Composting is a managed process that accelerates the natural cycle of decomposition, transforming organic waste into a rich soil amendment. This practice relies on microscopic organisms to break down materials, resulting in a nutrient-dense product that significantly improves soil health. By diverting household and yard waste from landfills, composting reduces the amount of methane gas released into the atmosphere, contributing to environmental sustainability.
The Foundation: Understanding Browns and Greens
Successful composting requires a balance between two fundamental material types: carbon-rich “browns” and nitrogen-rich “greens.” Carbon serves as the primary energy source and the building block for the microorganisms that drive decomposition. Nitrogen is necessary for the microbes to produce the proteins and enzymes required for their growth and reproduction.
The decomposition process proceeds most efficiently when the carbon-to-nitrogen (C:N) ratio of the combined materials is approximately 25:1 to 30:1 by weight. If the mixture contains too much carbon, decomposition slows down significantly because the microbes lack the necessary nitrogen to reproduce rapidly. Conversely, too much nitrogen can lead to excess nitrogen being released as ammonia gas, resulting in unpleasant odors and a loss of valuable nutrients.
Common Household Items That Can Be Composted
Many common items from the kitchen and yard fall into the “green” category, providing the necessary nitrogen for microbial activity. These items are typically fresh, moist, and break down quickly. Examples include fruit and vegetable scraps, such as apple cores, banana peels, and carrot tops. Used coffee grounds are particularly beneficial, offering a favorable C:N ratio of around 20:1, making them a balanced addition that acts almost like a green material.
Paper tea bags, provided they are free of plastic or metal staples, can also be added, along with fresh grass clippings. It is important to add grass clippings in thin layers, as thick clumps can quickly become dense and restrict the airflow needed for aerobic decomposition. Shredding or chopping these green materials into smaller pieces increases their surface area, allowing microbes faster access to the nutrients and speeding up the overall composting process.
The “brown” category consists of materials that are dry, fibrous, and high in carbon, offering structure and energy to the compost pile. These materials include dry leaves, which provide good bulk and help maintain proper aeration within the pile. Shredded newspaper, using only black and white ink, and plain corrugated cardboard are excellent carbon sources. Before adding cardboard, it is important to remove any plastic tape, glossy sections, or labels, and then tear or shred it into small pieces.
Other valuable brown materials include wood chips and sawdust, though these should only come from untreated wood, as pressure-treated lumber contains harmful chemicals. Egg cartons, typically made from untreated paper pulp, also serve as an easy-to-shred carbon source.
Materials That Must Be Kept Out of the Compost Pile
Certain organic materials should be strictly excluded from a home compost pile to prevent pest attraction, the spread of disease, and the introduction of harmful pathogens. Meat, dairy products, bones, and cooking oils are strongly discouraged because they attract pests like rodents and raccoons to the compost area. Additionally, these items decompose slowly and can create dense, airless pockets, which leads to foul odors and an undesirable environment for aerobic microbes. Fats and oils also coat other materials in the pile, creating water-resistant barriers that impede the decomposition of surrounding organic matter.
Animal waste from household pets, such as dogs and cats, must be avoided due to the risk of harboring parasites and human pathogens that may not be killed in a typical backyard system. The internal temperature of many home compost piles often fails to reach the necessary sustained heat required for complete thermal sanitization.
Diseased plants, including any material infected with fungus, bacteria, or viruses, should not be composted because the pathogens can survive and spread when the finished compost is used in the garden. Most backyard composting systems do not consistently achieve or maintain the temperature of 131–160°F needed to reliably kill these plant diseases. Similarly, weeds that have gone to seed should be avoided to prevent the seeds from surviving the process and re-establishing themselves in the garden soil later.
Synthetic materials and chemically treated items must also be kept out of the compost to prevent contamination. This includes pressure-treated wood, glossy magazine paper, plastics, and metals, which either do not break down or leach toxic substances into the final product. Even seemingly organic materials like dryer lint from synthetic fabrics should be excluded, as they can introduce microplastics into the soil.