February 25, 2014

MEMORANDUM

SUBJECT: Development of Air Quality Reference Case Upstream and Portable Fuel 

Container Inventories for Tier 3 Final Rule 

FROM: Rich Cook, Environmental Scientist

Margaret Zawacki, Environmental Engineer

Zoltan Jung, Mechanical Engineer

Assessment and Standards Division, Office of Transportation and Air Quality

TO: Docket

The purpose of this memorandum is to document the methods used to develop reference case 

upstream and portable fuel container inventories used in air quality modeling for the final Tier 3 

rule. While the Tier 3 final rule has no impact on portable fuel container (PFC) or upstream 

emissions, a significant number of modifications were made to the 2007v.5 platform inventory to 

create reference case PFC, point and nonpoint source inventories which account for expected 

impacts of renewable fuel requirements under EISA, as estimated by Annual Energy Outlook

(AEO) 2013,1as well as impacts of recent 2017-2025 light duty vehicle greenhouse gas emission 

standards and heavy-duty greenhouse gas standards. 

Upstream Impacts 

In addition to the effects of increased renewable fuel use on emissions from the vehicles and 

equipment that use the fuels, there are shifts in the fuel production and transport/distribution 

methods that can have substantial impacts on emissions. These "upstream" emissions are 

associated with all stages of biofuel production and distribution, including biomass production 

(agriculture, forestry), fertilizer and pesticide production and transport, biomass transport, 

biomass refining (corn or cellulosic ethanol production facilities), biofuel transport to 

blending/distribution terminals, and distribution of finished fuels to retail outlets. Additionally, 

changes in agricultural economics associated with increased biomass production can result in 

shifts in related agricultural production, such as livestock. Furthermore, greenhouse gas 
2

emission standards impact production, distribution, and consumption of fuel, as well as 

emissions associated with these processes.

Agricultural Sector

Inventory adjustments from final RFS2 rule modeling2 were used for 2030. For the Tier 3 

proposal, adjustments for 2017 were scaled by the ratio of 2017 renewable fuel volumes versus 

2030 volumes. Although 2018 was modeled for the final rule rather than 2017, we continued to 

use the 2017 adjustments. Impacts on farm equipment emissions were not accounted for, 

however. Emission rates from the GREET model (fertilizer and pesticide production)3or based 

on the 2002 National Emissions Inventory (fertilizer and pesticide application, agricultural dust, 

livestock waste) were combined with estimates of agricultural impacts from FASOM (Forest 

and Agricultural Section Optimization Model). Since FASOM modeling used a reference case 

of 13.2 billion gallons of ethanol, impacts used in the modeling for this rule are underestimates. 

Adjustment factors are provided in Table 1. Adjustments were applied equally to all counties 

having any of the affected sources. This is one area of uncertainty in the inventories, since there 

would likely be variation from one county to another depending on how much of the predicted 

agricultural changes occurred in which counties. By using percent change adjustments rather 

than attempting to calculate absolute ton changes in each county we have attempted to minimize 

the inventory distortions that could occur if the calculated change for a given county was out of 

proportion to the reference case emissions for that county. For instance, a different approach 

could estimate reductions that were larger than the reference case NEI emissions, since there was 

no linkage between the NEI inventories and the FASOM modeling. The specific sources (SCCs) 

and affected pollutants that these adjustments were applied to are listed in a docket reference.4

Table 1. Adjustments to Modeling Platform Agricultural Emissions for the Tier 3 

Reference Case

Source Description 2018 Adjustment 2030 Adjustment

Nitrogen Fertilizer Application 1.0417 1.0573

Fertilizer Production 1.0438 1.0603

Pesticide Production 0.9967 0.9954

Tilling/Harvesting Dust 1.0193 1.0265

Agricultural Burning 1.000 1.000

Livestock Dust 0.9988 0.9983

Livestock Waste 0.9988 0.9983

Biofuel Production

Emissions from the production of biofuels include the emissions from the production facility 

itself as well as the emissions from production and transport of the biomass and any other fuels 

used by the biofuel plant, such as natural gas, coal, and electricity. 
3

Corn Ethanol Plants

Significant changes were made to ethanol plant inventories for the Tier 3 final rule. For the 2007 

base year inventory, we used emission estimates in the 2007 platform (obtained from the 2008 

NEI version 2) where available. 

However, this inventory does not contain emission estimates for all facilities known to be in 

operation in 2007. For those facilities (except for ethanol), emission rates in Table 2 were used 

to develop inventories. For all pollutants except air toxics, emission rates in this table were 

obtained from an upstream impacts spreadsheet developed for the RFS2 rule.5 For air toxics 

except ethanol, toxic to VOC ratios were developed using emission inventory data from the 2005 

National Emissions Inventory (NEI). These ratios were then applied to VOC emission rates in 

Table 2, to obtain toxic emission rates. Ratios for different plant types are given in Table 3. 

Ethanol emission rates were obtained from SMOKE speciation profiles.

It should be noted that the RFS2 rule models future year emissions based on the assumption that 

fossil fuel prices will drive corn ethanol producers to switch to biomass feedstocks from 

conventional boiler fuels. Due to the difficulty in predicting potential changes in energy sources 

for individual plants, this assumption was not included in air quality inventories. 

Emission rates for the Tier 3 rule were multiplied by facility production estimates as of 2007, 

using industry characterization data initially developed for the RFS2 rule and last updated in 

early 2012.6Total domestic corn ethanol production in 2007 was approximately 6.9 billion 

gallons.

Initial geographic coordinates for ethanol plants were developed using data from the RFS2 rule 

and GoogleEarth searches. However, GIS-based automated quality assurance (QA) checks 

found many ethanol plants assigned to coordinates that were outside of their assigned statecounty FIPS. Additional research using GoogleEarth, web searches, and the NEI were used to 

determine correct coordinates, and in some cases a reassignment of the state-county FIPS.1 

Extensive additional effort would be required to detect incorrect assignments within counties. 

