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. 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 - PowerPoint PPT Presentation
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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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
1. Carbon to Nitrogen Ratio TABLE HERE
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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
Composting 101: Hot Composting
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