EMISSIONS AND ENERGY EFFICIENCY CHARACTERISTICS OF
METHANOL-FUELED ENGINES AND VEHICLES
Jeff Alson
Thomas M. Baines
Emission Control Technology Division
Environmental Protection Agency
Ann Arbor, MI
Presented at the institute of Gas Technology's Nonpetroleum venicular Fuels
III in Arlington, Virginia on October 14, 1982.
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2
EMISSIONS AND ENERGY EFFICIENCY CHARACTERISTICS OF
METHANOL-FUELED ENGINES AND VEHICLES
Jeff Alson, B.S.E.
Environmental Engineer
Thomas M. Baines, M.S.I.O.E.
Research Engineer
Environmental Protection Agency
Ann Arbor, MI 48105
ABSTRACT
This paper summarizes the emissions and energy
efficiency results from two recent EPA test programs
involving engines designed to utilize methanol fuel.
Two methanol-fueled 1961 model year passenger cars and
their gasoline-fueled counterparts were tested over the
EPA light-duty Federal Test Procedure. The
methanol-fueled vehicles emitted greater amounts of
methanol and formaldehyde emissions and smaller
quantities of hydrocarbons, particulate, and various
unregulated pollutants. Carbon monoxide and oxides of
nitrogen emission results were mixed. Methanol fueling
increased one vehicle's energy efficiency but had
little effect on the other. Four heavy-duty
engine/catalyst configurations were characterized over
the EPA heavy-duty transient and steady-state tests; a
conventional diesel engine without a catalytic
converter; a version of the same diesel engine modified
to utilize dual-injection of methanol and diesel fuels,
with and without catalytic aftertreatment; and a pure
methanol, direct-injected, spark-ignited engine with
catalyst. The engines which utilized methanol fuel
emitted higher levels of methanol but lower levels of
hydrocarbons, oxides of nitrogen, particulate, smoke
and benzo(a)pyrene compared to the diesel engine.
Results for carbon monoxide, formaldehyde, and sulfate
emissions were varied. The pure methanol engine
generally emitted lower emissions than the dual-fueled
engine configurations. The energy efficiencies of the
methano1-fueled engines were lower than that of the
conventional diesel engine. The results from these
test programs were compared to those reported in the
literature for previous methanol research projects and
found to be in general agreement.
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3
EMISSIONS AND ENERGY EFFICIENCY CHARACTERISTICS OF
METHANOL-FUELED ENGINES AND VEHICLES
INTRODUCTION
The unforeseen shortages and unstable prices of
Imported petroleum during the last decade have prompted
considerable interest in the development of a long-term
domestic fuel supply for our nation's transportation
system. Candidate alternative automotive fuels include
methanol, ethanol, hydrogen, methane, propane,
synthetic gasoline and diesel fuels, broadcut fuels,
and shale oil. In order to further our understanding
of the impacts of these fuels, the Environmental
Protection Agency (EPA) has undertaken a testing
program at the Southwest Research Institute to
characterize the emissions and energy efficiency
capabilities of vehicles and engines that use these
fuels•
Because methanol can by synthesized from coal, our
most abundant fossil fuel resource, and because it is
generally recognized as a viable fuel for
spark-ignited, homogeneous charge engines, it has been
the subject of much research over the last decade.
Unfortunately, such programs have generally involved
minor modifications to vehicles which were originally
designed and optimized for other fuels (e.g.,
gasoline). Only recently have manufacturers begun to
design engines specifically for methanol combustion.
The purpose of this paper is to present the
emissions and energy efficiency results from recent EPA
test programs involving light-duty vehicles and
heavy-duty engines designed to utilize pure methanol or
predominantly methanol fuels. Further, the paper will
compare the results of these programs with results from
various methanol research projects over the past decade
in order to help give the reader a broader
understanding of the possible emissions and energy
efficiency impacts of broader methano1-fueled vehicle
usage .
DESCRIPTION OF THE PROGRAMS
Test Vehicles and Engines
The light-duty vehicles characterized by EPA
included two 1981 Ford Escorts and two 1981 Volkswagen
Rabbits, with both pairs including one methano1-fue1ed
vehicle and one gasoline-fueled vehicle. Table 1
describes the light-duty vehicles tested. The methanol
and gasoline versions of each model are very similar
except for the higher compression ratios of the engines
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TABLE 1 - LIGHT-DUTY VEHICLES EVALUATED
Vehicle
Engine
Year Make Model
1981 VW
1981 VW
Body
Type
1981 Ford Escort Wagon
1981 Ford Escort; Wagon
Rabbit 4-dr
Rabbit 4-dr
Disp.,1 C.R.
1.6 8.8:1
1.6
1.7
1.6
11.Ail
8.2 ;1
12.5:1
Cyl.
4
4
Transmission
Manual-4
Auto-3
Auto-3
Auto-3
Odometer
Reading
(miles)
4872
5976
7919
1380
Fuel Used
Gasoline
Methanol
Gasoline
Methanol
Emission
Control
Devices*
EGR, PMP,
OXD, TWC,
CARB
EGR, PMP,
OXD, TWC,
CARB
3CL, MFI
3CL, MFI
EGR = Exhaust gas recirculation
PMP = Air pump
OXD = Oxidation catalyst
TWC = Three-way catalyst
3CL = Three-way catalyst with closed-loop fuel system
CARB = Carburetor fuel metering
MFI = Mechanical fuel injection (K-Jetronic)
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5
designed for methanol fuel use. Higher compression
ratios are possible because of the higher octane number
of methanol fuel. All four vehicles were equipped with
factory-installed three-way catalytic converters.
The four heavy-duty engine configurations tested
by EPA are described in Table 2. The Volvo TD-100C is
representative of current technology diesel engines
used in heavy truck applications. The TD-100A is a
modified version of this diesel engine and utilizes
pilot injection of diesel fuel and primary injection of
alcohol fuels (in this program, methanol). The primary
fuel is injected through the "original" fuel system
with an in-line injection pump while the pilot diesel
fuel is injected through a second fuel system
consisting of a small distributor-type injection pump.
