EPA/AA/CTAB/PA/81-16
REV. //1/Oct 81
Technical Report
Gasoline Equivalent Fuel Economy Determination
for Alternate Automotive Fuels
by
Craig A. Harvey
August, 1981
revised October, 1981
NOTICE
Technical Reports do not necessarily represent final EPA decisions
or positions. They are intended to present technical analysis or
summaries of programs from work which is currently being
conducted. The purpose in the release of such reports is to
facilitate the exchange of technical information and to inform the
public of programs and technical developments which may form the
basis for a final EPA decision, position or regulatory action.
Control Technology Assessment and Characterization Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, Noise and Radiation
U.S. Environmental Protection Agency
2565 Plymouth Road
Ann Arbor, Michigan 48105
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GASOLINE - EQUIVALENT FUEL ECONOMY DETERMINATION
Abstract
Due to the growing interest in and use of alternate automotive fuels, it is
necessary that EPA provide a method of calculating fuel economy values for
these vehicles than using fuels so that average fuel economies of
manufacturers can be determined. The relevant legislation is reviewed, and
various methodologies are discussed.
Possible fuel equivalency factors are presented for Diesel fuel, ethanol,
methanol, gasohol, and natural gas. A methodology is recommended that takes
into account the energy content of the fuel, the energy required to
manufacture the fuel, and the value of the raw material used to make the
fuel.
I. Introduction
A. Recommendation
In order to comply with the provisions of the Energy Policy and Conservation
Act (EPCA, PL 94-163) (1)* and the Chrysler Corporation Loan Guarantee Act
(PL 96-185) (2), which call for a determination of "... that quantity of any
other fuel which is the equivalent of one gallon of gasoline," it is
recommended that for the purpose of calculating the ?uel Econonry Values for
vehicles fueled wich fuels which differ substantially from gasoline, a
methodology similar to that used by Department of Energy (DOE) for electric
vehicles (3) be applied. This methodology would account for fuel energy
content and final processing energy requirement, and indirectly for energy
input in the earlier processing steps.
In essence, this methodology would consist of taking the mile-per-gallon
result from a vehicle test on an alternate (non-gasoline) liquid fuel and
adjusting it by (1) the energy content ratio of gasoline to the alternate
fuel (LIIV, BTU/gal), (2) the ratio of processing energy efficiency of the
alternate fuel to the efficiency of a petroleum refinery, and (3) the ratio
of raw material costs of gasoline to those of the alternate fuel.
* Numbers in parentheses indicate references at the end of the report
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The equation is:
FE = MPGalt. x LHVgas. x Salt, x Vgas.
LHValt. Egas. Valt.
where:
FE = gasoline equivalent Fuel Economy
MPGalt. = Mile per gallon test result for Alternate Fuel
LHVgas. = Lower heating value, standard test gasoline (BTU/gal)
LHValt. = Lower heating value, alternate fuel (BTU/gal)
Ealt. = Energy efficiency of processing plant, alternate fuel
Egas. = Energy efficiency of petroleum refinery (%)
Vgas. = Raw material value, gasoline (^/million BTU)
Valt. = Raw material value, alternate fuel (^/million BTU)
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B. Purpose of Report
With the increasing national emphasis on energy conservation and energy
independence, in conjunction with rapidly rising gasoline; costs, the
transportation industry, the energy industry, the U.S. Government, and other
interested parties are putting more attention on development of
vehicles/engines that either utilize petroleum fuels more efficiently or make
more use of fuels derived from domestic energy resources. Some examples of
this are the increased production of Diesel vehicles, the marketing of
Gasohol, the development of alcohol-fueled vehicles, and the development of
electric vehicles.
This report is intended to provide some of the basis for a decision on the
most appropriate methodology for calculating the gasoline "equivalent fuel
economy of a vehicle that uses fuel other than gasoline. Once this
methodology has been determined, it will provide vehicle manufacturers with a
way to gauge the effects of alternative marketing options on their average
fuel economy.
C. Background
C.I. Legislation
a) The Energy Policy and Conservation Act
The Energy Policy and Conservation Act (EPCA) mandates that the Secretary of
Transportation establish average fuel economy standards for major automobile
manufacturers and importers (production above 10,000 cars per year) beginning
with the 197.8 model year, as shown in Table 1. The 1980 standard was 20.0
mpg. The standard will increase progressively until the average fuel economy
is 27.5 mpg, as required in 1985. The standard is to be met by each
manufacturer and by each importer and applies to the total number of cars
produced or imported.
Civil penalties are prescribed for a violator of the law: $5 for each tenth
of a mile-per-gallon that their corporate average falls below the
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Table 1.
Automotive Average
Fuel Economy Standards Under
the Energy Policy and
Conservation Act
Model Year Standard (mpg)
1978
1979
1980
1981
1982
1983
1984
1985 and
thereafter
18.0
19.0
20.0
22.0
24.0
26.0
27.0
27.5*
*The Secretary of Transportation may alter this to the
"maximum feasible average fuel economy", but such action
may be disapproved by Congress for levels below 26.0 mpg
or above 27.5 mpg.
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year's standard, multiplied by the number of cars produced orr imported that
year. The National Energy Conservation Policy Act, P.L. 95-619, grants the
Secretary of Transportation the authority to raise this penalty up to $10 for
each tenth of a mile-per-gallon beginning in the 1981 model year. Credits for
exceeding the standard are calculated in a similar manner.
For purposes of EPCA, "The term 'fuel economy' means the average number of
miles traveled by an automobile per gallon of gasoline (or equivalent amount
of other fuel) consumed, as determined by the EPA Administrator in accordance
with procedures established under section 503 (d)."
Section 503 (d) contains the EPA mandate for activity on the fuel equivalency
issue: " (1) Fuel economy for any model type shall be measured, and average
fuel economy of a manufacturer shall be calculated, in accordance with
testing and calculation procedures established by the EPA Administrator, by
rule..." and " (2) The EPA Administrator shall, by rule, determine that
quantity of any other fuel which is the equivalent of one gallon of gasoline."
