SIP 106

GHG EMISSIONS
INVENTORY FOR
ASPHALT MIX
PRODUCTION
IN THE UNITED STATES
Current Industry Practices and
Opportunities to Reduce Future Emissions
Joseph Shacat
J. Richard Willis, Ph.D.
Ben Ciavola, Ph.D.
 6406 Ivy Lane, Suite 350, Greenbelt, MD 20770-1441
AsphaltPavement.org NAPA@AsphaltPavement.org
Tel: 301-731-4748 I Fax: 301-731-4621 I Toll Free: 1-888-468-6499

@NAPATweets /AsphaltPavement /company/AsphaltPavement

/c/NatlAsphaltPavement @GoAsphalt

The Road Forward is an initiative of the asphalt

pavement industry, with the committed support
of NAPA members, partners, and staff, to achieve
net zero carbon emissions by 2050.

Learn more about the initiative and find additional

resources at AsphaltPavement.org/Forward.

NAPA thanks the following members for their generous support of The Road Forward.

Sponsors shown as of June 28, 2022. Visit The Road Forward website to see additional partners or learn how to support this initiative.

ACKNOWLEDGMENTS
The authors would like to thank Heather Dylla for reviewing early drafts of this report and providing insightful
comments. The authors also thank Mark Buncher, John Hickey, Tom Lorenz, Amlan Mukherjee, and Ron Sines for
their time discussing the project approach, GHG emission reduction strategies, and data quality considerations.
Cover Photo: North Venice, FL, Asphalt Plant, courtesy Ajax Paving

SIP-106 published by and © National Asphalt Pavement Association, June 2022. All rights reserved. This publication
may not be republished or reproduced without written consent. Contact NAPA for more information.
 CONTENTS
Executive Summary..............................................................................................................................................2

1 Introduction............................................................................................................................................................4
1.1 Asphalt Mixture Materials and Production.....................................................................................................4
1.2 Goal and Scope........................................................................................................................................................5
1.3. Methodology............................................................................................................................................................6

2 GHG Emissions Inventory.....................................................................................................................7

2.1 General Trends in GHG Emissions....................................................................................................................8
2.2 Relative Contribution of Asphalt Mix Production to U.S. GHG Emissions.....................................9
2.3 Avoided Emissions Associated With Current Industry Practices....................................................10

3 Potential Emission Reductions from Deployment

of Available Technologies and Practices......................................................................... 13
3.1 Inputs and Assumptions for Emission Reduction Scenarios.............................................................. 13
3.1.1 Use of Recycled Materials........................................................................................................................... 14
3.1.2 Energy Inputs.................................................................................................................................................. 14
3.2 Results of Emission Reduction Scenarios.................................................................................................. 15

4 Research and Implementation Needs for More

Ambitious GHG Emission Reductions................................................................................ 18
4.1 Raw Materials (A1)................................................................................................................................................ 18
4.2 Transportation (A2)............................................................................................................................................ 19
4.3 Mix Production (A3)..........................................................................................................................................20

5 Summary and Conclusions............................................................................................................... 21

References.................................................................................................................................................................. 22

Appendix A – Assumptions and Data Inputs

for GHG Emission Calculations......................................................................................................... 26

Appendix B – Data Quality Considerations........................................................................ 31

1
 EXECUTIVE SUMMARY
The asphalt pavement production industry has From 2009 to 2019, the average cradle-to-
set an ambitious goal of achieving net zero gate emission intensity ranged from 50.2 to
greenhouse gas (GHG) emissions associated 52.1 kg CO2e /ton of mix produced. Based
with the production of asphalt pavements. on annual asphalt mix production rates, total
To reach net zero carbon, the industry must emissions ranged from 17.6 to 21.7 million metric
understand, identify, and continue to reduce tonne (MMT) CO2e per year, with the greatest
both the carbon intensity of materials used in, emissions occurring in 2019 due to that year’s
and energy consumption associated with, the increased production rates relative to prior
production of asphalt pavement mixtures. years. Cradle-to-gate emissions associated
with asphalt mix production represented
The focus of this report is to assess and approximately 0.3% of total U.S. GHG emissions
document a cradle-to-gate emissions inventory in 2019.
for asphalt pavement mixtures for the years
2009-2019. The emissions inventory includes In 2019, industry’s focus on environmentally
three primary life cycle stages: sustainable practices during asphalt mix
• A1 – GHG emissions associated with upstream production, like increasing recycled materials
raw materials inputs like extraction and and using lower-carbon fuels, reduced that
processing of asphalt binder, aggregate, and year’s total GHG emissions by 2.9 MMT CO2e,
asphalt modifiers; equivalent to the annual emissions from
• A2 – GHG emissions associated with approximately 630,000 passenger vehicles.
transportation of raw materials to the mix Almost 90% of these avoided emissions were
production facility; and achieved through the use of reclaimed asphalt
• A3 – GHG emissions associated with pavement (RAP). For example, each ton of RAP
production of asphalt pavement mixtures used in new asphalt mixtures reduced 2019
at the asphalt plant, including upstream GHG emissions by approximately 27 kg CO2e.
energy processes such as electricity Nationwide, increasing the amount of
production and transmission. RAP in new asphalt mixtures by one
percentage point (e.g., from 21.1% to
This report is the first national cradle-to-gate
assessment of GHG emissions associated with 22.1%) would result in 0.14 MMT CO2e
the production of asphalt pavement mixtures in avoided emissions, equivalent to the
focused on the A1-A3 life cycle stages. Unless annual emissions from approximately
indicated, GHG emission values identified in 36,000 passenger vehicles.
this report are cradle-to-gate and are intended
to convey the types of processes that might Cradle-to-gate GHG emissions could be
be implemented to reduce GHG emissions. reduced by up to 24% relative to 2019 emissions
Although this report provides an estimate by implementing certain environmentally
for the national average GHG emissions preferable technologies and practices including:
associated with asphalt mix production, it is • increased use of recycled materials;
not an industry average Environmental Product • increased use of natural gas as a burner fuel;
Declaration (EPD) and should not be used as • reduction of aggregate moisture content to
a benchmark for project-level decision making further reduce burner fuel consumption;
during procurement or project delivery.

2
• increased use of warm-mix asphalt (WMA) to achieve more significant GHG emission
technologies to reduce asphalt mix production reductions. Potential long-term research and
temperatures; and implementation strategies include the following:
• reduced electricity consumption through • Materials-related emission reduction strategies
energy efficiency measures. o Implementation of carbon capture,
utilization, and storage (CCUS)
Achieving such GHG emissions technologies during extraction of crude
reductions can be accelerated oils used for asphalt binder production
o Development and use of carbon-
by revising agency specifications that
sequestering bio-based binders and binder
currently limit the use of RAP and other extenders
recycled materials, and by offering o Development of carbon sequestering
economic incentives to offset the cost synthetic aggregates
of capital improvements, low-carbon • Transportation-related emission reduction
fuels, and reduced carbon intensity strategies
o Increased use of locally derived recycled
materials. Economic incentives may
materials in markets with limited local
include tax credits, grants, rebates,
supplies of natural aggregates
and project-level incentives. o Deployment of alternative fuels for trucking
operations
Even with widespread adoption of readily
• Mix production-related emission reduction
available technologies and practices, the 24%
strategies
reduction in GHG emissions is not sufficient o Use of alternative energy sources
to achieve net zero GHG emissions. New o Technologies that reduce burner fuel
technologies and additional innovative practices
consumption
will need to be developed and implemented

3
 1 INTRODUCTION
Asphalt pavements are the backbone of Asphalt mixtures are transported to the paving
America’s surface transportation infrastructure. jobsite by truck and placed while at elevated
With 94% of U.S. roads surfaced with asphalt temperatures. Approximately 3,000 asphalt
(FHWA, 2020a), pavement engineers choose plants across the United States produced 421.9
asphalt due to a combination of its engineering million tons of asphalt mixture in 2019 (Williams
properties and cost effectiveness. A national et al., 2020).
goal to reduce greenhouse gas (GHG)
emissions and achieve net zero by 2050 (Exec. Recycled materials are commonly used in
Order No. 14008, 2021) has been set, thus it asphalt mixtures to replace virgin aggregates,
becomes critically important to understand the asphalt binder, or both. Reclaimed asphalt
the role of the asphalt pavement industry pavement (RAP) is the most common recycled
in reducing emissions. This report material, with asphalt mixtures containing an
average RAP content of more than 21% of the
compiles the first national inventory
mix by weight (Williams et al., 2020). Recycled
of GHG emissions for the U.S. asphalt asphalt shingles (RAS) are also used in certain
pavement industry, explores the markets, typically constituting 1-5% of the mix
potential emission reductions that by weight in mixes that use RAS.
can be achieved through deployment
of readily available technologies and In accordance with FHWA’s Recycled
Materials Policy, recycled materials should
practices, and identifies future research
get first consideration in material selection
and implementation needs to further provided they are reviewed for engineering,
reduce GHG emissions. environmental, and economic suitability
(FHWA, 2015). Newcomb et al. (2016)
1.1 Asphalt Mixture Materials and Production provided an overview of the economic and
At the most basic level, asphalt mixtures are environmental benefits of using RAP and
composed of approximately 93-96% aggregates RAS in asphalt mixtures. They found that
and 4-7% asphalt binder. Asphalt binder is avoided GHG emissions of up to 16% can be
sometimes modified to enhance performance achieved for asphalt pavement materials and
by adding small quantities of polymers such as construction through use of RAP and RAS.
styrene-butadiene-styrene (SBS) or recycled Similarly, Williams et al. (2020) found that
tire rubber (RTR), typically less than 10% by use of RAP avoided 2.4 million metric tonnes
weight of asphalt binder, or less than 1% by (MMT) of GHG emissions and yielded $3.3
weight of total mix. Asphalt mixtures are billion in economic savings in 2019.
produced in asphalt plants, which use a rotary
drum to dry the aggregates and heat them to Polymers can increase the upstream GHG
approximately 300 °F. Asphalt plants can burn emissions associated with asphalt mixture
a variety of fuels, but the most common are production. For example, Mukherjee (2021) found
natural gas, used oil, propane, and diesel fuel. that an asphalt mixture that uses asphalt binder
The aggregates are then blended with asphalt modified with 3.5% SBS would increase cradle-
binder and recycled materials (as described in to-gate GHG emissions by 9%. On the other
the following paragraphs) to produce asphalt hand, a more holistic cradle-to-grave assessment
mixtures that are temporarily stored in silos. is needed to evaluate how the enhanced

