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Composting 101. The what, when, where, why and how of composting. Download a copy of the presentation Get a copy of Microsoft Power Point Viewer (free). Home Page: Minnesota waste facts. Statewide recycling rate - 47.2%

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composting 101
Composting 101

The what, when, where, why and how of composting

Download a copy of the presentation

Get a copy of Microsoft Power Point Viewer (free)

Home Page:

minnesota waste facts
Minnesota waste facts
  • Statewide recycling rate - 47.2%
  • Minnesotans threw away 3 million tons of garbage in 1999
  • Organic materials comprise of 25.4% of statewide residential waste (most of which is compostable)
  • Paper products make up 30.8% of statewide residential waste
what is compost
What is compost?
  • End product of the decomposition of organic materials by decomposers
  • Valuable soil amendment
  • Dark, crumbly and earthy smelling material
  • A resource that can be utilized in your own back yard
why should i compost
Why should I compost?
  • There are many benefits to composting
    • Valuable soil amendment
    • Effective mulch
    • Reduction in waste
soil amendment
Soil amendment
  • Improves soil structure
    • Increases aeration
    • Holds moisture
    • Especially important in sandy soil
  • Promotes plant growth
    • Contains essential micronutrients
  • Stores nutrients
    • Porous structure stores nutrients
soil amendment1
Soil amendment
  • Flower and vegetable gardens
    • Dig or till 8 to 10 inch deep
    • Mix 3 to 4 inches of compost through entire depth
  • Seeding new lawns
    • Till soil 6 inches deep
    • Mix in 4 inches of compost
  • Suppress weeds
  • Maintain moisture levels
  • Control temperature
  • Prevent soil erosion
  • Gardens
    • Sift compost to remove large, woody material
    • Apply 1/2 to 1 inch layer
    • Keep a few inches away from base of plants
  • Trees and shrubs
    • Remove sod from base of plant
    • Use coarse compost
  • Erosion control
    • Use 2 to 4 inches coarse compost
reduce waste
Reduce waste
  • Reduce the amount of waste sent to landfills and incinerators
  • Often illegal to dispose of yardwaste with other municipal solid waste
how does compost happen
How does compost happen?
  • Organic material is processed (for free) by numerous decomposers
    • Bacteria
    • Fungi
    • Invertebrates
      • Worms
      • Nematodes
      • Springtails
  • Decomposers need food, nutrients, air and water (you will need to supply these)
  • Decomposers also need heat but they supply their own
decomposers microorganisms and soil animals
Decomposers – microorganisms and soil animals

The food web in your compost pile supports a wide variety of lifeforms from microscopic bacteria to larger beetles and worms.

decomposers bacteria
Decomposers - bacteria
  • Most numerous organisms in compost pile
  • Don’t need to be added to compost pile, they are present virtually everywhere!
  • Generate heat associated with composting
  • Perform the primary breakdown of organic materials
  • There are different bacteria

