When my parents were growing up, plastic bags were somewhat of a luxury. I remember my mother telling me stories of weekly plastic bag washing - they really made the most of them.

As the plastic bags became cheaper and thinner, well, we ended up with the situation we have today. Literally billions of plastic bags discarded that won't break down in the environment for hundreds of years.

Most disposable plastic shopping bags are made from polyethylene, which is a by-product of the petroleum industry.

Not only are there issues with the rate at which these bags break down, but the chemicals released as part of the decomposition process; being organo-chlorine (highly toxic), methane (a greenhouse gas contributing to global warming) and nitrous oxide, another greenhouse gas.

One of the advantages of polyethylene is that it can be recycled, but that hasn't stopped the flood of discarded plastic bags assaulting the environment. Consequently, many governments are moving to ban them.

I recently wrote about reusable plastic bags; but there's still times when we need something disposable, such as dealing with dog poop, or general household rubbish. That's where the polyethylene disposable shopping bags were quite handy.

There are alternatives to disposable polyethylene bags and they've become increasingly available in supermarkets. They don't really stand out among the other bags, so you'll need to hunt around the plastic bag section and look for the term "degradable" on the label. The good news is, they really aren't all that much more expensive.

Degradable vs. biodegradable - what's the difference?

A degradable product is one that undergoes changes in structure when exposed to air, humidity or heat. Biodegradation is the action of microorganisms consuming a material.

Oxo-biodegradable plastic bags

Oxo-biodegradable plastic is still made from petroleum by-products, but doesn't produce the toxins that polyethylene does. The plastic first degrades through exposure to sunlight and air, then bacteria break down the plastic fragments into a little CO2, water, and humus - which is just basically organic matter mainly comprising of carbon.

Oxo-biodegradable plastic bags fragment in 3 - 4 months when exposed to plenty of air. Under landfill conditions they degrage within 12 to 18 months; still far shorter than polyethylene.

Another great aspect of oxo-biodegradable bags is that they can be made with the same machinery as polyethylene bags - so there's really no excuse for bag manufacturers not to make them.

We've been using degradable bags for a while now and they've been pretty good - just don't use them for other purposes except for rubbish. If you put other items in them for storage, you'll wind up cleaning up a zillion tiny little plastic fragments a few months later. It's happened to me :).

Hydro-biodegradable bags.

Hydro-biodegradable bags are made from starch-based plastics; i.e. plants. But it's not as earth-friendly as it sounds. Aside from expense and strength issues, in order to break down they must be in an environment with a lot of bacteria and during the decomposition process they give off a great deal of methane and carbon dioxide.

As mentioned, oxo-biodegradable and hydro-biodegradable bags are alternatives best left for single use purposes - such as wrapping up trash.

For other applications where you'd usually use plastic bags, consider reusable bags and wherever possible, buy earth friendly bags made of hemp or other renewable materials that aren't harsh on the environment in their production. Learn more in my article on reusable bags.