4
performance of polymer modified asphalt binders of asphalt mixtures at reduced temperatures
that yield thinner pavement sections or longer avoided GHG emissions of 0.05-0.21 MMT in
lasting roads can offset the increased upfront 2019, depending on the actual temperature
emissions and potentially reduce overall life cycle reduction achieved.
GHG emissions (Butt et al., 2012).
1.2 Goal and Scope
Warm-mix asphalt (WMA) technologies allow This study has two primary goals. The first is to
asphalt mixtures to be produced at reduced estimate the total GHG emissions associated
temperature, typically in the range of 25-50°F with the U.S. asphalt mix production industry.
lower than conventional hot-mix asphalt (HMA), The second is to estimate the potential
although temperature reductions as high as emission reductions that can be achieved by
90 °F have been documented (NASEM, 2014). increased utilization of available practices and
WMA technologies are sometimes used as technologies. Under the life cycle framework
a compaction aid without reducing the mix provided in ISO 21930, the scope of this analysis
production temperature. Williams et al. (2020) focuses on cradle-to-gate emissions (Figure 1).
found that approximately 19% of asphalt This includes extraction and manufacturing of
mixtures produced in 2019 used WMA raw materials (A1), transporting those materials
technologies to reduce the mix production to the asphalt plant (A2), and plant operations
temperature at least 10°F. (An additional (A3). This is the same scope reported in
20% of asphalt mixtures produced in 2019 environmental product declarations (EPDs)
used WMA technologies as a compaction for asphalt mixtures (NAPA, 2022). This study
aid without reducing the mix production also includes an estimate of GHG emissions
temperature.) They estimated that production associated with end-of-life transport (C2).

CONSTRUCTION WORKS ASSESSMENT INFORMATION

Optional
supplementary
Construction Works Life Cycle Information Within the System Boundary information
beyond the system
boundary
A1-A3 A4-A5 B1-B7 C1-C4
Production Stage Construction Use Stage End-Of-Life Stage D
(Cradle-to-Gate) Stage
A1 A2 A3 A4 A5 B1 B2 B3 B4a B5 C1 C2 C3 C4
Refurbishment (ind. production,
Replacement (ind. production,

Deconstruction / Demolition
Maintenance (ind. production,

processing or disposal
Repair (ind. production,
Extractional upstream

of necessary materials)
of necessary materials)

of necessary materials)
transport, and disposal

of necessary materials)
transport, and disposal

transport, and disposal

transport, and disposal

Transport to factory

Transport to waste

Waste processing

Disposal of waste
Transport to site
Manufacturing

Potential net
production

Installation

benefits from reuse,

recycling, and/or
Use

energy recovery
beyond the system
boundary

B6 Operational Energy Use Scenario

B7 Operational Water Use Scenario

Figure 1. Life Cycle Framework under ISO 21930. This study focuses on the cradle-to-gate life cycle stages (A1-A3)
and end-of-life transport (C2).

5
While this study focuses on the cradle-to-gate The data inputs and methodology used for
emissions associated with asphalt mixture this study are generally consistent with the
production, a holistic life cycle approach is Product Category Rules (PCR) for Asphalt
required to fully understand the opportunities to Mixtures (NAPA, 2022) and therefore provide
reduce GHG emissions throughout the asphalt a reasonable first-order national benchmark
pavement value chain. Shacat et al. (2022) provide for GHG emissions reported in EPDs for asphalt
a detailed analysis of GHG emission sources and mixtures. However, this study is not intended
opportunities to reduce emissions throughout to be an industry average EPD and it does not
the asphalt pavement life cycle. meet the requirements for industry average
EPDs. Deviations from the PCR are discussed
1.3. Methodology in Appendix A.
A first-order estimate of the U.S. asphalt
pavement industry’s cradle-to-gate (A1-A3) The national average benchmark for cradle-
GHG emissions inventory for the years to-gate GHG emissions associated with
2009-2019 was calculated using the life asphalt mixture production is intended to
cycle assessment (LCA) model developed provide appropriate context to understand
by Mukherjee (2021). This study is the the impacts of policy changes and industry
first comprehensive assessment of GHG adoption of new technologies and practices
at the national level. However, it is not
emissions associated with asphalt mix
appropriate for use as an agency- or
production at a national level. The input project-level global warming potential
dataset was assembled from a combination of (GWP) limit or benchmark. Factors such
publicly available datasets that were used as aggregate transport distance, local
to compile a representative average asphalt availability of fuels, local availability of
plant (fuel and electricity consumption), recycled materials, regional climatic
mix design (aggregates, asphalt binder, and conditions, agency specifications, and other
recycled materials), and material transport variables can significantly affect cradle-to-
distances for each ton of mix produced in the gate GHG emissions. Agency- or project-
United States. GHG emissions for each life cycle level GWP limits or benchmarks should be
stage were then calculated in the openLCA established through a comprehensive program
software platform using the LCA model of collecting and analyzing EPDs developed
developed by Mukherjee (2021). A summary by asphalt pavement material suppliers for
of the assumptions, calculations, and data the mix types specified by the agency to
sources is provided in Appendix A. Data quality establish and account for regional and mix
considerations are discussed in Appendix B. type-specific variability.

Aberdeen, WA, Asphalt Plant, courtesy Lakeside Industries

6
 2 GHG EMISSIONS INVENTORY
Total cradle-to-gate (A1-A3) GHG emissions for asphalt binder content, despite the substantially
U.S. asphalt mix production (MMT CO2e) and increased RAP use in 2016 relative to 2009
emission intensity (kg CO2e/ton of mix produced) (Table A-2). This demonstrates the importance
are shown in Figure 2. Total cradle-to-gate of quantifying both RAP use and virgin
emissions ranged from 17.6 to 21.7 MMT CO2e asphalt binder use to calculate GHG emissions
per year. The dominant factors are emissions associated with asphalt mix production.
during the asphalt mix production stage (A3) and
extraction and processing of raw materials (A1). The cradle-to-gate emissions presented in
Figure 2 do not include emissions associated
The average cradle-to-gate emission intensity with transporting RAP from the paving jobsite
ranged from 50.2 to 52.1 kg CO2e/ton of mix to the initial storage or processing location,
produced. The lowest GHG emission intensity which is considered an end-of-life process
of 50.2 kg CO2e/ton, which was observed in (C2) under ISO 21930 (Figure 1). An industry
2012 and 2013, coincided with the industry’s survey indicated that the average C2 transport
highest percentage of natural gas consumption distance for RAP is 33 miles (Shacat, 2022).
for energy as a fuel (Table A-4), as well as the Table 1 presents GHG emissions associated
lowest virgin asphalt binder content (Table with end-of-life RAP transport (C2), which
A-2). The highest GHG emission intensity (52.1 were calculated using an emission factor for
kg CO2e/ton) was observed in 2009 and 2016, truck transport of 0.1514 kg CO2e/ton-mile per
with 2016 having the highest reported virgin Mukherjee (2021).

20.0 52.5

18.0

Emissions Intensity, kg CO2e/ton

52.0
Total Emissions, MMT CO2e

16.0

14.0 51.5

12.0
51.0
10.0
50.5
8.0

6.0 50.0
4.0
49.5
2.0

0.0 49.0
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Total Emissions (A1-A3) 18.7 18.5 18.7 18.1 17.6 17.9 18.6 19.5 19.5 20.2 21.7
Mix Production (A3) 8.1 8.1 8.2 8.0 7.7 7.7 8.0 8.2 8.4 8.6 9.4
Transportation (A2) 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 1.0 1.0
Materials (A1) 9.7 9.5 9.6 9.2 9.0 9.3 9.7 10.4 10.2 10.6 11.3
Emissions Intensity 52.1 51.4 51.0 50.2 50.2 50.7 51.0 52.1 51.5 51.9 51.4

Figure 2. Total cradle-to-gate (A1-A3) emissions and emission intensity for U.S. asphalt mix production, 2009-2019.
The vertical scale of the secondary y-axis (Emissions Intensity) has a non-zero intercept to better illustrate the
changes in emissions intensity over time.

7
Table 1. GHG emissions associated with transporting RAP from paving jobsites to the initial stockpiling or
processing location (C2).

Parameter Units 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

RAP Accepted by million

Mix Producers1 tons 67.2 73.5 79.1 71.3 76.1 75.8 78.0 81.8 79.9 101.1 97.0

GHG Emissions, End-of- MMT 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.5 0.5
Life RAP Transport (C2) CO2e 0.3

1 Asreported in the IS-138 series of documents, estimates are based on RAP used in asphalt mixtures, as aggregate, as cold-mix asphalt,
in other applications, and landfilled.

2.1 General Trends in GHG Emissions RAP were not sufficient to offset the
The highest annual cradle-to-gate GHG combined effects of decreased RAS utilization,
emissions value was observed in 2019. decreased utilization of natural gas as a burner
This coincided with the greatest annual mix fuel, relatively high modified asphalt binder
production tonnage during the period 2009- content, and increased annual mix production
2019 (Figure 3). This shows that the emission in 2019. (See Appendix A for annual data for
reductions associated with increased use of these parameters.)

25.0 500.0

Total Mix Production, million tons

20.0 400.0
Total Emissions, MMT CO2e

15.0 300.0

10.0 200.0

5.0 100.0

0.0 0.0
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Total Emissions (A1-A3) 18.7 18.5 18.7 18.1 17.6 17.9 18.6 19.5 19.5 20.2 21.7
Total Mix Production 358.4 359.9 366.0 360.3 350.7 352.0 364.9 374.9 379.4 389.3 421.9

Total Emissions (A1-A3) Total Mix Production

Figure 3. Total cradle-to-gate (A1-A3) GHG emissions and total mix production for the U.S. asphalt industry,
2009-2019.