Therefore, it is necessary to know what is meant by "equivalent" and what
factors are included in it. Other references to equivalency in EPCA are as
follows:
Section 105 (b)(l) "... an average daily volume of 1,600,000
barrels of crude oil, natural gas liquids equivalents, and
natural gas equivalents. (2) one barrel of natural gas
equivalent equals 5,626 cubic feet of natural gas measured at
14.73 pounds per square inch (MSL) and 60 degrees Fahrenheit.
(3) one barrel of natural gas liquids equivalent equals 1.454
barrels of natural gas liquids at 60 degrees Fahrenheit."
These values for quantities of natural gas and natural gas liquids that are
equivalent to 1 barrel of crude oil are determined simply from the ratio of
average energy content (heating value) of the fuels. There is no attempt to
include any additional factors such as processing or transport energy
requirements.
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In Title III, Part B of EPCA, which deals with consumer products in general,
these definitions are given:
Section 321(a)(4) "The term 'energy use' means the quantity
of energy directly consumed by a consumer product at point of
use, determined in accordance with test procedures under
section 323. (5) The term 'energy efficiency' means the ratio
of the useful output of services from a consumer product to the
energy use of such product, determined in accordance with test
procedures under section 323."
Section 322(6)(2)(B) "The Btu equivalent of one
kilowatt-hour is 3,412 British thermal units."
From this it is apparent that the scope of consideration for these products
includes only the energy consumed at the final point of use, and equivalency
is determined by the direct conversion factor without including any
additional energy input factors.
The objective of EPCA is to accomplish the purposes listed below:
"SEC.2. The purposes of this act are-
(1) To grant specific standby authority to the President,
subject to Congressional review, to impose rationing, to
reduce demand for energy through the implementation of energy
conservation plans, and to fulfill obligations of the United
States under the international energy program;
(2) to provide for the creation of a Strategic Petroleum
Reserve capable of reducing the impact of severe energy supply
interruptions;
(3) to increase the supply of fossil fuels in the United
States, through price incentives and production requirements;
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(4) to conserve energy supplies through energy conservation
programs, and, where necessary, the regulation of certain
energy uses;
(5) to provide for improved energy efficiency of motor
vehicles, major appliances, and certain other consumer
products;
(6) to reduce the demand for petroleum products and natural
gas through programs designed to provide greater availability
and use of this Nation's abundant coal resources; and
(7) to provide a means for verification of energy data to
assure the reliability of energy data."
Examining EPCA, it is apparent that each of these points has been dealt with
by specific sections of EPCA. For instance, points three and six, above are
dealt with in Title I, "Matters Related to Domestic Supply Availability", Part
A, "Domestic Supply" and in Title IV, "Petroleum Pricing Policy and Other
Amendments to the Allocation Act"; point one is dealt with in Title II,
"Standby Energy Authorities", and in Title V, part C, "Congressional Review".
Point seven is dealt with in Title V, Part A, "Energy Data Base and Energy
Information".
The above mentioned points do not deal with automotive fuel use' at all, except
in a very indirect way, which leaves points four and five. Point four is
covered by Title III, Parts A - E of EPCA, which provide energy conservation
programs for the automotive sector, other consumer products, state energy use,
industrial energy use, and federal energy use. Point five is a narrower
application of point four and is dealt with in the first two parts of Title
III, which are (A) "Automotive Fuel Economy" and (B) "Energy Conservation
Program for Consumer Products Other Than Automobiles".
The average fuel economy program is one of the programs called for in point
four, and it is the only program from EPCA that addresses energy use by
currently available automobiles. Average fuel economy as put forth in EPCA
for gasoline-fueled vehicles, addresses only the energy efficiency of the
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vehicle itself in terms of miles per gallon. It does not include any
provision for considering the energy efficiency of drilling, refining or fuel
transport operations.
Therefore, there is nothing in EPCA itself which provides for the inclusion of
factors other than vehicle energy efficiency in the calculation of fuel
economy.
However, there is a House-Senate conference report (4) which accompanied the
bill to make EPCA law. That report explained the differences between the
House and Senate versions of the bill and explained what the compromise
version ("conference substititue") was. Regarding fuel equivalency the
conference report states, "It is anticipated that the EPA Administrator, in
determining 'equivalent amount of other fuel1 will make such determination on
the basis of BTU equivalency of different quantitities of various fuels,
taking into account energy required to process such fuels".
Since EPCA itself does not explicitly specify the inclusion of fuel processing
energy in fuel equivalency calculations, but the conference report
"anticipates" such inclusion, methods will be presented in Part II of this
report to cover each of these possible approaches.
b.) The Energy Tax Act of 1978
The Energy Tax Act of 1978, P.L. 95-618 (5), imposes an excise tax on fuel-
inefficient vehicles ("gas guzzlers") which may have an even more profound
impact on the strategy employed by the automobile manufacturers to comply
with the fuel economy standards than the $5 to $10 per tenth of a
mile-per-gallon penalty contained in EPCA. Table 2 shows the severity of this
tax. Imposition of the tax begins with vehicles whose fuel economy is
approximately 5 mpg less than the current year's average fuel economy
standard. The tax is steeply graduated, ranging in 1986, from $500 for each
vehicle whose fuel economy is 5 to 6 mpg below the 1986 standard to $3850
for each vehicle whose fuel economy is over 15 mpg below the standard.
