Composting is the aerobic decomposition of organic materials by microorganisms, resulting in a stable humus-like substance that improves soil structure and fertility. The process converts kitchen scraps, yard waste, and animal manures into a soil amendment that supplies nutrients, enhances water retention, and supports beneficial soil organisms. Composting occurs in three primary systems: hot composting, cold composting, and Mulching (worm composting).
The practice of recycling organic matter into soil dates back to early agricultural civilizations. In the modern era, Sir Albert Howard, a British agronomist working in India in the 1920s and 1930s, developed the Indore method of composting, which formalized the layering of green and brown materials. This system became the foundation for contemporary hot composting methods. Rodale Press and the organic farming movement in the United States further popularized home composting through the 20th century.
Hot composting maintains a carbon-to-nitrogen ratio of roughly 25 to 30 parts carbon to 1 part nitrogen, with moisture content of 40 to 60 percent and regular aeration through turning. Pile temperatures reach 55 to 65 degrees Celsius (130 to 150 degrees Fahrenheit), which accelerates decomposition and kills weed seeds and pathogens. Finished compost is produced in 3 to 6 months.
Cold composting is a simpler, slower process that requires no turning or temperature monitoring. Materials are added as they become available and decompose over 6 to 24 months. Weed seeds and pathogens are not reliably eliminated.
Vermicomposting uses red wiggler worms (Eisenia fetida) to process organic waste. Worms consume food scraps and produce nutrient-rich castings. The process operates at lower temperatures and produces compost in 2 to 4 months.
Composted material is incorporated into garden beds as a soil amendment, applied as a top dressing to lawns and perennials, or brewed into compost tea for foliar feeding. The organic matter in compost improves Soil Composition by increasing water-holding capacity in sandy soils and improving drainage in clay soils.