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RNG Pipeline Injection Station

Wobbe / HHV / SG blending · AGA Report 4 · GPA 2145-16 · NGC+ Interchangeability

RNG Composition (mol %)

RNG flow

scfm

CH₄

%

CO₂

%

N₂

%

O₂

%

C₂H₆ (trace)

%

C₃H₈ (enrichment)

%

Propane injection to lift Wobbe.

H₂ (trace)

%

Pipeline Base Gas (mol %)

Pipeline flow

scfm

CH₄

%

C₂H₆

%

C₃H₈

%

i-C₄H₁₀

%

n-C₄H₁₀

%

i-C₅H₁₂

%

n-C₅H₁₂

%

n-C₆H₁₄+

%

CO₂

%

N₂

%

Operating Conditions

RNG pressure

psig

Pipeline pressure

psig

RNG temperature

°F

Compressor isentropic η

%

Motor η

%

Electricity cost

$/kWh

Tariff Envelope

Tariff preset

Wobbe min

BTU/scf

Wobbe max

BTU/scf

HHV min

BTU/scf

HHV max

BTU/scf

Max inerts (CO₂ + N₂)

%

Max CO₂

%

Max O₂

%

MN target

—

Engineering Basis

HHV / SG / Wobbe: standard AGA Report 4 / GPA 2145-16 / ASTM D3588 method, reference 60°F / 14.696 psia / dry.
Wobbe = HHV/√SG — interchangeability parameter. NGC+ recommends ±4% of pipeline average.
Methane Number simplified component-weighted approximation — for engine warranty use vendor AVL/MWM test.
Pipeline tariff: SoCalGas Rule 30 (1290–1385) / El Paso (1330–1475) / typical US interstate (1300–1400).
Pure RNG (96–99% CH₄) has Wobbe ~1285 — typically below SoCalGas minimum without blending or propane enrichment.
Compression: W = c_p·T·[(P₂/P₁)^((γ−1)/γ) − 1] for CH₄-rich (γ=1.31).
Standards: AGA Report 4 / 5, GPA 2145-16, ASTM D1945 / D3588, ISO 6976:2016, NGC+ Interchangeability, SAE J1616.