Basic CompostingMichael Rowell

Composting is the accelerated decomposition of organic waste to

produce a stable useful soil amendment

This is not composting

Simple decomposition or rotting produces a useful mulch but it is of limited nutrient value

Composting blends organic residues together and manages the decomposition to optimize the value of the

product as a soil amendment.

• It can be a mulch– Improve water holding capacity– Help in water conservation– Help to suppress weed growth(perhaps)

• It is a slow release fertilizer– Nitrogen, potassium, phosphorus, sulphur, calcium & magnesium– Micronutrients

• It is a microbial inoculant– Addition of beneficial microbes

• It may be free of weed seeds and pathogens

Methods of Composting

Commercial windrows

Aerated barrel

Compost worms

Compost tea

Bokashi systemCompost Bins

Making a compost bin• Cheapest to make it out of wood

– 2x4 for frame; 1x6 for sides– Treated or untreated? Cedar, fir, spruce etc.

• Size (at least 1m x 1m x1m)– Essential for pile to be well insulated

• Two Bins better than one– One for active compost– One for mature compost

• Good aeration– Slatted system to allow passive air circulation

• Easy to mix contents– Variable baffles in front, leverage with fork

• Slatted top (optional)– Block excess rainfall with polythene sheet

• Drainage or no drainage– Solid or open at bottom

We could compost anything that is biodegradable“All organic things produced by living things are biodegradable, some more easily so than others

– Easy• Juicy fruits, grass clippings, non-waxy leaves, many dairy &

fish products; many meat products; animal manure

– Moderate• Finely shredded wood, corn cobs, hedge trimmings; straw

& tougher plant stems; light cooking oils; cardboard, paper and cotton & many other natural fibres

– Difficult• Bones, leather, feathers, hair, nut shells, pine cones, waxy

leaves, wood, grease, natural resins, coal, heavy fats and oils.

What things are not biodegradable?

Items that were never living and many synthetic substances made by humans

• Metals and alloys: Iron, aluminum, lead, gold, steel, copper• Minerals: Rocks, sand, lime, ash, shells, diatomaceous earth,

talcum powder, diamonds, pearls• Glass• Inorganic Chemicals: Bleach, battery acid, inorganic fertilizers,

baking soda, table salt etc. • Many synthetic products: Plastics, glue, rubber, pigments,

pesticides

[some synthetic organic products biodegrade slowly because their chemical structures have some similarities to natural products]

Things to avoid or treat with caution?

• Slow to decompose – Grass sod, conifer needles and cones– Waxy leaves, leather, bones– Fatty food residues

• Potentially toxic– Rhubarb leaves, walnut leaves (toxins in leaves)– Charcoal (toxic combustion residues)

• Be careful– Wood ashes (high pH)– Plant seeds (remain viable)– Biosolids (may contain hazardous residues)– Fish products (smell)

• Nuisance – Weed seeds and propagative parts– Diseased plants– Meat & high fat residues (smell & attract scavengers)– Pet and human excrement (risk from odour and pathogens)

Example of a compost pile started in mid summer• Phase 1 (week 1 & 2)

– Easily degradable things decomposed quickly by microbes that produce a lot of heat as a by-product. Insulation of pile maintains heat and these microbes die off.

• Phase 2 (week 3 and 4) – Decomposition at high temperature by specialist microbes.

Hot enough at 50-55C to kill weed seeds and many pathogens.

• Phase 3 (weeks 5 to 12) – Temperature decreases and other slower growing organisms

come in to degrade residues from phase 2 and other resistant residues.

• Phase 4 (fall and over winter) – Maturation of compost as reactions slow and carbon dioxide

production drops to a lower stable rate (ready for use in spring).