8
2.2 Relative Contribution of Asphalt Mix inventory of 6,558.3 MMT CO2e (Table 2)
Production to U.S. GHG Emissions and 1.3% of industrial emissions.
The U.S. GHG Emissions Inventory (U.S.
While these may seem like small percentages,
EPA, 2021) provides a national context for
this does not mean that emissions associated
understanding the relative contribution of
with asphalt mix production are insignificant,
asphalt mix production to U.S. GHG emissions.
since no single industry represents more than
Table 2 presents total U.S. GHG emissions
a few percent of total industrial emissions. For
and emissions for key sectors (transportation,
example, process-related emissions from iron
highway transportation, and industrial) that
and steel production and cement production (a
are relevant to the asphalt mix production
material input for concrete) were 41.3 and 40.9
industry along with the relative emissions
MMT CO2e (respectively) in 2019 (also included
from asphalt mix production. The cradle-to-
in Table 2), roughly double the cradle-to-gate
gate emissions reported in this study include
emissions for asphalt mix production (Table
emissions from both the industrial sector and
2). The process-related emissions for iron and
the transportation sector as defined in the
steel production and cement production (e.g.,
U.S. GHG Emissions Inventory (U.S. EPA, 2021).
calcination from cement production) reported
in Table 2 do not include emissions from
Cradle-to-gate (A1-A3) GHG emissions fuel and electricity consumption and do not
for asphalt mix production in the represent the complete cradle-to-gate life
United States were approximately 21.7 cycle stages. Thus, these values are intended
MMT CO2e in 2019. This represents to provide a contextual reference even
though they have different scopes and are
0.3% of the total U.S. GHG emissions
not directly comparable.

North Shore Asphalt Facility, courtesy Barriere Construction, A CRH Co.

9
Table 2. Comparison of 2019 cradle-to-gate (A1-A3) GHG emissions for asphalt mix production to the U.S. emissions
inventory for related sectors.

Percentage
Percentage of Emissions
of U.S. for Sector from
2019 Emissions Asphalt Mix
Emissions, from Each Production,
Sector MMT CO2e Sector, 2019 Cradle-to-Gate

Total United States Emissions1 6,558.3 0.3%

Transportation Emissions from Fossil

Fuel Combustion2 1,821.9 27.8% 1.2%

Highway Transportation Emissions 1,481.2 22.6% 1.5%

from Fossil Fuel Combustion4

Industrial Emissions3 1,661.5 25.3% 1.3%

Iron and Steel Production and Metallurgical

Coke Production, Process Emissions5 41.3 0.6%

Cement Production, Process Emissions6 40.9 0.6%

Asphalt Mix Production, Cradle-to-Gate7 21.7 0.3%

1
From U.S. EPA (2021), Table ES-2.
2
From U.S. EPA (2021), Table ES-3.
3
From U.S. EPA (2021), Tables ES-3 and ES-4.
4
U.S. EPA (2021) indicates that 81.3% of the fossil fuel combustion emissions in the transportation sector reported in Table ES-3 was from cars
and trucks.
5
U.S. EPA (2021), Table ES-2. This value only includes process-related emissions (e.g., use of metallurgical coke) and does not include emissions
associated with fuel or electricity consumption during iron, steel, and metallurgical coke production. This value also does not include upstream
processes associated with raw material extraction or downstream processes associated with transportation and end product manufacturing.
6
From U.S. EPA (2021), Table ES-2. This value only represents process-related emissions during cement production (viz., calcination).
Calcination represents 60% of GHG emissions during cement production, and fuel combustion represents the remaining 40% of GHG emissions
(PCA, 2011). This value does not include GHG emissions from fuel combustion during cement production. It also does not include upstream
processes associated with raw material extraction or downstream processes associated with transportation and end product manufacturing.
7
This value represents cradle-to-gate emissions (A1-A3) as defined by ISO 21930. It includes upstream processes associated with extraction
and manufacturing of raw materials and downstream processes associated with transportation (i.e., transporting those materials to the asphalt
plant), and end product manufacturing (i.e., plant operations).

Emissions from the transportation sector projects in Virginia were caused by vehicle fuel
are included in Table 2 to provide additional consumption during the use stage.
context since asphalt pavements are a critical
part of transportation infrastructure. Emissions 2.3 Avoided Emissions Associated
associated with asphalt mix production are with Current Industry Practices
equal to 1.5% of emissions from highway The asphalt pavement industry has a long
transportation, which is consistent with history of using recycled materials, such as
Chappat and Bilal (2003), who found that RAP and RAS, and adopting other technologies
vehicle emissions were 10 to 400 times and practices to reduce environmental impacts.
greater than emissions associated with Such practices include the choice of fuels
materials, construction, and maintenance consumed for asphalt mix production, stockpile
of the roads they travel on. Similarly, Amarh management to reduce aggregate moisture
et al. (2021) found that 98% of the life cycle content and reduce burner fuel consumption,
GHG emissions for recycled asphalt pavement adoption of WMA technologies, and electrical

10
system upgrades such as variable frequency vehicles assuming typical passenger
drives for high-powered motors. The dataset vehicle emissions of 4.6 tonne CO2e per
used in this analysis provides an opportunity
year (U.S. EPA, 2018).
to quantify the direct impact of two of
these practices: use of recycled materials Fuel Consumption
and the choice of fuels consumed for asphalt The U.S. industrial sector consumption of
mix production. natural gas represented 51.7% of total fossil fuel
consumption in 2019 (EIA, 2021a). The blend of
Use of RAP and RAS fuels consumed by the asphalt mix production
To assess avoided emissions from the asphalt industry is significantly cleaner, in part due to
pavement industry’s use of RAP and RAS, a greater natural gas consumption (69%).
scenario was developed in which no RAP or
RAS is used, and the average virgin binder To assess the avoided emissions associated
content of asphalt mixtures increased by with the blend of fuels consumed by the asphalt
adding the estimated recycled binder content mix production industry relative to the U.S.
of RAP and RAS. Use of RAP and RAS industrial sector as a whole, a scenario was
yielded 3.0 MMT in avoided cradle-to-gate developed in which the 2019 average relative
GHG emissions in 2019, compared to what consumption of natural gas was adjusted to
the emissions would be if no RAP or RAS 51.7% and the other fuels (diesel fuel, residual
were used. Most of the avoided emissions fuel oil, propane, and used oil) were adjusted
(approximately 2.9 MMT CO2e) were from use according to their 2019 relative quantities.
of RAP due to the relatively low quantities The output from this scenario indicates that
of RAS used in asphalt mixtures. Adding the the asphalt mix production industry’s 2019
emissions associated with end-of-life RAP emissions would increase by 0.4 MMT CO2e if
transport (C2, see Table 1) reduces the avoided the relative consumption of natural gas were
emissions associated with use of RAP to 2.4 comparable to the overall U.S industrial sector.
MMT CO2e. The benefits of avoided emissions
from not sending RAP and RAS to a landfill Overall Avoided Emissions
are not accounted for in this estimate. from Current Industry Practices
Together, the use of recycled materials and the
Each ton of RAP used in new asphalt mixtures blend of fuels consumed during asphalt mix
in 2019 resulted in 27 kg CO2e of avoided production resulted in avoided emissions of
upstream emissions. Assuming a payload 3.4 MMT CO2e in 2019 (Figure 4). Including the
of 20 tons per truckload of RAP, approximately GHG emissions associated with end-of-life RAP
1 metric tonne CO2e of avoided emissions can transport (Table 1) reduces the avoided GHG
be achieved for every two truckloads of RAP emissions associated with industry practices
that are used in new asphalt mixtures. to 2.9 MMT. Assuming that a typical passenger
vehicle emits 4.6 tonne CO2e per year (U.S. EPA,
Nationwide, increasing the amount of 2018), the avoided emissions of 2.9 MMT CO2e
RAP in new asphalt mixtures by one from the industry’s use of recycled materials
percentage point (e.g., from 21.1% to and the blend of fuels consumed relative to
22.1%) would result in 0.14 MMT CO2e the U.S. industrial sector are equivalent to the
annual emissions of approximately 630,000
in avoided emissions, equivalent to
passenger vehicles.
approximately 30,000 passenger

11
 25.0 0.4
Avoided
Emissions 3.0

20.0
Total Emissions, MMT CO2e

15.0

Actual
21.7
Emissions
10.0

5.0

0.0
2019

Cradle-To-Gate Emissions (A1-A3) Benefit from Use of RAP and RAS Benefit from Mix of Fuels

Figure 4. Cradle-to-Gate (A1-A3) GHG emissions and avoided emissions achieved through use of recycled materials
and type of fuel consumed at asphalt plants in 2019.

Gillette, WY, Asphalt Plant, courtesy Simon, a Colas Co.

12
3 POTENTIAL EMISSION REDUCTIONS
FROM DEPLOYMENT OF
AVAILABLE TECHNOLOGIES
AND PRACTICES
Technologies and practices already exist that 3.1 Inputs and Assumptions for
asphalt mix producers can use to help the Emission Reduction Scenarios
United States meet its goal of achieving net Three scenarios were developed to evaluate
zero GHG emissions in all sectors by 2050. the potential emission reductions that can
To this end, a scenario analysis was conducted be achieved over short-term, intermediate,
to quantify the additional emission reductions and long-term time horizons. A summary
that are readily achievable. The practices that is provided in Table 3 of the operational
were evaluated include increased use of recycled improvements that would be needed for
materials, increased use of natural gas as a each scenario. Details regarding each emission
burner fuel, reduction of aggregate moisture reduction practice are provided below.
content, increased use of WMA technologies to
reduce asphalt mix production temperatures,
and reduced electricity consumption through
energy efficiency measures.

Table 3. General parameters for GHG emission reduction scenarios.

Parameter 2019 Baseline Short-Term Intermediate Long-Term

RAP Content 21% 25% 30% 40%

Natural Gas Consumption as

69% 72% 75% 90%
Percentage of Fuel Combusted

Aggregate Moisture
N/A 0.25% 0.50% 1.0%
Content Reduction

Asphalt Mix Production

N/A 10 °F 25 °F 40 °F
Temperature Reduction

Reduction in Electricity
3.32 kWh/ton 5% 10% 20%
Consumption Intensity

N/A – National baseline has not been established.