Spreadsheets with coordinates for plants can be found in the docket for the rule.7

 

1

In some cases, bad coordinates were easily-identifiable typos such as switched latitude and longitudes or a missing 

negative sign for the longitude. In a couple of cases, ethanol plants FIPS and coordinates were in error. It is 

important to note that only ethanol plants that were erroneously assigned outside of their assigned counties were 

corrected. Other facilities may be assigned to incorrect coordinates within their correctly-assigned counties. 
4

Table 2. Corn Ethanol Plant Criteria Pollutant Emission Factors (grams per gallon produced)

Corn Ethanol Plant 

Type

Year VOC CO NOx PM10 PM2.5 SOx NH3

Dry Mill Natural 

Gas (NG)

2007, 2018 2.29 0.58 0.99 0.94 0.23 0.01 0.00

2030 2.29 0.58 0.94 0.94 0.23 0.01 0.00

Dry Mill NG (wet 

distillers grains with 

soluble (DGS))

2007, 2018 2.27 0.37 0.63 0.91 0.20 0.00 0.00

2030 2.27 0.37 0.60 0.91 0.20 0.00 0.00

Dry Mill Biogas 2007, 2018 2.29 0.62 1.05 0.94 0.23 0.01 0.00

2030 2.29 0.62 1.00 0.94 0.23 0.01 0.00

Dry Mill Biogas 

(wet DGS)

2007, 2018 2.27 0.39 0.67 0.91 0.20 0.00 0.00

2030 2.27 0.39 0.63 0.91 0.20 0.00 0.00

Dry Mill Coal 2007, 2018 2.31 2.65 4.17 3.81 1.71 4.52 0.00

2030 2.31 2.65 3.68 3.64 1.54 3.48 0.00

Dry Mill Coal (wet 

DGS)

2007, 2018 2.31 2.65 2.65 2.74 1.14 2.87 0.00

2030 2.28 1.68 2.34 2.62 1.03 2.21 0.00

Dry Mill Biomass 2007, 2018 2.42 2.55 3.65 1.28 0.36 0.14 0.00

2030 2.42 2.55 3.65 1.28 0.36 0.14 0.00

Dry Mill Biomass 

(wet DGS)

2007, 2018 2.35 1.62 2.32 1.12 0.28 0.09 0.00

2030 2.35 1.62 2.32 1.12 0.28 0.09 0.00

Wet Mill NG 2007, 2018 2.35 1.62 1.77 1.12 0.28 0.09 0.00

2030 2.33 1.04 1.68 1.00 0.29 0.01 0.00

Wet Mill Coal 2007, 2018 2.33 1.04 5.51 4.76 2.21 5.97 0.00

2030 2.33 3.50 4.86 4.53 1.98 4.60 0.00

Table 3. Toxic to VOC Ratios for Corn Ethanol Plants

Acetaldehyde Acrolein Benzene 1,3-Butadiene Formaldehyde

Wet Mill NG 0.02580 0.00131 0.00060 2.82371E-08 0.00127

Wet Mill Coal 0.08242 0.00015 0.00048 2.82371E-08 0.00108

Dry Mill NG 0.01089 0.00131 0.00060 2.82371E-08 0.00127

Dry Mill Coal 0.02328 0.00102 0.00017 2.82371E-08 0.00119

The industry characterization updated in 2012 was also used to project the 2007 inventory to 

future years, based on new plants, changes in production capacity since 2007 or changes in 

progress. These changes result in production of approximately 15 billion gallons in 2018 and 

2030. If emission estimates already existed in the 2007 platform, they were scaled up using 

changes in production, whereas if they were new plants or missing from the platform, emission 

rates from Table 2 were multiplied by production capacity estimates.

Finally it should be noted that, subsequent to air quality modeling, duplicate emissions were 

found for a very small number of plants. This error has an insignificant impact on modeling 

results.
5

Cellulosic Biofuel Refineries

As in previous air quality modeling exercises, cellulosic plants were treated as area sources and 

spread across the entire area of the county where they were located. Cellulosic biofuel refinery 

siting was determined based on utilizing the lowest cost feedstock, accounting for the cost of the 

feedstock itself as well as feedstock storage and the transportation of the feedstock to the 

cellulosic biofuel refinery. The total number of cellulosic biofuel refineries was projected using 

volumes from modeling using AEO 2013, early release. The methodology used to determine 

most likely plant locations is described in Section 1.8.1.3 of the RFS2 RIA8. 

In previous upstream modeling for the proposed Tier 3 rule, cellulosic plants were assumed to 

produce both cellulosic ethanol and cellulosic diesel. For this Tier 3 final rule modeling 

cellulosic biofuel refineries were categorized as either thermochemical or biochemical based on 

the available feedstock. Plants that were assumed to have forest or municipal solid waste 

feedstock available were projected to be thermochemical plants and plants that were projected to 

have agricultural residue feedstock available were projected to be biochemical plants. Emissions 

factors for each cellulosic biofuel refinery reflect the fuel production technology used rather than 

the fuel produced.

Emission factors were updated to reflect this change in cellulosic inventories. VOC and HAP 

emission factors from the cellulosic diesel work in the Tier 3 NPRM were used as the emission 

factors for the thermochemical plants (Tables 4 and 5). Cellulosic ethanol VOC and related HAP 

emission factors from the Tier 3 NPRM were used as the biochemical VOC and related HAP 

emission factors.

