The short answer
Effective on-site composting is a moisture, carbon-to-nitrogen, oxygen and temperature management problem. Odour is usually excess nitrogen, too much water, or insufficient air; pests usually follow exposed food scraps and poor bin design. The economics are often favourable when disposal is expensive: average US landfill tipping fees were above $60 per ton in 2024, while compost can sell for $40 to $100 per ton according to one industry source, though site, scale and labour costs determine the real net result.
Key takeaways
- Cornell's standard operating target is about 30:1 carbon to nitrogen, 40-60 percent moisture, and oxygen above 10 percent.
- Ammonia odour means too much nitrogen; putrid odour means too wet or too little air.
- Pest prevention starts with excluding meat, dairy and grease and burying food scraps under browns.
- Backyard piles should not accept animal products; commercial facilities may accept them only with controlled temperatures.
- A cost model must include labour, equipment, amendments and pad space, not just avoided tip fees.
- Average US landfill tip fees exceeded $60 per ton in 2024, but local markets and scale change the comparison.
The four operating dials: carbon, nitrogen, oxygen and water
Composting is an aerobic process, so the microorganisms doing the work need oxygen, moisture, carbon for energy and nitrogen for growth. Cornell Cooperative Extension lists optimal conditions as oxygen above 10 percent, moisture around 40-60 percent, a carbon-to-nitrogen ratio near 30:1 by weight, and a pile temperature between roughly 90 and 140 degrees Fahrenheit.
When oxygen drops, the pile goes anaerobic and offensive odours follow. Air enters through turning or through a built-in aeration system, and through good pile structure. If the material is too wet, anaerobic pockets form; too dry, decomposition slows sharply.
Temperature is a useful management signal. Above about 140 degrees Fahrenheit the active organisms begin to die, so turn the pile before it overheats. High temperatures also reduce pathogens and weed seeds, which is why hot composting is operationally valuable.
Reading odour before neighbours do
Ammonia smell usually means the mix has too much nitrogen relative to available carbon, and oxygen is being consumed faster than it can be replaced. The fix is to stop adding high-nitrogen material, add more browns such as dry leaves or wood chips, and turn the pile.
A rotten or putrid smell points to anaerobic conditions from excess moisture or insufficient air. Add dry structural material, turn thoroughly, and check drainage. The US EPA's home composting guidance gives the same logic: a bad odour means the pile may be too wet or need more air circulation.
For larger challenging feedstocks, forced aeration through pipes below a concrete pad can keep odour under control while increasing throughput. The LPELC case study describes using positive aeration with a moist wood chip or screened compost cap for the first seven to ten days on difficult feedstocks, and recommends forcing air through the pile several times per hour.
Pests: make the bin hard to enter and the contents boring
Pest problems are usually design and input problems. The US EPA advises that a well-managed home pile should not attract rodents: use a bin with a lid and preferably a floor, leave no gaps larger than a quarter inch, maintain two to three parts browns to one part greens by volume, and cover and bury food scraps.
Do not add meat, fish, bones, dairy, fats or greasy foods to a backyard pile. These attract animals and often do not reach high enough temperatures in a small pile to decompose safely. Commercial facilities can accept them only when temperature and turning controls are sufficient, and operators should confirm acceptance rules.
Turning is also a pest tool because regular disturbance destroys nests and runs. A hot, actively managed pile is less attractive to rodents than a static, warm, undisturbed one. Mechanical barriers perform better than rodenticides, which are generally inappropriate inside a compost system.
Feedstock decisions and the carbon-to-nitrogen balance
Cornell's ingredient fact sheet lists approximate ratios that help operators blend correctly. High-nitrogen materials include grass clippings at 19:1, digested sewage sludge at 16:1, food waste at 15:1, cow manure at 20:1 and horse manure at 25:1. High-carbon materials include leaves at 40-80:1, bark at 100-130:1, paper around 170:1, and wood or sawdust from 300:1 to 700:1.
A simple yard waste blend is one part grass clippings to three parts leaves by volume. The ratio does not need to be exact, but it must stay within a workable range so the microbial population can grow without creating ammonia or stalling.
The EPA's home guidance separates greens and browns: fruit and vegetable scraps, grass clippings, coffee grounds and eggshells are greens; dry leaves, stalks, shredded plain paper, cardboard and untreated wood chips are browns. Materials to avoid include meat, fish, dairy, oils, cooked food in significant amounts, herbicide-treated plants, weeds with seeds, pet waste, glossy paper and treated wood.
