Composting of wood, pruning, grass, etc.
(Composting of green waste)
Wakamatsu Environment Laboratory
JPec Co., Ltd.
May 2012
1
Important points in composting
For composting, the carbon rate (C/N ratio)
and the water content are important.
C/N ratio suitable for composting: 10-20
Water content suitable for composting: 40-60%
2
C/N ratio and water content of materials
(Examples)
Material
C/N ratio
Water content (%)
Cow dung
15.8
80.1
Swine excrement
11.4
69.4
Poultry manure
7.9
63.7
Rice straw
77
10.0
Rice hull
Sawdust
96
10.0
785-1400
30.0
Bark
154
-
Pruning waste
58.9
14.0
Cut grass
30-50
Fallen leaves
32.5
16～40
53.5
Coffee processing waste
25
66.0
Raw garbage
10 or so
80.0 or more
Source: FUJIWARA Shunrokuro, How to Make and Use Compost, Rural
Culture Association Japan (partly added; available in Japanese only)
3
Carbon and nitrogen for
microorganisms
 Carbon (C): Largely assimilated and
used as an energy source
 Nitrogen (N): Largely assimilated and
used to make their bodies
With a high C/N ratio, microorganisms have an energy
source but cannot increase (or cannot form fungus bodies).
4
Why is a high C/N ratio not good?
Nitrogen is indispensable to compose fungus bodies.
With less nitrogen, microorganisms increasing to decompose
compost assimilate nitrogen in soil and take away even nitrogen
required for plants. In serious case, microorganisms attack and
break down plant rootlets to get nitrogen.
N
N
N
N
N
N
N
N
N
N
N
N
N
N
5
N
N
How to adjust C/N ratios
High
Green Waste
Low
Livestock
feces
Sawdust
Acceleration of
fermentation by
adjusting the C/N
ratio
Rice bran
Rice straw
Garbage
Pruning
waste,
etc.
Carbon (C): Large
Return compost
Nitrogenous fertilizer,
etc.
Nitrogen (N): Large
Compost with a
balanced C/N ratio
6
Substances included in green waste
• Rice or wheat straw: Phenol acid
• Sawdust and bark: Phenol acid, tannin and
essential oil (terpene, etc.)
In anaerobic fermentation, in addition to these
substances above, organic acid and short-chain fatty acid
are generated in considerable amount.
It is necessary to take enough time to decompose those.
(Normally more then 6 months)
7
Pruning
Wood
Bark
Sawdust
Difficult to decompose
How to make woody compost
The more
proximal parts
are more difficult
to decompose.
Principal components: Cellulose, hemicellulose and lignin
In particular, wood has an overwhelming amount of lignin.
Cellulose or hemicellulose is highly bound to lignin to form lignin-cellulose
complexes.
Cellulose, normally easy to decompose, becomes difficult to decompose.
8
Characteristics of materials and recipes for composting
Sawdust
Bark
Pruning waste
Material
Characteristics
Recipe
Use and note
 Because this material contains not
only wood but also leaves, the C/N
ratio is lower among woody waste,
which facilitates composting.
 It is important to use a material portion with
leaves and branches mixed in a good balance.
 In case of softwood branches only, it is
desirable to compost them by supplying
nitrogen or using rice bran, oil cake, and/or
poultry manure.
 The effect of nitrogen cannot be expected, so
that the compost is used for physical
improvement in soil.
 Bark includes phenol acid, etc.
(difficult to be decomposed by
microorganisms) to protect the body.
Because these may cause problems
with crop roots, they should be
rendered completely harmless.
 Usually after bark is accumulated outdoor for
1-2 years in case of hardwood and for 2-3
years in case of softwood, it is mixed and
fermented for one year or so.
 The nitrogen source is generally poultry
manure. To one ton of bark, 50 kg of dried
poultry feces, 20 kg of ammonium sulfate or
10 kg of urea is add.
 The compost is also difficult to decompose. ⇒
Because that can give a more stable physical
improvement effect than other materials’
compost, it is used to maintain good physical
properties of potted plants or propagation
media for long periods.
 The decomposability vary by
regions or types of trees.
 Softwood is more difficult to
decompose than hardwood.
 It is difficult to compost this material alone.
 Livestock feces, etc. are usually used as
materials to adjust the water content and C/N
ratio in composting.
