them.
Another potential benefit of allowing organic matter to biodegrade in landfill is that there is an earlier reduction in the volume of waste, which prolongs the useful life of the landfill.
Critics of biodegradable bags as a solution suggest that there is insufficient oxygen available in landfills to aerobically biodegrade all the organic material in the bags. The use of source separation programs are generally considered preferable so that the bulk of organic waste materials and plastics bags are diverted from landfill through composting or recycling. The practical reality, however, is that western societies are a long way from executing against these ideals and the use of degradable plastic bags is a positive step in the right direction.