Composting 101

1. Composting 101 Kwantlen Farm School 2012 Chris Thoreau

2. Composting 101 • 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

3. 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

4. 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)

5. Composting 101 “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

6. Composting 101 So let’s breed some microorganisms…

7. 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

8. Composting 101: Hot Composting • 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

9. Composting 101: Hot Composting • Six key elements to good hot compost (and most other methods as well): • Carbon:Nitrogen (C:N) ratio • Air • Water • Surface Area • Critical Mass of Pile • Diversity of Materials

10. 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, but nitrogen lost as ammonia

11. Composting 101: Hot Composting

12. 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

13. Composting 101: Hot Composting 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

14. 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

15. 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

16. 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 • Forced air used for in-vessel systems

17. Composting 101: Hot Composting 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

18. 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 • Other materials will be very dry

19. 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

20. 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

21. 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 anaerobic Area of activity

22. 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

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

24. Composting 101: Hot Composting 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

25. Composting 101: Hot Composting 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?

26. Composting 101: Hot Composting 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

27. Composting 101: Hot Composting 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

28. Composting 101: Hot Composting 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

29. Composting 101: Hot Composting

30. Composting 101: Hot Composting 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

31. Composting 101: Hot Composting • Stockpile materialson farm • Materials will start to decompose • Import nitrogen (if required) and build the pile • Monitor pile temperature • Turn or aerate pile when temperature has dropped by 8 - 10ºC • Add N if required when turning for first time • Turn pile 3-5 times upon cooling • Let pile cure

32. Composting 101: Hot Composting 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

33. Composting 101: Hot Composting 2. Import Nitrogen • Nitrogen is limiting factor for rapid decomposition • Manure • Okara • Grass Clippings

34. Composting 101: Hot Composting 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

35. Composting 101: Hot Composting • 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

36. Composting 101: Hot Composting 5. Turn Pile • Use machine or fork depending on size • Mix materials well when turning • Add N if desired • Add water if needed

37. Composting 101: Hot Composting 6. Let Pile Cure • Larger organisms finish off decomposition • Bacteria and fungi continue to work