1. Agro-ecology By Maggie Hope-Simpson adapted by Wang
COMPOST:
“Making and Using It”
Agro-ecology By Maggie Hope-Simpson adapted by Wang
Section 3, Unit 3.2

2. Learning Objectives Define the following terms: Composting√
Active composting
Compost√
Feedstock 给料
Thermophilic喜温的
Mesophilic嗜温的
Curing (maturing)
Compost quality

3. Learning Objectives (cont’d)
List four ways in which stabilized compost differs from the starting raw material
Prepare a labeled diagram showing the four temperature phases of composting
Describe three factors that are considered in blending materials for composting
List four activities in managing the composting process
Describe four agronomic or horticultural uses for compost

4. What do YOU know about composting?
Purpose?
Process?
Product?
Ingredient materials?
How many of you have done composting at home or at place of employment?
Purpose: recycle organic materials or divert waste from landfills, generate compost which can be used as a soil amendment
Process: natural biological process, involves microorganisms
Product: compost – properly made compost is a valuable soil amendment – improves fertility and physical condition of soils
What kinds of materials? food waste, L&Y waste, wood/paper, sewage sludge, crop residues, manure- Virtually any organic material can be composted, provided that the right condits are met
Where is composting practiced? backyard, lg.scale municipal or commercially operated compost facilities, nursery/GHG/landscape operations, on-farms, anywhere that organic wastes are generated!

5. Composting systems vary in terms of:
Scale: large to small
Methods: hi- to low-tech
Feedstocks
Composting objective
Four composting systems in the Truro area-show diversity of composting systems with respect to….
Top: large in-vessel system at Truro balefill facility (operated by municipality) -source separated residential organics (food waste, leaf and yard waste)
Second from top: large scale outdoor windrow composting system (Brookfield) for composting sewage sludge and bark or woodchips
Third: small scale windrow at a farm in Masstown- on-farm composting of manure (turned using a sm bucket loader or skidsteer)
Bottom right: very small scale backyard bin-residential foodwaste, leaf and yard waste
Composting objectives: two main objectives-composting may be practiced primarily as a method of waste management (top two slides-municipal and privately operated facilities), or primarily as a means of generating a soil amendment (bottom two). For most farmers and gardeners, the agronomic value of the end product is usually considered to be the most important reason for composting.
Feedstock: ingredient materials
Composting objective: waste management, or soil amendment?

6. Composting is:
A controlled biological oxidation process whereby microorganisms (bacteria, fungi) convert raw organic “wastes” into a stabilized organic residue called COMPOST.

7. Compost is:
The stabilized product of a managed bio-oxidation process…to produce humus as a soil amendment or fertilizer.
Managed bio-oxidation process: organic materials mixed, piled, heated above 55oC, then cured.

8. Temperature Phases of Composting
*ignore pH!
Temp phases-reflect the pattern of microbial metabolic activity associated with the decomposition of various constituents in the waste (sugars, starches, cellulose, hemicell and lignin)
Mesophilic- rapid temp increase immediately after mixing (degred of sugars, starches); lasts several days
Thermophilic- another group of fungi sp forming bact, active above 40oC, longer high rate (active) phase; lasts several weeks-degredation of more resistant materials –cellulose, hemicellulose, lignin
Cooling – after active phase, steady, irreversible drop in temp (pile does not re-heat when turned); occurs over several weeks
Maturing – also known as the curing phase – lasts 1 to several months-reactions in the residual organic matter to produce the stable product of humus
A-Mesophilic: 10-40oC
C-Cooling: 65oC to ambient
B-Thermophilic: 40-65oC
D-Maturing (curing): ambient?