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Table 2
The Gas Guzzler Tax (in dollars)
Year (Fuel Economy Standard)
Vehicle Fuel Economy 1980
EPA Composite MPG (20.0)
Greater than 22.5
21.5-22.5
Greater than 21.0 0
20.5-21.5
20.0-21.0 0
19.5-20.5
19.0-20.0 0
18.5-19.5
18.0-19.0 0
17.5-18.5
17.0-18.0 0
16.5-17.5
16.0-17.0 0
15.5-16.5
15.0-16.0 Q/
14.5-15.5 /
14.0-15.0 200
13.5-14.5
13.0-14.0 300
12.5-13.5
Less than 13.0 550
Less than 12.5
1981 1982
(22.0) (24.0)
0
0
0
0
0
0
0
0
0 /
/ 200
o/
/ 350
'200
450
(
350
600
450 /
750
550 '
1 950
650 /
/ 1200
1983 1984
(26.0) (27.0)
0
xO~
o x x
o
/ 0
/ o
0
450
350
600
500
750"
650 x
/ 950
/800
/ 1150
1000
1450
1250
1750
1550
2150
1985 1986
(27.5) (27.5)
_____ fl
500
0
650
500
850
600
1050
800
1300
_ 1000 *" ~"
1500
1200
1850
1500
2250
1800
2700
2200
3200
2650 ^ - "
' ' 3850
Standard
minus
5 mpg
Standard
minus
10 mpg
Standard
minus
15 mpg
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More interesting is the effect on a given model which is retained unchanged
in a manufacturer's line. For example, if a vehicle's fuel economy is 15.1
mpg in 1980, it would not be subject to a gas guzzler tax. Beginning in
1981, it would have an ever-increasing tax levied$350 in 1981, $600 in
1982, £800 in 1983, $1150 in 1984, $1500 in 1985, and $2250 in 1986. It is
assumed that the effect of this tax will be to reduce the sale of gas
guzzlers.
This progressive increase in penalty will probably result in earlier
discontinuance of production of the less fuel-efficient vehicles in a
manufacturer's line. Fewer very fuel-efficient vehicles will then be needed
to achieve the average fuel economy standard. The result will be a tighter
clustering of vehicles around the standard.
c) The Chrysler Corporation Loan Guarantee Act of 1979
The Chrysler Corporation Loan Guarantee Act of 1979 (P.L. 96-185)
established:
"a seven-year evaluation program of the inclusion of
electric vehicles ... in the calculation of average fuel
economy ... to determine the value and implications of
such inclusion as an incentive for the early initiation
of industrial engineering development and initial
commercialization of electric vehicles in the United
States."
The Administrator of EPA was, in consultation with the Secretaries of
Energy and Transportation, to promulgate "regulations to include electric
vehicles in average fuel economy calculations ..." by March 7, 1980. The
Secretary of Energy has proposed "equivalent petroleum based fuel economy
values" for various classes of electric vehicles, and final values have been
promulgated (10 CFR Part 474). These equivalent values are to be reviewed
annually and revised as necessary.
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These "equivalent petroleum based fuel economy values" for electric
vehicles were to be determined taking into account the following parameters :
"(i) The approximate electrical energy efficiency of the vehicles
considering the vehicle type, mission, and weight;
(ii) The national average electricity generation and
transmission efficiencies;
(iii) The need of the Nation to conserve all forms of
energy, and the relative scarcity and value to
the Nation of all fuel used to generate electricity;
(iv) The specific driving patterns of electric vehicles as compared
with those of petroleum fueled vehicles."
According to the final rule issued by DOE, equivalent petroleum based fuel
economy values for electric vehicles will be calculated in the following
manner:
FE = FEee x DPF x et x AF x Etotal
where :
FE = the equivalent petroleum-based fuel economy
FEee = the energy-equivalent fuel economy value (miles per gallon) (ref. 5)
conversion factor: 1 13, 300 BTU x 1 KWH
gal 3412 BTU
DPF = driving pattern factor (1.00)
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e = average national electricity transmission efficiency ( = 0.91)
AF = Accessory Factor (= 1.00, no accessories; 0.90, heater; 0.81, heater
plus air conditioning)
E ^ = total amount of electricity generated from all fuel sources for
the model year (quadrillion BTU, or quads)
I. = input energy of fuel used to generate electricity from fuel
source- i (quads)
V. = relative value factor of fuel source i
In section II. D of this paper the adaptation of the above procedure to
alternative automotive fuels is discussed.
C. 2. Current Equivalency Methodologies
Up to now, tentative solutions to the equivalency issue have only been
provided for two specific areas - Diesel fueled vehicles and electric
vehicles. The documents that cover these provisions are:
1) Methodology for Calculation of Diesel Fuel to Gasoline Fuel
Economy Equivalence Factors, Technical Support Report for Regulatory Action,
January 1976 (Revised May 1976), EPA-ECTD report. (7)
2) Federal Register, Sept. 10, 1976, "Fuel Economy Testing; Calculation
and Exhaust Emissions Test Procedures for 1977-1979 Model Year Automobiles."
3) Final Rule, 10 CFR Part 474, "Electric and Hybrid Vehicle Research,
Development, and Demonstration Program; Equivalent Petroleum-Based Fuel
Economy Calculation"; 1981. (3)
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There has been much written on the subject of Diesel/gasoline fuel
equivalency but, so far, the solution has been to weight them equally. In
other words, the correction factor applied to Diesel fuel economy test
results is effectively 1.0. This is because the higher energy content of
Diesel fuel tends to be balanced by the decrease in refinery energy
consumption with increasing Diesel fuel production.
In attempting to characterize the increase in energy availability (decrease
in refinery energy consumption) with increasing Diesel fuel production
percentage, many variables enter into the calculation. For instance, there
are refinery-to-refinery differences, variations in refinery product mix with
time, and variations in raw material (such as the sulfur content of the crude
oil) with time and between refineries, all of which affect the process energy
requirements at any given Diesel/gasoline production ratio. There are some
specific problems with using the current Diesel/gasoline equivalency
methodology as a basis for future equivalency determinations, arid these issues
are discussed in part II. B. of this report.
Regarding equivalent petroleum-based fuel economy calculations for electric
vehicles, the methodology in use was discussed previously in Section C.l.c) of
this report.
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II. Possible Methodologies for Determining Equivalent Fuel Economies for
all Fuels
Following are three methodologies for calculating equivalent petroleum-based
fuel economies for a wide variety of potential automotive fuels. One
objective of this investigation is to determine a methodology that is
consistent for all automotive fuels, so a range of possible solutions is
presented including one solution (C) that is recommended due to its
consistency with the various legislative provisions outlined above.
Method A. Fuel Energy Content Considered
The simplest solution that would be in line with EFCA, but not necessarily
with the conference report as discussed in Part I, would be to use the ratio
of the heat content of a fuel to that of gasoline as a correction factor to
the actual mile per gallon test result. This would effectively rank vehicles
on the basis of miles per BTU of fuel used by the vehicle itself.
