What can I put in the compost heap?
Whatever style of composting system you choose, from a simple, small pile to a long windrow to an enclosed store-bought bin, the key is to vary the kinds of materials that go into the mix. There is no precise recipe; there is just common sense at work.
Green plus brown equals black gold. Layer the two basic categories of ingredients: green ones (nitrogen-rich materials such as grass clippings and leafy green plants) and brown ones (carbon-rich materials like dry, brown leaves or twiggy bits and pieces). Too much of either one will impede decomposition.
I liken successful composting to the combustion that goes on when my car is running smoothly: to ignite, the car needs fuel, air, and a spark. So does the compost heap. The spark is the nitrogen-rich green stuff; the fuel is the brown stuff; the air is supplied by occasional turning of the pile, and water must be available from rain or the hose, so the pile is slightly moist but not sodden.
Too much green stuff (particularly wet things like grass clippings) will produce a smelly heap; spread them around, and toss in a thin layer of soil or old compost to help things get going. I don’t bother with store-bought compost starters; there are plenty of beneficial micro-organisms in good garden soil and some well-rotted leaves.
Too much brown stuff will just sit there (and that includes things that are “brown” chemically if not in color, like piles of orange rinds from weeks of juicing). Chopping up difficult brown elements will speed decomposition; so will aerating the pile, and adding more greens.
Manures from farm animals (not domestic pets) are great additions to the heap, if you can get them from a nearby farm or stable, but remember that unless they are well-composted in a fast-decomposing (or “hot”) pile, between 120 and 160 degrees F, they will be full of the seeds of what the animals were fed, so plan to let them rot thoroughly in a heap that’s really cooking along. A compost thermometer will help eliminate the guesswork here.
And don’t site the heap in the dark; a position in at least part-day sun is essential to good decomposition.