I was looking for a formula to calculated the obtained energy yield via biohydrogen and biomethane production using anaerobic digestion process. The unit is in SI unit (x) mLH2/g VS and (y) mL CH4/gVS and energy yield unit is KJ/kg VS.
Suppose I have produced 100mL CH4 gas using biomass. What will be the energy value of this produced gas in kJ unit?
I asked if you could help me with the mathematical equation for the converting process?
I think you just have to multiply the methane (or hydrogen) yield (Nm³/gVS or Nm³/gCOD) by the methane (or H2) recovery of the separation system (Nm³/Nm³) and by the lower heating value of methane (kJ/Nm³).
The LHV is a constant and you can find it anywhere (e.g. Wikipedia, EngineeringToolbox), while the methane (or H2) yield and recovery varies for each feedstock and technology, respectively.
The lower heating value for pure methane is 35.8 MJ/m3. Note that it is per normal cubic metre (1 m3 at 0 C and 1 atm.).
The lower heating value of 100 ml CH4 at 0 C and 1 atmosphere equals 3.58 kJ.
If the temperature and pressure differ you can use the ideal gas law PV=nRT to calculate which volume it corresponds to at 0 C and 1 atm.
Thanks, Jörgen Held and Rafael Nogueira Nakashima. I will follow your instructions and continue my studies.
Thank you very much.
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