Composting 101

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

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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?

• 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?

• There are many benefits to composting – Valuable soil amendment – Effective mulch – Reduction in waste

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 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

Mulch

• Suppress weeds • Maintain moisture levels • Control temperature • Prevent soil erosion

Mulch

• 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 the amount of waste sent to landfills and incinerators • Often illegal to dispose of yardwaste with other municipal solid waste

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

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

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

• 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 - 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

• 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

• Most abundant invertebrate in the soil • Usually less then 1 millimeter in length • Prey on bacteria, protozoa, fungal spore and each other

Decomposers - mites

• Called fermentation mites or mold mites • Transparent-bodied creatures • Feed on yeast • Masses often develop over fermenting surfaces

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

• Build no webs • Run freely hunting prey • Prey on all sizes of arthropods

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

• Feed on rotting woody material and leaf tissue • Also know as pill bugs or roly polys

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

• 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

• 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

• 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”?

• Materials (C:N ratio) • Moisture and aeration • Particle size/surface area • Temperature

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

Generally...

• Green • Brown materials = nitrogen – ex. green grass clippings 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)

Food Scraps Grass Clippings Rotted Manure Corn Stalks Leaves Straw Paper

Average Carbon:Nitrogen Ratios

Sawdust, woodchips 15:1 19:1 25:1

GREENS

30:1 Ideal for Composting 60:1 40-80:1 80:1 170:1 500:1

BROWNS

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 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 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

Temperature

• High temperature compost pile – Faster decomposition – Helps insure weeds and pathogens are killed

What can be composted?

Grass and yard trimmings/clippings Leaves Coffee grounds/filters Tea leaves/bags Fruits and vegetable trimmings Wood chips Sawdust Egg shells Livestock manure

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

• 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

• 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

• 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

• Slowest rate of decomposition • Least expensive method • Minimal pest control and containment

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

• 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

Location

• 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

• 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 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?

• 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 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

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 – 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 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).

Vermicomposting

• 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

Credits

• 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

Questions?/Comments!