The pilot diesel fuel is used to initiate combustion at
all engine operating modes, with the primary fuel then
providing the remainder of the necessary energy.
Diesel fuel is used exclusively during low loads. (1)
The dual-injection TD-100A engine was tested both with
and without an oxidation catalyst. The catalyst,
manufactured by Unikat AB of Sweden, contained 915
in^ of catalyst pellets (catalyst content and loading
information not supplied by the manufacturer), and was
not necessarily optimized for this application.
The M.A.N. D2566 FMUH engine is a modified version
of a six-cylinder diesel engine originally developed
for bus applications. The primary modification is the
addition of a Bosch transistorized pointless ignition
system in order to facilitate the combustion of neat
methanol fuel. The methanol is injected directly onto
the wall of the spherical cavity in the piston which
forms the combustion chamber. Mixture formation occurs
through the evaporation of the fuel (due to the heat
supplied by flame radiation) and the optimized air
swirl action. (2) This engine was tested with two
catalysts, each handling exhaust from a manifold fed by
three cylinders. The catalyst assemblies utilized a
Corning substrate with a unit volume of 116 in^ and a
platinum loading of 78 g/ft^, which is a relatively
high noble metal content. The M.A.N. engine is the
only one of the four heavy-duty engine/catalyst
configurations which utilizes pure methanol fuel.
Unfortunately, transient test procedure emissions and
energy efficiency data are not available for the diesel
version of this engine so direct comparisons between
the use of methanol and diesel fuels in almost
identical engines will not be possible. The only
possible comparisons will be between the pure methanol
M.A.N. engine and the diesel-fueled and dual-fueled
Volvo engines. Such comparisons must be qualified by
the many significant differences between the M.A.N,
engine and the Volvo engine configurations as shown in
Table 2.
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TABLE 2 - HEAVY-DUTY ENGINES EVALUATED
Volvo
Volvo
Volvo
M.A.N.
TD-100 C 9.6 15:1 6 Direct
Manufacturer Model Dlsp.,1 C.R. Cyl. Injection Aspiration
Turbocharged
Turbocharged
Turbocharged
TD-100 A 9.6 15 ;1 6
TD-100 A 9.6 15;1 6
Dual
Dual
D2566
FMUU
11.A 18;1
Direct
Naturally
Aspirated
Maximum
Output
240 hp at
2200 rpm
253 hp at
2200 rpm
256 hp at
2200 rpm
198 hp at
2200 rpm
Fuel Used
Diesel
Diesel/Wethauol
Diesel/Methanol
Methanol
Emission
Control
Device
None
None
Oxidation
Catalyst
Oxidation
Catalyst
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7
Test Fuels
The methanol fuel used in these test programs was
at least 99.9 percent pure and was used as received.
Methanol has a research octane number of approximately
108 and a cetane number of 3. A fuel mixture of 94.5
percent methanol and 5*5 percent isopentane has been
recommended by Volkswagen and is being used by the
California Energy Commission in that state's Alcohol
Fleet Test Program. (3) The purpose of the isopentane
is to increase the volatility of the fuel thus aiding
cold-starting at low ambient temperatures. Since these
programs were conducted at Federal Test Procedure
temperatures (68 to 86°F), the isopentane was not
necessary. One Federal Test Procedure emissions test
was performed with the methano1-fueled Escort using a
methano1/isopentane blend. Emissions and subjectively
evaluated driveability with the blend were very similar
to those with pure methanol with the exception of
organic emissions which were slightly higher with the
blend.
The gasoline and diesel fuels used in this program
met the specifications for EPA test fuels found in the
Federal Register. (4) The gasoline fuel had a research
octane number of 97.7 and a sulfur content less than
0.01 percent. The diesel fuel had a cetane number of
45 and a sulfur content of 0.24 percent.
Emissions Evaluated
Exhaust from each of the light-duty vehicles and
heavy-duty engines tested in these programs were
analyzed for each of the currently regulated
pollutants; hydrocarbons (HC), carbon monoxide (CO),
oxides of nitrogen (NOx), and particulate. Tests were
performed for a range of other organic compounds such
as methanol, formaldehyde, other aldehydes and ketones,
and some individual hydrocarbons. In addition, several
other unregulated pollutants (nitrosamines and total
organic amines, ammonia, cyanide, and methyl nitrite)
were measured during tests with the methanol-fueled
Ford Escort. Phenols, smoke, sulfate, and
benzo(a)pyrene were also analyzed from the heavy-duty
engines. Finally, the energy efficiencies of all of
the vehicle and engine configurations were determined.
Test Procedures
Each light-duty vehicle was tested either two or
three times over the Federal Test Procedure (FTP). The
FTP is the primary basis for EPA emissions and fuel
economy certification testing and involves a simulated
urban dynamometer driving schedule with both cold and
hot start portions and an average speed of 19.5 mph.
(5) The light-duty vehicles were also tested over the
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8
Highway Fuel Economy Test (HFET) which involves a
relatively high-speed (averaging 48.2 mph) driving
cycle and is used primarily for highway fuel economy
measurement. (6)
The heavy-duty engines were tested over both
steady-state and transient operating cycles. The
steady-state tests were based on the 1979 13-mode
Federal Test Procedure (FTP) for heavy-duty engines.
(7) The steady-state unregulated pollutant
measurements were taken over a 7-mode test which is an
abbreviated version of the 13-mode FTP. Transient
testing was based on the 1984 transient FTP for
heavy-duty diesel engines as well as the 1986 proposed
FTP, which includes particulate measurement. (8 >(9)
The transient test involves both hot and cold start
operation and generally is a fairly lightly loaded
cycle. Because EPA believes that transient testing
provides a more realistic assessment of heavy-duty
engine emissions in urban environments than does
steady-state testing, we will present the transient FTP
data in this paper and will report steady-state data
only when it differs significantly and is thus of
additional interest.
