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 than 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 in the US.
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 |
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
CNG Vehicles
Since natural gas pipeline specifications are more stringent than the quality needed for natural gas engines, the ABC has developed the following gas purity specification for RNG to CNG vehicle projects where the gas does not have to enter a conventional natural gas pipeline:
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