(Picture taken from http://ecoble.com/category/sustainable-transit/hybrid-car/)
Plastic bags are still used for at shopping malls. A plastic bag can be in principle reused many, many times. If collected, plastic bags can be melted and transformed into products, as an additive for road asphalting and even to make diesel.
Plastic if not recycled then can be burned to generate electricity. Burning of chlorinated plastics can however lead to emission of dioxins and heavy metals if incineration if not done at right temperature and appropriate control systems are not in place. Plastic does not readily degrade in a landfill. Biodegradable plastic bags are now coming up that are “corn based”. Biodegradable plastic is however still more expensive.
There is a popular misconception that paper bags are more environmentally friendly than plastic bags. Paper comes from trees and unless sustainable forestry is practiced, making paper leads to depletion of green cover – affecting local ecosystems and extent of absorption of GHG emissions. According to a 2007 study by Boustead Consulting & Associates, it takes almost four times as much energy to manufacture a paper bag as it does to manufacture a plastic bag. Paper bags use twenty times as much fresh water vs plastic bags. These facts are just startling!
If we want to recycle paper, then the paper must be collected and converted to pulp. This is done by use of several different chemicals including sodium hydroxide, hydrogen peroxide, and sodium silicate. The pulp must be washed with clean water to “de-ink”. Ecological footprint of a recycled paper bag is therefore no different from a plastic bag. Both are equally sinful.
The best choice overall is perhaps to use a reusable bag. Most reusable bags last for 5-10 years and beyond. Reusable shopping bags are often made out of waste materials- so in some sense – help convert waste to a resource. In Australia, most green bags are made of 100% non-woven polypropylene which is recyclable but is not biodegradable. End of life impact of such reusable bags can therefore be complex.
An unpublished report from the UK’s Environment Agency found that when compared to a traditional plastic bag, a canvas or cotton reusable bag would have to be reused a total of 171 times to offset the GHG emissions. So reusable bags must be used sufficiently enough to claim the environment advantage.
A reusable bag if made from waste materials e.g. discarded textile fabric then it is much better. Making of such bags is often done by providing employment to women and underprivileged so there is a benefit of livelihood creation especially for the poor. The apparel industry promotes reusable shopping cotton bags today as sustainable fashion.
Many fashion czars and supermarkets have introduced incentives towards use of reusable bags. Some supermarkets give points to customers when they bring own shopping bags. When the customers collect a certain amount of points, they can usually get discount coupons or gifts, which motivate customers to reduce plastic bag use. Some retailers such as Whole Foods Market and Target offer a cash discount for bringing in reusable bags.This makes the adoption of reusable bag even a smarter choice.
There are however concerns in the use of reusable bags as well. Most reusable bag shoppers do not wash their bags once they return home and the bags may lead to food poisoning. Because of their repeated exposure to raw meats and vegetable there is an increased risk of food borne diseases.
Since reusable bags are often made out of waste, there are contamination risks. In January 2011, USA Today ran an article based on a report from the Center for Consumer Freedom, that bags sold in the U.S. by Walgreens, Safeway, Giant, Giant Eagle, Bloom and other grocery chains and retailers contained levels of lead in excess of 100 parts per million, the maximum amount allowed under law in many U.S. states. These findings are however not supported with adequate data.
To conclude, life cycle impacts of paper and plastic bags are roughly equal in pros and cons. When faced with the question of paper or plastic, the answer should be neither. Choosing a high-quality reusable bag will make you the real “green shopper”. But remember that reusable bags must meet certain product quality and safety standards. You must also clean or wash the reusable bags prior to each use. And most importantly, you must actually practice reuse!
(This article is a modified version of my column published by Green Prospects Asia in Malaysia)