[Economics] Calculate Electricity and RNG production from Anaerobic Digester Biogas

[KFosterReed]

What is needed:

The economics methods requires an estimate of the electricity and renewable natural gas that can be produced from the biogas that is produced from anaerobic digestion. The RuFaS model reports the volume of biogas (m3) that is assumed to be 60% methane and 40% CO2 so additional steps are needed to estimate how much electricity and RNG can be made with the RuFaS predicted biogas.

How to do it:

@jonahgreene01 provided this information to inform the calculations:

Electricity

• Volume of methane is 60% of the total biogas volume
• Convert methane volume (m3) to mass (kg) using methane density: 0.68 kg CH4/m3 CH4
• Calculate total energy input using energy content of methane: 13.89 kWh/kg CH4
• Calculate total electricity output using a CHP electrical conversion efficiency: Elec. out = 33% of energy in
• Calculate total heat output using a CHP thermal efficiency: Heat out = 43% of energy in

Rewable Natural Gas (RNG):

• Volume of methane is 60% of the total biogas volume and is flow to RNG upgrading
• Convert methane volume (m3) to mass (kg) using methane density: 0.68 kg CH4/m3 CH4
• Apply 2% loss for leakage in the RNG upgrading process
• Apply 3% loss representing the fraction of methane combusted for process heat required for upgrading process
• Resulting volume of methane (after 5% loss) is the output volume of RNG
• Calculate RNG energy yield: 13.10 kWh/kg RNG
• ToDo: add methods to estimate emissions from upgrading chemicals, pipeline transport, end-use in CNG vehicles, and credits from diesel displacement

Reference: SUMMIT model documentation