> Reverting to glass would add weight, breakages and collection costs
So how exactly is glass superior to plastic in this application? Seems to me that they moved to plastic because plastic is the better material for the job.
Need to ask not just which is better, but which is better for who?
With glass, producing new bottles for each delivery would be super expensive, so it is in their interest to bear the cost of collecting the bottles for reuse and recycling.
With plastic, producing new containers is super cheap, so it is fine to continuously produce new ones, but the waste is still produced, so the customers and their local government must bear the cost of waste disposal or recycling instead.
Essentially, moving from glass to plastic is good for the producers, as they no-longer need to care how much it costs to recycle, since they don't do it any more. But the overall cost to society might be higher, depending exactly on what the recycling costs are.
One problem is that we don't know the full cost, including the environmental impact, of each option.
Glass can be cleaned and reused, but it's heavier, so transporting it both ways results in increased emissions. They could also choose to use reusable plastic containers (soda companies did this in Norway up until around 5-6 years ago), but collecting the used containers takes up much more space if they can't be compacted, which I think some grocery stores do now.
There's quite a bit of energy that goes into washing containers as well. Supposedly sometimes more than what is required to manufacture new ones.
I'm not sure we as society are really able to quantify the environmental costs of each just yet.
We could at least get somewhat reasonable estimates I think, there should be enough countries with bottle-collecting schemes to get useful data about actual effort involved.
They can move to tin cans like soda cans, which have remarkably little metal in them. No need to wash them, just throw them in the hopper with the rest of the ore.
Glass bottles survived typically 25-50 round trips during reuse, sometimes much longer if there was a deposit paid. Plastic as used in milk cartons is extremely easy to spoil causing the recycled batch to be worthless. To avoid this the washing of the material (even after the householder has been required to do so) is done at higher temperature and pressure, with multiple hot, cold and abrasive steps.
They have to ensure any food residue, glue, labels and any remnants of the under-cap seal are removed or it's junk[0]. It's significantly more expensive than washing and rinsing glass bottles used to be.
So how exactly is glass superior to plastic in this application? Seems to me that they moved to plastic because plastic is the better material for the job.