Composting Information

Backyard composting speeds up the natural process of decomposition, providing optimum conditions so that organic matter can break down more quickly. As you dig, turn, layer and water your compost pile, you may feel as if you are doing the composting , but the bulk of the work is actually done by numerous types of decomposer organisms.

Both macro and microorganisms play an important role in the composting process. Microorganisms such as bacteria, fungi, and actinomycetes account for most of the decomposition that takes place in a pile because they are chemical decomposers (changing the chemistry of the waste). The larger decomposers, or macroorganisms, in a compost pile include different insects. They are considered to be physical decomposers because they grind, bite, suck, tear, and chew materials into smaller pieces.


Bacteria utilize carbon as a source of energy (to keep on eating) and nitrogen to build protein in their bodies (so they can grow and reproduce). The microorganisms oxidize the organic material (scraps) to obtain carbon for energy. During the oxidation process the compost pile heats up from the ambient air temperature. If proper conditions are present, the pile will heat up fairly rapidly (within days) due to bacteria consuming readily decomposable materials.

Changes in oxygen, moisture, temperature, and acidity can make bacteria die or become inactive. Aerobic bacteria need oxygen levels greater than five percent and once the oxygen levels fall below five percent, aerobes die and decomposition slows down. If the oxygen levels fall below five percent anaerobic microorganisms take over and produce a lot of useless organic acids and ammonia-like substances which are smelly, contain unavailable nitrogen and, in some cases, are toxic to plants.

Types of Aerobic Microorganisms:

Types of Macroorganisms:

The larger organisms that you may find in your compost pile are: ants, millipedes, centipedes, sow bugs, springtails, flies, beetles, snails, slugs, spiders and earthworms. These larger organisms are involved in physically transforming organic material into compost. They are active during the later stages of composting as the dig, chew, suck digest and mix the compostable materials.

Key Factors in Composting

There are four key factors to composting that you have control over to help the macro and microorganisms at work in your pile. The organisms need food (carbon and nitrogen), air, water and a maintained temperature.

Food Factor

"Greens" and "Browns" are necessary components to the compost pile. Greens are nitrogen rich material and browns provide the carbon. A carbon-nitrogen ratio should range between 25:1 and 30:1 for rapid decomposition.

Compost Materials

Nitrogen Rich (Green) Carbon Rich (Brown) Not Recommended
Algae Brown paper bags/napkins/towels, newspaper Dairy products
Coffee grounds, tea bags Coffee filters Plant/wood chemically treated
Egg shells Cotton/wool/silk scraps BBQ ashes/coal/charcoal
Food scraps, fruits/vegetables Hay, straw Fat (oils, grease, etc.)
Grass clippings, leaves Peat moss Thorny or waxy plants
Weeds (no seeds or pervasive roots) Wood chips/shavings, ash Manure from dogs, cats, birds, humans or ill herbivores

Possible Compost Problems

Symptom Possible Cause Possible Solution
Compost is not heating up Not enough nitrogen in the mix Mix in fresh grass clippings, manure, blood meal or other material high in nitrogen.
Not enough oygen In small, confined batches oxygen can burn off very quickly when it does start to heat. Keep mix aerated.
Not enough or too much water If mix is dry or too wet, microorganisms cannot do their work. Maintain proper moisture balance.
Particle size is too large Large bulky pieces of wood or stocks compost very slowly. For best results, keep particles in small batches less than one inch and wood products in sawdust size. Screen out large material.
Mix is dry throughout Lack of water Add water and mix. Mix should be as damp as a wrung-out sponge.
Matted or clumps of material Material is too compact and/or poor aeration Break up clumps and mix material. Aerate more frequently.
Compost has a bad ammonia smell May have too much nitrogen Mix in some dry carbon material. Maintain proper moisture control.
Compost is attracting rats, raccoons, dogs, or other pests Occurs when including food scraps, meat, or dairy products in the mix Avoid composting meat, dairy, and fatty materials. Use care when kitchen scraps are added. Keep compost screened or enclosed.
Compost contains earwigs, maggots, slugs or other insects Insects are a good sign of a productive compost mix Let the insects add to the composting process. A light sprinkling of lime may reduce them on the surface if desired.