Here is an example of this methodology as applied to a methanol-fueled
vehicle: In the fuel economy test assume a vehicle gets 20 miles per gallon
of methanol, as compared to a similar, but gasoline-fueled, car getting 30
miles per gallon. Since the heat content of methanol is 56,123 BTU/gal, the
methanol-fueled vehicle is getting 35.6 miles per 100,000 BTU. Typical
gasoline has a heat content of 113,300 BTU/gal, so 30 mpg gasoline equals 26.5
miles per 100,000 BTU.
In order to adjust the mile per gallon value for methanol (20 mpg) to correct
for the difference in heat content between methanol and gasoline, it would be
multiplied by the ratio of the heat content of gasoline to that of methanol.
FE = MPGalt. x LHVgas.
LHValt.
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FE = 20 mpg x 113,300 BTU/gal gasoline*
56,123BTU/galmethanol(S)
FE = 20 mpg x 2.02
FE = 40.4 mpg
In this case, for purposes of fuel economy calculations, the 20 mpg methanol
car could be rated at 40.4 mpg when converted to a gasoline-equivalent basis.
Another fuel that should be mentioned with respect to Method A is Diesel
fuel. Since Diesel fuel #2 has a 15% higher heat content than gasoline
(130,650 (7) vs. 113,300 BTU/gal), the equivalent gasoline-based fuel economy
of a 35 mpg Diesel vehicle, for instance, would be;
FE - 35 mpg x 113,300 BTU/gal gasoline
130,650 BTU/gal Diesel
FE = 30.4 mpg
Table 3 lists the fuel equivalency factors for various fuels calculated with
this methodology. FEF is the resultant adjustment factor, for methanol for
example, the value for FEF is 2.02.
* Today's motor gasolines range in BTU/gallon from about 112,000 BTU/gallon to
115,000 BTU/gallon.
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Table 3
Fuel Equivalency Factors
Based on Energy Content alone
*
Energy Content
Fuel (BTU/gal) FEF
Gasoline leaded regular 113,300 1.0
unleaded regular 113,300 1.0
unleaded premium 113,300 1.0
Diesel Fuel #2 130,650 0.87
#1 126,100 0.9
Methanol 56,123 2.02
Ethanol 78,987 1.43
Gasohol 109,869 1.03
Natural Gas (1080 BTU/ft3) **
*Lower Heating Value
** FE = Miles/BTU nat. gas x 113,300 BTU/gal. gasoline
The use of this methodology for Diesels could be taken to represent a 13%
penalty that could discourage use of Diesel vehicles (9). However, when
combined with the 30% average fuel economy benefit for Diesels over comparable
gasoline vehicles (10), there is still a 17% benefit for Diesels.
The only possible liability of this methodology is that, by itself, it does
not address the issue of energy used in processing fuels. This area of
concern is addressed in the next two methodologies.
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Method B. Energy Content Plus Refining Energy Considered
A second possible approach to determining gasoline equivalent fuel economies
would be one that includes the efficiency of the final fuel processing steps,
(eg. refinery efficiency for petroleum fuels).
In this methodology an additional factor is included in the fuel equivalency
calculation. In the case of Diesel vehicles this additional factor adjusts the
fuel economy value to reflect the refinery energy savings that occur when the
Diesel fuel output of a refinery is increased relative to the gasoline
output. The most recent investigation of this phenomenon is described by
Amoco in reference (11).
In the Amoco study it is concluded that decreasing the Gasoline/Distillate
(G/D)* production ratio from 1.6 to 0.7 would decrease the energy consumption
of the refinery by 13.7% - 16.8%, depending on the octane of the gasoline
produced.
The equation which characterizes this methodology for finding the gasoline-
equivalent fuel economy of a Diesel vehicle is:
FE = MPGD x LHVgas x DEO
LHVD DEO - RES
where: The subscript D indicates Diesel fuel
DEO is the Diesel fuel energy output
RES is the Refinery Energy Savings when
producing additional Diesel fuel
* G/D ratio is the volume of motor gasoline divided by the volume' of total
distillates - Diesel fuel, fuel oils, kerosene and jet fuels. It is commonly
used to describe refining operations. U.S. refineries currently average about
1.6 G/D ratio, but the ratio may vary among refineries and with season from
about 1.0 to 2.0
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The combination of LHV gas x Diesel Energy Output adjusts the Diesel fuel
energy output at any G/D ratio to the equivalent gasoline energy output. The
term in the denominator reflects the refinery energy savings that occur when
producing additional Diesel fuel. This increases the Diesel equivalency
factor because it gives the Diesel fuel energy output credit for the refinery
energy saved.
Using this methodology Amoco then developed the following table of Diesel
Equivalency Factors (DEF), which would be used in this formula:
FE = MPGD x DEF
DIESEL EQUIVALENCY FACTORS
BASED ON ALL DIESEL Fuel PRODUCED
Pool Gasoline/Distillate Ratio
RM/2 Octane* . 1.6 1.3 1.0 0.7
80 0.88 0.91 0.92 0.92
82 0.88 0.91 0.92 0.92
84 0.88 0.91 0.92 0.93
86 (Base) 0.88 0.92 0.93 0.92
88 0.89 0.94 0.94 0.94
90 0.89 0.96 0.97 0.96
92 0.90 0.98 0.97 0.98
* RM/2 = Anti-knock Index (AKI) = Research Octane + Motor Octane
2 ~~
From the MVMA national gasoline survey, the difference between Research and
Motor octane (sensitivity) of unleaded gasoline typically ranges from 9.0 for
regular to 9.6 for premium. So 91 Research Octane unleaded would have an AKI
of about 86.5.
For any fuel equivalency methodology, a specific base fuel needs to be used as
a reference point. Unleaded 91 Research Octane gasoline is the most suitable
choice for such a reference fuel.