2

Table 4. Criteria Pollutant Emission Factors for Cellulosic Plants (Tons/RIN gallon)

Cellulosic Plant 

Type

VOC CO NOx PM10 PM2.5 SOx NH3

Thermochemical 5.92E-07 8.7E-06 1.31E-05 1.56E-06 7.81E-07 1.17E-06 1.44E-10

Biochemical 1.82E-06 1.29E-05 1.85E-05 3.08E-06 1.23E-06 6.89E-07 0

Table 5. Toxic Emission Factors for Cellulosic Plants (Tons/RIN gallon)

Cellulosic Plant 

Type

Acetaldehyde Acrolein Benzene 1,3-

Butadiene

Formaldehyde Ethanol

Thermochemical 2.95E-08 1.27E-09 9.61E-10 0 5.07E-09 2.09E-07

Biochemical 3.98E-07 1.11E-08 1.39E-08 0 2.28E-08 6.41E-07

 

2

It should be noted that in the Tier 3 NPRM we meant to use different cellulosic ethanol non-VOC CAP emission 

factors depending on which feedstock the plant was using but instead we used the same emission factors (based on a 

forest waste feedstock) for all the plants. For the FRM we corrected that by using emission factors for the non-VOC 

CAPS that were based on a stover feedstock for the biochemical plants.
6

Biodiesel Plants

Emission rates for biodiesel plants were obtained from the impacts spreadsheet and are provided 

in Table 6. Plant location and production volume data came from the Tier 3 proposed rule and 

are provided in a docketed spreadsheet called “ABS2013 Biodiesel_Plant_Inv 041013.xlsx”.

Total volume of biodiesel came from the AEO 2013 early release, 1.3 BG for both 2018 and 

2030.9 To reach the total volume of biodiesel, plants that had current production volumes were 

assumed to be at 100% production and the remaining volume was split among plants with 

planned production.

Table 6. Emission Factors for Biodiesel Plants (Tons/Mgal)

Pollutant Emission Factor

VOC 4.3981E-02

CO 5.0069E-01

NOx 8.0790E-01

PM10 6.8240E-02

PM2.5 6.8240E-02

SOx 5.9445E-03

NH3 0

Acetaldehyde 2.4783E-07

Acrolein 2.1290E-07

Benzene 3.2458E-08

1,3-Butadiene 0

Formaldehyde 1.5354E-06

Ethanol 0

Petroleum Refineries

Air quality modeling inventories account for impacts of increased use of biofuels, and reduced 

gasoline and diesel fuel consumption from greenhouse gas standards, on emissions from 

petroleum refineries. While there will also be impacts on emissions associated with crude oil 

extraction and transport to refineries, for Tier 3 modeling these impacts were not included. The 

same assumption was made in air quality modeling for the RFS2 rule. 
7

Since projection year inventories in the modeling platform do not account for impacts of EISA 

on gasoline production, we first calculated what gasoline volumes would be with 2007 ethanol 

volumes in 2018 and 2030 (accounting for displacement of gasoline with lower energy content of 

ethanol.)10 Then the impacts of the changes in gasoline volume in 2018 and 2030 with 2007 

ethanol volumes versus projected volumes with EISA were calculated using an updated version 

of the impacts spreadsheet developed for the RFS2 rule.11 The resulting impacts were used to 

calculate scaling factors to apply to criteria pollutant emissions for SCCs associated with refinery 

gasoline and distillate production.

In addition to the impacts of EISA, the 2017-2025 light-duty greenhouse gas rule and heavy-duty 

greenhouse gas rule will significantly reduce gasoline and diesel production. The impact of 

these rules will be very small in 2018, but quite significant in 2030. To account for impacts of 

this rule in 2030, an additional scalar of 0.7944 was applied. The combined scalars applied to 

account for EISA and the greenhouse gas rules are given in Table 7. Toxic emissions were 

estimated in SMOKE by applying speciation to VOC emissions.

Table 7. Adjustment Factors Applied to Petroleum Refinery Inventories for the Tier 3 

Reference Case.

Pollutant 2018 Adjustment 2030 Adjustment

VOC 0.97 0.77

CO 0.98 0.77

NOX 0.99 0.78

PM10 0.98 0.78

PM2.5 0.98 0.77

SOX 0.98 0.77

NH3 0.95 0.75

Biofuel Transport

Increased use of biofuels has a number of impacts on upstream emissions associated with 

transport. These impacts include vapor losses of ethanol associated with storage and transport, 

vapor losses associated with storage and transport of gasoline ethanol blends, and combustion 

emissions associated with transport of feedstocks to fuel production facilities and ethanol 

transport via marine vessel, rail, and tanker truck. 

Vapor Losses from Transport of Ethanol

Vapor emissions of ethanol occur during storage, as well as loading and unloading. For the final 

Tier 3 rule air quality inventory, county level inventory impacts on ethanol production SCCs 
8

were estimated using AP-42 gasoline transport loss emission factors, adjusted for denatured 

ethanol vapor pressure and molecular weight3, along with data from a detailed Oak Ridge 

National Laboratory (ORNL) analysis of projected ethanol transport modes, distances and 

volume. The tons of transported ethanol from the ORNL analysis were adjusted to account for 

2013 AEO ethanol volumes.12 

Vapor Losses from Transfer and Storage of Gasoline and Gasoline/Ethanol Blends

VOC evaporative emissions are also produced by transfer and storage activities associated with 

distribution of gasoline and gasoline/ethanol blends. These are referred to as Stage I emissions. 

Stage I distribution begins at the point the fuel leaves the production facility and ends when it is 

loaded into the storage tanks at dispensing facilities. 

There are five types of facilities that make up this distribution chain for gasoline. Bulk gasoline 

terminals are large storage facilities that receive gasoline directly from the refineries via 

pipelines, barges, or tankers (or are collocated at refineries). Gasoline from the bulk terminal 

storage tanks is loaded into cargo tanks (tank trucks or railcars) for distribution to smaller 

intermediate storage facilities (bulk plants), or directly to gasoline dispensing facilities (retail 

public service stations and private service stations). When ethanol is blended into gasoline it 

usually occurs in the pipes which supply cargo tanks at bulk terminals.

Bulk plants are intermediate storage and distribution facilities that normally receive gasoline or 

gasoline/ethanol blends from bulk terminals via tank trucks or railcars. Gasoline and 

gasoline/ethanol blends from bulk plants are subsequently loaded into tank trucks for transport to 

local dispensing facilities. 

Gasoline and gasoline/ethanol blend dispensing facilities include both retail public outlets and 

private dispensing operations such as rental car agencies, fleet vehicle refueling centers, and 

various government motor pool facilities. Dispensing facilities receive gasoline and 

gasoline/ethanol blends via tank trucks from bulk terminals or bulk plants. Inventory estimates 

for this source category only include the delivery of gasoline at dispensing facilities and does not 

include the vehicle or equipment refueling activities.

