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*Compost is a mixture of decayed organic materials decomposed by microorganisms in a warm, moist, and aerobic environment, releasing nutrients into readily available forms for plant use.

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Composting is a process.

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Leaves

Food scraps

Grass clippings

Compost

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DecomposersDecomposers

These are the microbes (mainly bacteria and fungi) that do all the work for you.

Food for the decomposersFood for the decomposers

The organic materials to be The organic materials to be compostedcomposted..

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*Obtain energy to carry on life processes.

*Acquire nutrients (N, P, K) to sustain population.

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Anaerobic composting

Aerobic composting

oxygen absent or in limited supply

presence

toxicity

odor

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1 .Chemical makeup of raw ingredients or feedstocks.

2 .Physical size and shape of feedstocks and porosity of the pile.

3 .Population of organisms involved in composting process.

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Hot airlowO2

O2

rich

coolair

O2O2

1 .Oxygen and Aeration

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Turning the pile mixes fresh air into the pile

Turning the pile mixes fresh air into the pile

Turning tools can make the job easier

Turning tools can make the job easier

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*Optimal range 45-60% by weight.

*Low moisture impededs composting process because

1 .microbes need water

2 .dry pile will become cool, slow down composting.

2 .Moisture level

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3. Temperature

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*Particle size regulate microbial access to food.

*Small particles have more surface area than large particles ; easy access.

4 .Particle size

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shredding

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5 .Types of organic matter

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*Carbon (C) and nitrogen (N) are the primary nutrients required by the microorganisms

involved in composting .

*Microorganisms use carbon for both energy and growth, while nitrogen is essential for protein production and reproduction.

6 .Carbon/nitrogen ratio

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*If amount of C relative to N is too high, slows composting process.

*If C:N ratio is too low, more likely to lose N as ammonia gas (bad odor).

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*Green materials have lower C:N ratios than woody materials or dead leaves.

Rules of thumb

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Browns

High carbon materials such as

Leaves (30-80:1)

Straw (40-100:1)

Paper (150-200:1)

Sawdust (100-500:1)

Animal bedding mixed with manure (30-80:1)

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High nitrogen materials such as

Greens

Vegetable scraps (12-20:1)

Coffee grounds (20:1)

Grass clippings (12-25:1)

Manure

– Cow (20:1)

– Horse (25:1)

– Poultry (10:1), with litter (13-18:1)

– Hog (5-7:1)

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Feedstock C:N Ratios

Materials High in Carbon

C:N Ratio

Fall leaves30-80

Straw40-100

Wood chips or sawdust100-500

Bark100-130

Mixed paper150-200

Newspaper or cardboard560

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Materials High in Nitrogen

C:N Ratio

Vegetable wastes15-20

Grass clippings15-25

Manure5-25

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*Provides humus or organic matter, vitamins, hormones, and plant enzymes which are not supplied by chemical fertilizers.

*Kills pathogenic organisms, weeds and other unwanted seeds when temperatures of over 60oC is reached.

*Acts as buffer to changes in soil pH.

*Improves soil .

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1 .Biological Contributions:

*Inoculation or increased microbial diversity.

*Increases microbial activity in soil, primarily by providing carbon as a food source for the microorganisms

*Can reduce soil borne plant diseases

Improvement of soil by

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2 .Physical Contributions

*Increased water absorption

*Increased water retention

*Improved drought tolerance

*Reduced soil erosion

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3 .Chemical Contributions

*Increase cation exchange (more negative charges) which increases soil ability capacity to hold

nutrients .

*Good source of micro nutrients .

*May buffer pH ( greater stability or resistance to change pH).

Have many nutrients that not exist in chemical fertilizer .

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Garden trimmings

Kitchen scraps

Grass clippings

Leaves

Also• Used potting soil• Manure• Sawdust• Hair

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Cat or dog waste

(attracts pests, could spread disease)

Diseased or insect ridden plants

(could infect or attack garden plants when compost is used)

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*Lime (increases compost pH and promotes ammonia odor problems.

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*Simplest technologies are composting bins or backyard piles.

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Bin/pile construction

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Manufactured bins

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The Earth Machine Bin

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