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DIESEL EQUIVALENCY FACTORS
BASED ON ADDITIONAL DIESEL FUEL ONLY
Pool Gasoline/Distillate Ratio
RM/2 Octane 1.6 1.3 1.0 0.7
80 0.88 0.93 0.93 0.93
82 0.88 0.94 0.93 0.93
84 0.88 0.94 0.94 0.93
86 (Base) 0.88 0.95 0.94 0.93
88 0.89 0.99 0.96 0.95
90 0.89 1.02 0.99 0.98
92 0.90 1.04 1.00 1.00
It should be mentioned that Amoco also calculated a set of DEF's that included
the expected fuel economy advantage for gasoline-fueled vehicles attributable
to increasing gasoline octane number (1.5 mpg per RM/2). However, it would be
incorrect to include this effect in the Diesel Equivalency Factor, since any
expected fuel economy change, if valid, would show up in the actual mpg test
results.
The above factors are based on the change that would occur from what is
considered the base case (86 RM/2; 1.6 G/D). Therefore, the DEF for the base
case consists only of the energy content (lower heating value) of gasoline
divided by the energy content of Diesel fuel. In theory it would be possible
to avoid this somewhat arbitrary base case, but it would require many
assumptions on allocation of the energy used in each processing unit to each
product. This is due to the many interdependences of gasoline and Diesel
fuel production which make it impossible to simply separate and measure the
energy consumption attributable to each of the two fuels.
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DIESEL EQUIVALENCY FACTORS
BASED ON ADDITIONAL DIESEL FUEL ONLY
Pool Gasoline/Distillate Ratio
RM/2 Octane 1.6 1.3 1.0 0.7
80 0.88 0.93 0.93 0.93
82 0.88 0.94 0.93 0.93
84 0.88 0.94 0.94 0.93
86 (Base) 0.88 0.95 0.94 0.93
88 0.89 0.99 0.96 0.95
90 0.89 1.02 0.99 0.98
92 0.90 1.04 1.00 1.00
It should be mentioned that Amoco also calculated a set of DEF's that included
the expected fuel economy advantage for gasoline-fueled vehicles attributable
to increasing gasoline octane number (1.5 mpg per RM/2). However, it would be
incorrect to include this effect in the Diesel Equivalency Factor, since any
expected fuel economy change, if valid, would show up in the actual mpg test
results.
The above factors are based on the change that would occur from what is
considered the base case (86 RM/2; 1.6 G/D). Therefore, the DEF for the base
case consists only of the energy content (lower heating value) of gasoline
divided by the energy content of Diesel fuel. In theory it would be possible
to avoid this somewhat arbitrary base case, but it would require many
assumptions on allocation of the energy used in each processing unit to each
product. This is due to the many interdependencies of gasoline and Diesel
fuel production which make it impossible to simply separate and measure the
energy consumption attributable to each of the two fuels.
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In order to choose the most appropriate factor(s) from these tables, it is
necessary to look a little more closely at things that affect the
gasoline/distillate ratio. Distillate fuels include automotive (passenger car
and truck) Diesel fuels, jet aircraft fuel, residential and commercial heating
oil, and industrial Diesel fuels.
According to the DOE predictions in reference (12), increases that will occur
in the use of distillate fuels for transportation in the next decade will be
offset somewhat by decreases in the other distillate fuel uses. Due to these
decreases in non-transportation distillate fuels, the net change in
gasoline/distillate ratio is not as great as might be expected.
Even if we assume all jet fuel is distillate, the GDR in 1985 only comes down
to about 1.45, and in 1990 it would range from 1.28 - 1.34 depending on crude
oil prices. Therefore, the 1.3 G1)R column would be the most appropriate one
to consider through at least 1990, assuming the changes that actually occur
fall within the range of the DOE predictions.
The question of whether to base the DEF on all Diesel fuel produced or just on
the additional Diesel fuel produced is handled in the Sobotka report (13) by
simply neglecting the existence of the all-Diesel-fuel factors. However, a
valid rationale does exist for using the additional-Diesel-fuel factors, as
Sobotka did.
The refinery efficiency credit from decreasing GDR should be credited to that
portion of the distillate production which is most responsible for the
change. According the DOE projections, most of the distillate increase can be
attributed to the automotive sector (80% vs. 20% jet fuel) and furthermore,
all of that increase can be attributed to Diesel passenger cars, since truck
vehicle-miles are expected to be less in 1990 than in 1978 (12).
Therefore, the Sobotka analysis was correct in using the equivalency factors
based on additional Diesel fuel production only. Also, as described in the
Sobotka analysis, the unleaded gasoline pool AKI is expected to increase from
the base case of 86 to 88 in the 1980's and possibly 90 in the 1990's. So the
range of DEF's would be 0.95 - 1.02.
-------
-22-
For this methodology it is recommended that, due to the uncertainties in these
calculations, the fuel equivalency factor for Diesels be rounded to 1.0, thus
in effect, keeping it as it has been up to this point.
Another question with this type of methodology is how to apply it to other
fuels, such as alcohols. It is possible to define reasonably accurate
production efficiencies, and therefore energy consumptions, for the common
ethanol and methanol production processes within this methodology. But it
would not be possible to define a valid fuel equivalency factor directly
relating alcohol to gasoline, since there is no direct relationship between
alcohol and gasoline production like there is between Diesel and gasoline.
Futhermore, a corresponding efficiency for gasoline by itself would not be
calculable due to the refinery interdependencies mentioned above.
Despite these considerations, a possible approximation of an alcohol/gasoline
equivalency factor within this basic methodology could be calculated as
follows: 1) let the gasoline production efficiency be approximated as simply
the overall refinery efficiency.
c - REO REI - REG
Egas" * REI * REI
where:
Egas. = Energy efficiency of petroleum refinery
REO = Total refinery energy output
REI = Total refinery energy input
REC = Refinery energy consumption
-------
-23-
2) then let the alcohol production efficiency be calculated with this same
equation as applied to alcohol fuel plants. The following is how this would
look for ethanol.
_ , PEI - PEC
Eeth. =
PEI
where :
Eeth. = Energy efficiency of alternate fuel plant (ethanol)
PEI = Total plant energy input
PEC = Plant energy consumption
and 3) The equivalency factor would then be the fuel energy content ratio
multiplied by the ratio of the two fuel processing efficiencies,.
m~ , LHVgas. Eeth.
FE = MPGeth. x x
Due to the likelihood of change in average production efficiency with tech-
nological improvements and new plant construction, it probably would be
necessary to review and update these factors periodically.
