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.
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.
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.
From Composting from NC Division of Pollution Prevention and Environmental Assistance
3 things not to compost
Although any organic waste will rot down eventually, some things are best left out.
1) Large chunks of cheese, pieces of fat, etc, do compost eventually but they tend to attract vermin, so they’re best given to the dog or composted with Bokashi rather than added to your compost bin.
2) Anything that’s sharp or thorny should also be left out, because although the compost heap will destroy the thorns, you’re likely to scratch yourself later on, risking a trip for a tetanus injection.
3) Ideally, diseased plant material should not be composted. Although a good compost heap will get rid of most diseases, if your heap doesn’t heat up enough, the diseased cells may survive and inadvertently be spread to other parts of the garden.
For a comprehensive list of what you can and can’t compost, see our Compost Checklist.
From Making Compost
Good Compost Ingredients: Green and Brown
The key to making great compost is getting the right mix of ingredients so that the pile breaks down efficiently leaving us with compost that is both rich in nutrients and high in humus.
But before we delve into how much of each ingredient to use, here is a quick overview of the types of materials that we will be adding to our compost pile.
Compost ingredients can be divided into two basic categories, Brown Materials such as leaves, hay, straw and paper, and Green materials such as grass clippings, fresh manure, vegetable trimmings and most green plant cuttings.
To make the categories easier to remember it is often helpful to think of brown materials as hard, dry or dead, and green materials as soft, fresh or wet. There are a few exceptions but it is usually correct.
Brown
Leaves
Hay & Straw
Paper & Cardboard
Woody Prunings
Eggshells
Coffee Grounds
Tea Bags
Corn Cobs
Sawdust
Green
Vegetables & Fruit
Grass Clippings
Fresh Manure
Young Hedge Trimmings
Seaweed
Feathers
Plant cuttings
Hair
From Compost-Info Guide
Other Resources:
Backyard Composting Fact Sheet