I have a feeling you just sent me a private email on this subject, but you added something on this post. It's mainly the pH of the fresh coffee that you want to avoid. Run enough hot water through the coffee to lower the pH, and you can use all you want. It will also wash through that unknown chemical that is supposed to hinder tomato plants.

Thanks again, I didn't know you were here.
I plan to make a huge cheesecloth tea bag and soak then rinse the coffee grounds.