Memorandum

Date: December 12, 2012

From: Rich Cook, Environmental Scientist

Assessment and Standards Division, Office of Transportation and Air Quality

To: Docket

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

Container Inventories for Tier 3 Proposal 

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. While the Tier 3 

proposed rule has no impact on portable fuel container (PFC) or upstream emissions, a 

significant number of modifications were made to the 2005v.4.2 platform inventory to create 

post-EPAct/EISA reference case PFC, point and nonpoint source inventories which account for 

impacts of renewable fuel requirements under EISA. 

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. 

Agricultural Sector

Inventory adjustments from final RFS2 rule modeling1 were used for 2030, while adjustments for 

2017 were scaled by the ratio of 2017 renewable fuel volumes versus 2030 volumes. Impacts on 

farm equipment emissions were not accounted for, however. Emission rates from the GREET 

model (fertilizer and pesticide production)2or 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 
2

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.3

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

Reference Case

Source Description 2017 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. 

Corn Ethanol Plants

Except for ethanol, emission rates in Table 2 were used to develop inventories. For all pollutants 

except air toxics, emission rates were obtained from an upstream impacts spreadsheet developed

for the RFS2 rule.4 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 impacts spreadsheet 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. 
3

Emission rates were multiplied by facility production estimates for 2005, 2017 and 2030, based 

on analyses done for the industry characterization described in Chapter 1 of the RFS2 final rule 

regulatory impact analysis. 

Table 1. 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)

2005, 2017 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))

2005, 2017 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 2005, 2017 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)

2005, 2017 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 2005, 2017 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)

2005, 2017 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 2005, 2017 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)

2005, 2017 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 2005, 2017 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 2005, 2017 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 2. 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

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 

 

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 
4

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.5

Cellulosic Ethanol and Cellulosic Biodiesel Plants

For criteria pollutants, emission rates were obtained from the upstream impacts spreadsheet cited 

above. 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 3, to obtain toxic emission rates. Ratios for different 

plant types are given in Table 3. Ethanol emission rates were obtained from SMOKE speciation 

profiles. 

As in RFS2 rule air quality modeling, plants were treated as area sources spread across the entire 

area of whatever county they were considered to be located in. Cellulosic biofuel refinery siting 

was based on the types of feedstocks that were determined to be most economical, along with 

projected volumes from modeling using FASOM. The methodology used to determined most 

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

Design capacities for 2022 used in the RFS2 rule air quality modeling were adjusted to account 

for differences with estimated volumes of cellulosic fuels produced for 2017 and 2030, using 

final RFS2 rule data. Since the final RFS2 rule assumed about 57 percent of cellulosic fuel 

nationwide was cellulosic diesel, with the remainder cellulosic ethanol, we assumed this split 

would apply to every plant. In reality, however, depending on available feedstocks, plants are 

likely to produce one fuel or the other.

Table 3. Criteria Pollutant Emission Factors for Cellulosic Plants (Tons/Mgal)

Cellulosic Plant Type Year VOC CO NOx PM10 PM2.5 SOx NH3

Cellulosic Ethanol 2017-2030 1.82 5.68 8.19 0.941 0.480 0.299 0.00

Cellulosic Biodiesel 2017 1.01 14.79 22.35 2.65 1.33 1.99 0.00

2030 1.00 14.73 22.24 2.63 1.32 1.99 0.00

Table 4. Toxic Emission Factors for Cellulosic Plants (Tons/Mgal)

Cellulosic Plant 

Type

Acetaldehyde Acrolein Benzene 1,3-

Butadiene

Formaldehyde Ethanol

Cellulosic Ethanol 0.398 0.009 0.014 0 0.023 0.645

Cellulosic 

Biodiesel

0.050 0.002 0.002 0 0.009 0.355

 

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. 
5

Biodiesel Plants

Emission rates for biodiesel plants were obtained from the RFS2 impacts spreadsheet and are 

provided in Table 5. Plant location data were updated from RFS2 with newer information, and 

current production volumes were adjusted based on biodiesel volumes assumed for EISA 

implementation in the RFS2 rule (1.45 billion gallons/year in 2017 and 1.67 billion gallons/year 

in 2030). Plant location data are provided in a docketed reference.

Petroleum Refineries

Air quality modeling inventories account for impacts of increased use of biofuels 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. 

Calculation of the emission inventory impacts of the decreased gasoline and diesel production on 

refinery emissions was done in EPA's spreadsheet model for upstream emission impacts. 

Emission inventory changes for the post-EPAct/EISA reference case were used to develop 

adjustment factors that were applied to inventories for each petroleum refinery in the U. S.

(Table 6).6 Toxic emissions were estimated in SMOKE by applying speciation to VOC 

emissions. It should be noted that the adjustment factors in Table IV-24 are estimated relative to 

that portion of refinery emissions associated with gasoline and diesel fuel production. 

