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To produce high-grade compost, there needs to be a balance between the quantity of green and brown materials in the composter. This balance speeds up the decomposition of organic material. But there's no need for absolute precision – just keep in mind the approximate ratio of carbon to nitrogen (C/N) that should go into the bin to produce good compost.
The recommended ratio for good composting is 30:1, or 30 parts of carbon to one part nitrogen, which means three parts ‘'browns” for one part “greens”.
Here's how to calculate the C/N ratio of a mixture :
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Rm= n1*R1+ n2*R2
n1+n2
Rm= C/N ratio of mixture
R1= C/N ratio of component 1
n1= Amount of component 1
R2= C/N ratio of component 2
n2= Amount of component 2
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Examples :
Victoria has chosen composting as one way of cutting down her garbage. Using the chart of compostables, she decides on the following mixture :
Coffee grinds= C/N ratio 20*
Grass= 20
Household wastes= 35
Kitchen scraps= 16
Dead leaves= 45
* See Table 1
Knowing the C/N value for each material, she can decide how much of each component to add for an ideal mixture. If she chooses to put in one portion of coffee grounds, two portions of grass, two portions of household wastes, two portions of kitchen scraps and two portions of dead leaves, she will create a compost heap with an ideal C/N ratio of 28.
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Details :
Rm= n1*R1+ n2*R2
n1+ n2
RM= 1*20 + 2*20 + 2*35 + 2*16 + 2*45
1+2+2+2+2
RM= 252
9
RM=28
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Remember - this is not an exact science!
Tableau 1
C/N ratio of compostable materials1
urine 0.8
liquid manure 2-3
Blodd meal 3
Liquid pig manure 5-7
Fecal matter 6-10
Green vegetable matter 7
Bone meal 8
Liquid cow manure 8-13
humus, loam 10
Aged composted manure 10
Fresh chicken manure 10
Household water purification sediment 11
Kitchen wastes 12-20
Grass clippings 12-25
Vegetable refuse 13
Brewery wastes 15
Vines of leguminous plants 15
Alfalfa 16-20
Coffee grinds 20
Cow manure 20
Grass 20
Garden wastes 20-60
Potato vines 25
Horse Manure 25
Pine needles 30
Black peat 30
Household waste 30-40
Brown or light peat 30-50
Foliage 30-60
Residue of mushroon growing medium 40
Straw from leguminous plants 40-50
Dead leaves 45
Oat straw 50-60
Rye straw 65
Millet straw 70
Wheat straw 70-150
Bark 100-130
Tree prunings 100-150
Fresh sawdust 100-500
Decomposing sawdust 200
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1 Petit, Jacques, Le compost, théorie et pratique, p.70
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Copyright © 2005 Ecolosphere Inc. All rights reserved. |
