Prepare for the next LCFS Re-adoption Hearing – Part #1
As we approach the LCFS Re-adoption Hearing in July, several questions about how the Low Carbon Fuel Standard (LCFS) works remain unresolved. This discussion is one in a series intended to help clarify the subject.
The methane losses from bio Compressed Natural Gas (CNG) production is an important input for Renewable Natural Gas (RNG) pathways. The California Air Resources Board (ARB) has used a default assumption that 1% of the natural gas from processing systems is lost. Considering that 1 MJ of CNG releases 55 g CO2e, a 1% loss of the biogas would add 5 g CO2e/MJ to the fuel pathway.
1% of 1 MJ = 0.2 g with a lower heating value (LHV) of 50 MJ/kg.
The GHG impact is 25 x 0.2 g = 5 g CO2e/MJ with a Global Warming Potential (GWP) of 25 for methane.
The 1% default leak derives from the GREET model default of 2% leakage. This value is a parametric assumption in Table 8 of the Argonne National Laboratory (ANL) document that documents renewable natural gas pathways.
Han, L., M. Mintz, M. Wang (2011) Waste-to-Wheel Analysis of Anaerobic-Digestion-Based Renewable Natural Gas Pathways with the GREET Model, ANL Report ESD-11