2018 and 2030 inventories which included EISA impacts were developed by adjusting the 2007 

platform inventory. These adjustments were made using an updated version of EPA’s 

spreadsheet model for upstream emission impacts, developed for the RFS2 rule. Below we 

describe how we developed emission factors and fuel volumes to make these adjustments with 

the impacts spreadsheet. 

 

3

Net factor =0.20 = 3 psi/10 psi * 48.7 MW/72 MW
9

Vapor loss VOC emission factors (EFs) for gasoline were based on inventory estimates from the 

2005 NEI, divided by total volume of gasoline.

13

 Emissions were partitioned into a refinery to 

bulk terminal component (RBT), a bulk plant storage (BPS), and a bulk terminal to gasoline 

dispensing pump (BTP) component. Emissions for the BTP component are greater than the RBT 

and BPS components. Total nationwide emissions for these components were divided by the 

energy content of the total volume of gasoline distributed in 2005, to obtain emission factors in 

grams per million metric British Thermal Units (g/mmBTU). Total volume of gasoline was 

based on gasoline sales as reported by the Energy Information Administration.14 In addition to 

gasoline VOC emission factors for the RBT/BPS components, emission factors were developed 

for the BTP component, for 10 percent ethanol, 15 percent ethanol, and 85% ethanol. Emission 

factors for ethanol blends were calculated by applying adjustment factors to gasoline EFs. The 

adjustment factors were based on an algorithm from the 1994 EPA On-Board Refueling Vapor 

Recovery Rule15:

EF (g/gal) = exp[-1.2798 - 0.0049(ΔT) + 0.0203(Td) + 0.1315(RVP)]

where delta T is the difference in temperature between the fuel in the tank and the fuel being 

dispensed, and Td is the temperature of the gasoline being dispensed. We assumed delta T is 

zero, and the temperature of the fuel being dispensed averages 60 oF over the year. 

We used average summer RVPs at the Petroleum Administration for Defense Districts (PADD) 

level to calculate adjustments. The U.S. is broken into five PADDs for petroleum products data 

collection purposes via the U.S. Energy Information Administration; see: 

http://www.eia.gov/oog/info/twip/padddef.html. These PADD regions are shown in Figure 1.

The methodology used to develop these RVPs is described in Chapter 7.1.3.2 of the Regulatory 

Impact Analysis for this rule. All counties within a PADD received the same adjustment for 

BTP emissions. For the Tier 3 reference case, expected volumes were based on projections from 

Annual Energy Outlook 2013.

16

 Volumes for each fuel type and summer RVPs for 2018 and 

2030 are provided in Table 8 and 9.

Volumes for each fuel type and summer RVPs are provided for 2018 and 2030 with 2007 ethanol

volumes in Tables 10 and 11 . RVPs for these cases in 2018 and 2030 were obtained from 

analysis of 2007 fuel data. Since 2007 ethanol volumes were assumed for 2018 and 2030, the 

gasoline volume was increased to compensate for the difference in ethanol for 2018 and 2030, 

versus what is expected. 

A benzene g/mmgal emission factor for 2018 and 2030 was based on benzene inventory 

projections used in the 2011 Cross-State Air Pollution Rule and average 2015-2030 gasoline 

volumes obtained from the Annual Energy Outlook 2011 Early Release Overview. This 

emission factor was used to estimate g/mmBTU emission factors based on the energy content of 

E0, E10, and E15 gasoline. Aside from energy content, we did not account for the effect of 
10

Figure 1. Map of Petroleum Administration for Defense Districts (PADD)
Table 8. RVPs Assumed for 2018 with projected ethanol and gasoline volumes. Used to Estimate Transfer and Storage VOC 

Emissions.

Table 9. RVPs Assumed for 2030 with projected ethanol and gasoline volumes. Used to Estimate Transfer and Storage VOC 

Emissions.

PADD

Total Fuel 

Volume

Gasoline 

Volume

Ethanol 

Volume

E10 Only 

Volume

E15 Only 

Volume

E85(74) Only 

Volume

Weighted 

RVP

Weighted 

E10 RVP

Weighted 

E15 RVP

Weighted 

E85 RVP

1 3.92E+10 3.41E+10 5.02E+09 2.43E+10 1.43E+10 6.02E+08 8.444 8.763 7.962 7

2 2.97E+10 2.58E+10 3.91E+09 1.62E+10 1.31E+10 4.56E+08 8.942 9.333 8.525 7

3 1.95E+10 1.68E+10 2.63E+09 9.32E+09 9.85E+09 2.98E+08 8.245 8.644 7.905 7

4 4.69E+09 4.08E+09 6.14E+08 2.64E+09 1.98E+09 7.20E+07 9.063 9.524 8.524 7

5 2.05E+10 1.81E+10 2.47E+09 1.60E+10 4.24E+09 3.17E+08 7.884 7.93 7.774 7

TOTAL 1.14E+11 9.89E+10 1.46E+10 6.84E+10 4.34E+10 1.75E+09 8.464 8.716 8.126 7

PADD

Total 

Fuel 

Volume

Gasoline 

Volume

Ethanol 

Volume

E10 Only 

Volume

E15 Only 

Volume

E85(74) Only 

Volume

Weighted 

RVP

Weighted 

E10 RVP

Weighted 

E15 RVP

Weighted 

E85 RVP

1 4.50E+10 3.99E+10 5.18E+09 3.71E+10 7.43E+09 4.73E+08 8.536 8.651 8.056 7

2 3.46E+10 3.03E+10 4.25E+09 2.31E+10 1.11E+10 3.63E+08 9.051 9.35 8.493 7

3 2.14E+10 1.89E+10 2.48E+09 1.72E+10 3.95E+09 2.25E+08 8.399 8.515 7.973 7

4 5.07E+09 4.48E+09 5.89E+08 4.06E+09 9.53E+08 5.33E+07 9.322 9.536 8.536 7

5 2.35E+10 2.08E+10 2.71E+09 1.91E+10 4.13E+09 2.47E+08 7.906 7.974 7.645 7

TOTAL 1.30E+11 1.14E+11 1.52E+10 1.01E+11 2.75E+10 1.36E+09 8.567 8.696 8.175 7
Table 10. RVPs Assumed for 2018 with 2007 ethanol volumes. Used to Estimate Transfer and Storage VOC Emissions

