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To: Dom Mancini

From: David Bookbinder

Date: July 18, 2011

Re: Greenhouse Gas Emission Standards and Fuel Efficiency Standards for Mediumand Heavy-Duty Engines and Vehicles, Docket ID Nos. NHTSA-2010-0079 and EPAHQ-OAR-2010-0162 (the “Heavy-Duty Rule”).

Following up on our June 27 meeting, I wanted to address two issues that we did not 

cover at that time concerning the NGV Multiplier provision that the natural gas vehicle 

interests have asked be part of the final Heavy Duty Rule.

Implementation. Because the NGV Multiplier is identical to the provision Congress 

created for light-duty vehicles (49 U.S.C. 32905(c)), NHTSA and EPA have already 

dealt with implementing it in the context of a joint NHTSA-EPA fuel economy and 

greenhouse gas rule. In the Light-Duty Vehicle Greenhouse Gas Emission Standards 

and Corporate Average Fuel Economy Standards; Final Rule (75 FR 25324, May 7, 

2010)(the “Light-Duty Rule”), the agencies laid out exactly how, in light of the NGV 

Multiplier, that rule would treat natural gas vehicles (“NGVs”). Simply put, for reasons of 

administrative convenience EPA will use the 0.15 multiplier to calculate CO2 emissions 

just as NHTSA will use it to calculate fuel consumption: “As proposed, EPA will 

calculate CO2 emissions from dedicated alternative fuel vehicles for MY 2012-2015 by 

measuring the CO2 emissions over the test procedure and multiplying the results by the 

0.15 conversion factor described above.” Id. at 25433. As noted, EPA would do so only 

for Model Years 2012-2015; thereafter, the NGV Multiplier would continue to be used for 

fuel economy calculations, with no effect on GHG methodology or compliance:

for model years 2016 and later dedicated alternative fuel vehicles, CO2 will be 

measured over the 2-cycle test in order to be included in a manufacturer's fleet 

average CO2 calculations. As noted above, this is different than CAFE 

methodology which provides a methodology for calculating a petroleum-based 

mpg equivalent for alternative fuel vehicles so they can be included in CAFE. 

Id. at 25434. Thus NHTSA and EPA were able to implement the NGV Multiplier in the 

Light-Duty Rule without any difficulties whatsoever, and there is no reason why the NGV 

Multiplier could not be included in the Heavy-Duty Rule just as easily.

NGV Multiplier Magnitude. The second issue concerns the 0.15 value for a Heavy-Duty 

NGV Multiplier; as we made clear, we proposed using the 0.15 value because that was 

the number Congress deemed appropriate for NGVs. However, we believe that there is 

another way to structure this multiplier, one which would also resolve a pressing issue 

on the GHG side of the Heavy-Duty Rule. As explained in detail in the attached 

document (the “Unified Natural Gas Credit Proposal”), a .87 NGV Multiplier, 

accompanied by an equivalent GHG emissions credit, would provide an elegant solution 

to multiple regulatory issues. 
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UNIFIED NATURAL GAS CREDIT PROPOSAL

The purpose of the Unified Natural Gas Credit Proposal is to simultaneously address 

two Heavy-Duty Rule regulatory issues: how to account for the fact that NGVs eliminate 

100% of vehicle petroleum demand, and ensuring that NGVs can meet the Rule’s 

proposed methane emission standard. The Natural Gas Vehicle Interests have pointed 

out to the agencies that the proposed methane standard is extremely stringent, an order 

of magnitude lower that the lowest methane emissions limit we are aware of, the current 

EURO-VI standard of 0.5 g/kWh (0.37 g/bhp-hr). Comments of Natural Gas Vehicle 

Interests, Document No. EPA-HQ-OAR-2010-0162-2119.1, pp. 5-6.

The only way for natural gas engines to meet the proposed standard will be with a 

combination of the most advanced catalyst technology (approximately $2,000 per 

vehicle) plus GHG emission credits. Id. p. 6. And the most logical place to get such 

credits is from the upstream GHG emission benefits of natural gas.

