its not green to throw carrier bags away, but what do you do?

Ben84

If you want to  be green and money saving, switching to reusable bags is the way to go. It's pretty easy to keep one of the lightweight bags folded up in your coat pocket or handbag for unexpected shopping.

Be aware however that you do have to reuse them a good few times to save any resources, and natural fibre bags are (perhaps counter-intuitively to many people's expectations?) much heavier on the environment in many ways:

https://phys.org/news/2018-08-reuse-bags.html

The bags I still get at times get used up with things like those random times I give something to someone and they need to carry it home, etc. For rubbish bags,  I would recommend shifting to other harder to avoid waste plastic bags - like food packaging bags. The reduced waste we now throw out makes these smaller bags more practical too.