The regulated gaseous pollutants (HC, CO, and NOx)
were measured in accordance with standard EPA
certification test procedures for light-duty vehicles
and heavy-duty engines. (5)(10) The unregulated
compounds analyzed in these programs were measured by a
variety of different procedures, which are summarized
in Table 3. Details of the measurement procedures used
for these pollutants have been described elsewhere.
(11) (12)
RESULTS OF THE LIGHT-DUTY VEHICLE TEST PROGRAM
The average emission and energy efficiency results
for the gasoline and methanol-fueled Escorts and
Rabbits are shown in Table 4. The following discussion
will focus on these data. In an attempt to put these
results into perspective, a literature search has been
performed to identify the conclusions of previous
research projects utilizing pure methanol in light-duty
applications. It will be noted that the EPA light-duty
test program focused exclusively on Otto cycle
engines. This is convenient for comparative purposes
since nearly all previous methanol light-duty vehicle
research has involved Otto cycle engines and
appropriate since 95 percent of all new passenger cars
utilize Otto cycle engines.
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TABLE 3 - MEASUREMENT PROCEDURES FOR VARIOUS COMPOUNDS
Compound Sampling
Methanol Implnger
Aldehydes and Ketones Implnger
Individual tiydrocarbons Bag
Particulate Matter Filter
Nitrosamines (LDV* only) Trap
Ammonia (LDV only) Implnger
Total Cyanide (LDV only) Implnger
Method of Analysis
Gas chromatograph with flame ionization
detector.
Dinitrophenylhydrazone derivative; gas
chromatograph with flame ionization
detector.
Gas chromatograph with flame ionization
detector.
Weighed using mlcrobalance.
Gas chromatograph with TEA detector.
Ion chromatograph.
Cyanogen chloride derivative; gas
chromatograph with electron capture
detector.
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TABLE 3 - MEASUREMENT PROCEDURES
Compound Sampling
Organic Amines (LDV only) Impinger
Methyl Nitrite (LDV only) Bag
Phenols (HDE+ only) Impinger
Sulfate (HDE only) Filter
Benzo(a)pyrene (HDE only) Filter
Smoke (HDE only) —
Odor (HDE only) Trap
* LDV = Light-Duty Vehicles
+ HDE = Heavy-Duty Engines
FOR VARIOUS COMPOUNDS (CONT'D)
Method of Analysis
Gas chromatograph with ascarite
precolumn and nitrogen-phosphorus
detector.
Gas chromatograph with mass
spectrometer.
Gas chromatograph with flame ionization
detector.
Barium chloranilate.
Liquid chromatograph.
Smokemeter.
Liquid chromatograph.
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TABLE 4 - AVERAGE LIGHT-DUTY VEHICLE EMISSION AND ENERGY EFFICIENCY RESULTS
FTP
Ford Escorts
Gas.[a] Meth.[b] Gas.
VW Rabbits
Meth.
HFET
Ford Escorts
Gas.
Meth.
VW Rabbits
Gas.
Meth.
Hydrocarbons (FID), g/mi
0.37
0.42[c]
0.11
0.39[c]
0.16
0.08[c]
0.11
o.o;
Carbon Monoxide, g/mi
4.49
6.03
1.08
0.88
1.69
0.53
1.26
0.2.
Oxides of Nitrogen, g/mi
0.55
0.40
0.16
0.68
0.50
0.32
0.06
0.2]
Particulate, mg/mi
9.2
6.3
11.8
4.7
2.3
10.1
32.2
11.4
Methanol, mg/mi
ND[d]
407
ND
440
ND
61
ND
2
Total Aldehydes and Ketones, mg/mi
0.2
33.6
ND
10.3
ND
24.3
ND
ND
Formaldehyde, mg/mi
0.2
33.0
ND
10.3
ND
24.0
ND
ND
Total Individual Hydrocarbons, mg/mi
155
50
40
5
75
6
61
1
Methane, rag/mi
96.1
48.3
14.0
4.8
43.8
4.8
27.5
1.0
Ethylene, mg/mi
8.7
0.3
4.8
0.2
5.2
0.2
4.2
ND
Ethane, mg/mi
18.2
0.5
2.6
<0.1
12.2
0.2
6.3
ND
Acetylene, mg/mi
1.4
<0.1
1.8
<0.1
ND
ND
ND
ND
Propane, mg/mi
0.8
0.6
ND
ND
0.3
0.5
ND
ND
Propylene, mg/mi
6.1
ND
4.2
ND
4.7
ND
5.2
ND
Benzene, mg/mi
6.3
<0.1
5.3
ND
3.2
ND
10.5
ND
Toluene, mg/mi
17.2
<0.1
9.2
ND
5.6
ND
7.4
ND
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TABLE 4 - AVERAGE LIGHT-DUTY VEHICLE EMISSION AND ENERGY EFFICIENCY RESULTS (CONT'D)
FTP
Ford Escorts
Gas.
Meth.
VW Rabbits
Gas.
Meth.
HFET
Ford Escorts
Gas. Meth.
Vtf Rabbits
Gas.
Meth.
Nitrosamines, mg/ml
Ammonia, mg/mi
Total Cyanide, rag/mi
Total Organic Amines, mg/mi
Methyl Nitrite, ppm
Fuel Economy, mi/gal
Energy Efficiency, mi/10^Btu
ND
[e]
[e]
[e]
[e]
24.5
2.16
ND
10.0
ND
<0.1
0-0.5
12.6
2.25
ND
[e]
[e]
[e]
ND
23.8
2.10
ND
le]
le]
le]
0-1.1
13.8
2.46
[e]
[e]
[e]
le]
[e]
37.9
3.35
[ej
[e]
[ej
[e]
ND
18.0
3.21
[ej
[e]
le]
[e]
le]
30.5
2.69
[e]
le]
[e]
[e]
le]
17.2
3.06
[a] Gasoline-fueled
[b] Methanol-fueled
[c] Hydrocarbons as
[d] None detected.
[e] Analysis not conducted
measured by the FID (flame ionization detector) and expressed as methanol.