Production of jet fuel, still gas and other products also produce emissions. If these emissions 

were included, the adjustment factors would not be as large.

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 

RFS2 rule air quality inventory, county level inventory impacts on ethanol production SCCs 

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

ethanol vapor pressure and molecular weight2, along with data from a detailed Oak Ridge 

National Laboratory analysis of projected ethanol transport modes, distances and volume

 

2

Net factor =0.20 = 3 psi/10 psi * 48.7 MW/72 MW
6

Table 5. 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

Table 6. Adjustment Factors Applied to Petroleum Refinery Inventories for the Tier 3 

Reference Case.

Pollutant 2017 Adjustment 2030 Adjustment

VOC 0.953 0.918

CO 0.894 0.887

NOX 0.760 0.585

PM10 0.834 0.713

PM2.5 0.882 0.797

SOX 0.896 0.820

NH3 1 1

transfered under various ethanol volume scenarios.7,8  For the reference case scenarios in this 

air quality modeling analysis, RFS2 air quality inventories were adjusted to account for the 

difference in national ethanol volumes between the 2022 RFS2 air quality modeling control case 

and the 2017 and 2030 post-EPAct/EISA cases.

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

VOC 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 
7

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.

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

2005 NEI.9 Total volume of gasoline was based on gasoline sales as reported by the Energy 

Information Administration.10 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. 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). 

In addition to gasoline VOC emission factors for the RBT/BPS components, emission factors 

were developed for the BTP component, for 10 percent ethanol and 15 percent 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 On-Board Refueling 

Vapor Recovery Rule11:

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. 
8

We assumed delta T is zero, and the temperature of the fuel being dispensed averages 60 oF over 

the year. Average nationwide summer RVPs assumed for fuel blends for the pre- and postEPAct/EISA cases are provided in Table 7. These RVPs were obtained from an EPA analysis.12

RVPs for the pre-EPAct/EISA case in 2005, 2017 and 2030 were obtained from analysis of 2005 

fuel data. In developing emission factors, the air quality inventory did not account for the 

impacts of 5.7% ethanol (California) and MTBE blended gasoline on nationwide RVP. This left 

a significant volume of lower RVP reformulated gasoline out of the calculation of nationwide 

gasoline RVPs and thus overestimated average RVP for the base case. 

Table 7. Average Nationwide Summer RVPs Assumed in Estimating Transfer and Storage 

VOC Emissions

Scenario Fuel Blend RVP

2005, 2017, 2030 PreEPAct/EISAE0 8.7

E10 8.5

2017 Post-EPAct/EISA E10 8.8

E15 8

2030 Post-EPAct/EISA E10 8.7

E15 8.1

Benzene emission factors for 2005 were estimated from the 2005 NEI and gasoline volumes 

from Annual Energy Outlook. 2017 and 2030 emission factors were based on the benzene 

inventory used in the 2011 Cross-State Air Pollution Rule. 2017 and 2030 gasoline volumes 

were obtained from the Annual Energy Outlook 2011 Early Release Overview and 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 other fuel parameters on 

emission rates. Thus, the E15 emission rate is slightly lower than the E10 rate due to the lower 

energy content of E15. Emission factors are summarized in Table 8.

Emission factors for VOC and benzene were used in conjunction with EPA’s spreadsheet model 

for upstream emission impacts, developed for the RFS2 rule, to estimate national level inventory 

changes for the post-EPAct/EISA case relative to pre-EPAct/EISA case.13,14 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 9). Benzene 

emission estimates were obtained either by application of the adjustments in Table 9 or through 

speciation of VOC in SMOKE, following criteria described in EPA’s Technical Support 

Document for the 2005 modeling platform.15 
9

Table 8. Storage and Transport Vapor Loss Emission Factors (g/mmBtu)

Year Case Process Fuel VOC Benzene

2005, 2017,2030 Pre-EPAct/EISA BTP E0 25.447 0.260

E10 25.633 0.260

RBT/BPS E0 10.532 0.059

2017 Post-EPAct/EISA BTP E10 26.664 0.260E15 24.419 0.2635

RBT/BPS E0 10.532 0.059

2030 Post-EPAct/EISA BTP E10 26.316 0.260E15 24.742 0.264

RBT/BPS E0 10.532 0.059

Table 9. Adjustment Factors Applied to Storage and Transport Emissions

Year Process Pollutant

PreEPAct/EISA 

Reference 

Case 

PostEPAct/EISA 

Case

2017 BTP VOC 0.9329 0.8895

benzene 0.9182 0.9182

BPS/RBT VOC 0.9344 0.9344

benzene 0.9344 0.9344

2030 BTP VOC 0.7640 0.7640

benzene 0.7981 0.7981

BPS/RBT VOC 0.9074 0.9074

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 

program16 and have 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. E15 will also have higher RVP in the winter (like E10) since RVP is 

not controlled in winter. Significant evaporative emissions are not expected from storage and 

transport of biodiesel, renewable or cellulosic diesel fuel due to their low volatility.
10

Combustion Emissions from Transport of Biofuels

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. 

