By Katherine McGrow
March,2009
The ‘green bag’ is a type of reusable bag which was introduced into the Australian domestic retail market in 2002 as an alternative to single-use high-density polyethyline bags, and its use has grown rapidly. Evidence of this is a two-month survey conducted in 2008 for the Australian National Retailers Association and Sustainability Victoria, which reveals 98% of Victorians own at least one green bag; 24% own 1-5; 37% own 5-10; 25% own 10-20; and 12% own 20 or more.
Woolworths alone reported sales of almost 5.7 million reusable bags in 2007–08. Nevertheless, the overall number of such bags sold in Australia each year is hard to gauge due to limited Customs data and the many companies importing reusable bags.
The most commonly used reusable green bags sold by supermarkets are made from non-woven polypropylene (NWPP), a type of plastic manufactured as a by-product of oil refining, and stitched with cotton thread. These can be recycled, but the cotton stitching cannot so they have to be unpicked by hand before they can be reused. They are recycled overseas for cost reasons.
There has been some debate, mainly in the media and among manufacturers of different types of reusable and biodegradable bags, about the “green-ness” of the NWPP bag. “It’s manufactured in China, shipped thousands of miles overseas, made with plastic and could take years to decompose … the reusable shopping bag,” wrote the Wall Street Journal. One unnamed manufacturer of ecojute bags says polypropylene requires about 28 times as much energy to produce as the plastic used in standard disposable bags and eight times as much as a paper sack.
It may be true that on a single-use basis, green bags are no more environmentally friendly than the standard supermarket plastic bag. But green bags are designed to be reused.
Several reports describing life cycle assessment (LCA) of shopping bag alternatives have been released in recent years, most of them based on the same modelling and broadly similar assumptions. Such analysis evaluates the environmental impact of a product throughout its entire life cycle. In the case of green bags, this includes production of the raw materials used in them, how the bags are made, how they are transported to retailers and how they are disposed of at the end of their life.
The yardstick used to measure this was a hypothetical household bringing about 70 grocery items home from a supermarket each week for 52 weeks. The analysis assumed the capacity of the green bag is 1.2 times that of a single-use HDPE bag and that each bag has a lifespan of 104 trips. It also assumed that at the end of their lives 99.5% of green bags would end up in landfill. (Unwanted green bags can be taken to plastic bag recycling bins at supermarkets, but this is not happening to any extent.)
The results suggested that reusable bags have a lower overall impact on the environment than either single-use HDPE bags or degradable polymer bags. Looking specifically at the bags’ carbon footprint, the study found an emission of 1.95 kilograms of carbon dioxide associated with green bag use compared with a carbon dioxide emission of 6.13 kilograms associated with HDPE bag use. If the assumptions made in this study hold true, the green bag is far better for the environment than the single-use plastic bag or any of the other alternatives tested.
But does the average person actually use each of their, in some cases plentiful, green bags 104 times? Jim Cooper, a spokesman for Coles Myer, gave a much lower estimate in an ABC report: “… Our understanding is the average consumer will probably use their bag 10 to a dozen times”. This was based only on anecdotal evidence, but accurate data on the usage and lifespan of the average green bag, like figures for the number of the bags in circulation, appear to be unavailable for now.
A later report (2007) was released by Hyder Consulting for Sustainability Victoria. This study differed in some of its specifications, such as including a transportation factor for NWPP bags (lacking in the RMIT analysis despite the fact that most, if not all, NWPP green bags are imported), but also concluded reusable bags have less of an environmental impact than all single-use bags.
It calculated that a switch from single-use HDPE shopping bags to reusable green bags would mean a per household saving of six kilograms of greenhouse gas emissions, 190 megajoules of energy and seven litres of water. If every Australian household made the same switch, it would mean a saving of 24,100 tonnes of waste (equivalent of 2200 garbage trucks), more than 42,000 tonnes of greenhouse gas emissions (equivalent to taking more than 9800 Victorian cars off the road for a year), 1.4 million gigajoules of energy (equivalent to powering 22,600 Victorian homes for a year) and 50,000 kilolitres of water (equivalent to the water used by 210 Victorian homes for a year). Of course, there’s a long way to go before we come anywhere close to this.
Related links and references
http://www.cleanup.org.au/au/LivingGreener/plastic-bag-facts.html
http://www.noplasticbags.org.au/home/default.aspx
http://www.greenpeace.org/australia/news-and-events/media/releases/general/greenpeace-statement-on-plastic
Hyder Consulting, Plastic Retail Carry Bag Use 2006 and 2007 consumption, commissioned by Environmental Protection and Heritage Council, February 2008
KPMG, Trial of a Government and Industry Charge on Plastic Bags, for the Australian National Retailers Association and Sustainability Victoria, October 2008
http://crreport08.woolworthslimited.com.au/packaging.php
Centre for Design at RMIT University, What is the life cycle of plastic and green bags, teachers’ resource 2008 www.cfd.rmit.edu.au/content/download/743/5932/file/life%20cycle%20of%20bags%20POSTER%20and%20NOTE.
http://online.wsj.com/article/SB122238422541876879.html?mod=yhoofront
http://www.carbonsystems.com.au/page.cfm?id=30
Nolan-ITU Pty Ltd, Plastic shopping bags – Analysis of levies and environmental impacts, 2002
James K. Grant T. LCA of Degradable Plastic Bags, Centre for Design at RMIT University, 2005.
Hyder Consulting, Comparison of existing life cycle analysis of shopping bag alternatives, commissioned by Sustainability Victoria, April 2007
http://www.abc.net.au/local/stories/2007/10/24/2069376.htm