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Organic Emissions
Gasoline is composed of various hydrocarbon
compounds. One important class of emissions from
gasoline-fueled vehicles includes unburned fuel
hydrocarbons and their derivatives. Strictly speaking,
hydrocarbons are those compounds which include only
hydrogen and carbon in their molecular structure.
While most fuel-related emissions from gasoline-fueled
vehicles are hydrocarbons, derivatives such as
oxygenated hydrocarbons are also emitted. Because
hydrocarbons dominate these emissions, the custom has
been to use the term hydrocarbons to include all
unburned gasoline-related emissions as measured by the
approved procedure, even those derivatives which are
not strictly hydrocarbons. Accordingly, the EPA
standard for unburned fuel emissions is a hydrocarbon
standard based upon usage of a flame ionization
detector (FID). The FID measures most hydrocarbon
compounds very accurately. The FID does not measure
oxygenated hydrocarbons such as aldehydes and alcohols
very accurately.
Since methanol fuel is an oxygenated hydrocarbon
itself, the emissions from methanol-fueled vehicles are
predominantly oxygenated hydrocarbons such as unburned
methanol and aldehydes (specifically, formaldehyde).
Thus, reliance upon the term hydrocarbons may not be
appropriate, and therefore the term "organic" emissions
will be used in this paper to include all unburned fuel
and fuel derivative emissions (i.e., all hydrocarbon
and oxygenated hydrocarbon emissions). Because of the
inability of the FID to accurately measure oxygenated
hydrocarbons, the organic compounds in methanol-fueled
vehicle exhaust were determined by individual
measurement procedures.
Table 4 gives the emission values for various
organic species that were measured in this program —
hydrocarbons, methanol, total aldehydes and ketones,
formaldehyde, and 8 different individual hydrocarbon
compounds. The FID-measured hydrocarbons are presented
in the first row. As mentioned above, the hydrocarbons
from gasoline-fueled vehicles consist primarily of
unburned gasoline-derived hydrocarbons (accurately
measured by the FID) and a small quantity of aldehydes
(generally not accurately measured by the FID). For
each methanol-fue1ed vehicle, the FID-measured
hydrocarbon datum is assumed to be the result of the
FID measuring only unburned methanol (which is not
strictly correct as there are some hydrocarbons and
aldehydes in the exhaust stream). Therefore, the
reported FID hydrocarbon values for the methanol-fueled
vehicles are based on the molecular weight of the fuel,
which includes the oxygen component (i.e., the HC data
are reported as methanol). This results in mass
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14
emission measurements which are twice as high as they
would be if the oxygen were excluded.
Table 5 computes the total organic emissions for
the vehicles tested. This is done by adding the actual
measurements for hydrocarbon, methanol and formaldehyde
(the predominant aldehyde). For the gasoline-fueled
vehicles, the hydrocarbon data are the FID measured
hydrocarbon results. For the methanol-fueled vehicles,
the hydrocarbon data are the sum of the total
Individual hydrocarbon results.
Certain trends are apparent from Table 5. First,
organic emissions from the gasoline-fueled vehicles are
nearly all hydrocarbons while the methanol engine
exhaust is dominated by unburned methanol but contains
small amounts of formaldehyde and low molecular weight
hydrocarbons as well. In terms of total organic
emissions, both methanol vehicles emitted greater
amounts over the FTP but lesser amounts over the HFET
compared to the corresponding gasoline vehicles. The
total organic emissions from the methanol vehicles are
somewhat greater than the level of the current 0.41
g/mi hydrocarbon emission standard for light-duty
vehicles.
In this test program, the methanol-fueled vehicles
emitted greater amounts of organic emissions over the
FTP than did the gasoline-fueled vehicles. A survey of
the literature indicates that previous research has
resulted in levels of organic emissions from
methanol-fueled vehicles ranging from somewhat lower to
up to five times higher than organic emissions from
gasoline-fueled versions of the same model.
(13)(14)(15)(16) These projects all used either an
oxidation catalyst or no catalyst at all. Two other
projects have been reported which utilized three-way
catalysts on Ford Pintos. Both of these projects
reported methanol-fueled vehicle emissions to be
approximately one—half of the gasoline-fueled vehicle
emissions on an ionizable carbon basis, which would
result in similar or slightly higher methanol emissions
on a mass basis. (17)(18) Thus, the EPA results are
within the range of previous data for total organics
emissions >
The primary justification for the regulation of
organic emissions is their role as oxidant precursors
in urban atmospheres. As such, the relative masses of
organic emissions in gasoline and methanol exhausts are
not as important as the relative photochemical
reactivities of the organic species. Formaldehyde is
known to be very photochemically reactive, but unburned
methanol itself is generally considered to be of low
photochemical reactivity. Methanol vehicle exhaust
contains almost no alkenes, aromatics, or nonmethane
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TABLE 5 - AVERAGE LIGHT-DUTY VEHICLE ORGANIC EMISSION RESULTS (g/mi)
Hydrocarbons [c]
Methanol
Fo nnaldehyde
Total "Organics"
Ford Escorts
FTP
VW Rabbits
Gas.[a] Meth.[b] Gas. Meth.
0.37 0.050 0.11 0.005
0 0.41 0 0.44
0.0002 0.033 0 0.010
0.37 0.49 0.11 0.46
HFET
Ford Escorts
VW Rabbits
Gas. Meth. Gas. Meth.
0.16 0.006 0.11 0.001
0 0.061 0 0.002
0_ 0.024 0_ 0
0.16 0.09 0.11 0.003
[a] Gasoline-fueled.
[b] Methanol-fueled.
(cJ For the gasoline-fueled vehicles, this is the FID value. For
the methanol-fueled vehicles, this is the sum of the
"individual hydrocarbon" data from Table 4.
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16
alkanes which are the major reactive components of
gasoline exhaust. Thus, it is not immediately clear
whether methanol exhaust would be more or less reactive
than gasoline exhaust.