present at different temperatures

bacteria groups
Bacteria groups
  • Psychrophilic bacteria
    • Ideal temperature is around 55°F but they are able to survive right down to 0°F
  • Mesophilic bacteria
    • Thrive at temperatures between 70-90 °F and can survive from 40-110 °F
  • Thermophilic bacteria
    • Work fastest in temperatures from 104-170 °F
    • Most efficient decomposers
decomposers bacteria1
Decomposers - bacteria
  • Interesting fact - “less than a teaspoon of the common bacteria Escherichia coli, would become a pound in 3 hours and a mass the size of the Earth in a day and a half if sufficient food and proper conditions were available!”
decomposers fungi
Decomposers - fungi
  • Perform primary decomposition
  • Identified by their root-like fibers or presence of mushrooms
  • Not as efficient as bacteria
  • Less temperature tolerant than bacteria
decomposers nematodes
Decomposers - nematodes
  • Most abundant invertebrate in the soil
  • Usually less then 1 millimeter in length
  • Prey on bacteria, protozoa, fungal spore and each other
decomposers mites
Decomposers - mites
  • Called fermentation mites or mold mites
  • Transparent-bodied creatures
  • Feed on yeast
  • Masses often develop over fermenting surfaces
decomposers collembula
Decomposers - collembula
  • Also know as springtails
  • Feed mainly on fungi but also eat nematodes and organic detritus
  • Major population controlling factor of fungi
decomposers wolf spiders
Decomposers - wolf spiders
  • Build no webs
  • Run freely hunting prey
  • Prey on all sizes of arthropods
decomposers centipede
Decomposers - centipede
  • Frequently found in soil and compost microcommunities
  • Prey on almost any type of soil invertebrate near their size or slightly larger
decomposers sow bug
Decomposers - sow bug
  • Feed on rotting woody material and leaf tissue
  • Also know as pill bugs or roly polys
decomposers ground beetle
Decomposers - ground beetle
  • Many different types can be found in and around compost piles
  • Most feed on other organisms, but some feed on seeds and vegetable matter
decomposers redworms
Decomposers - redworms
  • Coat processed organic material with mucus films that
    • Binds small particles together
    • Leads to loose and well drained soil
    • Protects soil against nutrient leaching
other compost residents pests
Other compost residents - pests
  • Common pests may include house and fruit flies, rodents, raccoons, and domestic animals such as cats and dogs
  • Proper bin maintenance and selective material usage will reduce your risk of pest problems
pest control
Pest control
  • Avoid composting meat and dairy products and other fatty foods
  • Avoid adding pet food or feces to your compost pile
  • Cover other food waste with a layer of grass, straw, leaves, paper or finished compost
what are the key ingredients
What are the key “ingredients”?
  • Materials (C:N ratio)
  • Moisture and aeration
  • Particle size/surface area
  • Temperature
c n ratio
C:N Ratio
  • All living organisms need relatively large amounts of carbon and smaller amounts of nitrogen
  • Microorganisms in compost use carbon for energy and nitrogen for protein synthesis
  • Green materials = nitrogen
    • ex. green grass clippings
  • Brown materials = carbon
    • ex. autumn leaves, straw


The ideal ratio of carbon:nitrogen of 30:1 will ensure maximum bacteria decomposition
  • Mix based on weight not volume
  • These are only guidelines, actual values may very (Ex. leaves from different trees will vary in their carbon content)

Average Carbon:Nitrogen Ratios

Food Scraps 15:1 GREENS

Grass Clippings 19:1

Rotted Manure 25:1

30:1 Ideal for Composting

Corn Stalks 60:1

Leaves 40-80:1

Straw 80:1 BROWNS

Paper 170:1

Sawdust, woodchips 500:1

moisture and aeration
Moisture and aeration
  • All compost organisms need air and water to survive
  • Strive for moisture content around 50%
    • Without 40% the bacteria will slow down
    • At 80% and above there is not enough airspace and aerobic decomposition occurs which is slower and leads to odor problems
  • Avoid compacting materials - this

limits aeration in your pile

moisture and aeration1
Moisture and aeration
  • Optimal moisture levels occur when compost is as moist as a wrung out sponge
  • When watering a dry pile be sure to mix Water will just shed off a dry pile
  • Mixing once or twice a month will increase rate of decomposition by increasing air spaces
  • Takes 3–6 X’s longer if not turned
particle size
Particle size
  • Particle size is an important factor in composting
  • Reducing particle size increases the surface area available for decomposers
  • However, if the pieces are too small they may compact together and limit aeration
  • A mixture of small and larger particles is ideal
  • High temperature compost pile
    • Faster decomposition
    • Helps insure weeds and pathogens are killed
what can be composted
What can be composted?

Grass and yard trimmings/clippings


Coffee grounds/filters

Tea leaves/bags

Fruits and vegetable trimmings

Wood chips


Egg shells

Livestock manure

what should not be composted
What should not be composted?

