If you had asked me yesterday I would have said "Oil". Is that what you said? Turns out we're both wrong. According to Nimic of The Green Routine plastic bags are mostly made from natural gas, in the US at any rate. I wonder what British plastic bags are made from?
Some of the commenters there seem to think he's nit-picking because natural gas is also a non-renewable fossil fuel. But I agree with Nimic's argument that:
As a community of green bloggers, we NEED to stop the hyperbole of plastic bags being made primarily from foreign oil. We have many strong and valid points as to why we should reduce or even ban the use of plastic bags without it.
For example, I've been meaning for some time to investigate the comparison between plastic bags and paper bags. I know that paper manufacture can be a very environmentally damaging activity. And paper bags are much heavier and bulkier than plastic bags so it takes a lot more fuel to transport them from the manufacturer to the store. So I've heard it said that paper bags are actually worse for the environment than plastic bags, which is a counter-intuitive claim and I really want to know the truth of it.
It's not good enough to fall back on knee-jerk reactions and unresearched assumptions. Especially if we're lobbying parliament or starting campaigns to ban plastic bags from our towns. We need to know the facts otherwise we look foolish. And worse than that, we'll be putting all our energy into actions that won't help save the planet.
Of course, regardless of whether plastic bags are made from oil or gas, regardless of whether paper bags are better or worse for the environment, the best answer is to use a sturdy reusable bag to bring your groceries home.