Disposable plastic shopping bags are terrible for the environment, because they usually find their way into bodies of water and choke marine life. As well as this, plastic takes several thousand years to break down.
Re-usable shopping bags are a great way for people to do their bit for the environment by keeping plastics out of waterways.
As your collection of re-usable shopping bags grows, it’s a good idea to group them by size. Pick up a couple of baskets or storage bins from a home-wares shop, allocate big bags into one container and small bags into the other. To save money on storage containers, you can always set one bag aside, and store the other bags inside of it.
Whatever the container you choose, folding the shopping bags first is a good idea to maximize space. Many re-usable bags have a plastic base, so remove it and set it aside. Fold each re-usable bag into thirds along it’s height, then thirds along it’s width, twist the handle in half and wrap it around the rest of the bag and voilà! Your re-usable bag is now tiny.
Source: http://www.modernparentsmessykids.com/2013/06/how-to-organize-reusable-bags.html