Diseased or insect infested plants

Cat and dog manure

Evergreen needles

Poison ivy and other poisonous plants

Weeds that contain seeds

Meat and animal products

Fatty foods

Dairy products

compost bin size
Compost bin size
  • For fast efficient composting your bin needs to be
    • Large enough to hold heat and moisture
    • Small enough to admit air through the center
  • Rule of thumb
    • A compost pile need to be at least 3ft. by 3ft. by 3ft.
    • Upper limits are about 5ft. by 5ft. by any length
building your compost pile
Building your compost pile
  • Build in layers
    • 8 to 10 inches of ‘brown’ material
    • Several inches of ‘green’ material
    • One inch of soil
  • Establish proper moisture content
  • Avoid compacting materials
compost bin types
Compost bin types
  • There is a great deal of variety in composting structures
  • Compost bins vary in their cost, required labor, volume, and time required for finished compost
open piles
Open piles
  • Slowest rate of decomposition
  • Least expensive method
  • Minimal pest control and containment
holding units
Holding units
  • Helps keep decomposing materials organized
  • Reduces pest problems
  • Requires no turning
  • Relatively slow rate of decomposition (6 months to 2 years)
turning units
Turning units
  • Allow for easier mixing of materials
  • Result in a hotter pile and reduced composting time (as soon as 2-3 weeks)
  • Usually more expensive and more labor intensive

Three-chambered bin

Barrel or drum composter

  • Avoid areas with drying wind
  • Partial sun will help heat the pile
  • Should be easily accessible yet not interfere with yard activities
  • Should not be offensive to neighbors
finished compost
Finished Compost
  • Avoid using unfinished compost, organic acids may harm plant roots
  • If compost is still hot, smells like ammonia, or

you can still identify much of the

original organic material it is not

ready to use yet

finished compost1
Finished Compost
  • Composting is complete when the pile stays at or near the ambient temperature
  • Finished compost is dark, crumbly, and has an earthy smell
  • The volume of finished compost will

have been reduced by 30 to 50 percent

problem solving what if
Problem solving – what if?
  • The pile smells like rotten eggs?
    • Not enough air/too much water
    • Add coarse material like dry leaves
    • Pile should be wet like a wrung out sponge
  • The pile smells like ammonia?
    • Too much nitrogen, not enough carbon
    • Add dry leaves, sawdust or straw
problem solving what if1
Problem solving – what if?
  • My compost pile is not heating up?
    • Examine bin size, moisture content, air flow, and material ratios (C:N)
  • My compost pile is attracting pests?
  • Eliminate meat dairy products and fatty foods from bin
  • Bury food waste under a few inches of material like leaves and grass
other options
Other Options

Have too much yard waste to backyard compost?

Want to compost kitchen waste but don’t have the yard space to do it?

Here are some alternatives to backyard composting...

municipal composting
Municipal Composting
  • Municipal composting
    • Available though many cities and townships
    • Often take larger yard trimmings (and chip them)
    • Usually offered as a free service
    • Finished compost often available for free
  • Contact your local county Extension educator, county solid waste officer, or city recycling coordinator for more info
grass clippings
Grass Clippings

Grass clippings are a great source of nitrogen for your compost pile but usually you have more clippings then needed. What can you do with excess clippings? Leave them on your lawn! Leaving grass clippings on lawn returns nutrients to the soil (clippings will naturally decompose).

  • Method of composting kitchen scraps and other organic material
  • Materials are placed in an aerated container with redworms
    • Redworms are able to digest 2/3 their body weight in a day
  • Worm bins can be made out of any material that holes can be drilled into
  • This project was developed by the University of Minnesota Extension Service-Sherburne County and the Sherburne County Master Gardeners
  • Funding assistance provided by the Sherburne County SCORE grant
  • Some of the graphics used were taken from the Master Composter Manuel - Cornell Waste Management Institute