Probably the only way to compare the relative
photochemical reactivities of methanol and gasoline
exhausts is to utilize sophisticated smog chamber
testing. Bechtold and Pullman performed such a
comparison with a 1976 full-size Dodge (with and
without an oxidation catalyst) and four 1978 Ford
Pintos with three-way-catalysts. Generally, they found
that the photochemical reactivity of methanol exhaust
was similar to or less than the reactivity of gasoline
exhaust under the same vehicle operating conditions.
(17) Additional smog chamber work is necessary to
quantify the reactivity impacts of methanol vehicles.
A second major issue with methanol-fueled vehicles
is formaldehyde emission. As Table 5 shows, the
methanol-fueled Escort and Rabbit emitted 33 and 10
mg/mile of formaldehyde, respectively, while the
gasoline-fueled Escort and Rabbit emitted 2 and 0
mg/mile, respectively. Past studies confirm that
aldehyde emissions are higher from methanol vehicles.
(14)(15)(17)(18)(19) These higher emissions are of
concern because of formaldehyde's toxicity and possible
carcinogenicity, (28) in addition to its high
reactivity in the photochemical process. Table 6 gives
the formaldehyde emission levels for several different
types of gasoline-fueled light-duty vehicles from
previous EPA test programs. Table 6 shows that the
formaldehyde emissions from the lethanol-fueled Escort
and Rabbit were much higher than the three-way-catalyst
cars but lower than the 1970 non-catalyst cars.
Lowering the formaldehyde emissions from
methanol-fueled vehicles will likely be a high priority
for those manufacturers seeking to introduce such
vehicles into the market.
Carbon Monoxide Emissions
As shown in Table 4, CO emissions for the
methanol-fueled Escort and Rabbit over the FTP were
6.03 g/mi and 0.88 g/mi, respectively. The
methanol-fueled Escort emitted 34 percent more CO and
the methano1-fue1ed Rabbit emitted 19 percent less CO
than their gasoline-fueled counterparts over the FTP.
Highway CO values were lower for the methanol-fueled
vehicles in both cases. Previous studies had indicated
that CO levels from methanol-fueled vehicles were
similar to those from gasoline-fueled vehicles under
stoichiometric conditions. (13)(14)(15)(16 ) CO levels
are primarily a function of air/fuel ratios with more
CO formed as the mixture becomes richer. It has been
shown that at the leaner air/fuel ratios which are
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TABLE 6 - COMPARISON OF AVERAGE FTP FORMALDEHYDE EMISSIONS
FOR VARIOUS LIGHT-DUTY VEHICLES
Formaldehyde Emissions
Vehicles (mg/mlle)
Previous EPA Projects (20) - All Gasoline-Fueled Vehicles
1981 3-way-catalyst equipped cars 1
1978, 1979 3-way-catalyst equipped cars 2
1978 oxidation-catalyst equipped cars 3-11
1977 non-catalyst cars 16
1970 non-catalyst cars 51
This Project - All Methanol-Fueled Vehicles
1981 3-way-catalyst equipped, carbureted car (Escort) 33
1981 3-way-catalyst equipped, fuel injected car (Rabbit) 10
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18
feasible with methanol vehicles, CO emissions are
generally lower. (13)(16)
Oxides of Nitrogen Emissions
FTP NOx emissions were 0.40 g/mi and 0.68 g/mi for
the methanol-fueled Escort and Rabbit, respectively,
compared to 0.55 g/mi and 0.16 g/mi for the
gasoline-fueled models (see Table 4). The
methanol-fueled Escort emitted 27 percent less NOx but
the methanol Rabbit emitted four times more NOx (though
still well below the level of the standard of 1.0
g/mi). These mixed results for NOx emissions were
unexpected. NOx formation is a function of peak
combustion temperatures. As methanol combusts at a
lower flame temperature than gasoline, it could
theoretically be expected to result in lower NOx
levels. This possibility of lower NOx levels was one
of the driving forces behind early methanol research
projects and was substantiated by several studies
showing NOx reductions in the range of 30 to 65
percent. (13)(16)(19)(21) The higher compression
ratios of the methanol vehicles would be expected to
increase NOx formation somewhat, but higher compression
ratios also permit less spark timing advance which
decreases NOx emissions. In view of the lower CO and
higher NOx emissions (as well as better energy
efficiency, which will be discussed below) from the
methanol-fueled Rabbit, it seems plausible that the
Rabbit was operated leaner than the Escort, which could
make successful operation of the reduction catalyst
unlikely and lead to higher NOx emissions.
Particulate Emissions
As shown in Table 4, particulate levels over the
FTP were lower for both methano1-fueled vehicles than
for the corresponding gasoline-fueled vehicle. The
methanol-fueled Rabbit also emitted less particulate
over the HFET, although the methanol-fueled Escort
emitted more particulate over the HFET. All of the
particulate levels were well below the level of the
0.20 g/mi standard which is planned for 1985 light-duty
diesel vehicles.
Other Unregulated Pollutants
Ammonia, cyanide, and organic amine emissions were
measured from the methanol-fueled Escort over the FTP.
The resulting emissions were 10 mg/mi, 0 mg/mi, and
0.02 mg/mi, respectively. These levels are somewhat
lower than the average levels of 13 mg/mi ammonia, 3
mg/mi cyanide, and 0.05 mg/mi organic amines measured
from three-way-catalyst gasoline-fueled vehicles in a
previous project. (22) All four vehicles were tested
for nitrosamines over the FTP and none were detected.