Making Good Compost: The 5 Golden Rules

1: Get the correct balance of residues

2: Increase the surface area

3: Keep it moist

4: Mix frequently to aerate

5: Big enough pile to keep it hot

The 5 Golden Rules

1: Get the correct balance of residues

– Greens + Juicy + browns (high nitrogen + high energy + high carbon)

– Will allow fast composting with a “hot phase”

– Start with a full bin if possible; composting results in a big loss in mass

The 5 Golden Rules

2: Increase the surface area

– Fibrous plant matter & paper • Chop• Shred• Grind

The 5 Golden Rules

3: Keep it moist

– Add more water than you would give plants• Microbes work in water films• Keep it as wet as a wrung-out face cloth• If it is too wet it may get smelly & leach nutrients• If it is too dry the microbes will not work well

The 5 Golden Rules

4: Mix frequently to aerate

– Fast composting needs huge amounts of oxygen

– Mix and turn frequently after the first two weeks to add more oxygen

– Aerate even during the maturing phase

– Mixing moves dryer material at the edges into wetter centre of the pile

The 5 Golden Rules

5: Big enough pile to keep it hot

– The pile must be well insulated if you want to keep it hot– This means quite a large pile– A hot pile = fast reactions + killing weeds & pathogens

Other things to consider: Give it a boost: Add some high nitrogen residues (alfalfa meal, manure)

Two piles are better than one: Separate the active composting phase from the slow maturing phase.

.

green juicy brown

Water

Bacteria

Fungi

Worms & other critters

Air

mix... mix...mix

water.... water

water.... water

High temperature phase

Moderate temperature phase

Cooling phase

Long maturing phase

Examples of the three categories of composting materials

• Green (high nitrogen/fresh vegetation; living)– Grass & hedge clippings– Vegetable leaves, bean & pea vines

• Juicy (moist; high sugar, starch & hemicellulose)– Kitchen waste, surplus fruit & vegetables, apple cores, potato peelings

• Brown (high carbon/low nitrogen, cellulose-rich; dead)– End of season plant residues– Paper , cardboard, wood chips, twigs– Corn cobs and stems– Autumn leaves

Making a balanced mix of “greens”, “juicy” and “browns” will ensure that you have a prolonged hot phase which will be hot enough to kill most weed

seeds and pathogens.

Who does the work?

• Primary consumers of residues; directly digest carbohydrates, fats, proteins and even fibrous matter– Mainly bacteria and fungi

• Secondary consumers; small soil animals and other microorganisms that eat primary consumers– Chop, grind and move materials.– Earthworms, nematodes, mites, – springtails, protozoa, rotifers

• Tertiary consumers; eat the secondary consumers– Centipedes, mites, beetles, ants

Problems

• My new composter does not work• Slow composting• Bad Smells• It’s slimy

Problems

• My new composter does not work

– New compost piles often take a while to “condition” with the correct microbes

– Add small amounts of soil layered in with compost to add microbes

– Mix in compost from another active pile

– Make sure you are following the 5 golden rules.

Problems

• Slow composting– Too Dry

– Not enough “greens”; boost with something high in nitrogen

– Too much fibre (corn stalks, tough stems, cardboard, sawdust etc.)

– Weather too cold (4-10C slow: 11-18C medium: 20C+ fast)

Problems

• Bad Smells (ammonia, hydrogen sulphide, mercaptans, acrid organic acids)– Too much high nitrogen residues (meat, dairy

products, blood meal, fresh manures)– Unwanted animals using your pile as a bathroom– Too wet; you are making an alcoholic beverage or

silage not compost

• It’s slimy– Too much green and juicy residues relative to the

browns

Summary

• Choose the right type of composter for your needs– Pile, bin, barrel, red worms, apartment sized systems

• Follow the 5 Golden rules– Right mix; increase the surface area; water, aerate & mix; keep it hot

• Avoid buying unnecessary products– Magic activators, special microbes, power mixers and shredders and

other gimmicky hardware• Take heed of the climate

– Composting is a biological process; below 4C everything takes a rest.• Use the product wisely

– Make sure you have not added anything hazardous– Do not add too much ; e.g. Maximum of 1 part compost to 3 parts soil