Recycling food and other organic waste into compost provides a range of environmental benefits, including improving soil health, reducing greenhouse gas emissions, recycling nutrients, and mitigating the impact of droughts.
What is Composting?
Composting is the natural process of recycling organic matter, such as leaves and food scraps, into a valuable fertilizer that can enrich soil and plants. Anything that grows decomposes eventually; composting simply speeds up the process by providing an ideal environment for bacteria, fungi, and other decomposing organisms (such as worms, sowbugs, and nematodes) to do their work. The resulting decomposed matter, which often ends up looking like fertile garden soil, is called compost. Fondly referred to by farmers as “black gold,” compost is rich in nutrients and can be used for gardening, horticulture, and agriculture.
Organic discards can be processed in industrial-scale composting facilities, in smaller-scale community composting systems, and anaerobic digesters, among other options. This guide focuses primarily on home composting, which is a great way to keep your organic discards out of the waste stream and produce a valuable soil amendment for your use.
Benefits of Composting
Reduces the Waste Stream: Composting is a great way to recycle the organic waste we generate at home. Food scraps and garden waste combined make up more than 28 percent of what we throw away, according to the U.S. Environmental Protection Agency (EPA). Not only is food waste a significant environmental burden, but processing it is also costly. The average cost to landfill municipal solid waste in the United States was around $55 per ton in 2019. With the United States generating more than 267 million tons of municipal waste in 2017 and sending two-thirds of that to landfills and incinerators, we spent billions of dollars on waste management. Composting at home allows us to divert some of that waste from landfills and turn it into something practical for our yards.
Cuts Methane Emissions from Landfills: Typically, when organic matter decomposes, it undergoes aerobic decomposition, meaning that it’s broken down by microorganisms that require oxygen. When compostable waste goes to a landfill, it gets buried under massive amounts of other trash, cutting off a regular supply of oxygen for the decomposers. The waste then ends up undergoing anaerobic decomposition, being broken down by organisms that can live without free-flowing oxygen. During anaerobic decomposition, biogas is created as a by-product. This biogas is roughly 50 percent methane and 50 percent carbon dioxide, both of which are potent greenhouse gases, with methane being 28 to 36 times more effective than CO2 at trapping heat in the atmosphere over a century. Although most modern landfills have methane capture systems, these do not capture all of the gas; according to the EPA, landfills are the third-largest source of human-generated methane emissions in the United States.
Because our solid waste infrastructure was designed around landfilling, only about 6 percent of food waste gets composted. However, states, cities, and individual businesses and vendors can spearhead zero-waste strategies to increase composting and recycling rates within their jurisdictions and to keep waste from being generated in the first place. There have been many composting success stories around the country, one notable example being San Francisco. In 1996, San Francisco established a large-scale composting program, and by 2000, it was able to divert 50 percent of its waste from landfills. By increasing its goals over the years, San Francisco has been diverting more than 80 percent of waste from landfills since 2012. That means more than 90,000 metric tons of carbon emissions are avoided each year, equivalent to the annual greenhouse gas emissions from 20,000 passenger vehicles.
Improves Soil Health and Lessens Erosion: Compost is an essential tool for improving large-scale agricultural systems. Compost contains three primary nutrients needed by garden crops: nitrogen, phosphorus, and potassium. It also includes traces of other essential elements like calcium, magnesium, iron, and zinc. Instead of relying on synthetic fertilizers that contain harmful chemicals, composting offers an organic alternative. Research has shown the capability of compost to increase the soil’s water retention capacity, productivity, and resiliency.
Conserves Water: Agriculture is a major consumer of water in the United States, accounting for approximately 80 percent of the nation’s water use, according to the EPA. Irrigation systems are effective, but are expensive and time-consuming for farmers to manage. Additionally, water is becoming increasingly difficult to obtain across the country.
How can compost help? Research has shown that the water-retaining capacities of soil increase with the addition of organic matter. Each 1 percent increase in soil organic matter helps soil hold 20,000 gallons more water per acre. By using compost to foster healthy soil, farmers do not have to use as much water and can still have higher yields compared with farming with degraded soil.
