Composting

This page is a compilation of information I gathered, hopefully organized in an easy to understand layout.

Almost one third of our household garbage consists of kitchen and yard waste. Composting can dramatically reduce landfull waste. The chief advantage of composting is its ability to improve soil structure. The humus produced by composting is a valuable resource in itself.

All organic materials will decompose. But a optimum balance of carbon to nitrogen ratio will ensure speedy composition. A good compost also needs water, air and the right container.

C:N Ratio

This is proportion of carbon to nitrogen in your compost unit. The ratio will affect the speed of composition. Ideally, your C:N ratio should be 30:1. Grass clippings and plant trimmings and kitchen scraps are high in nitrogen. Sawdust, straw, wood chips and dry leaves are high in carbon. A mixture of kitchen and yard waste should give you close to the ideal ratio.

A pile that is too high in carbon will stay cool and sit a long time without breaking down. A pile too high in nitrogen will smell like ammonia gas. In both instances, the decomposition process is working on everything organic. If you have the time to wait and the space to keep these materials, you’ll eventually be rewarded with compost.

Water and Air

The right amount of water and air to keep the biological and chemical processes functioning. A compost should have the water content of a wrung out sponge. The “squeeze” test is an easy way to gauge the moisture content of composting materials. The material should feel damp to the touch, with just a drop or two of liquid being released when the material is tightly squeezed in the hand.

Containers

A composter can be made of wood, concrete blocks, wire mesh or almost any material you have available.

The three most essential features in a composter are:

1. A lid that protects the pile from rain and snow and allows you to control how much moisture gets in.

2. Holes or vents to allow air circulation

3. A means of removing the final product.

Some design ideas:

~ a wire mesh bin with a hinged front panel

~ a three sided cement block bin with an open front that allows you to turn the pile and remove the finished compost.

~ a circular unit made of chicken wire or snow fencing that can be opened up to collect the finished compost.

~ a metal barrel or garbage can with holes punched in it and the bottom removed.

~ for more advanced enthusiasts, a unit with several compartments can be used to manage compost at different stages – raw materials, active piles, and finished product.

A compost pile should be large enough to hold heat and small enough to admit air to its center. As rule of thumb, the minimum dimensions of a pile should be 3 feet by 3 feet by 3 feet (1 cubic yard) to hold heat. The maximum to allow air to the center of the pile is 5 feet tall by 5 feet wide and as long as you wish.

Getting Started

The compost pile can initially be prepared in layers. This will facilitate decomposition by insuring proper mixing.
To build a compost pile, start with a 4-6 inch layer of chopped brush or other coarse material set on top of the soil. This will let air circulate under the base of the pile.
Next, add a 3-4 inch layer of low carbon organic material such as grass clippings. This material should be damp when added to the pile. On top of this, add a 4-6 inch layer of high carbon organic material (leaves or garden waste) which should also be damp.
On top of this, add a 1-inch layer of garden soil or finished compost. This layer will introduce the microorganisms needed to break down the organic matter.
Mix the layers of high carbon organic matter, low carbon organic matter and soil before adding another layer to the pile. This will ensure a speedy and even composting of the organic matter.
Repeat the “layering” process until the composting bin is filled.

Maintaining
For the passive compost pile, nothing more needs to be done.
For the active compost pile, maintenance will involve turning the pile and adding water to maintain conditions conducive to the composting process. In an active compost pile, the temperature will increase rapidly and soon reach about 110F. After about a week, the pile should be opened to the air and any compacted material should be loosened. The the pile should be reconstructed; material previously on the top and sides of the pile should be moved to the center.
After about another week, the pile should be turned again. Each time the material should be turned back to the center of the pile. At each turning, the moisture content should be checked using the squeeze test. Water should be added if necessary.
The compost will be finished when the pile cools off and decreases to about one-third of its original volume. It will be dark, crumbly, and have an earthy odor.

Non-Compostable Organic Materials
~ cheese ~ whole eggs
~ butter ~ milk
~ grease ~ mayonnaise
~ oil ~ sour cream
~ lard ~ salad dressing
~ bones ~ dog and cat manure
~ meat/fish ~ grasses that spread rhizomes
~ peanut butter ~ harmful or succulent weeds
~ plants with severe disease or insect infestations

Using Compost
If the compost contains many material that are not broken down, it is only partly decomposed. Adding partly decomposed compost to soil can reduce the amount of nitrogen available to plants. The microorganisms will continue to decompose but will use soil nitrogen for their own growth, restricting the nitrogen’s availability to plants growing nearby. Allow partly decomposed compost particles to break down further or separate them out before using compost around growing plants. Or add extra nitrogen (such as in manure or commercial fertilizer) to ensure that growing plants will not suffer from a nitrogen deficiency.
Stable compost can be blended into soil mixes and is suitable for most outdoor planting projects. It is typically mixed with other ingredients such as peat moss, shredded bark, sand or loamy topsoil when used as an outdoor planting mix. Mixing ratios vary; but 10% compost is considered to be a minimum, 30% optimum, and 50% maximum in planting shrubs and trees

Carbon/Nitrogen Ratios of Some Common Organic Material

 

MaterialVegetable wastes
Alfalfa hay
Cow manure
Apple pomace
Leaves
Corn stalks
Oat straw
Wheat straw
Paper
Sawdust
Grass clippings
Coffee grounds
Bark
Fruit wastes
Poultry manure(fresh)
Horse manure

 

Ratio12-20:1
13:1
20:1
21:1
40-80:1
60:1
74:1
80:1
150-200:1
100-500:1
12-25:1
20:1
100-130:1
35:1
10:1
25:1

 

 

Here’s a helpful  link to composting: Compost Guide

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One response

  1. Pingback: Organic gardening – the soil « Prairie Sunrise

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