Example (methanol) //I
Egas. = - = 0.92 (ref. 11)
PEO
Emeth. = - = 0.56 (ref. 14, methanol from natural gas)
PEI
, 113,300 BTU/gal 0.56
FE = MPGmeth. x 56>123 BTU/*al * ^
MPGmeth. x 1.23
Example (methanol) //2
Emeth. = 0.60 (ref. 15, methanol and synthetic natural gas from coal)
113,300 0.60
FE = MPGmeth. x 56>123 x ^gj
= MPGmeth. x 1.32
-------
-24-
Table 4 lists fuel equivalency factors determined with Method B.
Table 4
Fuel Equivalency Factors
Based on Fuel Energy Content & Plant Process Energy
Plant
Fuel Efficiency FEF*
Gasoline 92% 1.00
Diesel Fuel 92% .95 - 1.02
Methanol from natural gas 56% - 70% 1.23 - 1.54
from coal 50% - 60% 1.10 - 1.32
Ethanol from corn 45% - 60% 0.70 - 0.93
Gasohol (10% of Ethanol effect) .97 - .98
Compressed Natural Gas 96% **
Liquified Natural Gas 86% **
* FEF = FEF from Table 3 x E alt.
Egas.
** FE = (Miles/BTU nat. gas) x 113,300 x Plant Efficiency/92%
-------
-25-
Method C. Energy Content, Process Efficiency Plus Fuel Value Considered
This fuel equivalency alternative is based on the Department of Energy (DOE)
proposed methodology for calculation of equivalent petroleum-based fuel
economies for electric vehicles which was described earlier in Section I.
This methodology accounts not only for the different energy contents of the
fuels themselves and the different energy efficiencies of the various fuel
processing routes, but also includes a raw material cost factor to account
for the energy needed to get a fuel as- far as the processing step.
The raw material assumed for gasoline production is crude oil, so gasoline
produced by any other means than refining of crude oil would need to have a
fuel equivalency factor calculated to account for any significant
differences in processing efficiencies and raw materials.
The raw material cost factor would be simply a ratio of the cost of crude
oil to the cost of any alternate raw material, on a dollar per BTU basis.
When this factor is included in the formula for calculating FEF's, the
equation looks like this:
= LHVgas. x Ealt. x Vgas.
LHValt. Egas. Valt.
where :
Vgas. = Raw Material Value for gasoline
(^/million BTU of crude oil)
Valt. = Raw Material Value for alternate fuel
(^/million BTU)
Using some projected figures for 1982 (12), Table 5 indicates the effect of
including this additional factor. For methanol, the inclusion of this raw
material cost factor more than compensates for the lower processing efficiency
of methanol compared to petroleum products. The resulting fuel equivalency
factor, 3.76 - 5.42 depending on raw material, would seem to provide a
significant impetus toward development and use of methanol fueled vehicles.
-------
-26-
Even if a methanol fueled vehicle only achieved half the mpg of a
corresponding gasoline vehicle, the FEF would result in a gasoline-equivalent
fuel economy 1.88 - 2.71 times as much as the gasoline fueled vehicle.
The figures for ethanol are a little surprising due to the effect of the corn
cost on the FEF. The cost of the corn needed to produce one million BTU of
ethanol is about 5 1/2 times the cost of the heat source, assuming coal is
used. Even when credit is given for the plant output of Distillers Dried
Grain (DDG) the raw material cost per million BTU output of an ethanol plant
is 1.9 times as high as a petroleum refinery operating with a current product
mix.
So even if a pure ethanol-fueled vehicle achieved the same mpg test result as
a gasoline-fueled vehicle (e.g. 25 mpg) the resulting gasoline-equivalent fuel
economy would only be 1/1.9 (=0.53) times the ethanol test result (0.53 x 25 =
13.3 mpg).
-------
-27-
Table 5
Fuel Equivalency Factors
Based on Energy Content, Plant Efficiency and Raw Material Cost
Fuel
Gasoline (from petroleum)**
Diesel Fuel (from petroleum)**
Methanol
(from natural gas)
(from coal)
Raw Material
Cost
Ethanol*** (from corn) and
all process energy from coal
@$1.45/MMBTU for the coal
Gasohol
Natural Gas
bu
$2.25
MMBTU
FEF*
$6.89
MMBTU
$6.89
MMBTU
$2.25
MMBTU
$1.45
MMBTU
$3.. 50
1.0
0.95 - 1.02
3.76 - 4.71
5.23 - 6.27
0.60 - 0.73
0.96 - 0.97
****
FEF = FEF from Table 4 x
Petroleum Cost
Raw Material Cost
** from petroleum at $37,88/barrel.
*** The higher FEF assumes all process energy comes from the input corn
without any additional process energy source.
**** Gasoline - Equivalent = Miles
Fuel Economy
x 113,300 BTU x plant eff. x $6.89
Btunat. gas. gal. gasoline 92% $2.25
-------
-28-
Gaseous and Other Fuels
The methodology discussed here could also be applied to other fuels besides
those listed in the tables. For instance, it is possible to produce
gasoline from coal rather than from crude oil. This would result in
different raw material costs as well as different processing efficiencies
for the synthetic gasoline in comparison to usual oil-derived gasoline.
To get a rough idea of how a synthetic gasoline such as this would compare
to the fuels considered in the tables, it could be directly compared to
methanol from coal. For the purpose of this comparison, we can assume that
the raw material (coal) is the same in both cases, and that the processing
efficiencies are approximately the same for converting coal to either
gasoline or methanol. Then the only part of the Fuel Equivalency Factor
that would be different for the two fuels would be the energy content (LHV)
which, for the gasoline, would be double that of the methanol. The FEF
computation would look like this:
Ealt. = 0.60 (using example #2, page 23)
Valt. = $1.45/MMBTU (from table 5)
FEF (methanol from coal) =6.27 (table 5)
FEF (gasoline from coal) = 3.14
Since synthetic gasoline could- be expected to yield approximately the same
measured fuel economy as conventional gasoline, the final
gasoline-equivalent fuel economy of the synthetic gasoline, according to
these calculations, would be approximately triple that of conventional
gasoline.
