Dear Ron
I followed your general point and wonder if you could consider these ‘typical’
examples and then fine tune the request.
Here is a wood analysis (without dilution by moisture)
FUELS:
Wattle
Ash %
0.50
Sulphur %
0.04
Hydrogen %
6.50
Carbon %
49.46
Oxygen %
43.00
Nitrogen %
0.50
Total %
100.00
HHV
18.70
LHV
17.38
DAF HHV
18.79
C:H ratio
7.61
And here is a Charcoal analysis:
FUELS:
Charcoal
Ash %
2.00
Sulphur %
0.10
Hydrogen %
1.69
Carbon %
83.00
Oxygen %
13.11
Nitrogen %
0.10
Total %
100.00
HHV
29.80
LHV
29.46
DAF HHV
30.41
C:H ratio
49.11
So the assumption (which is a big one but let’s go with it) is that the char
represents the difference between burning whole fuel and leaving some charcoal.
Then the conversion of that char into a CO2 saving (we can come back to the CO
as CO2e) is the difference between the char % in the remaining fraction and the
original (dry) fuel analysis. Let’s say it was 83% v.s. 50%.
So 1 kg of wood = 500 g of C
1 kg of Char = 830 g of C
The difference is 1.66 times the C in the char mass as an equivalent mass of
dry fuel.
CCHAR = 1.66
CWOOD
As there is always some mass of moisture in the wood and none in the char, it
is fair to include the moisture, let’s say 15% and use the formula:
____CCHAR _____= 830 = 1.95 for a factor of about 2.
CWOOD*(1-H2O%) 500*(1-0.15)
Weighing the remaining char, say 250 g, you multiple by 2 to get 500 g of wood
equivalent (at 15% moisture).
By not burning that 250 g of char, you have effectively not burned 500 g of
that particular fuel when viewed from the perspective of CO2 emitted.
Because most stoves made at least some char, the same calculation would have to
be done for both stoves to get a fair comparison. So you could have two
methods: either take a difference of char only and use the Carbon content of
the char to directly calculate an amount of CO2 avoided, or express it as a
mass of moist fuel not burned, deducting it from the total burned. Normally the
CO2 emitted is calculated from the mass of fuel burned so it might fly father
with the Carbon traders.
Regards
Crispin
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