13
3.1.1 Use of Recycled Materials in existing agency specifications (Williams
et al., 2020). However, adoption of Balanced
Use of RAP Mix Design (BMD) specifications offers an
As previously discussed, use of RAP reduces opportunity to increase the use of recycled
upstream GHG emissions by replacing virgin materials with confidence that pavement life
materials and reducing upstream emissions will meet or exceed agency expectations
associated with raw material extraction and (Yin and West, 2021).
processing. Under the short-term, intermediate,
and long-term scenarios, the industry’s average 3.1.2 Energy Inputs
RAP content would increase from the 2019 Many options are available to reduce GHG
baseline of 21% to 25, 30, and 40%, respectively. emissions associated with energy consumption
Mix composition under these scenarios was during asphalt mix production. For this analysis,
calculated consistent to the methodology four specific practices were considered:
presented in Appendix A. Other relevant increasing the percentage of natural gas
parameters, including total mix production, RAS consumed as a burner fuel, decreasing the
content, and raw material transport distances, aggregate moisture content, utilizing WMA
were held constant at the 2019 baseline. technologies to reduce mix production
temperature, and reducing the intensity of
Accelerated test track studies have shown that electricity consumption through energy
asphalt mixtures with RAP contents as high as conservation measures. The assumptions
50% can perform extremely well if designed and for each of these practices are provided in
constructed appropriately (West et al., 2021). this section. The resulting energy inputs for
The most significant barrier to increasing use the short-term, intermediate, and long-term
of RAP in new asphalt mixtures is limitations scenarios are provided in Table 4.

Table 4. Energy parameters for GHG emission reduction scenarios.

Parameter Units 2019 Baseline Short-Term Intermediate Long-Term

Electricity million kWh 1,400.7 1,330.7 1,260.6 1,120.6
Reduction in percent N/A 5% 10% 20%
Electrical Intensity
Fuel Consumption trillion Btu 121.9 114.9 105.7 93.6
Reduction in percent N/A 6% 13% 23%
Fuel Intensity
Diesel Fuel million gal 120.3 104.0 85.4 30.3

Natural Gas million MCF 81.5 79.6 76.3 81.1

Propane million gal 72.0 62.3 51.1 18.1
Residual Fuel Oil million gal 13.8 11.9 9.8 3.5
Used Oil million gal 86.8 75.0 61.6 21.8

14
Type of Fuel Consumed Btu/°F/ton (NASEM, 2014). For this analysis, a
The asphalt mix production industry already conservative assumption of 1,000 Btu/°F/ton
uses clean-burning natural gas at a higher was used. For the short-term, intermediate, and
rate than the U.S. manufacturing industry (see long-term scenarios, average mix production
Section 2.3). To assess the potential reductions temperature reductions of 10, 25, and 40 °F
that could be achieved by further increasing were modeled.
use of natural gas, the three scenarios adjust
the amount of natural gas in the 2019 mix of Electrical Energy Efficiency
fuels from a baseline of 69% to 72, 75, and 90%, There are numerous opportunities to reduce
respectively. The quantities of other fuels were electricity consumption at asphalt plants. For
adjusted to be consistent relative to each other. this analysis, reductions in electrical intensity of
5, 10, and 20% were modeled for the short-term,
Generally, natural gas is considered the burner intermediate, and long-term emission reduction
fuel of choice for asphalt plants due to its scenarios. Capital improvements such as
low cost, reduced emissions, and reduced installation of variable frequency drives (VFDs)
maintenance requirements relative to liquid for motors, pumps, and fans can substantially
fuels. When natural gas is not available, plants decrease electricity consumption. Energy
typically burn used oil or diesel fuel instead. efficiency measures that aim to decrease burner
However, there is a growing market for fuel consumption through more efficient heating
using liquid natural gas (LNG), which can and drying of aggregates also tend to decrease
be easily transported to asphalt plants by electricity consumption by reducing the volume
truck (Johns, 2019). of air handled by the baghouse fan. According
to the Fan Laws, the change in electrical power
Reduction of Aggregate Moisture Content required to run a fan is proportional to the cube
A significant amount of energy is required to of the change in air volume (Neese, 2019). Thus,
evaporate aggregate moisture in an asphalt a modest reduction in air volume can yield a
plant. At a nominal aggregate moisture content significant reduction in fan power. For example,
of 5%, evaporation accounts for more than 40% a co-benefit of reducing the aggregate moisture
of burner fuel consumption. Methods to reduce content is a reduction in the volume of exhaust
the moisture content of aggregates include gas (water vapor) that must be handled by the
sloping the grade under stockpiles, paving baghouse fan. Reducing the aggregate moisture
under stockpiles, and building structures to content by 1% (e.g., from 5% to 4%) would
cover stockpiles (Young, 2007). For the short- reduce the fan volume required for a drum plant
term, intermediate, and long-term scenarios, by 14% (Young, 2007), allowing for a substantial
the effects of reducing aggregate moisture by reduction in electricity consumption.
0.25, 0.5, and 1% were evaluated by reducing
the average energy intensity for asphalt mix 3.2 Results of Emission Reduction Scenarios
production by 27,100 Btu/ton for each 1% Potential GHG emissions associated with
reduction in aggregate moisture per Young achieving these short-term, intermediate,
(2007). For example, the asphalt mix and long-term emission reduction scenarios
production energy intensity was reduced are provided in Figure 5. The inputs and
by 6,775 Btu/ton for the 0.25% aggregate assumptions associated with these scenarios
moisture reduction scenario. are described in Section 3.1. Achievement of
these goals would reduce total cradle-to-gate
Use of WMA Technologies to Reduce (A1-A3) GHG emissions associated with asphalt
Mix Production Temperature mix production by 5, 12, and 24%, respectively.
WMA technologies have been demonstrated This demonstrates that meaningful reductions
to reduce burner fuel consumption by 1,100 in GHG emissions can be achieved through

15
adoption of readily available technologies conservative nature of engineers and agencies’
and practices such as increased use of RAP, aversion to risk. On the other hand, agency
increased utilization of natural gas as a adoption of BMD policies offers an opportunity
burner fuel, management of aggregate to allow industry to increase the use of RAP and
stockpiles to reduce moisture content, and other innovative materials without sacrificing
use of WMA technologies to reduce mix mixture quality and performance.
production temperatures.
Another policy barrier to increased use of RAP
While accelerating the adoption of these is the practice by a few agencies of retaining
readily available technologies and practices ownership of RAP instead of transferring
is technologically feasible, doing so may be ownership to the paving contractor. Typically,
hindered by policy and economic barriers. From these agencies use the RAP for low-value
a policy perspective, the industry’s use of RAP applications such as shoulder dressing and
is often constrained by agency specifications maintenance of unpaved roadways, both of
(Williams et al., 2020). But revising agency which could be substituted by using unbound
specifications across the country is a daunting aggregates. Policies that allow paving
task. There are hundreds of specifying agencies contractors to retain ownership and recycle
that include state departments of transportation RAP into new asphalt mixtures would yield
(DOTs), tollway authorities, local governments, net GHG emission reductions due to reduced
federal agencies, and others. The process of upstream emissions from avoided use of virgin
revising specifications can take years due to the asphalt binder.

20.0
Total Emissions, MMT CO2e

15.0
5% Reduction 12% Reduction 24% Reduction

10.0

5.0

0.0
2019 Baseline Short Intermediate Long-Term
Total (A1-A3) 21.7 20.6 19.1 16.5
Mix Production (A3) 9.4 8.8 8.0 6.8
Transportation (A2) 1.0 1.0 1.0 0.9
Raw Materials (A1) 11.3 10.8 10.1 8.8

Figure 5. Potential cradle-to-gate GHG emissions associated

with achieving short-term, intermediate, and long-term goals.

16
Economic barriers represent another obstacle Even with widespread adoption of readily
to adopting these readily available technologies available technologies and practices, the 24%
and practices due to the low bid environment of reduction in GHG emissions modeled in these
the asphalt paving industry. Financial incentives scenarios is not sufficient to achieve net zero
such as tax credits and rebates to offset the cost emissions across the asphalt paving industry.
of capital improvements would help accelerate The following section describes the research
industry adoption of energy efficiency retrofits. and implementation efforts that are needed to
Financial incentives, including mechanisms such achieve more ambitious GHG emissions based
as corporate tax credits, grants, and project level on the current state of knowledge.
incentives, could also help offset the differential
costs of low-carbon fuels and materials.

Jacksonville, FL, Asphalt Plant, courtesy Duval Asphalt

17
4 RESEARCH AND IMPLEMENTATION
NEEDS FOR MORE AMBITIOUS
GHG EMISSION REDUCTIONS
New technologies and practices will need to 4.1 Raw Materials (A1)
be developed and implemented to achieve
more significant GHG emission reduction goals Asphalt Binder
associated with the cradle-to-gate stages From a raw materials perspective,
(A1-A3) of asphalt mix production. Potential asphalt binder production is the most
materials-related emission reduction strategies
significant contributor of upstream
include the implementation of carbon capture,
utilization, and storage (CCUS) technologies GHG emissions in an asphalt mixture,
during extraction of crude oils used for asphalt comprising 94% of the emissions
binder production, development and use associated with raw materials (A1)
of carbon-sequestering bio-based binders and 53% of cradle-to-gate emissions
and binder extenders, and development of (A1-A3) (Shacat et al., 2022).
carbon-sequestering synthetic aggregates. Some aspects of asphalt binder production,
Transportation-related emission reduction such as transportation of crude oil and finished
strategies include the increased use of locally products within the binder production value
derived recycled materials in markets with chain, are likely to see reduced GHG emissions
limited local supplies of natural aggregates in the coming years as a result of national and
and deployment of alternative fuels for international commitments to reduce GHG
trucking operations. Potential strategies for emissions in the transportation sector. But the
reducing emissions associated with asphalt most significant contributor to GHG emissions
mix production include use of alternative within the asphalt binder production value
energy sources and use of technologies that chain is crude oil extraction (Figure 6), which is
reduce the intensity of burner fuel consumption. largely driven by the GHG intensity of extracting
These strategies are evaluated in more detail Canadian oil sands (Asphalt Institute, 2019).
in this section. Despite ongoing efforts to reduce the GHG
emissions during oil sand extraction through
CCUS technologies, significant policy-related
and economic hurdles must be overcome to
reduce the carbon footprint of this process
(Israel et al., 2020). To put it simply, CCUS will
continue to be cost prohibitive until significant
economic incentives are available.

