That would be a chemistry test that involves 1 large test tube and rack, chlorine to add to the liquid to precipitate out the Potassium, an accurate scale, filter paper and funnel (to collect the KCl precipitate and to dry it on) and a calculator to do the math.
Many commercial labs will do a Potassium test for you (here they cost between 25 and 50 dollars for the singular test).

good idea

I have a composting area, and it's taking its sweet old time creating any 'compost', but I know I need to chop up larger pieces of vegetable matter to make it all break down. Just lazy!

I think this is a great idea

I store food scraps in the freezer (so there is no smell) and then I take it to my community garden in the library where they have a tumbler - type composter.