PAPER BAGS and DURABLE BAGS
Compare different materials, according to criteria like weight, energy and volume of reduction. If we take 100% as a starting point - without plastic we would have about 484% in terms of weight. In terms of energy consumption, with plastics if we take 100%, without plastic we will have around 300%. The same in volume of waste - with plastic and without plastic we have almost 300%.1 The Denkstatt study in Austria2 has found that plastic saves 2.300 million GJ in energy per year.This equates to 50 million tonnes of crude oil - that is 194 very large oil tankers products. They equally prevent GHG emissions of 120 million tonnes per year.
The process of making paper bags causes 70% more atmospheric pollution than plastic bags. Paper bags use 300% more energy to produce, and the process uses huge amounts of water and creates very unpleasant organic waste. When they degrade they emit methane and carbon dioxide. Paper bag production use and disposal results in 3.3 times the greenhouse gas emissions associated with HDPE plastic bags. The global-warming impact of paper bag use is almost twice that of conventional plastic bags.3
Water use for paper and compostable-plastic bags is more than 16 times the use for HDPE plastic bags.4 Solid waste production is 2.7 times greater by weight for paper bags than for HDPE plastic bags.5
A stack of 1000 new plastic carrier bags would be around 2 inches high, but a stack of 1000 new paper grocery bags could be around 2 feet high. It would take at least seven times the number of trucks to deliver the same number of bags, creating seven times more transport pollution and road congestion.
Also, because paper bags are not as strong as plastic, people may use two or three bags inside each other. Paper bags cannot normally be re-used, and will disintegrate if wet.
Long-term re-usable shopping bags are not the answer. They are much thicker and more expensive, and a large number of them would be required for the weekly shopping of an average family. 30,000 jute or cotton bags can be packed into a 20-foot container, but the same container will accommodate 2.5 million plastic carrier-bags. Therefore, to transport the same number of jute or cotton bags 80x more ships and trucks would be required than for plastic bags, using 80x more fuel and emitting 80x more CO2.
Because of high emissions associated with cotton production and the fact that waste bags would need to be used in addition to the cotton bags, the cotton bag would have to be used more than 180 times before its climate impact is smaller than recycled plastic bags.6
In fact UK Government (DEFRA) research shows that 80 per cent of people re-use their plastic carrier bags in the home.7
Long-term reusable bags are not hygienic if a tomato is squashed or milk is spilled. Whilst Cloth bags are not hygienic if a tomato is squashed or milk is spilled. Research by Guelph Chemical Laboratories in Canada in 2008 (http://www.carrierbagtax.com/downloads/Microbiological_Study_of_Reusable_Grocery_Bags.pdf) has shown that "re-usable grocery bags can become an active microbial habitat and a breeding-ground for bacteria, yeast, mold, and coliforms. .... The unacceptable presence of coliforms - ie intestinal bacteria, in some of the bags tested, suggests that forms of E.Coli associated with severe disease could be present in a small but significant proportion of the bags."
The Environment and Plastics Industry Council of Canada commissioned a study on re-usable bags in 2009 which found that 64% of the bags showed bacterial contamination. Almost 30% had bacterial counts higher than those considered safe for drinking water. They noted that although in theory these bags can be cleaned, it is difficult to thoroughly dry them without encouraging microbial growth.
Shoppers do not always go to the shop from home, where the re-usable bags would normally be kept, and consumers are unlikely to have a re-usable bag with them when buying on impulse items such as clothing, groceries, CDs, magazines, stationery etc. Research conducted for the Scottish Government (http://www.scotland.gov.uk/Topics/Environment/funding-and-grants/carrier-bag-case-studies/Q/EditMode/on) showed that 92 per cent of people think re-using carrier bags is good for the environment but 59 per cent forget their re-usable bags and have to take new ones at the checkout.
Why not just re-use an oxo-biodegradable carrier bag many times over? It is much smaller and lighter and can be carried in a pocket or handbag.
As durable bags are a cost to the consumer and carrier-bags are a cost to the supermarket, one can easily understand why supermarkets are in favour of reducing the number of carrier bags and increasing the number of durable bags! Even those who give the profit to charity have still passed the cost to their customers.
For those who believe in long-term re-usable bags, they can be made from washable extended-life oxo-biodegradable plastic and will last for 3-5 years.
1. Prof. Emo Chiellini, Professor of Fundamentals of Technologies, University of Pisa. Simpósio Internacional de Plásticos Degradáveis e Biodegradáveis 6th June 2007. See also Polymers and the Environment, 1999, Chapter 4, Management of Polymer Wastes, p. 78-81 and Degradable Polymers 2nd edition, Chapter 1).
2. June 2010
3. California Master Environmental Assessment March 2010 page 31
4. Ibid. page 35
5. Ecobilan (2004)
6. Ibid. pages 31/32