Table 11. RVPs Assumed for 2030 with 2007 ethanol volumes. Used to Estimate Transfer and Storage VOC Emissions

PADD

Total Fuel 

Volume

Ethanol 

Volume

Gasoline 

Volume

E0 Only 

Volume

E10 Only 

Volume

Weighted 

RVP

Weighted E0 

RVP

Weighted E10 

RVP

1 4.42E+10 2.47E+09 4.17E+10 1.95E+10 2.47E+10 8.63 8.301 8.883

2 3.38E+10 1.92E+09 3.19E+10 1.47E+10 1.92E+10 9.48 8.925 9.907

3 2.09E+10 1.02E+09 1.99E+10 1.07E+10 1.02E+10 8.77 8.391 9.166

4 4.96E+09 2.54E+08 4.71E+09 2.43E+09 2.54E+09 9.18 8.674 9.674

5 2.30E+10 1.27E+09 2.17E+10 1.03E+10 1.27E+10 7.77 7.602 7.911

TOTAL 1.27E+11 6.93E+09 1.20E+11 5.76E+10 6.93E+10 8.75 8.372 9.059

PADD

Total Fuel 

Volume

Ethanol 

Volume

Gasoline 

Volume

E0 Only 

Volume

E10 Only 

Volume

Weighted 

RVP

Weighted E0 

RVP

Weighted E10 

RVP

1 3.83E+10 2.47E+09 3.59E+10 1.36E+10 2.47E+10 8.68 8.301 8.883

2 2.90E+10 1.92E+09 2.71E+10 9.88E+09 1.92E+10 9.57 8.925 9.907

3 1.89E+10 1.02E+09 1.79E+10 8.78E+09 1.02E+10 8.81 8.391 9.166

4 4.57E+09 2.54E+08 4.32E+09 2.04E+09 2.54E+09 9.23 8.674 9.674

5 2.02E+10 1.27E+09 1.89E+10 7.48E+09 1.27E+10 7.80 7.602 7.911

TOTAL 1.11E+11 6.93E+09 1.04E+11 4.18E+10 6.93E+10 8.80 8.372 9.059
other fuel parameters on emission rates for E0, E10, and E15 blends. Thus, the E10 emission 

rate is slightly higher than the E0 rate due to the lower energy content of E10, and the E15 

emission rate is higher still. The E85 emission rate was estimated for the RFS2 rule. Emission

factors are summarized in Table 12.

Table 12. Storage and Transport Vapor Loss Emission Factors (g/mmBtu)

Process Fuel Benzene

BTP

E0 0.250

E10 0.259

E15 0.264

E85 0.023

RBT/BPS E0 0.059

Emission factors for VOC and benzene were used in conjunction with an updated version of 

EPA’s spreadsheet model for upstream emission impacts, developed for the RFS2 rule, to 

estimate PADD level level inventory changes of the changes in gasoline volume in 2018 with

2007 ethanol volumes versus projected volumes with EISA.17 VOC inventory changes were 

used to develop nationwide adjustment factors that were applied to modeling platform inventory 

SCCs associated with storage and transport processes (Table 13). This created the 2018 

reference case inventory. Benzene emission estimates were obtained either by application of the 

adjustments in Table 12 or through speciation of VOC in SMOKE, following criteria described 

in EPA’s Technical Support Document for the 2005 modeling platform.18 

A similar approach was used to develop adjustment factors for 2030. However, in addition to the 

impacts of EISA, the 2017-2025 light-duty greenhouse gas rule will significantly reduce gasoline 

production. The impact of this rule was small enough to ignore for 2018, but quite significant in 

2030. To account for impacts of this rule in 2030, an additional scalar of 0.7916 was applied.

Ethanol emissions were estimated in SMOKE by applying the ethanol to VOC ratios from 

headspace profiles to VOC emissions. These ratios are 0.065 for E10 and 0.272 for E15. The 

profiles were obtained from an ORD analysis of fuel samples from the EPAct exhaust test 

program19 and have been submitted for incorporation into EPA’s SPECIATE database. The E85 

profile was obtained from data collected as part of the CRC E-80 test program20 and has also 

been submitted for incorporation into EPA’s SPECIATE database. 

It should be noted that these adjustment factors are based on summer RVP, but applied to 

emissions for the whole calendar year. However, higher RVPs in winter corresponding to lower 

temperatures result in roughly the same vapor pressure of the fuel and roughly the same 

propensity to evaporate. Significant evaporative emissions are not expected from storage and 

transport of biodiesel, renewable or cellulosic diesel fuel due to their low volatility.
14

Table 13. Adjustment Factors Applied to Storage and Transport Emissions

Year Process PADD Pollutant

Adjustment 

Factor

2018 BTP 1 VOC 0.9515

benzene 0.9905

2 VOC 0.9619

benzene 0.9882

3 VOC 0.9778

benzene 0.9879

4 VOC 0.8983

benzene 0.9885

5 VOC 0.9430

benzene 0.9901

RBT/BPS All VOC 0.9553

benzene 0.9893

2030 BTP 1 VOC 0.8005

benzene 0.7871

2 VOC 0.8436

benzene 0.7865

3 VOC 0.8318

benzene 0.7824

4 VOC 0.7905

benzene 0.7840

5 VOC 0.7700

benzene 0.7888

RBT/BPS All VOC 0.8114

benzene 0.7863

Combustion Emissions from Transport of Fuels

Emissions are produced by the vehicles and engines used to transport feedstocks such as crude 

oil, corn, and cellulosic biomass to fuel production facilities, as well as transport/distribution of 

the finished fuels from the production plants to distribution terminals and retail outlets. For 

example, corn would be transported from farms and grain facilities to ethanol plants by truck and 

possibly rail. The finished ethanol would be transported from there to bulk distribution terminals 

by truck, rail, or barge, and distribution from terminal to retail outlet is by truck. We did not 

account for emissions associated with feedstocks, but did account for transport of finished fuels.

