(a) Biogas and RNG continuous measurement. Any party required to measure the volume of biogas, RNG, or renewable CNG/LNG under this subpart must continuously measure using meters that comply with the requirements in paragraphs (a)(1) and (2) of this section, or have an accepted alternative measurement protocol as specified in paragraph (a)(3) of this section:

(1) 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.

(2) Flow meters compliant with one of the following:

(i) API MPMS 14.3.1, API MPMS 14.3.2, API MPMS 14.3.3, and API MPMS 14.3.4 (incorporated by reference, see § 80.12).

(ii) API MPMS 14.12 (incorporated by reference, see § 80.12).

(iii) EN 17526 (incorporated by reference, see § 80.12) compatible with gas type H.

(3) EPA may accept an alternative measurement protocol if all the following conditions are met:

(i) The party demonstrates that they are unable to continuously measure using meters that comply with the requirements in paragraphs (a)(1) and (2) of this section, as applicable.

(ii) The party demonstrates that the alternative measurement protocol is at least as accurate and precise as the methods specified in paragraphs (a)(1) and (2) of this section, as applicable.

(b) Biogas and RNG sampling and testing. Any party required to sample and test biogas or RNG under this subpart must do so as follows:

(1) Collect representative samples of biogas or RNG using API MPMS 14.1 (incorporated by reference, see § 80.12).

(2) Perform all the following measurements on each representative sample:

(i) Methane, carbon dioxide, nitrogen, and oxygen using EPA Method 3C (see Appendix A-2 to 40 CFR part 60).

(ii) Hydrogen sulfide and total sulfur using ASTM D5504 (incorporated by reference, see § 80.12).

(iii) Siloxanes using ASTM D8230 (incorporated by reference, see § 80.12).

(iv) Moisture using ASTM D4888 (incorporated by reference, see § 80.12).

(v) Hydrocarbon analysis using EPA Method 18 (see Appendix A-6 to 40 CFR part 60).

(vi) Heating value and relative density using ASTM D3588 (incorporated by reference, see § 80.12).

(vii) Additional components specified in the natural gas specifications submitted under § 80.135(d)(5) or specified by EPA as a condition of registration under this part.

(viii) Carbon-14 analysis using ASTM D6866 (incorporated by reference, see § 80.12).

(c) 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:

(1) Samples must be tested in accordance with Part G of SM 2540 (incorporated by reference, see § 80.12).

(2) 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).

(3) 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.

(d) 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:

(1) Digester temperature readings must be recorded no less frequent than every 30 minutes and represent the average temperature in the tank.

(2) 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.

(3) Other parameters must be measured and calculated as specified in the facility's registration under § 80.135(c)(10)(vi)(A)(4).

(e) Third parties. Samples required to be obtained under this subpart may be collected and analyzed by third parties.

(f) 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).

(g) Liquid measurement and standardization. Any substance that is liquid at STP must be measured in gallons and standardized according to § 80.1426(f)(8).