18
 Terminal Operations
0.101 kg CO2e/kg binder
16% Crude Oil Extraction
0.403 kg CO2e/kg binder
63%

Asphalt Binder Transport

0.033 kg CO2e/kg binder
5%

Refinery Operations
0.077 kg CO2e/kg binder
12%

Crude Oil Transport

0.023 kg CO2e/kg binder
4%

Figure 6. GHG Emissions Associated with Asphalt Binder Production. From Asphalt Institute (2019).

Another opportunity to reduce the upstream Aggregates

GHG emissions associated with asphalt binder The GHG emissions associated with extracting
is the use of carbon-sequestering bio-based and processing aggregates are relatively
binders and binder extenders. Various small, limiting the potential of reducing GHG
feedstock materials have been investigated, emissions by substituting virgin materials with
including animal fat, palm oil, lignin, and swine recycled materials. However, the development
manure (Kousis et al., 2020; Khandelwal, of synthetic aggregates offers an opportunity
2019; Samieadel et al., 2018). A review of to sequester atmospheric CO2 into the mineral
alternative asphalt binder extenders indicates structure of the aggregates (Rowland, 2020).
that performance of pavements made with This technology was developed for the concrete
these materials is a primary concern from industry and has not been evaluated or tested
an engineering perspective, although the for use in asphalt mixtures.
BMD framework allows an opportunity to
address this concern through performance 4.2 Transportation (A2)
testing during the asphalt mix design process Transportation of raw materials represents
(Hand, 2018). A significant research effort a relatively minor portion of the cradle-to-
will be needed to further develop these gate (A1-A3) GHG emissions associated
with asphalt mix production at a national
innovative asphalt binder technologies,
level, but can be significant in markets
assess their life cycle GHG emissions, with limited aggregate supplies due to local
and bring them to market.

19
geology and other supply constraints (Shacat et that the ability of LCFS programs to actually
al., 2022). In these areas, use of locally derived mitigate climate change is an area of active
recycled aggregate materials (including RAP) research and debate (Plevin et al., 2017).
can be leveraged as an opportunity to reduce
transportation-related GHG emissions. Another potential energy source is
electrification of process heating requirements
Another opportunity to reduce GHG emissions at asphalt plants to replace burner fuels
associated with transportation is the altogether. While microwave technologies
development and deployment of alternative have been developed for producing asphalt
fuels for trucking operations, including pavements (e.g., Lombardo, 2015), no such
advanced biofuels such as renewable diesel units are commercially available. An analysis
and renewable natural gas, hydrogen fuel of electrifying thermal processes in
cells, and battery electric heavy-duty vehicles other industries suggests that various
(Shacat et al., 2022). How quickly these technologies may be available, although
technologies are adopted in the asphalt mix economic considerations present barriers to
production supply chain will depend on their implementation (Hasanbeigi et al., 2021).
cost effectiveness and the availability of financial
incentives to accelerate implementation. Reducing Burner Fuel Consumption Intensity
As documented in this report, asphalt mixtures
4.3 Mix Production (A3) produced at reduced temperatures using WMA
The primary source of GHG emissions technologies can reduce the energy intensity
during asphalt mix production is burner fuel of asphalt mix production. The mix production
consumption for the heating and drying temperature reductions achieved with most
of aggregates. There are many different WMA technologies are generally in the range of
pathways to significantly reduce emissions 25-50 °F (Prowell et al., 2012). A practical limit
from burner fuel consumption beyond the to the reductions in fuel consumption using
energy efficiency measures modeled in this WMA technologies is the need to completely
study. They can generally be classified as either dry the aggregates to ensure proper coating
use of alternative energy sources or use of and adhesion of the asphalt binder to the
technologies that reduce the intensity of aggregates. Development and implementation
burner fuel consumption. of technologies that are not constrained by
this limitation, generically referred to as half-
Alternative Energy Sources warm mix asphalt, offers an opportunity to
Alternative energy sources for burner fuel further reduce mix production temperatures
consumption include use of low carbon and substantially reduce the energy intensity of
fuels and electrification of process heating asphalt mix production (EAPA, 2014). Another
requirements. Programs at the state level such option is adoption of cold central plant recycling
as California’s Low Carbon Fuel Standard (LCFS) (CCPR) technology, which produces asphalt
have accelerated production and consumption mixtures with high RAP contents at ambient
of low carbon fuels including renewable natural temperatures (FHWA, 2020b). Further research,
gas (RNG), biodiesel, and renewable diesel in including the ongoing National Cooperative
that state’s transportation sector (Boutwell, Highway Research Program (NCHRP) 09-62
2018). Development of similar programs for project, Rapid Tests and Specifications for
the industrial sector could enable supply of Construction of Asphalt-Treated Cold Recycled
low carbon fuels for asphalt mix production at Pavements, is needed to support broader
competitive prices. It should be noted, however, deployment of CCPR technologies.

20
 5 SUMMARY AND CONCLUSIONS
This report compiled the first national to increase the industry’s use of RAP and
assessment of the U.S. asphalt paving industry’s other recycled materials, with BMD offering a
GHG emissions during the cradle-to-gate stages performance-based mix design framework that
(A1-A3) of asphalt mixture production and end- does not compromise pavement performance.
of-life transport (C2) for asphalt pavements for To ensure competitiveness in a low bid
the period 2009-2019. The industry’s cradle-to- environment, economic incentives such as tax
gate GHG emissions represented 0.3% of total credits, rebates, and project level incentives
GHG emissions in the United States in 2019. can help offset the increased cost of capital
Current practices related to the use of recycled improvements and the differential cost of other
materials and the type of fuel consumed by low carbon technologies.
asphalt plants resulted in avoided emissions
of 2.9 MMT in 2019, equivalent to the emissions Significant research and implementation
of 630,000 passenger vehicles. efforts will be needed to achieve more
ambitious GHG emission reductions in support
A scenario analysis was conducted to evaluate of the U.S. goal of reaching net zero GHG
the potential emission reductions associated emissions in the U.S. economy by 2050. The
with adoption of readily available technologies following areas were identified as key priorities
and practices including: for research and implementation:

• increased use of recycled materials, • Reduction in upstream emissions associated

• increased use of natural gas as a burner fuel, with asphalt binder production, particularly
• reduction of aggregate moisture content to with respect to emissions during extraction
reduce burner fuel consumption, of Canadian oil sands;
• increased use of WMA technologies to reduce • The potential use of carbon-sequestering bio-
asphalt mix production temperatures, and based asphalt binders and binder extenders;
• reduced electricity consumption through • The potential use of carbon-sequestering
energy efficiency measures. synthetic aggregates;
• Development and deployment of alternative
Achieving short-term, intermediate, and fuels for trucking and other material transport
long-term goals could reduce the industry’s activities;
cradle-to-gate GHG emissions by 5, 12, • Use of alternative energy sources for asphalt
and 24%, respectively, relative to 2019 mix mixture production, including low carbon
production and emissions (Figure 5). Several biofuels and electrification of process heating
policy changes are needed to accelerate equipment; and
adoption of the technologies and practices • Reducing burner fuel consumption through
needed to achieve these emission reductions. development and deployment of half-warm
Revision of agency specifications is required mix asphalt and CCPR technologies.

21
 REFERENCES
Amarh, E.A., S.W. Katicha, G.W. Flintsch, and B.K. Diefenderfer (2021). Life-Cycle Impact Assessment
of Recycled Pavement Projects in Virginia (VTRC 22-R12). Virginia Transportation Research Center,
Charlottesville, Virginia. https://www.virginiadot.org/vtrc/main/online_reports/pdf/22-R12.pdf.

Asphalt Institute (2011-2020). Annual Asphalt Usage Surveys for the United States and Canada,
2010-2019.

Asphalt Institute (2019). Life Cycle Assessment of Asphalt Binder. M. Wildnauer, E. Mulholland, and
J. Liddie. Asphalt Institute, Lexington, Kentucky. https://www.asphaltinstitute.org/engineering/life-cycle-
assessment-of-asphalt-binder/.

Boutwell, M. (2018). LCFS 101 – An Update. Stillwater Associates. https://stillwaterassociates.com/

lcfs-101-an-update/. Website accessed on June 7, 2021.

Butt, A.A., B. Birgisson, and N. Kringos (2016). Considering the benefits of asphalt modification
using a new technical life cycle assessment framework. Journal of Civil Engineering and
Management, vol. 22, pp 597-607. https://www.tandfonline.com/doi/abs/10.3846/13923730.2014.
914084.

Chappat, M. and J. Bilal (2003). Sustainable Development: The Environmental Road of the Future:
Life Cycle Analysis. Colas, Paris, France.

EAPA (2014). The Use of Warm Mix Asphalt: EAPA – Position Paper. European Asphalt Pavement
Association, Brussels, Belgium. https://eapa.org/download/15118/.

EIA (2013). Manufacturing Energy Consumption Survey: 2010 MECS Survey Data. U.S. Energy
Information Administration. https://www.eia.gov/consumption/manufacturing/data/2010/.

EIA (2017). Manufacturing Energy Consumption Survey: 2014 MECS Survey Data. U.S. Energy
Information Administration. https://www.eia.gov/consumption/manufacturing/data/2014/.

EIA (2018). 2018 Manufacturing Energy Consumption Survey: Form EIA-846. U.S. Energy
Information Administration. https://www.eia.gov/survey/form/eia_846/form_a.pdf.

EIA (2021a). March 2021: Monthly Energy Review. Report No. DOE/EIA-0035(2021/3).
U.S. Energy Information Administration, Washington, DC. https://www.eia.gov/totalenergy/data/
monthly/archive/00352103.pdf.

EIA (2021b). Manufacturing Energy Consumption Survey: 2018 MECS Survey Data. U.S. Energy
Information Administration, Washington, DC. https://www.eia.gov/consumption/manufacturing/
data/2018/.

22
Exec. Order No. 14008 (2021). Executive Order on Tackling the Climate Crisis at Home and Abroad.
86 Fed. Reg. 7619. https://www.regulations.gov/document/EPA-HQ-OPPT-2021-0202-0012.

FHWA (2015). FHWA Recycled Materials Policy. Federal Highway Administration, Washington, DC.
https://www.fhwa.dot.gov/legsregs/directives/policy/recmatpolicy.htm. Website accessed on
June 7, 2021.

