composting 101

Composting 101 What is Composting?

The rapid biological decomposition of organic matter into an inorganic form available for plant uptake

Microorganisms turning organic matter into plant food Nutrient cycling

Breeding of microorganisms or worms This is my approach to composting Our goal in composting: to provide microorganisms with the

food they need to thrive and thus rapidly decompose organic materials while retaining the maximum amount of nitrogen in those materials

Composting 101 Many types of composting

Anaerobic Composting/Digestion Slow process in absence of oxygen or in low oxygen

environment Easy method for small-scale composting Retains nitrogen very well

“Backyard” Composting Small-scale; good for home waste diversion Requires little management

Composting 101 Worm Composting

Can be done indoors or on large scale Results in nutrient-rich compost or “castings” Finished compost in 3-5 months or sooner depending on system Relatively high management needs (harvesting)

“Hot” Composting Method for large quantities of organic matter Rapid decomposition - as little as 4-8 weeks for certain

materials Requires some management to ensure high quality

We will focus on these two methods

Composting 101

So let’s breed some microorganisms…

Composting 101: Hot Composting Hot Composting

Best method for rapidly making large volumes of compost Heat can destroy weed seeds and pathogens Good for soil fertility and structure building Requires frequent monitoring and turning Process of building pile is important Often benefits from off-farm nitrogen source Works good as soil inoculant Quality of compost depends on:

Quality of feedstock/composting materials Quality of monitoring Effort in preparing pile

Composting 101: Hot Composting

Six key elements to good hot compost (and most other methods as well):

1. Carbon:Nitrogen (C:N) ratio2. Air3. Water4. Surface Area5. Critical Mass of Pile6. Diversity of Materials


1. Carbon to Nitrogen Ratio Food for the compost pile – must be balanced Ideal ratio: 24:1

Microorganisms need 24 carbon molecules for every 1 nitrogen molecule they consume

Ratio too wide (e.g., 50:1)? Process is slower

Ratio too Narrow (e.g., 10:1)? Process is faster Nitrogen lost as ammonia


1. Carbon to Nitrogen Ratio TABLE HERE


1. Carbon to Nitrogen Ratio How to Balance:

General rule: equal parts browns and greens This shifts depending on how brown or green

Increased surface area in nitrogen materials: Increases decomposition rate Acts like higher N content, but used up quicker

Get familiar with common materials available to you

Composting 101: Hot Composting1. Carbon to Nitrogen Ratio

Essentially, the C:N ratio determines how hot the compost pile will get

The heat is a by-product of microbial activity An indicator of how happy your

microorganisms are Nitrogen is often a limiting factor

Importing nitrogen is crucial for good hot compost

Manure, okara, grass clippings Too much heat = too much N = N loss to

ammonia Also reduces diversity of microorganisms


2. Air Your microorganisms need air to breathe

Gas exchange is crucial for life Think of your compost pile like your soil

How much air does it need (by volume)? About 20-25%

How do we promote good aeration? Mix pile consistently as you build it Use some woody and fibrous materials to

promote porosity Small twigs (e.g., willow) work very well


2. Air Even with good porosity air space will

decline Pile becomes more dense as it decomposes –

filling pores Passive aeration tubes can be used to

maintain air flow

How do I reintroduce air into the pile? Usually by turning the pile and mixing the

contents More nitrogen can be added at this point if

needed


2. Air Air is used to control rate of decomposition

Adding air can increase decomposition rate Removing air slows the process Can be used to help correct high C:N ratio

Air can be added passively or actively Passive:

Building good porosity into the pile using “twiggy” materials

Using perforated pipes horizontally layered in the pile Active:

Physically turning or manipulating the pile Forced air used for in-vessel systems


3. Water Your microorganisms need water – just like

you Water also softens materials for

decomposition Good porosity allows extra water to drain

away Makes it difficult to over water your pile

Some materials with have a higher water content

Fresh plant matter Other materials will be very dry

Sawdust; leaves; manure


3. Water Water usually needs to be added to the

pile Add water while building your pile

How much water? 50% water by weight!

Pile should be quite wet “As damp as a wrung out sponge” Organic matter will absorb water and allow

pore space to remain for air flow


4. Surface Area Microorganisms are small – their food

should be too! Increased surface area = easier and faster

dining Chopping up materials greatly increases

decomposition rate – especially high C materials

Materials can be screened after composting to reduce large pieces before adding to soil

Large pieces of OM in soil can tie up nitrogen – especially high carbon materials


5. Critical Mass of Pile Microorganisms create heat when eating

and they like to stay warm Larger pile = increased insulation 1 metre cube pile is sufficient for good

insulation Larger piles insulate well

Bottom of pile may be anaerobicArea of activity


6. Diversity of Materials Your microorganisms like a diverse diet

Also results in more diverse microorganisms Diversity of materials = diversity of

nutrients Also makes it easier to balance C:N ratio Dynamic accumulators can be grown

specifically to be added to pile to improve quality and N content

Use large, fast-growing plants that re-grow after cutting

Comfrey Angelica


6. Diversity of Materials Diversity of materials is not essential to

make compost But it is essential to make good compost

Compare the following compost piles Horse manure and leaves

Horse manure, chicken manure garden waste, comfrey, okara, grass clippings, leaves, sawdust, willow branches


Other things to consider: The seasonality of composting materials

Carbon materials are prevalent in the fall Nitrogen materials are prevalent in the growing

season What off-farm materials are easily available?

Manures; leaves or other carbon materials Composting of weed seeds, rhizomes and

diseased plants Is it safe? How to do so safely?

Where and how will you compost? Do you have a staging area? Do you have a tractor? Using a bin or windrows?


Other things to consider: Protect the pile from the weather

To control water level in pile Knowing the C:N ratio of the most common

materials is important in making a good pile Learn how to judge C:N ratio of new materials

Very active soil food web in compost pile Many trophic (feeding) levels Different organisms digest different materials at

different times

Composting 101: Hot CompostingSoil Food Web

Bacteria are primary decomposers of OM Work quickly on diversity of materials Generate heat in compost pile

Fungi also important Only organism that breaks down lignin (found in wood) Thrive in acidic environments Active in latter parts of decomposition

Arthropods Consume OM and each other Work on outside of pile when hot

Worms Consume their weight each day in OM Help aerate compost pile

Composting 101: Hot Composting Soil Food Web Image Here


The Evolution of a Hot Compost Pile:

Our goal: To build a compost pile, taking into

consideration the six principles of hot composting, that will heat up to a temperature of 55ºC and maintain that heat for up to several weeks

Making a Hot Compost Pile

1. Stockpile materials on farm Materials will start to decompose

2. Import Nitrogen (if required) and build the pile3. Monitor pile temperature4. Turn or aerate pile when temperature has

dropped by 8 - 10ºC Add N if required when turning for first time

5. Turn pile 3-5 times upon cooling6. Let pile cure


1. Stock pile materials on farm Weeds Leaves


1. Stock pile materials from on farm These are organic materials

generated on the farm Weeds Leaves Harvest trimmings

When pile is of sufficient size bring in manure source for hot compost

Composting 101

composting 101

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