According to the most rigorous analysis yet conducted, natural gas has 30-50% less 

upstream GHG emissions than diesel.

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 Allowing NGVs to take upstream emissions 

benefits into account not only solves the methane stringency issue, it fits perfectly within 

EPA’s policy goals. For example, natural gas upstream GHG emissions are not only 

lower than diesel, but those upstream emissions are decreasing as renewable natural 

gas (biomethane from landfills and other sources) comes on the market. Biomethane 

achieves nearly a 90% reduction in upstream GHGs compared to diesel, and DOE

estimates future U.S. production of up to 16 billion gasoline gallons equivalent. 74 FR 

24982. In contrast, diesel upstream GHG emissions are increasing as more diesel is 

refined from tar sands, which increase upstream GHG emissions by up to 80%.

Accounting for upstream GHG reductions accords with EPA’s own rule that upstream 

GHG emissions will be included in vehicle compliance calculations. Under the LightDuty Rule, vehicles will have “compliance values calculated according to a methodology 

that accounts in full for the net increase in upstream GHG emissions”, because “[t]here 

is a rational basis for EPA to account for this net difference, as that best reflects the real 

world effect on the air pollution problem we are addressing.” 75 FR 25436.2

 

1 Compare CARB “Detailed California-Modified GREET Pathway for Compressed 

Natural Gas (CNG) from North American Natural Gas”, February 28, 2009, p.4; 

“Detailed California-Modified GREET Pathway for Liquefied Natural Gas (LNG) from 

North American and Remote Natural Gas Sources”, September 23, 2009, p. 5; “Detailed 

California-Modified GREET Pathway for Ultra Low Sulfur Diesel (ULSD) from Average

Crude Refined in California”, February 28, 2009, p. 3. Each is available at 

http://www.arb.ca.gov/fuels/lcfs/workgroups/workgroups.htm#path.

2 EPA was referring to electric vehicles, which have higher upstream emissions than 

gasoline ones; in contrast, natural gas has lower upstream emissions than diesel.
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(Ironically, while EPA takes full credit for these upstream reductions in its cost-benefit 

analysis of the Heavy-Duty Rule -- where reduced upstream emissions are 

approximately 20% of the Rule’s total GHG reductions (75 FR 74282-83) -- EPA did not 

propose to allow manufacturers to do likewise.) 

Based on the following credit calculation, we propose a “unified” NGV credit consisting 

of a 13% GHG emission credit and a substantially modified NGV Multiplier of 0.87 (i.e., 

a 13% credit).

Using the California Air Resources Board’s 2009 analysis for the California Low-Carbon 

Fuel Standard, our calculation is as follows:

Upstream GHG emissions for Ultra Low Sulfur Diesel (“USLD”): 19.81 gCO2e/MJ

Upstream GHG emissions for CNG: 10.31 gCO2e/MJ

Upstream GHG benefit for CNG compared to diesel: 9.50 gCO2e/MJ

Tailpipe ULSD GHG emissions: 74.90 gCO2e/MJ

Ratio of Upstream CNG Benefit to Tailpipe ULSD emissions: (9.50/74.9) = 13%

Credit: 13% of the 2017 HHD standard (460 g/bhp-hr) = 60 g/bhp-hr

13% of the 2017 MHD standard (487 g/bhp-hr) = 63 g/bhp-hr

Thus the appropriate upstream GHG credits for MY 2017 would be 60 g/bhp-hr for 

Heavy Heavy-Duty vehicles, and 63 g/bhp-hr for Medium Heavy-Duty Vehicles, 

representing 13% of the proposed tailpipe GHG standards for these two classes (460 

and 487 g/bhp-hr, respectively). 

The magnitude of this upstream GHG emission credit also provides the value for a 

modified NGV Multiplier, i.e., 13% or 0.87; giving the same value to both simplifies the 

regulatory requirements and, as noted above, is exactly what EPA did in the Light-Duty 

Rule for MY 2012-2015.