FHWA (2020a). Highway Statistics 2019, Table HM-12. Federal Highway Administration,
Washington, DC. https://www.fhwa.dot.gov/policyinformation/statistics/2019/hm12.cfm.
Website accessed on October 15, 2021.

FHWA (2020b). In-Place and Central-Plant Recycling of Asphalt Pavements in Virginia

(FHWA-HIF-10-078). Federal Highway Administration, Washington, D.C. https://www.fhwa.dot.gov/
pavement/sustainability/case_studies/hif19078.pdf.

Hand, A. (2018). Impact of Alternative Asphalt Binder Extenders on Asphalt Mixture Design,
Production and Performance. University of Nevada, Reno, Nevada. https://scholarworks.unr.edu/
handle/11714/8109.

Hasanbeigi, A., L.A. Kirshbaum, B. Collison, and D. Gardiner (2021). Electrifying U.S. Industry:
A Technology- and Process-Based Approach to Decarbonization. Renewable Thermal Collaborative,
Arlington, Virginia. https://www.renewablethermal.org/wp-content/uploads/2018/06/Electrifying-
U.S.-Industry-2.1.21-1.pdf.

ISO 21930:2017 Sustainability in buildings and civil engineering works – Core rules for environmental
product declarations of construction products and services. International Organization for
Standardization, Geneva, Switzerland. https://www.iso.org/standard/61694.html.

Israel, B., J. Gorski, N. Lothian, C. Severson-Baker, and N. Way (2020). The Oil-Sands in a
Carbon-Constrained Canada: The Collision Course Between Overall Emissions and National Climate
Commitments. Pembina Institute, Calgary, Alberta, Canada. https://www.pembina.org/reports/the-
oilsands-in-a-carbon-constrained-canada-march-2020.pdf.

Johns, S. (2019). Switching to LNG Can Simplify Life for Asphalt Manufacturers. Asphalt Contractor.
https://www.forconstructionpros.com/asphalt/plants/article/21033058/switching-to-lng-can-
simplify-life-for-asphalt-manufacturers.

Khandelwal, M. (2019). Carbon footprint of Lignin modified Asphalt mix: A tree to gate LCA
assessment (30 ECTS Master thesis). Utrecht University, Utrecht, Netherlands. https://www.
researchgate.net/publication/333654681_Carbon_footprint_of_Lignin_modified_Asphalt_mix.

Kousis, I., C. Fabiani, L. Ercolanoni, A.L. Pisello (2020). Using bio-oils for improving environmental
performance of an advanced resinous binder for pavement applications with heat and noise
island mitigation potential. Sustainable Energy Technologies and Assessments, vol. 39. https://doi.
org/10.1016/j.seta.2020.100706.

23
Lombardo, J. (2015). 100% Recycled Asphalt a Reality with Low Energy Asphalt Pavement
Technology. Asphalt Contractor. https://www.forconstructionpros.com/asphalt/plants/article/
12070022/recycled-asphalt-pavement-takes-a-giant-leap-with-low-energy-asphalt-pavement.

Miller, L. (2020). Emerald Eco-Label: Methods for Correctness Checks. National Asphalt Pavement
Association, Greenbelt, Maryland. https://www.asphaltpavement.org/uploads/documents/EPD_
Program/Emerald_Eco-Label_CorrectnessCheckMethodology.pdf.

Mukherjee, A. (2016). Life Cycle Assessment of Asphalt Mixtures in Support of an Environmental

Product Declaration. National Asphalt Pavement Association, Lanham, Maryland. https://www.
asphaltpavement.org/uploads/documents/EPD_Program/NAPA_LCA_2016.pdf.

Mukherjee, A. (2021). Updates to the Life Cycle Assessment for Asphalt Mixtures in Support of
the Emerald Eco Label Environmental Product Declaration Program. National Asphalt Pavement
Association, Greenbelt, Maryland. https://www.asphaltpavement.org/uploads/documents/
Programs/Emerald_Eco-Label_EPD_Program/PCR_Public_Comment_Period/LCA_Asphalt_
Mixtures_07_29_2021.pdf.

NAPA (2022). Product Category Rules (PCR) for Asphalt Mixtures. National Asphalt Pavement
Association, Greenbelt, Maryland. https://www.asphaltpavement.org/uploads/documents/EPD_
Program/NAPA_PCR_AsphaltMixtures_v2.pdf.

National Academies of Sciences, Engineering, and Medicine (NASEM) (2014). Field Performance of
Warm Mix Asphalt Technologies. Washington, DC: The National Academies Press. https://www.nap.
edu/catalog/22272/field-performance-of-warm-mix-asphalt-technologies.

Neese, E. (2019). Understanding and Applying the 3 Basic Fan Laws. Eldridge Ventilation and
Noise Control. https://eldridgeusa.com/blog/understanding-and-applying-the-3-basic-fan-laws/.
Website accessed on June 7, 2021.

Newcomb, D.E., J.A. Epps, and F. Zhou (2016). Use of RAP & RAS in High Binder Replacement
Asphalt Mixtures: A Synthesis (SR-213). National Asphalt Pavement Association, Lanham, Maryland.
https://member.asphaltpavement.org/Shop/Product-Catalog/Product-Details?productid=
{99A571B7-7701-EA11-A811-000D3A4DBF2F}.

Plevin, R.J., M.A. Delucchi, M. O’Hare (2017). Fuel carbon intensity standards may not mitigate
climate change. Energy Policy, vol. 105, pp 93-97. https://www.sciencedirect.com/science/article/
abs/pii/S030142151730112X.

PCA (2011). Carbon Footprint – Integrated Paving Solutions. Portland Cement Association,
Washington, DC. https://www.cement.org/docs/default-source/th-paving-pdfs/sustainability/
carbon-foot-print.pdf.

Prowell, B.D., G.C. Hurley, and B. Frank (2012). Warm-Mix Asphalt: Best Practices, 3rd Ed. (QIP-125).
National Asphalt Pavement Association, Lanham, Maryland. https://member.asphaltpavement.org/
Shop/Product-Catalog/Product-Details?productid={79A571B7-7701-EA11-A811-000D3A4DBF2F}.

24
Rowland, J. (2020). Artificial Aggregates: New Technologies to Produce Artificial Aggregates Have
the Potential to Dramatically Mitigate Manmade Emissions of Carbon Dioxide and Help Close the
Circular Economy Loop. Rock Products, July 6, 2020. https://rockproducts.com/2020/07/06/
artificial-aggregates/.

Samieadel, A., K. Schimmel, E.H. Fini (2018). Comparative life cycle assessment (LCA) of
bio-modified binder and conventional asphalt binder. Clean Technologies and Environmental Policy,
vol. 20, pp. 191-200. https://doi.org/10.1007/s10098-017-1467-1.

Shacat, J. (2022). Asphalt Pavement Industry Survey on RAP Haul Distance. Report in preparation.

Shacat, J., J. R. Willis, and B. Ciavola (2022). The Carbon Footprint of Asphalt Pavements: Life Cycle
Considerations for Agencies and Industry. Report in preparation.

U.S. Census Bureau (2021). Economic Census: All Sectors: Geographic Area Series: Economy-Wide
Key Statistics: 2012. https://data.census.gov/cedsci/table?q=324121&tid=ECNBASIC2012.EC1200A1.
Website accessed on May 25, 2021.

U.S. EPA (2000). Hot Mix Asphalt Plants Emission Assessment Report (EPA-454/R-00-019).
U.S. Environmental Protection Agency, Research Triangle Park, North Carolina. https://www.epa.
gov/sites/default/files/2020-10/documents/ea-report.pdf.

U.S. EPA (2018). Questions and Answers: Greenhouse Gas Emissions from a Typical Passenger
Vehicle (EPA-420-F-18-008). U.S. Environmental Protection Agency, Washington, DC. https://nepis.
epa.gov/Exe/ZyPDF.cgi?Dockey=P100U8YT.pdf.

U.S. EPA (2021). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2019
(EPA430-R-21-005). https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-
and-sinks-1990-2019.

West, R., D. Timm, B. Powell, N. Tran, F. Yin, B. Bowers, C. Rodezno, F. Leiva, A. Vargas, F. Gu, R.
Moraes, and M. Nakhaei (2021). Phase VII (2018-2021) NCAT Test Track Findings (NCAT Report
21-03). National Center for Asphalt Technology, Auburn, Alabama. https://www.eng.auburn.edu/
research/centers/ncat/files/technical-reports/rep21-03.pdf.

Williams, B.A., J.R. Willis, and J. Shacat (2020). Annual Asphalt Pavement Industry Survey on
Recycled Materials and Warm-Mix Asphalt Usage: 2019, 10th Annual Survey (IS 138). National
Asphalt Pavement Association, Greenbelt, Maryland. https://member.asphaltpavement.org/Shop/
Product-Catalog/Product-Details?productid=%7b9BC71D4C-2307-EA11-A812-000D3A4DBC41%7d.

Yin, F. and R. West (2021). Balanced Mix Design Resource Guide (IS-143). National Asphalt
Pavement Association, Greenbelt, Maryland. https://member.asphaltpavement.org/Shop/Product-
Catalog/Product-Details?productid={695C89AA-A56B-EB11-A812-000D3A984636}.

Young, T.J. (2007). Energy Conservation in Hot-Mix Asphalt Production (QIS-126). National Asphalt
Pavement Association, Lanham Maryland. https://member.asphaltpavement.org/Shop/Product-
Catalog/Product-Details?productid={7DA571B7-7701-EA11-A811-000D3A4DBF2F}.

25
 APPENDIX A
ASSUMPTIONS AND DATA INPUTS
FOR GHG EMISSION CALCULATIONS
General Approach components: virgin aggregates, neat asphalt
GHG emissions were calculated with openLCA binder, modified asphalt binder, RAP, and RAS.
software using the LCA model developed by The average mix designs were derived from a
Mukherjee (2021). combination of the annual Asphalt Pavement
Industry Survey on Recycled Materials and
The input data and methodology for calculating Warm-Mix Asphalt Usage (NAPA’s IS-138 series
GHG emissions in this study are generally of reports e.g., Williams et al., 2020) and the
consistent with the Product Category Rules Asphalt Institute’s (AI’s) annual Asphalt Usage
(PCR) for Asphalt Mixtures (NAPA, 2022) Survey for the United States and Canada
to maintain consistency with the emissions (Asphalt Instutute, 2011-2020). Raw data inputs
reported in EPDs for asphalt mixtures. However, to the mix design calculations are provided in
there are some deviations from the PCR Table A-1. Average mix design compositions for
requirements due to limitations related to each year are provided in Table A-2. Calculation
data availability: methodologies are explained below.

