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N.C. Department of Environment and Natural Resources

NC Department of Environment and Natural Resources
Environmental Assistance and Customer Service - Basics

Environmental Assistance and Customer Service

Composting: Organics RecyclingComposting Logo

For questions regarding Organics Recycling contact:
919-707-8123

What is compost?

Compost is the product resulting from the controlled biological decomposition of organic material that has been sanitized through the generation of heat and stabilized to the point that it is beneficial to plant growth. Compost bears little physical resemblance to the raw material from which it originated. Compost is an organic matter source that has the unique ability to improve the chemical, physical and biological characteristics of soils or growing media. It contains plant nutrients but is typically not characterized as a fertilizer.

How is compost produced?

Compost is produced through the activity of aerobic (oxygen-requiring) microorganisms. These microbes require oxygen, moisture and food in order to grow and multiply. When these resources are maintained at optimal levels, the natural decomposition process is greatly accelerated. The microbes generate heat, water vapor and carbon dioxide as they transform raw materials into a stable soil conditioner. Active composting is typically characterized by a high-temperature phase that sanitizes the product and allows a high rate of decomposition, followed by a lower temperature phase that allows for the product to stabilize while still decomposing at a lower rate. Compost can be produced from many feedstocks. State and federal regulations exist to ensure that only safe and environmentally beneficial composts are marketed.

Why should homeowners compost?

Composting helps keep organic matter out of landfills, saves money by reducing the need for fertilizer, water and garden supplies, and helps to limit pollutants contributed to the environment. Composting organic wastes at home (leaves, yard trimmings, food scraps, etc.) can reduce the waste annually disposed in landfills by 640 pounds per household.

What factors affect the composting process?

  • Carbon to nitrogen ratio of the compostable materials
  • Amount of surface area exposed
  • Amount of aeration in the pile
  • Moisture content
  • Temperature
  • Time

What are the benefits of using compost?

  • Improves the soil structure, porosity and bulk density, creating a better plant root environment
  • Increases moisture infiltration and permeability of heavy soils, improving drainage and reducing erosion and run-off
  • Improves moisture-holding capacity of light soils, reducing water loss and nutrient leaching
  • Improves and stabilizes soil pH
  • Improves cation exchange capacity (CEC) of soils, improving their ability to hold nutrients for plant use
  • Supplies a variety of macro and micro nutrients
  • Supplies significant quantities of organic matter
  • Supplies beneficial microorganisms to the soil, improving nutrient uptake and suppressing certain soil-borne diseases
  • Can bind and degrade specific pollutants

Differences between finished and immature compost:

Be aware that the use of incompletely decomposed compost in the garden may damage plants. If unfinished material is used, than the decomposer bacteria in the compost compete with plants for nitrogen in the soil to break down materials. As a result, plant leaves may turn yellow and growth can be stunted. In addition, organic acids in decomposing materials may cause harm to plant roots.

Finished compost qualities:

  • Smells earthy
  • Will not reheat when turned or wetted
  • Looks like dark soil, original trimmings are not identifiable

Immature Compost Qualities:

  • Smells sour or like ammonia
  • Significant heat is generated when compost is turned or dry compost is wetted
  • Is light colored; leaves, clumps of grass or other trimmings are identifiable

What are some uses of compost?

  • Soil Incorporant:

    • Turf establishment
    • Garden bed preparation
    • Crop production
    • Reclamation/remediation
    • Nursery production
    • Sod production
    • Roadside vegetation
  • Growing Media Component:

    • Container/potting
    • Landscape (e.g. rooftop, raised planters)
    • Backfill mixes (tree and shrub planting)
    • Golf courses (e.g. tee, green, divot mixes)
    • Manufactured topsoil
    • Bioremediation
  • Surface Applied:

    • Garden bed mulch
    • Crop production mulch
    • Nursery production mulch
    • Erosion control media
    • Silt/sediment control berm
    • Turf top dressing
  • What are new and emerging uses of compost?

    • Bioremediation and pollution prevention
    • Disease control for plants and animals
    • Erosion control
    • Composting of contaminated soils
    • Reforestation and wetlands restoration
    • Habitat revitalization

Mulching with compost

On flower and vegetable beds:

  • Remove weeds and grass that may grow through mulch.
  • Screen or pick through compost to remove large, woody materials. They may be unattractive and will compete for nitrogen if mixed into the soil.
  • Apply 1"-3" of compost over the entire bed, or place in rings around each plant extending to its outermost leaves.
  • Always keep mulches a few inches away from the base of the plant to prevent damage by pests and disease.

On lawns:

  • Use screened commercial compost, or sift homemade compost through a ½" or finer mesh.
  • Spread compost in ¼" or ½" layers after thatching, coring, or reseeding.

On trees and shrubs:

  • Remove sod from around trees and shrubs as far as branches spread. If this is impractical, remove sod from within a minimum 4" diameter circle around plants.
  • Use coarse compost or material left after sifting. Remove only the largest branches and rocks.
  • Spread 1"–3" of compost.

For erosion control:

  • Spread coarse compost, or materials left after sifting, in layers 2"-4" deep over entire planting area or in rings extending to the drip line.
  • Mulch exposed slopes or erosion-prone areas with 2"-4" of coarse compost.

What is grasscycling?

Grasscycling - the natural decomposition of grass clippings left on the lawn after mowing - encourages those tending lawns to leave clippings where they are cut instead of bagging them. Grass clippings are a major component of residential yard waste, sometimes as much as 50 percent. Four good reasons to start grasscycling:

  1. You'll need less fertilizer
  2. You'll save water
  3. You'll save your community money
  4. You'll also save one of your most precious resources: time

What is xeriscaping?

Xeriscaping is landscaping with less water while maintaining a traditional look. Americans routinely overwater their lawns by as much as 20 to 40 percent. By not overwatering, water use can be reduced by about 12 percent during summer months.

What is vermicomposting?

Vermicomposting is a composting technique that uses earthworms to break down organic material. Several earthworm species can consume organic wastes rapidly and then fragment the materials into fine particles. These particles contain essential nutrients such as nitrogen, phosphorus, potassium and calcium that are valuable to plant growth.

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