Purity Recommendation

ABC RNG Purity Recommendation
Renewable natural gas (RNG) is fully interchangeable with natural gas (click here for definitions). Today, more and more gas utilities want to encourage RNG production and injection into their pipelines, but the quality each utility requests can vary greatly, based on the utility’s experience with RNG, perceptions, and other factors. This variation increases the cost and time it takes to connect an RNG producer to the gas grid.  To help gas utilities, utility commissioners and RNG producers drive to a more uniform gas quality specification, the American Biogas Council (ABC) has developed this RNG purity recommendation.  The ABC’s members include more thatn 200 organizations and 2,000 individuals representing all players in biogas industry, including RNG producers and gas utilities. To develop this recommendation, the ABC surveyed the many dozens of US RNG production facilities, some that have been operating for more than twenty years, plus dozens of gas quality specifications, and aligned this recommendation with the most typical natural gas quality requirements and which the constituents in the RNG produced today.  

The American Biogas Council also helped develop the Interconnect Guide for Renewable Natural Gas in New York State. The objective of this document is “to provide the technical framework and guidance necessary for the introduction of renewable natural gas (RNG) into the natural gas distribution pipeline network” not just in New York, but anywhere across the country.  The first project to inject RNG into a natural gas pipeline was the Fresh Kills landfill, Staten Island, NY in 1982.

Pipeline

For RNG to natural gas pipeline facilities, in general the ABC advocates the use of the same specifications as conventional natural gas. Since these vary considerably within the continental US, the ABC through its RNG Committee and members has developed the gas purity specifications below for RNG projects injecting into gas distribution systems (for a PDF click here):

Physical Property

Units

Lower Limit

Upper Limit

Heating Value

BTU/ft3

960

1100

Carbon Dioxide

mol %

2

Oxygen

mol %

0.4

Total Inerts

mol %

5

Hydrogen Sulfide

gr./100 ft3

1/4

Total Sulfur

gr./100 ft3

1

Water

lbs/mmSft3

7

Siloxanes

ppm(v)

1

Hydrocarbon Dew Point

Fahrenheit

-40

Temperature

Fahrenheit

50

120

Dust, Particulate

commercially free*

Biologicals

commercially free*

Heavy Metals

commercially free*

*Commercially free is defined as equal or less than the levels present in conventional natural gas

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   CNG Vehicles

Since CNG specifications also vary considerably within the continental US, the ABC has developed the following gas purity specifications for RNG to CNG vehicle projects where the gas does not have to enter a conventional natural gas pipeline to be used in vehicles:

Physical Property

Units

Lower Limit

Upper Limit

Heating Value

BTU/ft3

940

1100

Carbon Dioxide + Nitrogen

mol %

4

Oxygen

mol %

1

Hydrogen

ppm(v)

300

Total Sulfur

wt%

0.001

Hydrogen Sulfide

ppm(v)

6

Siloxanes

ppm(v)

3

Liquids

commercially free*

Dust, Particulate

commercially free*

Chlorine Additives

commercially free*

Heavy Metals

commercially free*

*Commercially free is defined as equal or less than the levels present in conventional natural gas

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