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19
Very low levels of methyl nitrite were detected under
certain testing conditions with the methanol-fueled
vehicles* A more detailed discussion of the
nitrosamine and methyl nitrite testing and results is
presented elsewhere. (20)
Energy Efficiency
The fuel economy and energy efficiency results are
also given in Table 4. The fuel economy values for the
methanol-fueled vehicles are low, due to the volumetric
heating value of methanol being about one-half that of
gasoline* But fuel economy is usually not as important
as energy efficiency. Accordingly, the fuel economy
results have been translated into miles per 10^ Btu,
a measure of how far a fuel can propel a vehicle on
10,000 Btu. On this basis, the gasoline-fueled Escort
had a value of 2.16 mi/104 Btu over the FTP while the
methanol-fueled Escort had a value of 2.25 m i/104
Btu, an improvement of 4 percent. On the HFET, the
methanol-fueled Escort was 4 percent less efficients
Overall, then, the efficiencies of the gasoline and
methanol-fueled Escorts were similar. The
methanol-fueled Rabbit was 17 percent more efficient
over the FTP and 14 percent more efficient over the
HFET, for an overall efficiency increase of
approximately 15 percent. One reason why the use of
methanol fuel increased the efficiency of the Rabbit
but not that of the Escort may be that Ford made a more
concerted effort to maintain very low NOx levels which
could have resulted in some detrimental energy
efficiency tradeoffs (more spark timing retard,
possibly not as lean, etc.).
There are several reasons why methanol-fueled
vehicles would be expected to have higher energy
efficiencies than their gasoline-fueled counterparts!
methanol's high octane number allows the usage of
higher compression ratios, its wider flammability
limits and higher flame speeds provide acceptable
engine performance at leaner operation, and its high
heat of vaporization acts as an internal coolant
reducing the mixture temperature during the compression
stroke and allowing a larger charge to be inducted.
(16) Improvements in energy efficiency as high as 25
to 30 percent have been hypothesized, (29) but only
recently have entire vehicles been assembled to operate
on pure methanol which can be evaluated against these
expectations. In view of the above discussion,
Volkswagen's 15 percent energy efficiency improvement
is not unexpected.
Summary of Light-Duty Vehicle Test Program
Total mass organic emissions were somewhat higher
for both methanol-fueled vehicles over the FTP (though
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20
lower over the HFET), but resulting impacts on urban
atmosphere photochemical reactivities cannot be
predicted at this time. Formaldehyde emissions were
higher for both of the methanol-fueled vehicles under
all testing conditions. Both CO and NOx results were
mixed, with methanol fueling sometimes increasing and
sometimes decreasing these emissions* Theoretical
expectations and previous data both indicate that
methanol-fueled vehicles should emit lower levels of
NOx emissions compared to equivalent gasoline-fueled
vehicles. Emissions of particulate and unregulated
compounds such as ammonia, cyanide, and organic amines
were consistently lower from the methanol-fueled
vehicles than from similar gasoline-fueled vehicles.
The energy efficiency results were also mixed. The
methanol-fueled Escort showed no overall improvement
while the methanol-fueled Rabbit was approximately 15
percent more efficient than the gasoline-fueled
Rabbit. A more extensive discussion of this light-duty
vehicle testing program is presented elsewhere. (20)
RESULTS OF THE HEAVY-DUTY ENGINE TEST PROGRAM
The average emission and energy efficiency results
for the heavy-duty engines evaluated over the transient
FTP are shown in Table 7. The following discussion
will focus on these data, but the results of
steady-state testing will also be discussed when they
are of additional interest. Diesel engines have always
dominated the most demanding heavy truck applications,
but there are indications that diesels will soon
dominate nearly all classes of heavy-duty vehicles.
Thus, one of EPA's interests in the heavy-duty area has
been engines which utilize methanol and which could
replace existing diesel engines. Attempts will be made
to compare these results to past projects found in the
literature, but this is the first program to be
publically reported that characterizes the emissions of
methanol-fueled diesel-cycle engines over the EPA
heavy-duty transient test procedure. Thus, comparisons
to a large data base are not possible.
Organic Emissions
As discussed above in the section on light-duty
vehicle results, the issue of organic emissions from
gasoline and methanol-fueled vehicles can be somewhat
confusing because of the different types of exhaust
products and measurement procedures. Diesel fuel, like
gasoline, is composed of hydrocarbons and a diesel
engine's unburned fuel-related emissions are dominated
by hydrocarbons. Thus, there is the same difficulty in
comparing diesel and methanol-fueled engine organic
emissions as there is with gasoline and methanol-fueled
vehicle organic emissions.
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TABLE 7 - AVERAGE HEAVY-DUTY ENGINE EMISSION AND ENERGY EFFICIENCY
RESULTS OVER THE TRANSIENT FEDERAL TEST PROCEDURE
Volvo TD-100 A
Volvo TD-100 A
MAN D2566 FMUH
Volvo TD-100 C
Methanol/Diesel
Methanol/Diesel
Spark-Ignited
Conventional Diesel
Dual-Injection
Dual-Injection
Methanol
No Catalyst
No Catalyst
With Catalyst
tfith Catalyst
Hydrocarbons,[a] g/hp-hr
0.85
1.45
0.12
0.04
Carbon Monoxide, g/hp-hr
3.01
7.67
2.69
0.31
Oxides of Nitrogen,[b] g/hp-hr
8.34
5.45
5.51
6.61
Particulate, g/hp-hr
0.52
0.30
0.27
0.04
Methanol, rag/hp-hr
[c]
3700
670
680
Total Aldehydes and Ketones, mg/hp-h
r 10
190
200
<1
Formaldehyde, mg/hp-hr
10
170
200
<1
Total Phenols, mg/hp-hr
26
18
36
0
Total Individual Hydrocarbons, mg/hp
-hr 97
130
50
1
Methane, mg/hp-hr
11
26
22
1
Ethylene, mg/hp-hr
78
71
23
<1
Ethane, mg/hp-hr
<1
1
<1
<1
Acetylene, mg/hp-hr
2
<1
<1
<1
Propylene, mg/hp-hr
6
30
4
<1
Benzene, mg/hp-hr
1
5
1
<1
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TABLE 7 - AVERAGE HEAVY-DUTY ENGINE EMISSION AND ENERGY EFFICIENCY
RESULTS OVER THE TRANSIENT FEDERAL TEST PROCEDURE (CONT'D)
Sulfate, rag/hp-hr
Benzo(a)pyrene, jig/hp-hr
Brake Specific Fuel Consumption
lb fuel/hp-hr
lb diesel equivalent/hp-hr
Smoke, peak percent opacity
Volvo TD-100 C
Conventional Diesel
No Catalyst
28
2.8
0.476
0.476
33
Volvo TD-100 A
Methanol/Diesel
Dual-Injection
No Catalyst
12
1.3
0.878
0.492
23
Volvo TD-100 A
Me thanol/Diesel
Dual-Injection
With Catalyst
73
0.2
0.856
0.487
MAN U2 566 FMUH
Spark-Ignited
Methanol
With Catalyst
No t Run
0.01
1.171
0.538
0
N3
K>
[a] Hydrocarbons as measured by the HFID (heated flame ionization
detector) and expressed as diesel-like species.