Combustion Emissions from Water and Rail Transport of Fuels

To develop the C1, C2 and rail air quality modeling reference case inventories for this Tier 3 

final rule, C1, C2 and rail platform inventories were adjusted to account for (a) differences in C1, 
15

C2 and rail emission rates in 2018 and 2030 versus 2007, (b) the difference in ethanol volume 

impacts for AEO 2013 future year projections versus the 2007 platform volume of 8.7 Bgallons 

(domestic and imported) and (c) impacts on gasoline production and distribution from the 2017-

2025 light duty vehicle GHG emissions standards.

21

 Adjustments to C1, C2 and rail emission 

rates were calculated using ton/ton-mile emission factors that were obtained from the Tier 3 

proposed rule inventory and AEO 2013 projected domestic shipping estimates .

22,23

 The ethanol 

volume impacts were allocated to individual counties using factors developed from the ORNL

analysis. 24 Impacts on C1, C2 and rail emissions from the 2017-2025 light duty vehicle GHG 

emission standards were calculated using the RFS2 impacts spreadsheet. Impacts from the 2017-

2025 light duty vehicle GHG emission standards were assumed to be negligible in 2018 and 

were accounted for by the scalars in Tables 14 and 15 for 2030.

Table 14. Scalars Applied to Rail Combustion Emissions in 2030 to account for 2017-2025 

LDGHG emission standards

Pollutant Scalar

CO 0.998

NOx 0.998

PM2.5 0.997

PM10 0.996

SO2 0.997

VOC 0.997

Table 15. Scalars Applied to C1/C2 Combustion Emissions in 2030 to account for 2017-

2025 LDGHG emission standards

Pollutant Scalar

CO 0.996

NOx 0.993

PM2.5 0.994

PM10 0.993

SO2 0.991

VOC 0.978

Combustion Emissions from Truck Transport of Fuels

Tank trucks are used to transport fuel from production facilities to bulk terminals and from 

terminals to bulk plants and dispensing facilities. Impacts of this activity on emissions from tank 

trucks (Class 8) are accounted for in reference case inventories by adjusting VMT used in 

SMOKE-MOVES.25 The VMT adjustments were derived from the ORNL analysis of ethanol 

transport, scaled to account for the difference in ethanol volume impacts for AEO 2013 future 
16

year projections versus the 2007 platform volume of 8.7 Bgallons and impacts on gasoline 

production and distribution from the 2017-2025 light duty vehicle GHG emissions standards. 

Impacts from the 2017-2025 light duty vehicle GHG emission standards were assumed to be 

negligible in 2018 and were accounted for with a 0.997 scalar in 2030.

Combustion Emissions Associated with Transport of Gasoline by Pipeline

In addition to combustion emissions associated with transport of gasoline by water, rail and 

tanker truck transport, there are also combustion emissions associated with transport of gasoline 

by pipeline. These emissions are impacted by 2017-2025 light duty vehicle greenhouse gas 

emission standards, as well as EISA. To account for impacts of the 2017-2025 light-duty 

standards, scalars developed for that rule were applied to refinery and bulk terminal SCCs. They 

were applied to these SCCs due to the difficulty in isolating the emissions along pipelines from 

pumps and other equipment by SCC. Impacts in 2018 were assumed to be negligible. 

Additional impacts of EISA were added to these scalars. Estimated impacts of these rules were 

obtained from by first estimating overall impacts on combustion emissions associated with 

transport, using the RFS2 impacts spreadsheet, then using nationwide emission fractions for 

combustion emission fractions associated with pipelines from GREET 1.8.c to obtain the portion 

attributable to pipelines.26,27 The scalars are provided in Table 16.

Table 16. Scalars Applied to Pipeline Combustion Emissions

Pollutant 2018 2030

CO 0.996 0.981

NOx 0.981 0.890

PM2.5 0.998 0.989

PM10 0.997 0.985

SO2 0.998 0.986

VOC 0.999 0.994

Portable Fuel Container Impacts

There are several sources of emissions associated with portable fuel containers (PFC) used for 

gasoline. These sources include vapor displacement and spillage while refueling the gas can at 

the pump, spillage during transport, permeation and evaporation from the gas can during 

transport and storage, and vapor displacement and spillage while refueling equipment. Increased 

use of ethanol in gasoline fuels can increase evaporative emissions from PFCs for a number of 

reasons. If, E10 fuels have higher volatility than corresponding E0 fuels, that can increase

evaporation and vapor displacement. Second, ethanol in gasoline increases permeation of fuel 

through gas can materials. Finally, the lower energy content of ethanol fuels leads to more 

frequent refueling, and, thus, greater emissions from spillage and displacement while filling the 

gas can at the pump.
17

The use of ethanol also changes the mix of hydrocarbons in the evaporated fuel. In particular it 

can change the fraction of ethanol, benzene and naphthalene as described below.

As part of the 2007 regulation controlling emissions of hazardous pollutants from mobile sources 

(MSAT2 rule), EPA promulgated requirements to control VOC emissions from gas cans. The 

methodology used to develop emission inventories for gas cans is described in the regulatory 

impact analysis for the rule and in an accompanying technical support document.28, 29 The large 

majority of spillage emissions occur when refueling equipment, and this is already included in 

the nonroad equipment inventory. Thus we did not include these emissions in the PFC inventory 

for this rule. Vapor displacement for nonroad equipment container refueling was also subtracted 

from vapor displacement in the PFC inventory to avoid double counting these emissions.

