§80.155. Sampling, testing, and measurement.
40 C.F.R. § 80.155
Continuous measurement—
Biogas, treated biogas, and RNG measurement. Except as specified in paragraph (a)(3) of this section, any party required to measure the volume of biogas, treated biogas, or RNG under this subpart must continuously measure using meters as specified in paragraphs (a)(1)(i) and (ii) of this section or have an accepted alternative measurement protocol as specified in paragraph (a)(2) of this section.
In-line GC meters compliant with ASTM D7164 (incorporated by reference, see § 80.12), including sections 9.2, 9.3, 9.4, 9.5, 9.7, 9.8, and 9.11 of ASTM D7164.
Flowmeters compliant with one of the following—
Alternative measurement protocols. EPA may accept an alternative measurement protocol if the party demonstrates that the alternative measurement protocol is at least as accurate and precise as the methods specified in paragraph (a)(1) of this section. An alternative measurement protocol may include less frequent measurement or recording than specified in the definition of continuous measurement.
RNG RIN separator measurement. An RNG RIN separator must measure natural gas or renewable CNG/LNG using one of the following:
A method specified in paragraph (a)(1) or (2) of this section.
Documentation (e.g., pipeline or utility statements, scale tickets, or bills of lading) that establishes the volume of natural gas or renewable CNG/LNG. Documentation must be specified in Btu LHV or converted as specified in paragraph (f) of this section.
Biogas and RNG sampling and testing. Any party required to sample and test biogas or RNG under this subpart must do so as follows:
Collect representative samples of biogas or RNG using API MPMS 14.1 (incorporated by reference, see § 80.12).
Perform all the following measurements on each representative sample—
Methane, carbon dioxide, nitrogen, and oxygen using EPA Method 3C (see appendix A-2 to 40 CFR part 60), ASTM D1945, ASTM D1946, or ASTM D7833 (all incorporated by reference, see § 80.12).
Hydrogen sulfide and total sulfur using ASTM D5504, ASTM D6228, or ASTM D6968 (all incorporated by reference, see § 80.12).
Siloxanes using ASTM D8230 (incorporated by reference, see § 80.12).
Moisture using ASTM D1142, ASTM D4888, ASTM D5454, or ASTM D7904 (all incorporated by reference, see § 80.12).
Hydrocarbon analysis using EPA Method 18 (see appendix A-6 to 40 CFR part 60), ASTM D1945, ASTM D1946, ASTM D7833, or EPA Method TO-15 (all incorporated by reference, see § 80.12).
Heating value and relative density using ASTM D3588 (incorporated by reference, see § 80.12).
If the RNG producer blends non-renewable components into RNG, carbon-14 analysis using ASTM D6866 (incorporated by reference, see § 80.12).
EPA may approve a party's request to use a method other than those specified in paragraph (b)(2) of this section if the party demonstrates one of the following:
The alternative analysis provides information that is reasonably accurate to that determined by the applicable method specified in paragraph (b)(2) of this section.
The alternative analysis is required by pipeline specifications or has been approved to be used by a State or Federal government agency.
Digester feedstock. Any party required to test for total solids and volatile solids of a digester feedstock under this subpart must do so as follows:
Samples must be tested in accordance with Part G of SM 2540 (incorporated by reference, see § 80.12).
Samples must be obtained, stored, and tested in accordance with Part A of SM 2540, including Sections 2, 3, and 5 (Sources of Error and Variability, Sample Handling and Preservation, and Quality Control).
Parties must test each daily representative sample under paragraphs (c)(1) and (2) of this section unless the party has a composite sampling plan submitted to EPA under § 80.135(c)(10)(vi)(D). Parties with a composite sampling plan must either test each daily representative sample or test samples in accordance with Part A of SM 2540 and as specified in the facility's composite sampling plan.
Digester operations. Any biogas producer required to measure or calculate digester operating conditions under this subpart must determine digester operating conditions for each mixed digester that meet all the following requirements:
Digester temperature readings must be recorded no less frequent than every 30 minutes and represent the average temperature in the tank.
Digester hydraulic and solids mean residence times must be calculated no less frequent than once a day using measurements of inflows, outflows, and tank levels, as applicable.
Other parameters must be measured and calculated as specified in the facility's registration under § 80.135(c)(10)(vi)(A)(4).
Third parties. Samples required to be obtained under this subpart may be collected and analyzed by third parties.
Unit conversions.
A party converting between Btu HHV and Btu LHV for biogas, treated biogas, natural gas, or CNG/LNG must use the ratio of HHV and LHV of methane as specified in ASTM D3588 (incorporated by reference, see § 80.12).
A party with documentation under paragraph (a)(3) of this section that is not specified in Btu must convert to Btu LHV as follows:
A party converting between scf and Btu LHV for CNG must use 934 Btu LHV/scf.
A party converting between pounds and Btu LHV for LNG must use 21,240 Btu LHV/lb.
Liquid measurement and standardization. Any substance that is liquid at STP must be measured in gallons and standardized according to § 80.1426(f)(8).
Notes, amendments, and revision history
Amendments
[88 FR 44564, July 12, 2023, as amended at 90 FR 29759, July 7, 2025; 91 FR 16486, Apr. 1, 2026]
Source
Source: 88 FR 44564, July 12, 2023, unless otherwise noted.
Authority
Authority: 42 U.S.C. 7414, 7521, 7542, 7545, and 7601(a).
Source
Source: 38 FR 1255, Jan. 10, 1973, unless otherwise noted.
Amendments
[88 FR 44564, July 12, 2023, as amended at 90 FR 29759, July 7, 2025; 91 FR 16486, Apr. 1, 2026]