I recently read an article which discussed how we could tackle the problem of the 800,000 tonnes of plastic bags thrown away each year in Europe, an average of 191 for every citizen of the European Union. It highlighted the much smaller carbon footprint of disposable single use plastic carrier bags compared with alternatives. Part of the article described re-using plastic bags as bin liners rather than using purpose made bin liners and it had a nifty graphic . To a point, this makes sense but considering that many people use plastic bags for almost all of their domestic purchases, then to use every carrier bag once as a bin liner would require all that was bought to be disposed of in the bin. I know that there is a lot of waste packaging in groceries but it does generally compact down to a smaller volume than the original (unless you live entirely on tinned produce) therefore assuming that all plastic bags are re-used in this way is stretching things a bit. To then hypothesise that they could be used three times as bin liners is clearly not relevant.
Further, using plastic bags as bin liners can be counterproductive when it comes to recycling. I often see plastic bags full of recyclable materials (plastic bottles and cans) overflowing from recycling bins. This may be convenient for the householder but causes problems with processing and separating the different materials, especially if the plastic bags themselves are not recycleable. Only 6% of plastic bags are recycled in the EU, which is a very small proportion compared with other plastics. Most areas do not routinely recycle plastic bags and plastic films because of the difficulty in untangling from other wastes, separating contaminants and splitting into similar polymer types.
Finally, using the carbon footprint of plastic bags as a measure of how environmentally friendly they are is missing the point, which is that they are light and easily blown away by the wind from bins, landfill sites or where they have been carelessly disregarded and they do not subsequently break down naturally. As illustrated in the photograph above, they are unsightly, hazardous to wildlife and domesticated animals then when sunlight or mechanical processes do eventually embrittle them, they crumble into small pieces of plastic just right for ingestion by fish, birds and other creatures, then on into the human food chain.
Of course, if all bags are bad the easy answer is that we just stop buying stuff.