Composting

On this page:

EPA's Wasted Food Scale
Impacts of Sending Food and Other Organic Materials to Landfills
Definitions
Composting Basics and Approaches
Benefits of Composting
Benefits of Compost Use
Composting-Related Policies and Regulations
Additional Resources
Sources of Statistics

EPA's Wasted Food Scale

Composting is nature’s way of recycling and is one of the most powerful actions we can take to reduce trash in landfills, address climate change, and build healthy soil. Composting is in the fourth tier of EPA's Wasted Food Scale.

Impacts of Sending Food and Other Organic Materials to Landfills

pie chart of total municipal solid waste landfilled by material — Total Municipal Solid Waste Landfilled (by material), 2018. *EPA Advancing Sustainable Materials Management: 2018 Fact Sheet (pdf)(4.9 MB). Click on the pie chart to enlarge it.*

In 2019, 66.2 million tons of wasted food were generated in the food retail, food service and residential sectors in the United States. Only 5% of that wasted food was composted.¹

In the U.S., food is the single most common material sent to landfills, comprising 24.1 percent of municipal solid waste. When yard trimmings, wood and paper/paperboard are added to food, these organic materials comprise 51.4 percent of municipal solid waste in landfills.²

When food and other organic materials decompose in a landfill where anaerobic (without oxygen) conditions are present, bacteria break down the materials and generate methane, a powerful greenhouse gas. Municipal solid waste landfills are the third largest source of human-related methane emissions in the U.S, accounting for approximately 14% of methane emissions in 2021.³ Wasted food is responsible for 58% of landfill methane emissions.⁴

pie chart depicting 2021 U.S. Methane Emissions, By Source — 2021 U.S. Methane Emissions, By Source. *EPA Landfill Methane Outreach Program. Click on the pie chart to enlarge it.*

Composting is a form of organics recycling. Organics recycling is when facilities collect and process organic materials (that would otherwise be landfilled or incinerated) into new products, such as soil amendments. When we send food and other organic materials to landfills or combustion facilities, we throw away the valuable nutrients and carbon contained in those materials. By composting our food scraps and yard trimmings instead and using the compost produced, we can return those nutrients and carbon to the soil to improve soil quality, support plant growth and build resilience in our local ecosystems and communities.

Composting is a fundamentally local process. Organic materials are typically collected and processed into compost near where they are generated, often in the same county, city or even neighborhood. In this way, composting also supports local jobs and economies.

Definitions

Composting is the managed, aerobic (oxygen-required) biological decomposition of organic materials by microorganisms. Organic (carbon-based) materials include grass clippings, leaves, yard and tree trimmings, food scraps, crop residues, animal manure and biosolids. Compost products for commercial sale typically go through thermophilic composting, where compost reaches high temperatures that reduce pathogens.

Compost is a biologically-stable soil amendment produced by the aerobic decomposition of organic materials.

Biodegradable kitchen waste on rich, black soil.

Composting Basics and Approaches

Regardless of size or scale, the basic principles of composting are generally the same. The composting process requires a proper ratio of carbon-rich materials (such as dry leaves or wood chips) to nitrogen-rich materials (such as food scraps or grass clippings). Maintaining adequate moisture level, oxygen flow, particle size, and temperature ensures microorganisms effectively break down organic materials into quality compost.

The method of composting used, as well as the equipment, is often determined by the scale or size of the site and the volume and type of materials, or feedstocks, being composted. The feedstocks accepted vary by composting facility and should always be free of contaminants such as herbicides, non-compostable packaging, and produce stickers.

Composting can take place at many scales/sizes – backyard, community, on-farm, municipal and regional – and at a range of locations in urban to rural areas. A small-scale system can be as simple as a backyard compost pile or vermicomposting (worm composting) bin, whereas a large-scale system may be a centralized, commercial composting facility processing organic materials from around the region.

Learn more about the composting process as well as composting at home and community composting. Interested in starting a composting program in your area? Visit EPA's webpage of resources for help.

Benefits of Composting

Protects the climate by reducing methane emissions from landfills.
Reduces waste.
Recycles organic materials into a valuable soil amendment – compost.
Recovers organic materials and keeps them local.
Creates green jobs.
Extends municipal landfill life by diverting organic materials and saving space in landfills.
Reduces solid waste management costs because food scraps are one of the largest and heaviest portions of the waste stream, making their recovery increasingly cost-effective compared to disposal.

