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Wakamatsu Environment Laboratory

JPec Co., Ltd.

May 2012

Composting of wood, pruning, grass, etc.　　 (Composting of green waste)

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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%

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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 　 96 10.0

Sawdust 785-1400 30.0

Bark 154 -

Pruning waste 58.9 14.0

Cut grass 30-50 16 ～ 40

Fallen leaves 32.5 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)

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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).

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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.

NN

N

N

N

N

N

N

N

N

N

N

N

N

N

N

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How to adjust C/N ratios

Green Waste

Sawdust

Rice straw

Pruning waste,

etc.

Livestock feces

Rice bran

Garbage

High Low

Carbon (C): Large Nitrogen (N): Large

Return compost

Nitrogenous fertilizer, etc.

Acceleration of fermentation by adjusting the C/N ratio

Compost with a balanced C/N ratio

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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)

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How to make woody compostThe more proximal parts are more difficult to decompose.

Bark

Sawdust

Pruning

Wood

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.

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Characteristics of materials and recipes for composting

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.

Source: FUJIWARA Shunrokuro, How to Make and Use Compost, Rural Culture Association Japan (available in Japanese only)

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How to compost pruning waste• Key pointsIt is important to use that with leaves and branches mixed in a good balance.☆It is difficult to compost

branches alone.☆Hardwood is suitable.

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.

The substances can be almost decomposed by accumulation for 6 months.

[Composting time]

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How to compost pruning waste

About 2 m

Crush and accumulation (in 2-3-centimeter chips)

Turn it once a month.

Water content adjustment

Water content adjustment

What to do to accelerate composting?

Outdoor accumulation is preferred because the pile is easy to dry.

Materials to accelerate fermentation

Compost

Crusher

[Composting time]

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What accelerates fermentation

Choose auxiliary materials so that the C/N ratio becomes 10-20 or so.

e.g.

Usually the ratio is adjusted by using livestock feces.

Raw garbage can be used.

Collect appropriate fungi.

Actinomycete and bacidiomycete (mushrooms)

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.

Native Microorganisms

Adjustment by using auxiliary materials

(Balanced C/N ratio)

Adjustment by using microorganisms (Decomposition)

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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.

Crush and accumulation (in 2-3-centimeter chips)

Water content adjustment

For one ton of bark:50 kg of dried poultry manure, 20 kg of ammonium sulfate, or 10 kg of ureaTo sawdust: Increase each by 20%.

Turn it twice a month or so.

Leave it outdoor for 2-3 years.

1-2 months

Turn it once a month or so.

Six months or soCompost

Bark

Sawdust

Crusher

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Composting coffee processing waste

Coffee processing wasteWater content

(%)Nitrogen

(%)Phosphoric

acid (%)Potash (%) C/N ratio

Original content

Dry-matter content

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.

Cow dung/Coffee processing waste = 1:2

Swine excrement

Poultry manure /Coffee processing waste = 1:1

Coffee processing waste alone Accumulation for over half or one year is required.

To accelerate fermentation

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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.

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Return composting (Successive composting)

Materials

Compost Compost

Source: MATSUZAKI Toshihide, Soil, Compost and Organic Matter, Ie-No-Hikari Association (available in Japanese only)

Seed compostSeed compost

Primary fermentation

Secondary fermentation

Fermentation

Half All

Compost

Materials

Fermentation

Return composting General composting

17Source: Survey for Composting of Fallen Leaves, Sapporo Sewerage Resource Corporation

C/N ratioFallen leaves: 32.5

Fallen leaves alone: 22.8

Fallen leaves mixed with compost: 13.3

Zone with compost mixed by 5%Control zone (with fallen leaves alone)Ambient temperature

Pile

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Turning and water content adjustment

Turning and water content adjustment

Turning and water content adjustment in the zone with compost mixed by 5%

Turning and water content adjustment in the zone with compost mixed by 5%

Turning in the zone with compost mixed by 5%

Number of days

Effect of the use of fermentation accelerator or return composting