• Many of the data inputs such as fuel The mix design percentage for each component
consumption, electricity consumption, represents the reported or calculated
and transportation distances are estimated consumption of that component divided by
based on extrapolation from industry surveys total mix production. For example, in 2019,
conducted by NAPA and government 421.9 million tons of mix were produced in the
agencies. In contrast, the PCR for Asphalt U.S. and 921,000 tons of RAS were consumed,
Mixtures requires these parameters to be yielding an average RAS composition of 0.22%
directly collected as primary data. (Williams et al., 2020).
• With the exception of modified asphalt
binders, the upstream emissions (A1) For each year, the virgin aggregate content for
associated with manufacturing mix additives the average mix design was calculated using
and binder additives are not accounted for. Equation 1:
• The downstream emissions (A3) associated
with transporting and processing off-spec MCAgg =100-(BCNeat +BCMod +MCRAP +MCRAS )
materials and waste generated during asphalt
plant operations (e.g., startup and shutdown where MCAgg is the virgin aggregate content,
waste) are not accounted for. BCNeat is the neat asphalt binder content, BCMod
• The operational emissions (A3) associated is the modified asphalt binder content, MCRAP
with transporting portable asphalt plants is the RAP content, and MCRAS is the RAS
are not accounted for. content, all expressed as percentages of total
mix by weight.
Raw Material Inputs (A1)
An average mix design was developed for each
year, with the mix design comprised of five

26
Table A-1. Material quantities used to calculate average mix design compositions, 2009-2019.

Total Quantity, million tons

Parameter
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Mix Production1 358.4 359.9 366.0 360.3 350.7 352.0 364.9 374.9 379.4 389.3 421.9
Asphalt Binder Use,
N/A 12.3 11.0 12.6 12.6 13.0 13.5 14.3 13.7 14.3 15.3
Neat2

Asphalt Binder Use,

N/A 2.1 2.1 2.1 1.9 2.0 2.2 2.4 2.7 2.6 2.7
Modified2
RAP Use1 56.1 62.1 66.7 68.3 67.8 71.9 74.2 76.9 76.2 82.2 89.2
RAS Use1 0.7 1.1 1.2 1.9 1.6 2.0 1.9 1.4 0.9 1.1 0.9

1
From IS-138 series of reports (e.g., Williams et al., 2020).
2
From Asphalt Institute (2011-2020).

Table A-2. Average mix design composition for asphalt mixtures produced in the United States, 2009-2019.

Average Mix Design Composition

Parameter
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Asphalt Binder Content,
Neat (BCNeat) 3.69% 3.60% 3.49% 3.49% 3.58% 3.69% 3.69% 3.80% 3.60% 3.69% 3.63%

Asphalt Binder Content,

Modified (BCMod) 0.62% 0.60% 0.67% 0.58% 0.55% 0.57% 0.59% 0.65% 0.71% 0.68% 0.65%

RAP Content, Average

(MCRAP) 15.65% 17.26% 18.23% 18.96% 19.33% 20.42% 20.33% 20.51% 20.08% 21.11% 21.14%

RAS Content, Average

(MCRAS) 0.20% 0.31% 0.33% 0.52% 0.47% 0.56% 0.53% 0.37% 0.25% 0.27% 0.22%

Aggregate Content,
79.84% 78.23% 77.30% 76.45% 76.06% 74.75% 74.85% 74.66% 75.35% 74.25% 74.36%
Average (MCAgg)

NAPA’s IS-138 series of reports provide Where BCTotal is the total asphalt binder content
annualized total mix production, RAP use, and in the mix, BCRAP is the recycled asphalt binder
RAS use for all years, allowing MCRAP and MCRAS content from RAP, and BCRAS is the recycled
to be easily calculated for the entire time series. asphalt binder content from RAS, all expressed
AI’s Annual Asphalt Usage Survey provides as percentages of total mix by weight. We
the neat and modified paving asphalt binder assume that RAP has a 5% binder content and
consumption for the years 2010-2012. Because RAS has a 20% binder content. BCRAP and BCRAS
the AI survey reports provide reported asphalt were calculated by multiplying these binder
usage data without estimating total asphalt contents by MCRAP and MCRAS, respectively.
binder consumption, a reasonableness check
was established to ensure data quality. For the A minimum value of 5% was established for the
reasonableness check, the total asphalt binder total asphalt binder content reasonableness
content was calculated according to Equation 2: check. The total asphalt binder content
exceeded the reasonableness check for all years
BCTotal =BCNeat +BCMod+BCRAP+BCRAS except 2010 and 2011 (Figure A-1). This suggests
that neat and modified asphalt binder usage may
have been under-reported for 2010 and 2011.

27
 This approach assumes
5.60% that the total asphalt
5.40% binder content in 2009
Total Asphalt Binder Content

was equal to the total

5.20%
asphalt binder content
5.00% in 2012. It also assumes
the relative percentages
4.80%
of neat and modified
4.60% asphalt binder usage
in 2009 were equal
4.40%
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 to the values reported
for 2010.
Figure A-1. Total asphalt binder content based on reported use of neat and modified
asphalt binder and estimated use of RAP and RAS (see Equation 2).
Modified asphalt
binder was assumed
For the years 2012-2019, BCNeat and BCMod were to be modified using 3.5% SBS, which is the
calculated directly using the neat and modified most conservative (the highest emissions
asphalt binder usage data from AI’s Annual intensity) of the three modified asphalt
Asphalt Usage Survey reports. binder datasets provided by Asphalt Institute
(2019). The upstream impacts associated
For 2010 and 2011, the virgin asphalt binder with manufacturing and transporting other
content was calculated according to Equation 3: mix additives and binder additives are not
accounted for in this study due to a lack of
BCVirgin,n=BCTotal,2012-BCRAP,n-BCRAS,n available estimates regarding the types and
quantities of additives used on a national basis.
Where BCVirgin,n is the virgin asphalt binder
content for year n, BCTotal,2012 is the total asphalt Transportation (A2 and C2)
binder content for 2012, BCRAP,n is the recycled Average transportation distances are provided
asphalt binder content from RAP for year in Table A-3. All material transportation was
n, and BCRAS,n is the recycled asphalt binder assumed to be via truck. The average transport
content from RAS for year n, all expressed as distances reported by Mukherjee (2016) were
percentages of total mix by weight. BCNeat and used for aggregates and asphalt binder.
BCMod were then calculated for 2010 and 2011 by The RAP transport distance was broken down
multiplying BCVirgin,n by the relative percentage into two components based on the LCA cut-
of neat and modified asphalt binder usage off method using data collected in an industry
reported for each of these years. This approach survey (Shacat, 2022). End-of-life RAP transport
assumes that the total asphalt binder content (C2) is the distance from the paving jobsite
in 2010 and 2011 was equal to the total asphalt to the initial stockpile or processing location.
binder content in 2012. It also assumes there Processed RAP transport (A2) is the weighted
was no bias in the apparent under-reporting average distance from the initial stockpile or
of neat and modified asphalt binder in 2010 processing location to the asphalt plant.
and 2011.
The RAS transport distance was assumed to be
For 2009, BCNeat and BCMod were calculated 50 miles per Mukherjee (2016). This conservative
using the same method as 2010 and 2011, estimate accounts for transport that occurs
except the relative percentages of neat and during the A2 stage (from the processing
modified asphalt for 2010 were applied. This was location to the asphalt plant). NAPA intends to
necessary because the AI Annual Asphalt Usage refine this estimate through an industry survey
Survey Reports did not provide data for 2009. in 2022.
28
 provided by NAPA’s IS-138 series of reports,
Mix Production Energy Consumption (A3) the annual Asphalt Pavement Industry Survey
The Manufacturing Energy Consumption Survey on Recycled Materials and Warm-Mix Asphalt
(MECS), jointly conducted by the U.S. Energy Usage (e.g., Williams et al., 2020). The average
Information Administration (EIA) and the blend of fuels for each year (Table A-4) was
U.S. Census Bureau, was used to estimate the then multiplied by the total fuel consumption
average blend of fuels consumed by asphalt for the respective year to calculate the
plants. The average blend of fuels consumed total quantity of each fuel (in thermal units)
(Table A-4) for the years 2010, 2014, and 2018 consumed per year (Table A-5).
was calculated using the Energy Consumption
as a Fuel data reported in Tables 3.2 and 3.5 Annual fuel consumption for asphalt mix
of EIA (2013, 2017, and 2021b) for the Asphalt production in the United States was then
Pavement Mixture and Block sector (NAICS converted from thermal units to physical
Code 324121). The average blend of fuels was units, as reported in Table A-6. Conversion
interpolated for the intermediate years (2011- factors are provided in Table A-7. Table A-6
2013 and 2015-2017) and held constant for also reports annual electricity consumption
2009 and 2019 (e.g., the 2010 average blend of based on the average electricity consumption
fuels was also used for 2009). of 3.32 kWh/ton reported by Mukherjee
(2016). The electricity region was set to the
The MECS dataset provides a good estimate national average rather than defining a
for the relative percentage of fuels consumed regional balancing authority.
during asphalt mix production. However, it’s
not a reliable source for total fuel consumption It should be noted that although energy
because it significantly underestimates the efficiency measures and use of WMA
number of asphalt plants in the U.S., which technologies at asphalt plants have reduced
leads to an underestimate of the total fuel energy intensities during the period 2009-2019,
consumption (see discussion in Appendix there is insufficient data to quantify this effect
B). Also, mix production is not collected in on a national level. For example, although the
the MECS dataset, complicating efforts to MECS survey is collected every four years,
estimate and benchmark mix production energy the dataset does not include a key parameter
intensity. Instead, the average fuel consumption (mix production) that would be required
of 0.289 MMBtu/ton reported by Mukherjee to calculate the energy intensity of mix
(2016) was used. This value was multiplied by production. In contrast, the industry-wide LCA
the total annual mix production to quantify conducted by Mukherjee (2016) provides an
the total annual fuel consumption (Table A-5). estimate for average energy intensity, but this
Estimates of total annual mix production were is only for a snapshot in time.

