Banning plastic bags will not have the slightest effect on global warming

A village in Cambridgeshire has won a small but no doubt satisfying victory: its local branch of Tesco has become the first store in Britain to ban entirely the use of disposable plastic bags. Somersham High Street has been a plastic-bag-free zone for the last three years, after a campaign by local residents, and the new Tesco Express has – eventually – agreed to join in.

It’s the latest in a long line of assaults on the shopping bag: the Welsh Assembly has voted to put a charge of 5p on every one; M&S has been charging customers the same amount for a few years, and Tesco, nowadays, rewards customers who bring their own bags with Club Card points.

All of this is very laudable. But it’s important to realise what it does and doesn’t achieve. What it won’t achieve is any sort of meaningful effect on global carbon emissions, and, therefore, climate change.

That’s not to say they’re not worthwhile. There are lots of things wrong with plastic bags: for a start, they’re an especially ubiquitous and unsightly form of litter, blowing around in the wind and getting stuck in trees. They take up landfill space. They’re a danger to wildlife, especially marine life, and some (though not, so much, British ones) end up in great litter agglomerations in the south Pacific. But, if you’re re-using them in an attempt to prevent global warming, I’m afraid it’s an exercise in tokenism. The creation of each bag produces just 31 grammes (one ounce) of carbon dioxide, according to George Marshall of the Climate Outreach and Information Network – about the same as driving your car 300 feet. The plastic is usually non-biodegradable, so it’s stable in landfills and doesn’t give off methane from there. (Perhaps ironically, moves towards producing biodegradable bags may actually be harmful.) And, depending on the kind of “Bag for Life” that is used instead and how many times they are used, the apparently “green” alternative may be more carbon-intensive.

Worse, they’re an easy PR victory for retailers and governments, which distracts attention from bigger, related problems. A 2009 study by the Local Government Association found that nearly 40 per cent of supermarket packaging could not be recycled: this is costly in landfill, and a far greater producer of carbon. Furthermore, the stuff contained in that packaging is frequently discarded: the Government’s Waste abd Resource Action Programme (Wrap) claimed that growing, producing, storing and transporting the nearly seven million tons of food we throw away accounts for two per cent of the country’s carbon emissions. Worse, that stuff does rot in landfill, emitting methane, a potent greenhouse gas.

What the War On Plastic Bags has shown – once again – is the power of the market, properly directed, to work as a force for good in environmental issues. The M&S 5p charge led to an 80 per cent drop in the use of disposable bags. Overall, the move towards rewarding the reuse of bags reduced plastic bag use by 40 per cent in Britain between 2006 and 2009 – a drop from 11 billion bags per year to a rather more manageable 6.5 billion. “Incentivising”, while an ugly word, is a powerful tool.

In his book Naked Economics, Charles Wheelan, the former Economist writer, wondered why, if we are trying to reduce landfill and carbon emissions, governments do not make households pay by volume for removal of non-recyclable waste. Targeted taxes like these could push consumers into more sustainable behaviour, while allowing other, more blunt-force taxes (perhaps council) to be reduced. The broad lesson of plastic bags is that environmentalism and the free market need not be opposed: but the plastic bags themselves are largely an irrelevance from a carbon point of view.


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