 If accumulation and fermentation are not
enough, nitrogen starvation, root rot or pest
damage may be occurred in crops. Therefore,
accumulation and fermentation for at least 6
months is required.
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Source: FUJIWARA Shunrokuro, How to Make and Use Compost, Rural Culture Association Japan (available in Japanese only)
How to compost pruning waste
• Key points
It is important to use that with leaves and branches
mixed in a good balance.
☆It is difficult to compost
branches alone.
☆Hardwood is suitable.
[Composting time]
Winter: The majority is branches.
[One year]
Summer: Leaves are included.
[Six months]
(Softwood contains more harmful phenol.)
Cherry, chestnut and ginkgo among
hardwood contain more harmful phenol.
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The substances can be almost decomposed by accumulation for 6 months.
How to compost pruning waste
[Composting time]
Materials to accelerate fermentation
Crusher
Water
content
adjustment
Crush and accumulation
(in 2-3-centimeter chips)
About 2 m
Water content
adjustment
Compost
Outdoor accumulation
is preferred because the
pile is easy to dry.
Turn it once a month.
What to do to accelerate composting?
11
What accelerates fermentation
Adjustment by using
auxiliary materials
(Balanced C/N ratio)
Adjustment by using
microorganisms
(Decomposition)
Choose auxiliary materials so that the
C/N ratio becomes 10-20 or so.
Collect appropriate fungi.
e.g.
Actinomycete and bacidiomycete
(mushrooms)
Usually the ratio is adjusted by using
livestock feces.
Raw garbage can be used.
Native Microorganisms
It is good to collect fungi from soil at
places with those to decompose such as
forests or grass fields.
It is also effective to use return compost.
12
How to compost sawdust or bark
• The C/N ratio is 100-1200 or so.
• Softwood bark has a lower pH level (around 5.0).
• As an auxiliary material, poultry manure with a
high lime content is good.
For one ton of bark:
50 kg of dried poultry manure,
20 kg of ammonium sulfate, or
10 kg of urea
To sawdust: Increase each by 20%.
Sawdust
Water content
adjustment
Crusher
Bark
Leave it outdoor
for 2-3 years.
Crush and accumulation
Turn it twice a month or so.
(in 2-3-centimeter chips)
1-2 months
Compost
Six months or so
Turn it once a month or so.
13
Composting coffee
processing waste
Coffee processing waste
Original content
Dry-matter content
Water content
(%)
Nitrogen
(%)
Phosphoric
acid (%)
Potash (%)
C/N ratio
65
0.81
2.3
0.06
0.2
0.12
0.3
25
That has a high water content and a slightly high C/N ratio.
It includes nitrogen but
microorganisms can hardly use that.
It may cause nitrogen
starvation.
Coffee processing waste alone  Accumulation for over half or one year is required.
To accelerate
fermentation
Cow dung/Coffee processing waste = 1:2
Swine excrement
Poultry manure
/Coffee processing waste = 1:1
14
Return composting
(Successive composting)
• Process in which part of made compost is mixed as seed compost with raw
materials to make new compost
Merits: (1) The water content can be adjusted.
(2) Useful microbial groups can be supplied.
(3) Quality compost can be made in a short time.
Demerits: (1) If the pile is not dried, the water content can hardly be adjusted.
(2) The salt level gradually gets high.
(3) With continuous addition of seed compost only, the ventilation is
reduced.
 Constantly add auxiliary materials such as rice hull.
15
Return composting
(Successive composting)
Seed compost
Compost
Return composting
General composting
Materials
Materials
Primary
fermentation
Secondary
fermentation
Fermentation
Fermentation
Compost
Compost
Half
All
16
Source: MATSUZAKI Toshihide, Soil, Compost and Organic Matter, Ie-No-Hikari Association (available in Japanese only)
Effect of the use of fermentation
accelerator or return composting
Zone with compost mixed by 5%
Control zone (with fallen leaves alone)
Ambient temperature
Pile temperature
C/N ratio
Fallen leaves: 32.5
Fallen leaves alone: 22.8
Fallen leaves mixed with
compost: 13.3
Turning and water
content adjustment
Turning and water
content adjustment
Turning and water
content adjustment in
Turning and water
content adjustment in the zone with compost
the zone with compost mixed by 5%
mixed by 5%
Turning in the zone with
compost mixed by 5%
Number of days
17
Source: Survey for Composting of Fallen Leaves, Sapporo Sewerage Resource Corporation