[b] No NOx correction factor used.
[c] Does not apply.
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23
Table 8 simplifies the organic emissions results
from four of the heavy-duty engines evaluated in this
program. The total organic emissions are the sum of
the hydrocarbon, methanol, total aldehydes and ketones,
and total phenols measured by the specific testing
procedures used for each pollutant or class of
pollutants. Only the hydrocarbon values in Table 8
need explanation* The hydrocarbau value for the
conventional diesel engine is the value in Table 7 for
the heated flame ionization detector (EF1D) minus the
value for total phenols. This is appropriate since the
HF1D detects and measures phenols very accurately. The
hydrocarbon values for the dual-injection Volvo and the
pure methanol M.A.N. engines are based on the
individual hydrocarbon measurements in Table 7.
Propane and toluene are not listed in Table 7 nor
included in the data in Table 8, the former because it
was not detected in any of the tests and the latter
because of suspected chromatographic interferences.
As Table 8 shows, the dual-injection Volvo without
catalyst emitted 4.04 g/hp-hr of organics, a level 4 to
6 times higher Chan the other three engina/catalyst
configurations tested. The dual-injection Volvo engine
with catalyst emitted 0.96 g/hp-hr, the conventional
diesel Volvo engine emitted 0.86 g/hp-hr, and the pure
methanol M.A.N. engine emitted 0.68 g/hp-hr. The
emissions from these three configurations are all under
the level of the 1.3 g/hp-hr standard scheduled for
future heavy-duty engines. The organics from the
conventional diesel engine were nearly all
hydrocarbons, while the organics from the dual-fuel
engine (with and without catalyst) were primarily
methanol but also included significant amounts of
aldehydes and ketones and hydrocarbons. The organic
emissions from the pure methanol engine were almost all
unburned methanol with only trace amounts of aldehydes
and hydrocarbons detected. The pure methanol M.A.N,
engine emitted even less aldehydes than the
conventional diesel engine over the transient FTP cycle.
As a check on the M.A.N, aldehyde results during
transient operation, we will report the aldehyde
results for the 7-mode steady-state tests. The pure
methanol engine emitted negligible amounts of aldehydes
over five of the seven modes of the steady-state test,
but did emit very significant amounts during the two
2-percent loaci speeds. In terms of the 7-mode
composite, the pure methanol M.A.N, engine emitted 48
mg/hp-hr; this compares to 14 mg/hp-hr for the
conventional diesel engine, 64 mg/hp-hr for the
dual-fuel Volvo engine without catalyst, and 110
mg/hp-hr for the dual-fuel Volvo engine with catalyst.
(23) Note that the use of the catalyst on the
dual-injection engine actually increased aldehyde
emissions for both the transient and steady-state
-------
TABLE 8 - AVERAGE HEAVY-DUTY ENGINE ORGANIC EMISSION RESULTS OVER THE TRANSIENT FTP (g/hp-hr)
Hydrocarbons
Me thanol
Total Aldehydes
and Ketones
Total Phenols
Total "Organics"
Volvo TD-100 C
Conventional Diesel
No Catalyst
0.82[a]
0
0.01
Volvo TD-100 A
Me thanol/Diesel
Dual-Injection
No Catalyst
0.13[b]
3.70
0.19
Volvo TD-100 A
Me thanol/Diesel
Dual-Injection
With Catalyst
0.05[b]
0.67
0.20
MAN D2566 FMUH
Spark-Ignited
Methanol
With Catalyst
0.001[b]
0.68
0.001
0.03
0.02
0.04
0.86
4.04
0.96
0.68
[a] From Table 7, hydrocarbons less phenols.
[b] From Table 7, total individual hydrocarbons.
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25
testing. This is likely due to the partial oxidation
of unburned methanol to formaldehyde. A larger or more
efficient catalyst might solve this problem.
Thus, the pure methanol engine emitted over 3
times more aldehydes than the conventional diesel
engine over the composite 7-mode test, but less
aldehydes than the conventional diesel over the
transient test. The high level of aldehydes during the
steady-state 2-percent load speeds and the likelihood
of aldehyde formation due to partial oxidation in the
catalyst indicates that more research into aldehyde
control is necessary and that improvements may be
possible.
In comparing the organic emission results of the
four engine/catalyst configurations in Table 8, two
conclusions seem apparent. The first is that the pure
methanol engine, with catalyst, actually produces lower
organic emissions than the conventional die3el without
catalyst (catalysts are difficult to utilize with
diesel engines because of particulate matter buildup
and subsequent blockage) . This improvement was even
more apparent over the steady-state testing where the
organic emissions with the conventional diesel engine
were nearly twice those from the pure methanol M.A.N,
engine. (23) The second is that dual-injection of
methanol and diesel fuel increases organic emissions
significantly without an oxidation catalyst and
increases them slightly with an oxidation catalyst.
The use of dual-injection did not provide the same
organic emission reductions as did the use of pure
methanol fuel.
Of course, this discussion has centered on the
mass organic emissions and not the effects on urban
atmosphere photoehemical reactivities . Again, research
needs to be performed on the relative reactivity
impacts of methanol and diesel exhausts.
