Determine the Carbon(C):Nitrogen(N) ratio for an equal blend of 1 part chicken manure & 1 part sawdust?

Question

Chicken Manure
Moisture Content = 70%
N dry Weight basis = 60%
C:N ratio = 10:1

Sawdust
Moisture Content = 35%
N dry Weight basis = 0.11%
C:N ratio = 500:1

If you can help with this problem, could you please explain how you solved it, cheers for the help.

Answer 1

Eh Parky,

Something doesn't make sense. For the Chicken Manure, you can't have N have a dry weight basis of 60% and have a C:N ratio of 10:1. That would mean that it was 600% Carbon. Impossible.

Lets solve for 6% N dry weight instead.
then C would be 10x N or 60% dry weight.

Since the moisture content is 70%, we are going to have to reduce both numbers
N= 6% * (1-.7) = 1.8% Wet weight
C= 60%* (1-.7) = 18% Wet weight

Now on to the Sawdust
N =.11%
C= 500*N = 55%

Find the wet weight
N=.11%* (1-.35) =.0715%
C= 55% (1-.35) = 35.75%

Now, since we are adding together, for the new N and C percentages add the old together and divide by 2

N= (.0715+ 1.8)%/2=.9356%
C=(18+35.75)%/2 = 26.875

New ratio C:N= C/N:1=26.875/.9356:1=28.7:1