Typical sources of carbon for compost are: lawn clippings, dry leaves, pine needles, kitchen vegetable waste. What does your township do with all the fall leaves? Ours piles them up in the fall and lets anyone take them away for free once they have rotted down in the spring.

It's in a document called the U.S. Constitution.

It's not gravity that's doing the work. The work comes from placing an object where it can fall and gain energy. Essentially, YOU did the work when you placed the object in the gravity field, increasing its potential energy. Allowing it to fall and gain kinetic energy is just giving back the potential energy you created.