Combustion Emissions from Water Transport of Biofuels

In EPA’s RFS2 final rule, impacts of water transport of ethanol on combustion emissions from 

the C1 and C2 commercial marine inventory were estimated for 2022, based on the difference 

between ethanol volumes mandated by EISA versus RFS1 rule volumes.17,18 These impacts were 

based on an Oak Ridge National Laboratory analysis.19 It should be noted that the Oak Ridge 

analysis only addressed ethanol transport and did not account for impacts of other biofuels on 

transportation activity. To develop the air quality modeling reference case inventories for this 

rule, RFS2 rule impacts were adjusted to account for (a) differences in commercial marine vessel 

emission rates in 2017 and 2030 versus 2005, and (b) the difference in ethanol volume impacts 

for post EPAct/EISA minus pre-EPAct/EISA scenarios, versus the EISA minus RFS1 volume 

impact used in the RFS2 rule analyses.20 Emission factors used to make these adjustments were 

obtained from analyses done to support the 2010 Category 3 Marine Diesel Rule.21,22 The 

adjusted national inventory impacts were allocated to individual counties using factors developed 

from the Oak Ridge analysis. These impacts were then applied to the model platform inventory.

Combustion Emissions from Rail Transport of Biofuels

In addition to barges, rail is used to transport ethanol from production facilities to bulk terminals. 

As with the marine inventory, 2022 RFS2 rule rail impacts were adjusted to account for 

differences in fuel volumes and emission rates to obtain post-EPAct/EISA inventories. Emission 

factors used to make adjustments were obtained from an EPA locomotive emission factor fact 

sheet.23 The adjusted national inventory impacts were allocated to individual counties using 

factors developed from the Oak Ridge analysis.24 These impacts were then applied to the model 

platform inventory.

Combustion Emissions from Truck Transport of Biofuels

Tank trucks are used to transport ethanol 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 Oak Ridge National 
11

Laboratory analysis of ethanol transport, scaled to account for the difference in ethanol volume 

impacts for post EPAct/EISA minus pre-EPAct/EISA scenarios, versus the EISA minus RFS1 

volume impact used in the RFS2 analyses.

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. As the 

calculation of emissions for refueling non-road equipment includes spillage and some vapor 

displacement, these impacts are not included here. 

Increased use of ethanol in gasoline fuels increases evaporative emissions from PFCs for a 

number of reasons. First, E10 fuels often have higher volatility than corresponding E0 fuels, 

increasing 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.

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.26, 27

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 E10.28 Interpolation was used to estimate PFC VOC emissions that reflected the mix of E0 

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

national VOC estimates for all E0 were adjusted to create inventories that reflect postEPAct/EISA conditions. These inventories were adjusted to account for impacts of RVP and 

oxygenate, using adjustment factors derived from modeling done with the NONROAD2008b 

model.29 NONROAD was run at the national level using average nationwide fuel parameters for 

an all E0 case, the low ethanol base case, and the 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 2017 and 2030, the base case summer average inputs were 8.0 RVP, with fuel 

nationwide containing on average 2.768 vol% ETOH, 1.415 vol% MTBE, 0.003 vol% ETBE, 
12

and 0.084 vol% TAME. The reference inventory in 2017 assumes 100% market share of E10 

with 8.8 RVP. The 2030 Tier 3 reference inventory assumes 99% E15 (8.1 RVP) and 1% E10 

(8.7 RVP). This was modeled as 100% E14.9 with 8.1 RVP. We assumed spillage emissions 

would be unaffected by changes in these parameters. Adjustment factors developed using these 

inputs are provided in a docket reference.30 

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.

31

 For spillage emissions, 

speciation of EPAct fuels was used.

32

 For permeation emissions, vehicle permeation speciation 

data from Coordinating Research Council (CRC) technical reports E-77-2b and E-77-2c were 

used.33,34 We relied on three day diurnal profiles from the CRC data. Since data were collected 

for E10 and E20, but not E15, an E15 profile was developed by linear interpolation. For 

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

Auto/Oil program were used for E0 and E10.35 Table 9 lists the toxic to VOC ratios for each 

type of PFC emission.

