How Compost Happens, Bulletin #1159

This fact sheet will help you create rich compost to use in the garden, on the lawn and as a soil builder around special shrubs and plants. We include answers to common questions and include a troubleshooting guide to common compost problems.

Q: What can I add to my compost pile?
A: Although almost all natural, organic material will compost, you shouldn't put everything in your pile. Some wastes, such as fish scraps, bones, butter and meat, will attract pests and may smell. Other items, such as dog or cat manure, contain disease organisms that can survive the compost process and may attract other animals. Plants that are diseased or are infested with insects should not be added to your compost pile because they can cause future problems.

Some types of weeds and grasses (such as quack grass) may not be killed and can regrow. If you add weeds to the pile, be sure the pile heats up enough to kill them. Turning the pile regularly will help.

Easy to Compost	Hard to Compost	Slow Composters
seaweed bread coffee grounds egg shells pine needles fruit peels and rinds garden waste grass clippings leaves paper sawdust straw sod tea bags vegetables wood ash wood shavings	butter bones cheese chicken fish scraps lard mayonnaise meat milk cooking oils peanut butter salad dressing sour cream vegetable oil wood chips	wood chips, branches, twigs corncobs, husks and stalks sawdust straw apple pulp nut shells Cut these materials into small pieces and mix them with high-nitrogen materials (manure, fresh grass clippings) to make them decompose faster.

Q: What are the benefits of making compost?
A: When you compost, you convert vegetable scraps, leaves, grass clippings and other organic materials into useful, soil-building material. You can use compost in your garden and around shrubs or other plants. Composting reduces the amount of materials that go into landfills, which cuts down on the waste stream.

Q: How long does it take to make compost?
A: Generally, you can create usable compost in two to six months. It depends on materials, temperature, aeration and management.

Woody materials, such as wood chips, branches and twigs, may take up to two years to break down, unless you finely chip or shred them. If you add these to your pile, the whole pile may decompose more slowly. However, these materials will improve the pile structure and allow air to move through it. This is important if you add dense material, such as manure, to the pile.

Q: Why is the carbon-to-nitrogen ratio important? How can I be sure I have the right amounts of both?
A: Microorganisms in the pile are what make the materials decompose. They use the carbon (C) for food and the nitrogen (N) to build proteins. Without carbon or nitrogen, microorganisms can't do their job.

You should have about 30 parts carbon to one part nitrogen by weight. This combination will help microorganisms do their job quickly.

This doesn't mean you have to weigh everything that goes into the pile. Even C and N ratios of 25:1 and 40:1 work well. Just be aware of how much carbon and nitrogen material you add to the pile. In general, coarse, woody material is very high in carbon. Moist, dense material is high in nitrogen (see chart). If there is too much carbon, the pile won't decompose very fast. If there is too much nitrogen, it will start to form ammonia gas, which can cause odor problems.

Q: Should I add sod to my compost pile?
A: Yes, you may mix sod into your compost pile. Break up small amounts and combine it with other wastes. You can also compost it separately. Here's how:

Q: What if some of the material I put into the compost has been treated with
pesticides? Will this cause a problem?
A: If yard waste has been composted at least one year, pesticides should not be a problem. They break down faster in a compost pile than they do in the soil.

Compost Materials that are High in Carbon and Nitrogen (from highest to lowest)
Nitrogen horse manure with litter horse manure grass clippings cow manure coffee grounds vegetable waste poultry manure (with litter) poultry manure (fresh) pig manure	Carbon wood chips and sawdust paper bark straw corn stalks foliage (leaves)
Note: These are listed based on estimates. The amount of nitrogen or carbon may vary depending on the material. For example, brown grass clippings from a dry lawn will have less nitrogen than lush, green grass clippings. If you fertilize your lawn, the clippings will have an even higher nitrogen content.

Compost Troubleshooting Guide
Problem	Possible Cause	Solution
Rotten smell	Excessive moisture (anaerobic conditions)	Turn pile or add dry, porous material, such as sawdust, wood chips or straw
Rotten smell	Compaction (anaerobic conditions)	Turn pile or make the pile smaller
Ammonia smell	Too much nitrogen; not enough carbon	Add high-carbon material, such as sawdust, wood chips or straw
Pile not heating up	Pile too small	Make pile bigger or insulate with straw
	Not enough moisture	Add water while turning pile
	Poor air circulation	Turn pile
	Lack of nitrogen	Mix in nitrogen sources, such as grass clippings or manure
	Cold weather	Make the pile bigger or insulate the pile with a layer of straw
Pile too hot	Pile too large	Make smaller
Pile too hot	Not enough air	Turn pile
Pests (raccoons, rats, etc.)	Meat scraps or fatty food waste in the pile	Remove meat and fatty foods

For more information on composting, contact your county Extension office.
(Telecommunications Device for the Deaf 1-800-287-8957).

Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

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Last Modified: 08/12/08
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