Compost Impact Calculator
See how much food waste and CO₂ composting diverts each year.
Results update as you type.
How it works
Food waste sent to landfill is a hidden climate problem: buried scraps decompose without oxygen and release methane, a greenhouse gas far more potent than CO₂. Composting avoids this by breaking waste down aerobically, and this compost impact calculator shows the difference your compost bin makes. Enter how much food waste you compost each week and it estimates the annual mass you divert from landfill and the greenhouse gas emissions you avoid. The logic is straightforward. Your weekly food waste scaled across 52 weeks reveals a yearly total most people underestimate — a household easily composts hundreds of kilograms a year. Applying an emissions factor converts that diverted mass into kilograms of CO₂-equivalent kept out of the atmosphere, representing the methane that landfilling would otherwise have generated. Seeing both figures makes composting's value tangible beyond the finished soil improver it produces. It reframes food scraps as a resource rather than rubbish and motivates diverting more. Households starting a compost bin, community gardens tracking their impact, and councils promoting food-waste collection all use a compost impact calculator to quantify benefits. Composting also returns nutrients to soil, reducing the need for synthetic fertiliser, so the carbon saving shown here is only part of a wider environmental gain that comes from closing the loop on the food you would otherwise throw away.
annual diverted = weekly waste × 52; CO₂ avoided = diverted × 0.5
Composting keeps food scraps out of landfill, where they would rot without oxygen and release methane, a powerful greenhouse gas. Multiplying your weekly food waste by 52 weeks gives the annual mass you divert. Multiplying that diverted mass by a factor of 0.5 estimates the kilograms of CO₂-equivalent emissions avoided, capturing the methane that landfilling would have produced. Composting instead breaks the waste down aerobically, releasing far less potent gases and returning nutrients to soil.
Source:U.S. EPA food waste and landfill methane estimates
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter food waste per week.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Waste diverted updates instantly as you type — no button to press.
Frequently asked questions
Why does composting reduce greenhouse gases?
When food waste is buried in landfill it breaks down without oxygen, producing methane, a greenhouse gas roughly 25 times more potent than carbon dioxide over a century. Composting instead exposes the waste to air, so it decomposes aerobically and releases mostly carbon dioxide and far less methane. Diverting scraps to compost therefore avoids the intense warming impact of landfill methane, which is what the CO₂-avoided figure here estimates.
What does the 0.5 factor represent?
It is a simplified estimate of the kilograms of CO₂-equivalent emissions avoided for each kilogram of food waste diverted from landfill to composting. It captures the methane that anaerobic landfill decomposition would have released, converted into its warming equivalent. Real values depend on landfill gas capture, waste type, and local conditions, so treat this as a reasonable average that illustrates the benefit rather than a precise site-specific measurement.
How much food waste does a household produce?
It varies with household size and habits, but many families discard several kilograms of food scraps a week — peelings, cores, coffee grounds, eggshells, and spoiled leftovers. Weigh your food waste for a typical week to get an accurate input; a small kitchen caddy fills faster than people expect. Across a year the total often reaches hundreds of kilograms, which is why diverting it from landfill has a meaningful climate impact.
What can I compost, and what should I avoid?
Most fruit and vegetable scraps, coffee grounds, tea, eggshells, and garden trimmings compost well and are counted here. Meat, fish, dairy, and oily foods are usually avoided in home compost because they attract pests and smell, though some industrial systems handle them. Balancing green nitrogen-rich scraps with brown carbon-rich material like leaves and cardboard keeps a compost pile healthy and speeds decomposition into usable soil improver.
Does compost benefit the environment beyond carbon?
Yes, considerably. Finished compost enriches soil with nutrients and organic matter, improving its structure, water retention, and fertility, which reduces the need for synthetic fertilisers whose manufacture emits carbon. Healthier soils also store carbon and support biodiversity. So while this calculator focuses on the greenhouse gases avoided by diverting waste from landfill, composting closes a natural loop that delivers wider soil, water, and ecosystem benefits on top of the carbon saving.