Taxing waste is one part of the story but it's actually a really good thing that vaping is cheaper than smoking so this can only go so far before it's counterproductive.
I think the answers lie in stuff like banning sale of pre-filled ones. If you make people buy a separate bottle of nicotine liquid (and you enforce that this is quite a large minimum size, like we already do with tobacco) and fill the device up before they use it, I think they are much more likely to refill it when it's empty and recharge it when it's dead.
Maybe another thing could be restricting points of sale. I bet a lot of the waste comes from drunk people buying them at 10pm in the corner shop near the pub. If you make people plan ahead that might also help.
Well that is fixable, it's even one of the solutions posited here. Just make them artificially expensive by adding a deposit, which you'll get back when you return it to the shop (instead of throwing it away).
I think a better thing to do may be to try to embed disposal costs into the price of the original product. That changes prices to hopefully incentivise reuse.
I'm in favour of a full ban but it's complex
This guy[1] explains the problem quite well.
[1]https://www.youtube.com/watch?v=dy-wFixuRVU