Table A-3. Average transportation distances.

Material Distance Units Reference

Aggregates 21.5 ton-miles/ton Mukherjee (2016)

Asphalt Binder 3.9 ton-miles/ton Mukherjee (2016)

RAP – Jobsite to Processing Site (C2) 33 ton-miles/ton Shacat (2022)

RAP – Processing Site to Plant (A2) 7.2 ton-miles/ton Shacat (2022)

RAS – Processing Site to Plant (A2) 50 ton-miles/ton Mukherjee (2016)

29
Table A-4. Average blend of fuels consumed by the U.S. asphalt mix production industry.1

Parameter Units 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Residual Fuel Oil % of Fuel 4.9% 4.9% 4.6% 4.3% 4.0% 3.7% 3.2% 2.7% 2.2% 1.7% 1.7%
Diesel Fuel % of Fuel 19.7% 19.7% 17.1% 14.5% 11.9% 9.3% 10.3% 11.4% 12.5% 13.6% 13.6%
Natural Gas % of Fuel 63.9% 63.9% 67.4% 70.9% 74.3% 77.8% 75.7% 73.6% 71.6% 69.5% 69.5%
Propane (HGL)2 % of Fuel 1.6% 1.6% 1.7% 1.7% 1.8% 1.9% 2.7% 3.5% 4.3% 5.1% 5.1%
Used Oil3 % of Fuel 9.8% 9.8% 9.2% 8.6% 8.0% 7.4% 8.1% 8.8% 9.5% 10.2% 10.2%

1
Data for 2010, 2014, and 2018 are derived from EIA (2013), EIA (2017), and EIA (2021b), respectively. Relative fuel consumption percentages
are interpolated for intermediate years (e.g., 2011-2013) and held constant for 2009 and 2019 (e.g., 2010 values were used for 2009).
Percentages for individual years may not total 100 due to rounding.
2
HGL is hydrocarbon gas liquids. This parameter may include other fuels such as ethane, ethylene, propylene, butane, and butylene. This
parameter is assumed to be propane for this study.
3
Used oil includes other fuels and waste oils (e.g., biodiesel and used cooking oil) not otherwise quantified in EIA (2013, 2017, and 2021b).

Table A-5. Annual fuel consumption for U.S. asphalt mix production, 2009-2019, thermal units.

Parameter Units 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Mix Production 1
million tons 358.4 359.9 366.0 360.3 350.7 352.0 364.9 374.9 379.4 389.3 421.9
Total Fuel
trillion Btu 103.6 104.0 105.8 104.1 101.3 101.7 105.5 108.3 109.6 112.5 121.9
Consumption2
Residual Fuel Oil3 trillion Btu 5.1 5.1 4.9 4.5 4.1 3.8 3.4 2.9 2.4 1.9 2.1
Diesel Fuel3 trillion Btu 20.4 20.5 18.1 15.1 12.0 9.4 10.9 12.4 13.7 15.3 16.5
Natural Gas3 trillion Btu 66.2 66.5 71.3 73.8 75.3 79.1 79.8 79.8 78.5 78.2 84.7
Propane (HGL)3 trillion Btu 1.7 1.7 1.8 1.8 1.8 1.9 2.8 3.8 4.7 5.7 6.2
Used Oil3 trillion Btu 10.2 10.2 9.8 9.0 8.1 7.5 8.5 9.5 10.4 11.4 12.4

1
Mix production estimates are from NAPA’s IS-138 series of reports (e.g., Williams et al., 2020).
2
Total Fuel Consumption is based on an assumption of 0.289 MMBtu/ton per Mukherjee (2016).
3
Fuel quantities are calculated by multiplying Total Fuel Consumption by the relative percentage of fuel reported in Table A-4. Values reported
here may vary slightly due to rounding.

Table A-6. Annual electricity and fuel consumption for U.S. asphalt mix production, 2009-2019, physical units.1

Parameter Units 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Electricity 1
million kWh 1,190 1,195 1,215 1,196 1,164 1,169 1,212 1,245 1,260 1,292 1,401
Residual Fuel Oil million gal 34.0 34.2 32.6 30.0 27.1 25.2 22.6 19.5 16.1 12.7 13.8
Diesel Fuel million gal 148.3 148.8 131.3 109.6 87.5 68.5 79.3 89.9 99.6 111.0 120.3
Natural Gas million MCF 63.7 64.0 68.6 71.0 72.5 76.2 76.8 76.8 75.5 75.2 81.5
Propane (HGL) million gal 19.7 19.8 20.8 21.1 21.2 21.9 32.6 43.6 54.5 66.4 72.0
Used Oil million gal 71.3 71.6 68.3 62.8 56.9 52.8 59.8 66.7 72.8 80.1 86.8

1
Electricity consumption is based on an assumption of 3.32 kWh/ton per Mukherjee (2016).

Table A-7. Conversion factors for fuel

consumption calculations. From EIA (2018).

Parameter Value Units

Residual Fuel Oil 6.287 million Btu/bbl
Diesel Fuel 5.773 million Btu/bbl
Natural Gas 1.039 million Btu/MCF
Propane (HGL) 0.0861 million Btu/gal
Used Oil 6 million Btu/bbl
Volume Conversion 42 gal/bbl

30
 APPENDIX B
DATA QUALITY CONSIDERATIONS
Total Mix Production and Virgin Asphalt Binder Consumption
Recycled Material Contents Quantities for neat and modified asphalt
The estimates of total mix production and binder consumption are based on voluntary
recycled material contents provided in participation in AI’s Annual Asphalt Usage
NAPA’s IS-138 series are based on relatively Survey. The annual survey reports publish
large datasets, with the number of plants asphalt sales at the retail level as reported
that participate in each annual survey by terminals and refineries. The reports
ranging from 1,027 to 1,328. Geographical are unaudited and unverified. They do not
representativeness is good, with nearly all estimate asphalt binder use, suggesting that
50 states represented in most years. Other actual asphalt binder usage might be higher
measures of representativeness include the than reported. For the 2014 usage report,
relative percentages of the number of asphalt AI’s member manufacturers and first sellers
plants and total mix production covered in represented approximately 92% of the asphalt
the IS-138 series. and road oil supply reported by the EIA.
Therefore, any variance between reported
There are various estimates for the number usage and actual usage of asphalt binder is
of asphalt plants in the United States. The likely to be within about 10%. This variance
U.S. Environmental Protection Agency (EPA) was only evaluated for 2014.
estimated that there were 3,600 asphalt
plants in 1996 (U.S. EPA, 2000). In contrast, Despite the potential under-reporting of actual
the U.S. Census Bureau estimated a total of asphalt binder usage, AI indicated that the
1,324 establishments in 2012 with a primary paving asphalt binder usage is likely over-
North American Industrial Classification reported, since the reported values include
System (NAICS) code of 324121, Asphalt asphalt binder that is subsequently converted
Pavement Mixture and Block Manufacturing to asphalt emulsion by customers. Additionally,
(U.S. Census Bureau, 2021). The Census Bureau the modified asphalt binder usage is likely
likely underestimates the number of asphalt under-reported, since some of the neat asphalt
plants since it is organized by primary NAICS binder is subsequently modified by customers.
code; asphalt plants that are co-located with These uncertainties have not been quantified.
other operations may be categorized under (M. Buncher, personal communication, February
other NAICS codes. Another estimate of the 25, 2022)
number of asphalt plants can be calculated
by dividing the total annual asphalt mix In addition to the uncertainties associated
production by the average annual mix with the reported values of neat and modified
production per plant reported in NAPA’s asphalt binder consumption, the actual type
IS-138 series, which suggests a range of and quantity of modifiers used is unknown.
2,700 to 3,000 asphalt plants. The assumption that 3.5% SBS is representative
of all modified binders was selected because it’s
the most conservative (highest GHG emissions)
of the modified asphalt binder products
reported by Asphalt Institute (2019).

31
Transportation of Raw Materials Survey (MECS), which includes relative standard
The average transportation distances reported errors for all parameters that are generally
by Mukherjee (2016) for aggregates and below 5%. However, the MECS data suggest
asphalt binder are based on sample sizes of 15 a total population size for the number of U.S.
and 19 plants, respectively. With such a small asphalt plants in 2010, 2014, and 2018 of 1,338,
sample size, these estimates are subject to 1,285, and 1,289, respectively (EIA, 2013, 2017,
large uncertainties. and 2021b). This is less than half the number
of estimated U.S. asphalt plants. It’s unknown
The average transportation distances reported whether or to what extent any bias in the
by Shacat (2022) for RAP are based on an MECS data would affect the blend of fuels
industry survey representing 124 companies consumed for asphalt mix production used in
and 756 asphalt plants. Confidence in the RAP this analysis. Thus, the uncertainty for these
transport distances is high. values is unquantifiable.

Energy Intensity of Asphalt Mix Production Additives

Mukherjee (2016) reported an average energy Asphalt mixtures and asphalt binders often
intensity of 289,000 Btu/ton of mix produced include small quantities of additives to
with a 95% confidence interval of +_ 52,000 Btu/ improve pavement performance or provide
ton based on a survey of approximately 50 other desirable qualities, such as enhancing
asphalt plants. A separate analysis by Miller workability during paving operations.
(2020) of user data entered in the Emerald With the exception of asphalt modifiers,
Eco-Label environmental product declaration additives are not accounted for in this study.
(EPD) software for 43 asphalt plants indicated Additive quantities are typically less than 1%
an average energy intensity of 290,000 of the mix by weight, and many mixes do not
_ 74,000 Btu/ton. Given the consistency of
+ include any additives. There are no publicly
average mix production energy intensities from available estimates of the quantity of additives
two independent datasets, confidence in the used in the U.S. asphalt pavement industry.
estimate used for this study is high. There is also relatively little publicly available
information on the carbon footprint of most
Blend of Fuels Consumed asphalt additives. Information regarding the
for Asphalt Mix Production upstream GHG emissions associated with
The blend of fuels consumed for asphalt mix asphalt additives remains an important data
production is based on data reported in the gap for informed decision-making (Shacat
EIA’s Manufacturing Energy Consumption et al., 2022).

32