Kwantlen Farm School 2012 Chris Thoreau

What is Composting? The rapid biological decomposition of organic matter Microorganisms turning organic matter into plant food Rapid 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

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

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 this method

So lets breed some microorganisms…

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

Hot Composting 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

Six key elements to good hot compost (and most other methods as well): 1. Carbon:Nitrogen (C:N) ratio 2. Air 3. Water 4. Surface Area 5. Critical Mass of Pile 6. 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, but nitrogen lost as ammonia

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

1. 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 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

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 Forced air used for in-vessel systems

2. Air 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 Other materials will be very dry

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

Area of activity 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 anaerobic

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

Other things to consider: 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

Soil 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

Soil Food Web 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

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

1. Stockpile materials on farm Materials will start to decompose 2. Import nitrogen (if required) and build the pile 3. Monitor pile temperature 4. Turn or aerate pile when temperature has dropped by ºC Add N if required when turning for first time Turn pile 3-5 times upon cooling 5. Let pile cure

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

2. Import Nitrogen Nitrogen is limiting factor for rapid decomposition Manure Okara Grass Clippings

3. Build Pile Start with rough materials on the bottom Layer carbon and nitrogen materials Mix every 3-4 layers Water pile while building Add aeration pipe while building Top with carbon materials; cover with tarp

4. Monitor Pile Use thermometer to check temperature If T too low – Too dry? Too wet? Not enough N? Watch for falling temperature – Signal to turn pile

5. Turn Pile Use machine or fork depending on size Mix materials well when turning Add N if desired Add water if needed

6. Let Pile Cure Larger organisms finish off decomposition Bacteria and fungi continue to work