[Digestion] Farmware 3.0 overestimating BTU output

[Jason Perry]

Hi all,

I've been messing about with FarmWare 3.0, the USDA's pre-feasibility 
tool for on-farm AD. I just noticed that it is calculating a BTU output 
for a given volume of methane based on about 1600 BTU/ft3. Biogas 
(assumed to be 57.5% methane) is given a heating value of 923 BTU/ft3. 
These numbers are based on dividing the software's prediction of BTU 
output by the predicted methane and biogas volumes.

Looking in Appendix C of the accompanying handbook, page C-51, it says 
it is multiplying the volume of methane by 923 BTU/ft3 to arrive at the 
BTU output. The software's output indicates otherwise.

Anyone else notice this?

Cheers,
Jason