Composting Balance Calculations

Alken-Murray recommends a C/N ratio of 20 to 30 for composting of manure and various high carbon wastes To balance the C/N ratio to the desired level of 30, use the following algebraic equations, courtesy of the Water Quality & Waste Management website belonging to the North Carolina Cooperative Extension Service: Alken-Murray's compost-augmenting microbial cultures in Alken Clear-Flo 7014 can be used to initiate a wide assortment of composting applications.

6/18/2008

 

 

Example waste ..........

6/18/2008......................C/N ratio
 Poultry carcass

 5
 Fresh manure, swine

 6
 Fresh manure, poultry

 6
 Fresh manure, cattle

 8
 Poultry house litter, cake

 7.5
 Poultry house litter, mixed

 10
 Poultry house litter, stockpiled

 15
 Yard waste

 14
 Grass clippings

 19
 Horse stable manure

 25
 Legume grass hay

 25
 Potato tops

 25
 Fruit waste

 35
 Leaves

 40 - 80
 Peanut hulls

 50
 Cornstalks

 60
 Straw, oat

 80
 Straw, wheat

 130
 Bark

 100
 Paper

 170
 Sawdust or pellets

 500
 Wood chips

 700
 Desired final compost mix

 20 - 30



Composting ratio

  Let:                         A     =    weight of poultry  litter
                               1 - A     =    weight of wheat straw
                          A + (1 - A)    =    1

   Formula =  A x [manure C/N ratio]  +  (1 - A) x [wheat straw C/N ratio  = 1 x 30
     7.5A  +  130  -  130 A    =   1 x 30 (desired compost ratio)

7.5 A  -  130 A    =    30  -  130
                             -122.5 A    =   -110      which is the same as,
                              122.5 A    =    110
                                                           Parts by weight
                                                        ______________________
      litter:       A   =  110 / 122.5   =    0.90      0.90 / 0.90   =   1.00
      straw:    1 - A   =   1  -  0.90   =    0.10      0.10 / 0.90   =   0.11
                                             _____                       _____
                                              1.00                        1.11

Therefore, in this example, for every 90 lbs. of manure, 10 lbs. of straw would be required to bring the C/N ratio to 20. Keep in mind that for this to work, extra fungi and/or bacteria with strong cellulase enzyme are needed to break this difficult carbon source into a useable offset for the excess nitrogen and phosphorus in the swine (or chicken) manure, using Alken Clear-Flo 7014, 7014C or 7016.

 To balance the moisture content, use these algebraic computations:

Average moisture content of litter/straw mixture = 0.90 x 50% + 0.10 x 10% = 46 %

Let:                         B     =    weight of litter/straw mixture
                               1 - B     =    weight of water needed
                          B + (1 - B)    =    1

   Formula =  B  x 46  +  (1 - B) x 100 = 1 x 50
     46B  +  100  -  100B    =   50 - 100

                             -54B   =   -50   which is the same as,
                              54B    =   50
                                                           Parts by weight
                                                        ______________________
      litter/straw:       B   =  50/54   =    0.92      0.92 / 0.92   =   1.00
      water:    1 - B   =   1  -  0.92   =    0.08      0.08 / 0.92   =   0.08
                                             _____                       _____
                                              1.00           

 

 

Litter Compost Recipe:

weight compost mix
litter: 1.00 x 1.00 = 1.00
straw: 0.11 x 1.00 = 0.11
__________________ ...........
water: 1.11 x 0.08 = 0.09

 

Part by Pounds per 100 lbs. compost mix

manure: 0.9 x 0.92 x 100 = 83 lbs.
straw 0.1 x 0.92 x 100 = 9 lbs.

__________________
water 1.00 x 0.09 x 100 = 8 lbs.

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