Composting Impact Calculator
Measure the greenhouse gas reduction from composting your kitchen and garden organic waste. Combine waste weight, compost conversion rate, and a methane reduction factor to get CO₂-equivalent savings.
About this calculator
When organic waste is sent to landfill, it decomposes anaerobically and releases methane — a greenhouse gas roughly 25 times more potent than CO₂ over a 100-year period. Composting diverts that waste to an aerobic process that produces stable humus instead of methane. The formula is: CO₂ equivalent reduction (kg) = organicWaste (kg) × compostRatio × methaneReduction (kg CO₂e per kg compost). The compostRatio represents how much finished compost is produced per kilogram of raw organic input — typically 0.3 to 0.5 for home composting. The methaneReduction factor converts that compost yield into avoided greenhouse gas emissions. Multiplying all three values gives a tangible climate metric: kilograms of CO₂-equivalent emissions prevented by composting instead of landfilling.
How to use
Assume you compost 50 kg of kitchen scraps over a month. Your home bin has a compost conversion rate of 0.4 (meaning 40% of input weight becomes finished compost) and a methane reduction factor of 0.5 kg CO₂e per kg of compost produced. Enter 50 in Organic Waste Weight, 0.4 in Compost Conversion Rate, and 0.5 in Methane Reduction Factor. The calculator computes: 50 × 0.4 × 0.5 = 10 kg CO₂ equivalent avoided. That is a meaningful monthly reduction equivalent to not driving a petrol car for roughly 60 km.
Frequently asked questions
How does composting reduce methane emissions compared to sending food waste to landfill?
In a landfill, organic materials are buried under other waste and break down without oxygen — an anaerobic process that produces methane as a byproduct. Composting exposes the same materials to oxygen, driving aerobic decomposition that produces carbon dioxide and water vapor instead of methane. Since methane is approximately 25 times more potent as a greenhouse gas than CO₂ over a 100-year horizon (and 84 times over 20 years), diverting even small amounts of organic waste to composting produces a disproportionately large climate benefit. This is why composting is highlighted in national and municipal climate action plans worldwide.
What is a typical compost conversion rate for home composting bins?
Home compost bins typically convert between 30% and 50% of input weight into finished compost, giving a compostRatio of 0.3 to 0.5. The conversion rate depends on the balance of 'greens' (nitrogen-rich materials like food scraps) and 'browns' (carbon-rich materials like cardboard and dry leaves), moisture levels, and how frequently the pile is turned. Industrial in-vessel composting systems achieve higher and more consistent conversion rates, often 0.4 to 0.6, due to controlled temperature and aeration. Starting with a ratio of 0.4 is a reasonable default for most home composting setups.
What types of organic waste are best suited for composting?
Fruit and vegetable peelings, coffee grounds, tea bags, eggshells, and garden clippings are ideal composting inputs and break down quickly. These 'green' materials should be balanced with 'brown' materials such as cardboard, paper, straw, and dry leaves to maintain the carbon-to-nitrogen ratio needed for efficient decomposition. Meat, dairy, cooked foods, and oily waste are generally not recommended for home composting as they attract pests and can create odor problems, though they are handled well in hot industrial composting facilities. Avoiding these items in your home bin keeps the process clean, fast, and effective.