If you are in the UK, you might be aware that the Bank of England uses tallow (rendered fat - a slaughterhouse by-product) in the production of the new £5 notes, and the bank has plans to do the same for the future notes they are going to release. We get those notes in Wales, too.
The bank is doing a consultation as to whether this bothers people. I know it bothers me and many vegetarians. If it bothers you too then the details of the consultation can be found here and you can respond here.
Vegans and most vegetarians exclude animal products because of the cruelty involved in their production. By using animal products in the production of the money, the bank is excluding many people from using those notes. For many other people it is offensive to know that the money is connected to slaughterhouse byproducts.
This should have been investigated and fixed BEFORE producing any of the new notes. I am amazed that the Bank Of England ignored the issue for so long. There is a moral responsibility to fix it and stop using animal products in the money as soon as possible.
If they switch to palm oil it should be sustainable. Even better would be to avoid it completely - there is nearly always an alternative. And if the most sustainable note is the paper one, they should revert back to that. The environment and ethical issues take precedence over other issues.