For liquid alternate fuels, as discussed above, the basic approach starts
with measuring the fuel consumption (mile/gallon) and then multiplying it by
the energy content ratio of gasoline to alternate fuel to obtain a
-------
-29-
gasoline-equivalent fuel economy. For gaseous fuels, the more likely
starting point would be a mile per BTU measurement. This would then simply
be multiplied by the energy content of gasoline (BTU/gal) to get the basic
gasoline-equivalent fuel economy corresponding to Method A. The other
adjustment factors for Methods B and C could then be applied as described
above.
-------
-30-
III. DISCUSSION
Three different methodologies have been presented here which cover a range
of approaches for dealing with the fuel equivalency issue. Other
methodologies were considered, such as basing equivalency solely on retail
price per BTU, but it is felt that the methodologies presented here
sufficiently encompass all the possibilities.
Looking first at Method A presented above (fuel energy content only), it is
apparent that the factors not accounted for would include (a) plant/refinery
energy consumption, (b) fuel transport energy consumption, and (c)
differences in origin of fuel (imported crude, domestic coal, corn, etc.).
It should be kept in mind that the Energy Policy and Conservation Act (EPCA)
itself does not specifically call for any of these factors to be taken into
account for non-electric vehicles.
In Method B (fuel energy content/process efficiency) the differences in fuel
origin and energy consumption prior to reaching the plant/refinery are still
not taken into account. (Again, these are not specifically required by
EPCA.)
The major inconsistency introduced by this methodology is the way Diesel
fuel equivalency would be handled compared with other fuels. For the
process energy of Diesel fuel relative to that of gasoline it was necessary
to consider the change in overall plant efficiency when the
gasoline/distillate ratio was changed from an arbitrary baseline. This
approach was due to the virtual impossibility of separating the efficiencies
for Diesel and gasoline production since they are produced in the same plant
from the same raw material and have many interdependencies in the production
process.
This is in contrast to the handling of non-petroleum fuels within this
methodology. For these other fuels, such as methanol, the production
efficiency would be an actual, current efficiency to be compared directly
-------
-31-
with the current gasoline production efficiency. Not only would this be
inconsistent with the handling of Diesel fuel equivalency, but it is also a
very imprecise comparison due to the inability to determine an efficiency
for gasoline by itself. (The overall refinery efficiency would be a
composite of all the refinery products).
In Method C (energy content/efficiency/raw material value), the plant energy
consumption is accounted for directly, while the fuel transport energy
consumption, and the differences in origin of fuel are all taken into
account indirectly via the raw material cost factor (price per BTU). The
more energy that is consumed in getting raw material to the plant whether
crude oil, coal, or corn, the higher the cost will be. Some of the factors
that could influence the cost of the raw material to the plant are a) the
cost of drilling, mining or growing it in the first place: b) the cost of
transporting it to the plant, whether by pipeline, ship, rail or truck; and
c) any taxes such as import duties; d) any subsidies granted to domestic
drilling, mining or farming activities, or direct government price controls
on raw materials such as oil, coal, and corn.
Since these cost factors include more than just direct energy dependent
costs, the use of this factor actually goes a little beyond the legislated
requirement for liquid fuels equivalency factors. Using a factor such as
this would, however, be consistent with one of the parameters given for fuel
equivalency calculation of electric vehicles in the Chrysler Corporation
Loan Guarantee Act (PL 96-185), which takes into account the need of the
nation to conserve all forms of energy, and the relative scarcity and value
to the nation of various fuels.
Therefore, taking into account the .various fuel equivalency methodologies
and the legislative requirements, Method C seems to best serve the purposes
set up for fuel equivalency determination provided all the needed input data
can be accurately determined and updated when and if necessary.
-------
-32-
APPENDIX
-------
-33
This Appendix gives some more calculations of Fuel Equivalency Factors
(FEFs) for various parameters such as the efficiency of various production
processes and costs of various raw materials.
-------
-34-
Table A-l
Fuel Equivalency Factors
Considering fuel energy content and process energy
Methanol Plant Petroleum Refinery
Efficiency
50%
60%
70%
Ethanol Plant
Efficiency
30%
45%
60%
Natural Gas*
Efficiency
96% (compressed)
86% (liquified)
88%
1.14
1.36
1.59
0.49
0.73
0.98
1.09
0.98
Efficiency
90%
1.11
1.33
1.56
0.48
0.72
0.95
1.07
0.95
92%
1.09
1.30
1.52
0.47
0.70
0.93
1.05
0.94
not expected that mile/gallon figures will be found f<
fueled vehicles, the gasoline-equivalent fuel econoi
.culated as follows:
it miles
V
113,300 BTU
T717T7
Gasoline-Equivalent
Fuel Economy ~ ~BTU natural gas " gal. gasoline
-------
-35-
Table A-2
Fuel Equivalency Factors
Methanol
