Compost is decomposed organic matter—food scraps, yard waste, and other biodegradable materials—broken down into a nutrient-rich soil amendment. Composting is both a process (decomposition) and a product (the resulting material). Municipal composting programs collect organic waste through green bins and process it at industrial composting facilities. The resulting compost can be used in gardens, parks, and agriculture, returning nutrients to the soil. Composting diverts organic waste from landfills, where it would decompose anaerobically and produce methane (a potent greenhouse gas). Home composting and municipal programs both contribute to waste reduction. Compost programs require proper sorting—contaminants like plastics can ruin batches.