Table 9. Toxic to VOC ratios for PFCs

Pollutant Process Speciation Surrogate E0 E10 E15

Benzene

Vapor Displ. Vehicle Headspace 0.0077 0.0087 0.0109

Spillage Fuel 0.0064 0.0073 0.0071

Permeation Vehicle Permeation 0.0250 0.0227 0.0236

Evaporation Vehicle Evap 0.0336 0.0340 0.0275

Naphthalene

Vapor Displ. Vehicle Headspace 0.0000 0.0000 0.0000

Spillage Fuel 0.0009 0.0018 0.0019

Permeation Vehicle Permeation 0.0004 0.0004 0.0000

Evaporation Vehicle Evap 0.0004 0.0004 0.0000

Ethanol

Vapor Displ. Vehicle Headspace 0 0.0645 0.2719

Spillage Fuel 0 0.0887 0.1935

Permeation Vehicle Permeation 0 0.2020 0.2694

Evaporation Vehicle Evap 0 0.1190 0.1627

Table 10 presents national air quality modeling inventories for PFCs in 2017 and 2030. National 

level were allocated to the county level. Using the PFC inventory in the year 2020 version 3
13

modeling platform was used to. Ethanol emissions for the low ethanol case were allocated only 

to those counties where ethanol was used in 2005.

Table 10. PFC Emissions in 2017 and 2030 for the NPRM and Air Quality Inventories 

(Tons)

Scenario VOC Benzene Ethanol

2017 123,186 1,368 11,565

2030 146,593 1,622 31,632

 

1 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>.

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

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

4 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>.

5 U. S. EPA. 2011. Spreadsheet “Corn Ethanol Plant Inv T3 Corrected.xls.” Docket EPA-HQ-OAR-2011-0135.

6 U. S. EPA. 2011. Spreadsheet “Refinery scalars ref and control.xlsx.” Docket EPA-HQ-OAR-2011-0135.

7

“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.

8 U. S. EPA. 2008. AP-42, 5th Edition, Volume 1. Chapter 5.2: Transportation and Marketing Of Petroleum Liquids, 

July 2008. http://www.epa.gov/ttn/chief/ap42

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

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

10 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>

11 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>

12 U. S. EPA. 2011. Spreadsheet “Tier 3 NPRM RVP Estimates by PADD and Fuel Type 6.22.11.xls.” EPA Docket 

EPA-HQ-OAR-2011-0135

13 U.S. EPA. 2009. “Impact Calculations RFS-Docket.xls.” Docket EPA-HQ-OAR-2011-0135

14 U. S. EPA. 2011.“T3Up_2017Low E 080511.xlsx,” T3Up_2017Ref 080511.xlsx,” “T3Up_2030LowE 080511 

rev.xlsx,” “T3Up_2030Ref 080511.xlsx.” Docket EPA-HQ-OAR-2011-0135.

15 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>
14

 

16 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.

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

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

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

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

18 U. S. EPA. 2009. Spreadsheet “C1C2 emissions by county for RFS2 cases_12-14-09.xls.” Docket EPA-HQOAR-2011-0135

19 “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.

20 U. S. EPA. 2011. Spreadsheet “Tier_3_water_transport_allocation_factors to OAQPS revised July 11 2011.xls.” 

Docket EPA-HQ-OAR-2011-0135

21 U. S. EPA. 2009. Regulatory Impact Analysis: Control of Emissions of Air Pollution from Category 3 Marine 

Diesel Engines. Office of Transportation and Air Quality, Assessment and Standards Division, Ann Arbor, MI. 

Report No. EPA-420-R-09-019. Available at <http://www.epa.gov/otaq/regs/nonroad/marine/ci/420r09019.pdf>

22 U. S. EPA. 2011. Spreadsheet C1&C2_EFs_byCY_7-13-09_w no ctl EFs.xls.” Docket EPA-HQ-OAR-2011-

0135

23 U. S. EPA. 2009 Emission Factors for Locomotives. Office of Transportation and Air Quality, Assessment and 

Standards Division, Ann Arbor, MI EPA-420-F-09-25. Available at <

http://www.epa.gov/otaq/regs/nonroad/locomotv/420f09025.pdf>.

24 U. S. EPA. 2011. Spreadsheet “Tier_3_rail_transport_county level inventory revised July 11 2011.xlsx.” Docket 

EPA-HQ-OAR-2011-0135

25 U. S. EPA. 2011. Spreadsheet “Comparison_VMT_future_15jul2011.xlsx.” Docket EPA-HQ-OAR-2011-0135

26 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

27 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

28 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>.

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

30 U. S. EPA. 2011. Spreadsheet “Gas can adj for Tier 3_ABS.xlsx.” EPA Docket EPA-HQ-OAR-2011-0135

31 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.

32 U. S. EPA. 2013. EPAct/V2/E-89: Assessing the Effect of Five Gasoline Properties on Exhaust Emissions from 

Light-Duty Vehicles Certified to Tier 2 Standards: Final Report on Program Design and Data Collection. EPA 

Report No. EPA-420-R-13-004, March, 2013.
15

 

33 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

34 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.

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

Applications International, Inc.