Thanks for that. I firstly should say that
these bladders are washable and I have used one three times already so I am not sure why you would need to throw it out unless you wanted to. It probably will not last as long as one of these plastic
20L cubes.
If you really want to compare the environmental aspect I think it's important to look at the numbers.
The bladders are made from 85grams of plastic
The 20L plastic cubes are made from 1150grams of plastic.
Even if you did throw away the bladder after a single use you can at least be comfortable knowing that you have used 13-14 times less plastic than manufacturing a 20L plastic cube. Based on the number of plastic cubes that we sell I don't think we have every customer using every 20L plastic cube on average more than 13-14 times. So just be aware that the cube is only better if re-use it more than 13 times.
With that said many home brewers do sadly leave the hobby as they do not have that much time to brew beer. Time is the largest casualty in this hobby and when customers stop home brewing and move to commercially purchased beer in bottles or cans. If you compare the 85grams of plastic used in one of these bladders it's far less than what 20L of commercial packaging uses in plastic, cardboard, stretch wrap, glass, labels, glue etc. So if you need disposable bladders to save time and keep you in a hobby I would say it's still orders of magnitude better than purchasing beer at the bottle shop.