Real economics: from avoided tip fees to net compost cost
A composting operation should be evaluated as a cost model, not only as a sustainability project. According to Green Mountain Technologies, the average US landfill tip fee was above $60 per ton in 2024, while compost market value was commonly $40 to $100 per ton depending on type and market. Those figures are directional and vary widely by state and product quality.
The more reliable comparison for an on-site operator is avoided disposal cost plus avoided fertilizer or soil amendment purchases, minus the full cost of labour, equipment, amendments, water and pad space. On a farm, the economics improve if the feedstock is already on site and the finished material replaces purchased manure or compost.
The LPELC case shows that capital choices change labour. An aeration floor reduced touches from twelve to nine compared with un-aerated windrows and shortened composting plus curing time from 90 to 45 days, but required concrete, blowers, piping and a turner. Small sites can start with low-cost bins and manual labour, but must accept slower throughput and more attention to moisture and turning.
Put it into practice
On-Site Composting Feasibility and Startup Checklist
Use this before investing and again each season. A failed system is usually caused by an input, moisture or labour mismatch that this checklist surfaces early.
- Estimate weekly and peak organic volume in cubic yards or tons, including seasonality.
- Confirm a reliable source of carbon or browns before accepting food scraps or manure.
- Test moisture by squeeze and target 40-60 percent, like a wrung-out sponge.
- Select a pad with drainage and controlled runoff away from water bodies.
- Choose a method: backyard bin, windrow, aerated static pile or in-vessel based on volume, labour and capital.
- Set a turning or aeration schedule and a temperature log with target range.
- Install pest barriers and exclude meat, dairy, fats and grease unless the system is designed for them.
- Plan separate curing space and a screen or sifter for finished material.
- Build a full cost model including labour hours, equipment, amendments, water, pad and avoided disposal or fertilizer costs.
- Confirm local permits, setbacks, buffer distances and any feedstock restrictions before accepting outside material.
Questions people ask
Why does my compost pile smell like ammonia and what should I do?
Ammonia odour indicates too much nitrogen relative to carbon and usually insufficient oxygen. Stop adding high-nitrogen materials such as fresh grass clippings, add more carbon-rich browns like dry leaves, sawdust or wood chips, and turn the pile thoroughly. If the pile is wet, the added browns will also help restore air space.
How do I keep rats and flies out of an on-site composting system?
Use a bin with a tight lid and ideally a floor, with no openings larger than one quarter inch. Maintain roughly two to three parts browns to one part greens by volume, bury food scraps under at least four to eight inches of dry browns, and avoid meat, fish, dairy and grease. Turn the pile regularly to disturb nesting and make the environment less attractive.
Which food scraps should never go in a backyard bin?
Exclude meat, fish, bones, dairy, fats, oils and large amounts of cooked food. These attract animals and a typical backyard pile does not reliably reach the temperatures needed to process them safely. Small amounts of cooked vegetable food may be acceptable if buried well, but animal products belong in a commercial facility that is designed for them.
How much does on-site composting really cost compared with landfill disposal?
The comparison depends on local rates. One industry source reported average US landfill tip fees above $60 per ton in 2024 and compost market values from $40 to $100 per ton. But a real model must subtract labour, equipment, amendments, water and pad costs. On-site composting often wins when feedstocks are already on site and the product replaces purchased soil amendment or fertilizer.
What temperature should an active compost pile reach and how do I monitor it?
A well-managed pile can reach 130 to 160 degrees Fahrenheit during active composting, which helps reduce pathogens and weed seeds. Cornell's general operating range is about 90 to 140 degrees Fahrenheit. Use a compost thermometer inserted into the centre and turn the pile if it exceeds the upper range, because overheating can kill the beneficial microorganisms.
Sources and further reading
Sources were checked when this page was generated. Confirm changing dates, rules and prices with the original publisher.
- Municipal Yard Waste Composting Operator's Fact Sheet #1 of 10 - The Compost ProcessCornell Waste Management Institute
- Municipal Yard Waste Composting Operator's Fact Sheet #2 of 10 - Composting IngredientsCornell Waste Management Institute
- Composting At HomeUS EPA
- Concise CompostingLivestock and Poultry Environmental Learning Community
- Landfill Costs Are Tipping the Scale Toward CompostingGreen Mountain Technologies
- Компост под защитой: стратегия борьбы с грызунами и профилактикаФГБУ Россельхозцентр
- Как приготовить органическое удобрение для своего участкаФГБУ Россельхозцентр