Coffee grounds are great for worm bins and they’re also great for before the bin.
I find coffee grounds keep away smells and fruit flies when collecting scraps for your bin.
It doesn’t take a lot, about 1/4 cup of used coffee grounds every 2-3 days allows me to keep a container of scraps near my sink for 5-6 days. You can even throw in the paper coffee filter.
If you don’t drink coffee, many coffee shops are more than happy to give away used coffee grounds to composters. Just pick up a bag and keep it in a container by your scrap collection and add as needed.
As always too much of a good thing can be harmful, I’ve read that too much coffee can make a bin go sour, so far I haven’t had an issue with 1/4 cup every 2-3 days but if you are picking up coffee from your local coffee shop maybe don’t use it all at once just in case.