For the RFS2 rule, based on the MSAT work, we generated two sets of hypothetical nationwide 

annual estimates of PFC VOC emissions, for calendar years 2017 and 2030, based on all E0 and 

all E10.30 Interpolation was used to estimate PFC VOC emissions that reflected the mix of E0

and E10 for reference and control cases. To develop inventories for this rule, the national VOC 

estimates for all E0 in 2017 and 2030 were adjusted to create inventories that reflected 100% 

E10. We concluded that the 2017 inventory could be used to adequately represent 2018. These 

inventories were adjusted to account for impacts of RVP and oxygenate, using adjustment factors 

derived from modeling done with the NONROAD2008b model.31 NONROAD was run at the 

national level using average nationwide fuel parameters for an all E0 case and the E10 reference 

case. The percent change in refueling emissions from gasoline equipment was used to adjust 

the vapor displacement emissions, the percent change in tank permeation was used for PFC 

permeation, and the percent change in diurnal emissions was used for evaporation. Summer 

RVPs were used to develop these adjustments. Because significant PFC use occurs in winter, 

this will overestimate emission impacts. In 2018 and 2030, theE0 case assumed an nationwide 

average 8.7 psi RVP. The reference inventory in 2018 assumes E10 with 8.70 psi RVP for E10

and 2030 E10 with 8.72 psi RVP. Adjustment factors developed using these inputs are provided 

in a docket reference.32 

MSATs found in liquid gasoline will be present as a component of VOC emissions. These 

MSATs include benzene, ethanol, and naphthalene. For vapor displacement, toxic to VOC ratios 

were obtained from headspace vapor profiles from EPAct test fuels.

33

 For permeation emissions, 

vehicle permeation speciation data from Coordinating Research Council (CRC) technical reports 

E-77-2b and E-77-2c were used.34,35 We relied on three day diurnal profiles from the CRC data. 

For evaporative emissions resulting from changes in ambient temperatures, speciation data from 

the Auto/Oil program were used for E0 and E10.36 Table 17 lists the toxic to VOC ratios for 

each type of PFC emission.
18

Table 17. Toxic to VOC ratios for PFCs

Pollutant Process Speciation Surrogate E0 E10

Benzene

Vapor Displ. Vehicle Headspace 0.0077 0.0087

Permeation Vehicle Permeation 0.0250 0.0227

Evaporation Vehicle Evap 0.0336 0.0340

Naphthalene

Vapor Displ. Vehicle Headspace 0.0000 0.0000

Permeation Vehicle Permeation 0.0004 0.0004

Evaporation Vehicle Evap 0.0004 0.0004

Ethanol

Vapor Displ. Vehicle Headspace 0 0.0645

Permeation Vehicle Permeation 0 0.2020

Evaporation Vehicle Evap 0 0.1190

Table 18 presents national air quality modeling inventories for PFCs in 2018 and 2030. National 

emissions were allocated to the county level. 

Table 18. PFC Emissions in 2018 and 2030 for the FRM Air Quality Inventories (Tons)

Scenario VOC Benzene Ethanol Naphthalene

2018 29,119 641 3,687 7

2030 37,946 829 4,969 9

 

1 U. S. Energy Information Administration. 2013. Annual Energy Outlook, 2013, Early Release. Report No. 

DOE/EIA-0383ER(2013). Available at <http://www.eia.gov/forecasts/aeo/er/index.cfm>

2 U. S. Environmental Protection Agency. 2010. Renewable Fuel Standard Program (RFS2) Regulatory Impact 

Analysis. Assessment and Standards Division, Office of Transportation and Air Quality, Ann Arbor, MI. Report 

No. EPA-420-R-10-006, February, 2010. Available at 

<http://www.epa.gov/otaq/fuels/renewablefuels/regulations.htm>.

3 GREET, version 1.8c. Available at < http://greet.es.anl.gov/>.

4 U. S. EPA. 2011. Spreadsheet “agricultural sector adjustments.xls.” Docket EPA–HQ–OAR–2011–0135.

5 U. S. Environmental Protection Agency. 2010. Renewable Fuel Standard Program (RFS2) Regulatory Impact 

Analysis. Assessment and Standards Division, Office of Transportation and Air Quality, Ann Arbor, MI. Report 

No. EPA-420-R-10-006, February, 2010. Available at 

<http://www.epa.gov/otaq/fuels/renewablefuels/regulations.htm>.

6 U. S. EPA. 2012. Spreadsheet “Corn and Starch Ethanol Plants.xlsx. EPA Docket EPA-HQ-OAR-2011-0135.

7 U. S. EPA. 2013. Spreadsheet “2018rg_ethanol_facilities_12nov2013.xls” Docket EPA-HQ-OAR-2011-0135.
19

 

8

 U.S. EPA. 2010. Renewable Fuel Standard Program (RFS2) Regulatory Impact Analysis. Assessment and 

Standards Division, Office of Transportation and Air Quality, Ann Arbor, MI. Report No. EPA-420-R-10-006, 

February, 2010. Available at <http://www.epa.gov/otaq/fuels/renewablefuels/regulations.htm>.

9

 U.S. Energy Information Administration. 2012. Annual Energy Outlook 2013 Early Release. Report #:DOE/EIA0383ER(2013) Available at < http://www.eia.gov/forecasts/aeo/er/>

10 U. S. EPA. 2013. Spreadsheet “2018 and 2030 volumes with 2007 ethanol levels.xlsx.” EPA Docket EPA-HQOAR-2011-0135.

11 U. S. EPA. 2013. Spreadsheet “upstream_emissions_rev T3.xls. Docket EPA-HQ-OAR-2011-0135

12

 U.S. EPA 2013. Spreadsheet “Tier 3 round 2 EtOH_transport_vapor 040813.xlsx”.

