1 Wakamatsu Environment Laboratory JPec Co., Ltd. May 2012 Composting of wood, pruning, grass, etc. (Composting of green waste)
2 Important points in composting For composting, the carbon rate (C/N ratio) and the water content are important. C/N ratio suitable for composting: Water content suitable for composting: 40-60%
3 C/N ratio and water content of materials (Examples) MaterialC/N ratioWater content (%) Cow dung Swine excrement Poultry manure Rice straw Rice hull Sawdust Bark154- Pruning waste Cut grass ~ 40 Fallen leaves Coffee processing waste Raw garbage10 or so80.0 or more Source: FUJIWARA Shunrokuro, How to Make and Use Compost, Rural Culture Association Japan (partly added; available in Japanese only)
4 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).
5 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 N N
6 How to adjust C/N ratios Green Waste Sawdust Rice straw Pruning waste, etc. Livestock feces Rice bran Garbage High Low Carbon (C): LargeNitrogen (N): Large Return compost Nitrogenous fertilizer, etc. Acceleration of fermentation by adjusting the C/N ratio Compost with a balanced C/N ratio
7 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)
8 How to make woody compost The 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. Difficult to decompose
9 Characteristics of materials and recipes for composting MaterialCharacteristicsRecipeUse 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) Pruning waste Bark Sawdust
10 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. 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]
11 How to compost pruning waste About 2 m Crush and accumulation (in 2-3-centimeter chips) Turn it once a month. 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]
12 What accelerates fermentation Choose auxiliary materials so that the C/N ratio becomes 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)
13 How to compost sawdust or bark The C/N ratio is 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 urea To 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 so Compost Bark Sawdust Crusher
14 Composting coffee processing waste Coffee processing waste Water content (%) Nitrogen (%) Phosphoric acid (%) Potash (%)C/N ratio Original content Dry-matter content 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
15 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.
16 Return composting (Successive composting) Materials Compost Source: MATSUZAKI Toshihide, Soil, Compost and Organic Matter, Ie-No-Hikari Association (available in Japanese only) Seed compost Primary fermentation Secondary fermentation Fermentation HalfAll Compost Materials Fermentation Return compostingGeneral composting
17 Source: Survey for Composting of Fallen Leaves, Sapporo Sewerage Resource Corporation C/N ratio Fallen 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 temperature Turning and water content adjustment 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