This graphic conveys how composting food scraps reduces emissions and can help adapt to climate change. On the left side of the graphic, wasted food is decomposing in the landfill, causing greenhouse gas emissions. On the right side of the image, wasted food is being composted and next to the compost is a field where crops are being grown. — *Click to enlarge.*

Benefits of Compost Use

In the United States, our soils suffer from topsoil loss and erosion, which can lead to water quality issues and reduce the productivity of agricultural land. Compost adds much-needed organic matter to soil to enhance soil health. Compost has other uses as well in green infrastructure and stormwater management. Additionally, the use of compost sustains green jobs throughout the organics recovery cycle.

Markets and applications for compost include agricultural and horticultural, landscape and nursery, vegetable and flower gardens, sod production and roadside projects, wetlands creation, green infrastructure, soil remediation and land reclamation, sports fields and golf courses, sediment and erosion control, and stormwater management.

Compost Enriches and Builds Healthy Soil

Adds organic matter to the soil and increases the nutrient content and biodiversity of microbes in soil.
Conserves water and reduces water use by helping soils retain moisture.
Helps prevent soil erosion by reducing soil compaction and runoff.
Reduces reliance on chemical fertilizers and pesticides.
Improves plant growth and promotes higher yields of agricultural crops.
Improves water quality by filtering stormwater and reducing nutrient and sediment runoff.
Helps regenerate poor soil and remediate (clean up) soils that have been depleted by overuse or contain contaminants.

Compost Aids Climate Adaptation and Resilience

Improves a community’s ability to adapt to adverse climate impacts by helping soil absorb water and prevent runoff of pollutants during floods. It also helps soil hold more water for longer, mitigating the effects of drought.
Sequesters carbon in the soil, helping reduce greenhouse gas emissions.
Strengthens sustainable, local food production by using locally generated food scraps and other organic materials to create a valuable soil amendment that supports plant growth.

this is a wooden bin with food scraps in it for composting

Composting Policies and Regulations

Composting policies and regulations are set at the state and local government level.

Some states ban or restrict landfill disposal of organic materials such as yard and tree trimmings and wasted food. Some bans only affect large generators of organic materials, whereas others affect all generators of wasted food, down to the household level.

Below are some composting and compost use policy resources:

The Environmental Law Institute offers a Toolkit for Incorporating Food Waste in Municipal Climate Action Plans (Environmental Law Institute).
The Institute for Local Self-Reliance has a guide for Healthy Soils and Compost Policy (pdf)(1.1 MB). They also maintain a list of different compost-related rules by state, and much more on its Compost Policy Resource Hub.
The National Resources Defense Council and Environmental Law Institute showcase a Model Municipal Zoning Ordinance on Community Composting and a Model Policy for Compost Procurement.
ReFED offers the U.S. Food Waste Policy Finder, a searchable tool of wasted food and organics recycling policies.
The Sustainable Economies Law Center, in collaboration with the Institute for Local Self-Reliance, maintains a website on compost law and policy. The website focuses on community and small-scale composting.
The U.S. Composting Council compiles information on state compost regulations, has a Model Compost Rules Template for States to use in updating their composting permitting regulations, and maintains a map of states’ organics bans.
The Zero Food Waste Coalition provides a toolkit and template legislation on how to start the process of enacting an organics ban in your community.

Additional Resources

Visit the other EPA composting webpages for more information and resources:

Mention of or referral to commercial products or services or links to non-EPA sites does not imply official EPA endorsement of or responsibility for the opinions, ideas, data, or products presented at those locations or guarantee the validity of the information provided. Mention of commercial products/services on non-EPA websites is provided solely as a pointer to information on topics related to environmental protection that may be useful to EPA staff and the public.

Visit the webpages below for more composting information:

Sources of Statistics

U.S. EPA, 2019 Wasted Food Report (pdf)(1.39 MB).
U.S. EPA, Advancing Sustainable Materials Management: 2018 Fact Sheet (pdf)(4.9 MB).
U.S. EPA, Landfill Methane Outreach Program.
U.S. EPA, Quantifying Methane Emissions from Landfilled Food Waste.