13 U. S. EPA. 2005 National Emissions Inventory. Available at < 

http://www.epa.gov/ttn/chief/net/2005inventory.html#inventorydata>

14 Source: Energy Information Administration. 2006. Annual Energy Outlook 2006. Report #:DOE/EIA0383(2006) Available at <http://www.eia.gov/oiaf/archive/aeo06/aeoref_tab.html>

15 EPA. 1994. Final Regulatory Impact Analysis: Refueling Emission Regulations for Light Duty Vehicles and 

Trucks and Heavy Duty Vehicles. Office of Mobile Sources, Ann Arbor, MI. Available at 

<http://www.epa.gov/otaq/orvr.htm>

16 U.S. Energy Information Administration, Annual Energy Outlook 2013 (April 15, 2013).

<http://www.eia.gov/forecasts/aeo/data.cfm>

17 U. S. EPA. 2013. Spreadsheet “upstream_emissions_rev T3.xls.

18 U. S. Environmental Protection Agency. 2010. Technical Support Document: Preparation of Emission 

Inventories for the Version 4, 2005-based Platform. Office of Air Quality Planning and Standards, Air Quality 

Assessment Division, July 7, 2010. Available at 

<ftp://ftp.epa.gov/EmisInventory/2005v4/2005_emissions_tsd_07jul2010.pdf>

19 U. S. EPA. 2011. Hydrocarbon Composition of Gasoline Vapor Emissions from Enclosed Fuel Tanks. Office of 

Research and Development and Office of Transportation and Air Quality. Report No. EPA-420-R-11-018. EPA 

Docket EPA-HQ-OAR-2011-0135.

20 Coordinating Research Council. 2011. Exhaust and Evaporative Emissions Testing of Flexible-Fuel Vehicles. 

Agust, 2011. http://www.crcao.org/reports/recentstudies2011/E-80/E-80%20Final%20Report+Appendices.pdf

21 U. S. EPA. 2013. Spreadsheets “Adjusted C1C2 emissions for Tier 3 scenarios 042213.xlsx” and “Adjusted Rail 

emissions for Tier 3 scenarios 041713 for OAQPS.xlsx”. Docket EPA-HQ-OAR-2011-0135

22 U. S. EPA. 2013. Draft Regulatory Impact Analysis: Tier 3 Motor Vehicle Emission and Fuel Standards. Office 

of Transportation and Air Quality, Assessment and Standards Division, Ann Arbor, MI. Report No. EPA-420-D-13-

002. Available at < http://www.epa.gov/otaq/documents/tier3/420d13002.pdf>

23 U. S. Energy Information Administration. 2013. Annual Energy Outlook, 2013, Early Release. Report No. 

DOE/EIA-0383ER(2013). Available at <http://www.eia.gov/forecasts/aeo/er/index.cfm>

24 “Analysis of Fuel Ethanol Transportation Activity and Potential Distribution Constraints,”

Oak Ridge National Laboratory, U.S. Department of Energy, March 2009. Docket EPA-HQ-OAR-2011-0135.

25 U. S. EPA. 2013. Spreadsheets “FF10_2018_VMT_20130207 truck SCC only adjusted 030713 for OAQPS.xls; 

FF10_2030_VMT_20130222 truck SCC only 03212013 for OAQPS.xls”.Docket EPA-HQ-OAR-2011-0135

26 U. S. EPA. 2012. Final Regulatory Impact Analysis: Final Rulemaking for 2017-2025 Light-Duty Vehicle 

Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards. Report No. EPA-420-R-12-

016, August 2012. Available at <http://www.epa.gov/otaq/climate/documents/420r12016.pdf>

27 Argonne National Laboratory’s The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation 

(GREET) Model, Version 1.8c.0, available at MY 2017 and Later Regulatory Impact Analysis 4-165 
20

 

http://www.transportation.anl.gov/modeling_simulation/GREET/). EPA Docket EPA-HQ-OAR-2009-0472. (Docket 

No. EPA-HQ-OAR-2010-0799-1105)

28 U. S. EPA. 2007. Final Regulatory Impact Analysis: Control of Hazardous Air Pollutants from Mobile 

Sources; EPA420-R-07-002; Office of Transportation and Air Quality, Ann Arbor, MI. 

http://www.epa.gov/otaq/toxics.htm

29 Landman, L. C. (2007) Estimating Emissions Associated with Portable Fuel Containers (PFCs). U. S. EPA, 

Assessment and Standards Division, National Vehicle and Fuel Emissions Laboratory, Ann Arbor, MI, Report No. 

EPA420-R-07-001. http://www.epa.gov/otaq/toxics.htm

30 U. S. Environmental Protection Agency. 2010. Renewable Fuel Standard Program (RFS2) Regulatory Impact 

Analysis. Assessment and Standards Division, Office of Transportation and Air Quality, Ann Arbor, MI. Report 

No. EPA-420-R-10-006, February, 2010. Available at 

<http://www.epa.gov/otaq/fuels/renewablefuels/regulations.htm>.

31 http://www.epa.gov/otaq/nonrdmdl.htm#model

32 U. S. EPA. 2013. Spreadsheet “Tier 3 PFC Iventory_REV2.” EPA Docket EPA-HQ-OAR-2011-0135

33 U. S. EPA. 2011. Hydrocarbon Composition of Gasoline Vapor Emissions from Enclosed Fuel Tanks. Office of 

Research and Development and Office of Transportation and Air Quality. Report No. EPA-420-R-11-018. EPA 

Docket EPA-HQ-OAR-2011-0135.

34 U. S. EPA. 2010. Evaporative Emissions from In-Use Vehicles: Test Fleet Expansion (CRC E-77-2b). Prepared 

by Harold Haskew and Associates for Assessment and Standards Division, Office of Transportation and Air Quality, 

October, 2010. http://www.epa.gov/otaq/emission-factors-research/420r10025.pdf

35 Coordinating Research Council. 2010. Study to Determine Evaporative Emission Breakdown, Including 

Permeation Effects and Diurnal Emissions, Using E20 Fuels on Aging Enhanced Evaporative Emissions Certified 

Vehicles. Report No. E-77-2c. http://www.crcao.org/reports/recentstudies2011/E-77-2c/E-77-

2c%20Final%20Report%20for%20sure%201-28-11.pdf.

36 Auto/Oil Air Quality Improvement Research Program. 1996. Phase I and II Test Data. Prepared by Systems 

Applications International, Inc.