9. In the composting process:
heat, CO2, and water vapour are released
OXYGEN is consumed
there is a ~50% reduction in volume
stabilized residue is physically, bio-chemically different than raw material

10. How does compost differ from the starting raw materials?
Raw materials (e.g. manure):
Compost:
No odour
N (NH4)is converted to stable organic forms
Reduction/elimination of pathogens
Non-phytotoxic
Improved handling and spreading
Odorous
Unstable N (NH4 is susceptible to loss)
Contains pathogens
May be phytotoxic
Difficult to handle and apply
Note that this slide highlights the main advantages of using composted vs raw livestock manures

11. Composting Process Factors
What conditions do compost microorganisms need??

12. Recommended conditions for active composting * :
C:N of 25:1-30:1
Moisture 40-65%
Oxygen >5%
Porosity > 40%
Particle sizes-range of sizes
Temperature oC
Recommended conditions for active (thermophilic, high rate) composting. Note that these are the conditions that must be provided by the initial composting mix to promote rapid and sustained reproduction and growth of compost microorganisms
C:N-nutritional balance
*active composting = thermophilic, high rate

14. Moisture and C:N of some common composting materials
C:N ratio
Straw
4-27
48-150
Sawdust 锯屑
19-65
Cattle manure 80
18-20
Vegetable wastes
60-80
11-13
Creating a composting mixture with the recommended characteristics is accomplished by selecting materials which are too wet (manure, vegetable wastes, other fresh plant material) and combining these with materials that are too dry (straw, sawdust), and at the same time trying to balance C:N ratio of the mixture.

15. Blending materials Materials are mixed with an eye to:
Acceptable moisture content (45-60%)
Mixture C:N ratio between 20:1 and 40:1
Include materials that add porosity and structure (e.g. straw, sawdust, wood chips)
Feedstock piles of manure and bedding (sawdust)

16. How do you know if you have the “right mix” ?
Test feedstocks
Test mixture
“Look and feel” of mix
Useful tests: C:N, moisture, bulk density
Performing the “squeeze test”: when material is squeezed, it should feel like wrung-out sponge (40-65% moisture)

17. Managing the composting process
Process monitoring and evaluation
Regular turning (porosity, aeration, mixing)
Maintaining moisture content within opt range
Troubleshooting 解决composting problems
Note that composting process management will be covered more fully in next week’s lab.

18. How long does the process take?
Anywhere from 3-12 wks to more than a year; 9 wks is typical (turned windrows)
Length of time depends on composting method, nature of materials, and process management (i.e., frequency of turning)
Also, length of composting and curing phase depends on the intended use for the compost
Anywhere from 3-12 weeks to more than a year (leaf and yard waste), 9 weeks is typical for on-farm composting (frequently turned windrows)
Length of time depends on composting method, nature of materials, and process management.
For example, woody materials take longer, and frequent mixing and turning speeds up the process
Also length of composting and CURING period depends on the intended use for the compost i.e., use as a potting mix requires more stable product than field soil amendment
Curing (maturing) phase: follows active composting; occurs at ambient To and lasts for 1-several mos. Curing allows compost to develop the desired characteristics for its intended use.

19. Compost Quality
…refers to various characteristics of compost that determine its value or marketability as a soil amendment.
What types of characteristics do you think might be considered important?

20. Compost Quality Characteristics
Potting mix
Soil amendment
Maturity
Very stable
Stable
Organic matter
Very high
High
Soluble salts
Very low
Low-mod
Nutrients
Low
Mod-high
Odour
Good, earthy
Not objectionable
Contaminants
(glass, plastic, metals)
See limits set by compost quality standards*
*Compost Quality standards by CCME and BNQ

21. starting feedstock materials
Compost quality characteristics which may be important at a given time are determined by:
intended market or use
starting feedstock materials
Some uses require highly stable, uniform, consistent quality product
Some feedstock materials (i.e., municipal sources) may contain higher levels of contaminants (e.g., plastic, glass, metals)

22. Uses for Compost Soil amendment Growing medium component Organic mulch
Topsoil replacement/amendment for soil blending

23. The effect of compost on root rot in ornamental trees (after G
The effect of compost on root rot in ornamental trees (after G. Tuitert)
+ compost
- compost
diseased source plants
diseased source plants

24. Soil amendment for field or garden soil, topdressing turfs
soil conditioning main benefit
slow-release nutrients (approx of N-P-K)

25. Growing medium component
greenhouse, nursery, bagged product
compost provides loose, friable, moisture retentive, growing medium
some composts are disease suppressive

26. Organic mulch
for annual and perennial crops, trees, shrubs, vines, etc.
compost provides moisture retentive, weed suppressive mulch that adds organic matter to soil

27. Topsoil replacement/ soil blending
landscaping, construction, remediation, reclamation uses
use of compost allows rapid establishment of vegetative cover on disturbed or degraded soils

28. Thank you!