Petroleum Refinery Efficiency and Cost
Raw Plant
L*
88%
M*
H*
L
9i
0%
M
H
L
92%
M
H
Material/Efficiency/Cost
coal/50%/L**
coal/50%/M**
coal/50%/H**
coal/60%/L
coal/60%/M
coal/60%/H
coal/70%/L
coal/70%/M
coal/70%/H
4
3
2
5
4
3
6
5
4
.77
.65
.95
.73
.38
.55
.68
.11
.14
6.36
4.87
3.94
7.64
5.84
4.73
8.91
6.81
5.52
7.95
6.08
4.92
9.55
7.30
5.91
11.14
8.52
6.89
4.66
3.57
2.88
5.60
4.28
3.47
6.53
5.00
4.04
6
4
3
7
5
4
6
5
.22
.76
.85
.47
.71
.62
.71
.66
.39
7.77
5.94
4.81
9.33
7.14
5.78
10.89
8.33
6.74
4.56
3.49
2.82
5.48
4.19
3.39
6.39
4.89
3.96
6.08
4.66
3.77
7.30
5.59
4.52
8.52
6.52
5.28
7.60
5.82
4.71
9.13
6.98
5.65
10.65
8.15
6.59
nat.gas/50%/L***
nat.gas/50%/M***
nat.gas/50%/H***
nat .gas/60%/L
nat.gas/60%/M
nat.gas/60%/H
nat.gas/70%/L
nat.gas/70%/M
nat.gas/70%/H
* crude oil,
** coal, $/ton
*** natural gas
3
2
1
3
2
1
4
2
2
$/bbl
.10
.07
.55
.72
.48
.86
.34
.89
.17
, ^/million
4.14
2.78
2.07
4.96
3.31
2.48
5.79
3.86
2.90
BTU
5.17
3.45
2.59
6.20
4.14
3.10
7.24
4.83
3.62
L
30.00
31.20
2.00
3.03
2.02
1.52
3.64
2.43
1.82
4.25
2.83
2.12
Raw
4
2
2
4
3
2
5
3
2
.04
.70
.02
.85
.24
.43
.66
.77
.83
Material
M
40.00
40.80
3.00
5.06
3.37
2.53
6.07
4.04
3.03
7.08
4.72
3.54
Costs
2.97
1.98
1.48
3.56
2.37
1.78
4.15
2.77
2. 08
H
50.00
50.40
4.00
3.96
2.64
1.98
4.75
3.17
2.37
5.54
3.69
2.77
4.95
3.30
2.47
5.93
3.96
2.97
6.92
4.62
3.46
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Table A-3
Fuel Equivalency Factors
Method C for Ethanol
Petroleum Refinery Efficiency
Raw Plant
Material/Efficiency/Cost
corn/30%/L
corn/30%/M
corn/30%/H
corn/45%/L
corn/45%/M
corn/45%/H
corn/60%/L
corn/60%/M
corn/60%/H
*
* crude oil, $/bbl
** coal, $/ton
*** corn, ^/bushel
L*
.44
.40
.37
.71
.65
.60
.76
.70
.66
88%
M*
.58
.53
.49
.95
.87
.81
1.01
.94
.88
Raw
H*
.73
.67
.62
1.19
1.09
1.01
1.26
1.17
1.09
Material
L
30.00
31.20
3.30
L
.43
.39
.36
.70
.64
.59
.74
.69
.64
Costs
90%
M H
.57 .71
.52 .65
.48 .60
.93 1.16
.85 1.07
.79 .99
.99 1.23
.92 1.15
.86 1.07
M
40.00
40.80
3.50
and Cost
92%
L M
.42 .56
.38 .51
.35 .47
.68 .91
.63 .83
.58 .77
.72 .96
.67 .90
.63 .84
H
50.00
50.40
3.70
H
.70
.64
.59
1.14
1.04
.96
1.21
1.12
1.05
I
CO
assuming coal is used for all the process energy
-------
Table A-4
FUEL EQUIVALENCY FACTORS
FOR NATURAL GAS
(A) Compressed, (B) Liquified
Petroleum Refinery Efficiency and Cost
Raw Plant L
Material/Efficiency/Cost*
(A)
Natural gas/96%/L
Natural gas/96%/M
Natural gas/96%/H
(B)
Natural gas/86%/L
Natural gas/86%/M
Natural gas/86%/H
2.
1.
1.
2.
1.
1.
Gasoline - Equivalent
Fuel Economy
natural gas
crude oil,
, $/MMBTU
fc/bbl
88%
M
98 3.97
99 2.65
49 1.99
67 3.56
78 2.37
33 1.78
miles
BTUng
*Raw
L
2.00
30.00
H L
4.96 2
3.31 1
2.49 1
4.45 2
2.97 1
2.23 1
113
gal
Material
M
3.00
40.00
.91
.94
.46
.61
.74
.31
,300
90%
M H L
3.88 4.86 2.85
2.59 3.24 1.90
1.94 2.43 1.42
3.47 4.35 2.55
2.32 2.90 1.70
1.74 2.18 1.27
BTU
UAU TjtjEi
92%
M H
3.80 4.75
2.53 3.17
1.90 2.37
3.41 4.26
2.27 2.84
1.70 2.12
gasoline
Costs
H
4.00
50.00
-------
-38-
References
1. Energy Policy and Conservation Act, Public Law 94-163, 1975.
2. Chrysler Corporation Loan Guarantee Act of 1979, Public Law 96-185,
Jan. 7, 1980.
3. "Electric and Hybrid Vehicle Research, Development and
Demonstration Program; Equivalent Petroleum-Based Fuel Economy
Calculation," Final Rule, U.S. Department of Energy, 10 CFR Part
474, (Docket No. CAS-RM-80-202).
4. Energy Policy and Conservation Act, Conference Report, U.S. Senate
Report No. 94-516, December 8, 1975, page 154.
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Aerospace Corporation, Report ATR-80(7766)-1, May 1980.
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Summer Season - October 15, 1980, sampling date - July 15, 1980.
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Economy Equivalence Factors," Technical support report for
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U.S. EPA, January 1976 (Revised May 1976).
8. Energy From Biological Processes, U. S. Congress Office of
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10. "Comparison of Gasoline and Diesel Automobile Fuel Economy as Seen
by the Consumer," B. McNutt, U.S. DOE, SAE Paper 810387, February
1981.
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-39-
11. "Automotive Fuels - Refinery Energy and Economics," D. Lawrence, D.
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800225, February 1980.
12. Energy Information Administration Annual Report to Congress, Volume
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13. "Review of Diesel Equivalency Factors," Sobotka & Company, Inc.,
December 5, 1980.
14. "Methanol From Coal: Prospects and Performance as a Fuel and as a
Feedstock," IGF Inc., December, 1980.
15. "Methanol as a Major Fuel," Paul W. Spaite Co., December 8, 1980.
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Chambers, R. Herendeen, J. Joyce, P. Penner, Science, Vol. 206,
November 16, 1979.
17. "Commercial Production of Ethanol for Fuel Applications" Energy from
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Institute of Gas Technology, May 1980.
18. "Preliminary Perspective on Methanol," Draft ECTD Report, February
1981.
19. "Net Energy Analysis of Alcohol Fuels," American Petroleum Institute
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McGraw-Hill Book Co., New York, 1951, 1978.
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Economics Program Report No. 18, February 1981.
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