1 For outdoor composting, buy a plastic or metal garbage-can composter (inexpensive versions are available at nyccompost.org, or make your own by drilling aeration holes in a garbage can). Indoor composting requires worms. A bin plus a pound of worms is $55 through the Lower East Side Ecology Center (212-477-4022). Or splurge for an electric composter, which uses heat to break scraps down faster (NatureMill Plus Edition, $299 at Green Depot, 222 Bowery, nr. Prince St.; 212-226-0444).
Start collecting vegetable and fruit scraps, coffee grounds, tea bags, and so on (no meat, fish, dairy, or pet waste).
2 Food waste (nitrogen-rich “greens”) needs carbon to break down, so mix an equal amount of autumn leaves, eggshells, potting soil, or newspaper (called “browns”) into your scraps.
3 Stir the mixture with a long-handled trowel, rake, or compost “crank” (a special tool designed to turn compost) once a week to aerate it. Test the moisture and add water, if necessary. The compost should be moist, but not so wet that it drips if squeezed. If it’s too wet, stir daily to dry it out.
4 After about three months, put a few handfuls in a Ziploc bag overnight, then sniff. A sour or ammonia-like odor means it’s not fully cured. When ready, it should have a nice earthy smell and look like topsoil.
5 Enrich your houseplants with the loamy goodness, and scatter any leftovers around the trees on your block to improve their health.