I wrote recently about the dismal failure of the much-vaunted plastic bag policy that the government forced on supermarkets, noting research which showed that people were using so-called bags for life in much the same way as the thinner alternatives variety. I'm now wondering if the policy wonks responsible ever read the 120-page report from Environment Agency in 2011: Lifecycle assessment of supermarket carrier bags. It was based on 2006 data.
This Environment Agency paper examines the environmental impacts of various forms of bag, from the thin disposable HDPE plastic bag to heavier LDPE plastic bags and those made of paper, cotton, starch polyester, and polyproplyene (PP). Taking all relevant factors into account (land, water and energy used in production), the study found:
- The environmental impact of all types of carrier bag is dominated by resource use and production stages. Transport, secondary packaging and end-of-life management generally have a minimal influence on their performance.
- Whatever type of bag is used, the key to reducing the impacts is to reuse it as many times as possible and where reuse for shopping is not practicable, other reuse, e.g. to replace bin liners, is beneficial.
- The reuse of conventional HDPE and other lightweight carrier bags for shopping and/or as bin-liners is pivotal to their environmental performance and reuse as bin liners produces greater benefits than recycling bags.
- Starch-polyester blend bags have a higher global warming potential and abiotic depletion than conventional polymer bags, due both to the increased weight of material in a bag and higher material production impacts.
- Recycling or composting generally produce only a small reduction in global warming potential and abiotic depletion
- The paper, LDPE, non-woven PP and cotton bags should be reused at least 3, 4, 11 and 131 times respectively to ensure that they have lower global warming potential than conventional HDPE carrier bags that are not reused. The number of times each would have to be reused when different proportions of conventional (HDPE) carrier bags are reused are shown in the table below.
|
Type of carrier |
HDPE bag (No secondary reuse) |
HDPE bag (40.3% reused as bin liners) |
HDPE bag (100% reused as bin liners) |
HDPE bag (Used 3 times) |
|
Paper bag |
3 |
4 |
7 9 |
|
|
LDPE bag |
4 |
5 |
9 12 |
|
|
Non-woven PP bag |
11 |
14 |
26 33 |
|
|
Cotton bag |
131 |
173 |
327 393 |
|
So there you have it.
It would have been a brave minister who tried to explain this to a middle-class enraged by the sight of dirty beaches and the plight of marine mammals. But those problems were not caused by supermarkets but by individuals and families with slovenly litter habits. And such folk are still out there, discarding madly (have you looked at a roadside verge lately?). Except that this time, they have a bigger, heavier bag to throw aside in the knowledge that a bag isn't for life.
Meanwhile, I see that some environmental NGOs are arguing for a £1 charge for a LDPE bag and I wonder if Gove the Green Guru will be able to resist what is obviously a highly regressive tax.
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