Reduces Personal Food Waste: Consumers are responsible for a staggering amount of wasted food. An average American family of four throws out about $150 worth of food per month, a 50 percent increase since the 1970s. NRDC research in three U.S. cities indicated that the category of edible food most wasted by households was fruits and vegetables. According to a 2016 report in The Guardian, U.S. retailers and consumers throw away about 60 million tons (or $160 billion) worth of produce annually. The best way to reduce impacts from food waste is to prevent waste from occurring in the first place, so NRDC works through its Save the Food campaign and other tools to educate consumers on how to shop for, prepare, and store food to minimize waste. However, even if we do everything possible to decrease food waste, there will still be food scraps that cannot be consumed (e.g., a banana peel). Composting is a great way to recycle those discards instead of tossing them in the trash.

How to Compost?
1. Compost Ingredients
Organisms that decompose organic waste need four key elements to thrive: nitrogen, carbon, air, and water. Since all compostable materials contain carbon, with varying amounts of nitrogen, composting successfully is just a matter of using the right combination of materials to achieve the best ratio of carbon to nitrogen and maintaining the right amounts of air and water to yield the best results. The ideal carbon-to-nitrogen ratio for a compost pile is 25 to 30 parts carbon for every 1 part nitrogen. If your pile has too much carbon-rich material, it will be drier and take longer to break down. Too much nitrogen-rich material can end up creating a slimy, wet, and smelly compost pile. Fortunately, these problems are easily remedied by adding carbon-rich or nitrogen-rich material as needed.
“Greens” for Nitrogen
Nitrogen is one of the basic building blocks of life, and it is an essential element for growth and reproduction in both plants and animals. A higher nitrogen-to-carbon ratio is most commonly found in fresh organic material (often referred to as greens). Having plenty of greens in your compost pile makes sure the decomposers can grow and reproduce quickly. Some household greens you can add to your home compost pile are fresh grass clippings, food scraps, and coffee grounds.
“Browns” for Carbon
Another essential compound for all life forms is carbon, higher proportions of which can be found in brown plant material. Carbon acts as a food source for decomposers, helping to keep them alive while they break down waste. Typical browns you can add to a compost pile include dead leaves, branches, twigs, and paper.
To achieve the best carbon-to-nitrogen ratio in your home compost, a rule of thumb is to put in two to four parts brown materials for every one part green materials.
Oxygen and Water
Finally, like any other living organism, decomposers need oxygen and water to survive. To ensure a faster home composting process, you will need to make sure your compost system has the right amount of air and water. As mentioned above, if you are not in a rush for finished compost, you do not have to maintain your waste; the decomposition will still take place, just at a much slower pace. Optimal air flow can be achieved by layering materials, making sure your materials are in small pieces (ideally no thicker than a finger), and turning piles regularly (or adding another type of aeration system). As for water, the ideally moist household compost pile will be about as wet as a wrung-out sponge. If you are including food waste in your pile, it’s likely it will be wet enough, but if not, just add water.
2. Temperature
Hot composting is achieved when the balance of greens, browns, air, and water creates ideal conditions for aerobic organisms to thrive. The optimal peak temperature for aerobic composting is 130 to 140 degrees Fahrenheit, which occurs when aerobic macro- and microorganisms are breaking down waste and reproducing at a fast rate. This high temperature also kills any lingering bacteria or weed seeds.
3. Consistent Aeration
Aeration encourages an aerobic environment, which helps to speed up the composting process and reduce odors. It is recommended you turn your pile (or rotate your tumbler) around once a week during summer and at a minimum once every three to four weeks during winter. You can also add piping or large sticks to help increase natural airflow.
4. Maintaining Moisture
Moisture is essential for composting—your pile should always feel like a wrung-out sponge. Too dry a pile may cause the composting process to slow down. Too wet a pile may create an anaerobic environment, which can cause bad odors and also slow down decomposition. Water your pile (or add more wet materials) if it becomes too dry, and add carbon-heavy browns if it becomes too wet.
Composting Machine is a device designed to convert organic waste—such as food scraps, garden trimmings, and biodegradable materials—into nutrient-rich compost through accelerated biological decomposition. These machines are widely used in households, restaurants, hotels, schools, and industries to manage waste sustainably and reduce landfill contributions.