compostage

Compostage, or composting, is the biological decomposition of organic matter by microorganisms and soil-dwelling invertebrates into a stable, humus-like material called compost. It is used to recycle kitchen scraps, yard waste, and agricultural residues into a resource for soil improvement.

The process requires a balanced mix of carbon-rich materials (brown) such as dry leaves, straw, and wood chips, and nitrogen-rich materials (green) like fruit and vegetable scraps, grass clippings, and coffee grounds. Adequate moisture, aeration, and particle size support microbial activity. The product improves soil structure, water retention, and nutrient availability.

This decomposition proceeds through mesophilic and thermophilic phases, with temperatures rising often above 50°C to accelerate pathogen reduction, before cooling and maturation. Decomposition times vary from a few weeks in fast systems to several months in slower ones.

Common approaches include backyard composting in bins or piles, vermicomposting with red wigglers, bokashi fermentation (anaerobic pre-composting), and large-scale industrial composting in windrows or in-vessel facilities. Finished compost is dark, crumbly, and earthy-smelling, and ready to use as a soil amendment.

Benefits include diverting waste from landfills, reducing methane emissions, recycling nutrients, and enhancing soil fertility and structure, which can improve drought resistance and reduce the need for chemical fertilizers. Limitations include not all materials being suitable for home systems; meat and dairy can attract pests, and improper management can cause odors or contaminants. In many regions, composting is part of municipal waste management and garden practices. The quality of compost depends on maturity and stability, with immature products potentially causing nutrient imbalances.