Carbon Monoxide Emissions
The carbon monoxide emissions for each of the
configurations evaluated are shown in Table 7. They
were 3.01 g/hp-hr for the Volvo diesel engine, 7.67
g/hp-hr for the dual-injection Volvo engine without
catalyst, 2.69 g/hp-hr for the dual-injection Volvo
engine with catalyst, and 0.31 g/hp-hr for the pure
methanol M.A.N, engine. All of these levels are well
below the levels of present and future heavy-duty CO
standards. The M.A.N, engine's very low CO emissions
are due both to very low engine-out emissions and
effective catalytic aftertreatment.
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26
Oxides of Nitrogen Emissions
As Table 7 indicates, the transient NOx emissions
were 8.34 g/hp-hr for the conventional diesel engine,
5.45 g/hp-hr for the dual-fueled engine without
catalyst, 5.51 g/hp-hr for the dual-fueled engine with
catalyst, and 6.61 g/hp-hr for the pure methanol
engine. The heavy-duty NOx standard is currently 10.7
g/hp-hr, but the Clean Air Act Amendments of 1977
require EPA to promulgate a new standard representing a
75 percent reduction from baseline values. It might be
expected that the utilization of methanol, with its
lower flame temperature, would lower NOx emissions.
Previous dual-fuel, single-cylinder testing had shown
NOx reductions as high as 50 percent. (24) (25) The
dual-fuel Volvo, both with and without catalyst,
produced 38 percent less NOx than the Volvo diesel
engine, while the pure methanol M.A.N- engine emitted
21 percent less than the conventional diesel engine.
Reductions during steady-state testing were even
larger, ranging from 23 percent for the pure methanol
engine to 56 percent for the dual-injection engine
without catalyst, all compared to the conventional
diesel engine- Thus, these results do agree with both
the theoretical expectation of lower NOx emissions and
previous results.
Particulate and Related Emissions
Methanol has no carbon-carbon bonds and generally
has not been observed to form carbonaceous particles.
In addition, methanol does not typically contain
inorganic materials like sulfur or lead which can also
be sources of solid particulate. For these reasons, it
has been hypothesized that pure methanol usage in
diesel engines would result in zero or near zero
particulate emissions. (26) If true, this would be a
primary advantage for methanol usage as particulate
emissions from diesel engines have become a major
environmental concern.
The data in Table 7 confirm the hypothesis that
methanol produces little or no particulate. The
conventional diesel engine produced 0.52 g/hp-hr of
particulate during transient testing. The dual-fuel
Volvo engine, which on average used approximately 20
percent diesel fuel by weight, emitted 0.30 and 0.27
g/hp-hr of particulate, respectively, for the
non-catalyst and catalyst versions (decreases of 42 and
48 percent). The pure methanol M.A.N, engine emitted
just 0.04 g/hp-hr, a reduction of 92 percent from the
conventional diesel engine. The particulate values
under steady-state testing were similar, with an even
lower level for the pure methanol engine. The M.A.N,
engine results were the only data below the level of
the proposed EPA particulate standard of 0.25 g/hp-hr.
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27
No carbon (soot) particulate was visible on any of the
filters taken from the pure methanol engine. These
results suggest that methanol combustion may Inherently
produce low particulate emissions and that the
particulate emitted by the dual-Injection engine was
likely due to diesel fuel combustion.
Smoke is a measure of the visible fraction of
particulate matter. As such, smoke levels do not
necessarily correlate with particulate mass emission
values* In this program, acceleration, lug, and peak
smoke measurements were taken with the FTP smoke
procedure. Table 7 gives the peak opacity readings.
Generally, the diesel engine produced the highest smoke
levels, followed by the dual-fuel engine without
catalyst, the dual-fuel engine with catalyst, and the
pure methanol engine. There was essentially no smoke
opacity for the M.A.N, engine at any time. Note that
these smoke levels do correlate directionally with the
particulate values discussed above.
Sulfate is frequently one component of particulate
matter. It is formed by the oxidation of fuel sulfur
to sulfate. Because chemical-grade methanol contains
no sulfur, the use of methanol should reduce sulfate
emissions. The conventional diesel engine emitted 28
mg/hp-hr of sulfate. The dual-fuel engine without
catalyst emitted 12 mg/hp-hr, a reduction of 57
percent. But the addition of the oxidation catalyst
increased the sulfate emissions of the dual-fuel engine
to 73 mg/hp-hr, an increase of six times compared to
the non-catalyst dual-fuel configuration and an
increase of 2.6 times compared to the diesel engine.
It is well known that catalysts increase sulfate
formation. (30) It was assumed that because the
methanol contained no sulfur, the sulfate emissions
from the pure methanol engine would be zero.
Therefore, the test was not even run for the M.A.N,
engine.
Benzo(a)pyrene is a polynuclear aromatic
hydrocarbon and a known carcinogen. (31) Table 7 shows
that the use of pure methanol as a fuel produces very
little benzo(a)pyrene• As with total particulate, the
data suggest that the more you displace diesel fuel
with methanol, the less benzo(a)pyrene is emitted.
Energy Efficiency
As shown in Table 7, the actual fuel consumption
in kilograms of fuel per horsepower-hour is much higher
for those engines which used methanol; this is to be
expected since methanol has a much lower volumetric
heating value than diesel fuel. Table 7 also gives the
fuel consumption results in terms of diesel fuel
equivalent per horsepower-hour, utilizing the different
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28
Btu contents of the fuels to develop a measure of
energy efficiency. This calculation was straight-
forward for the pure methanol engine, but for the
dual-injection configurations it was necessary to
determine the relative proportions of methanol and
diesel fuel that were consumed over the transient test
cycle- It was found that approximately 80 percent of
the total fuel used (by weight) by the dual-fuel engine
was methanol and 20 percent was diesel fuel.
The data indicate that the dual-fuel configu-
rations were about 3 percent less efficient than the
diesel engine, while the pure methanol engine was
approximately 13 percent less efficient during the
transient testing. The higher fuel consumption for the
M.A.N, engine is likely due to the higher fueling rates
at low speeds. (32) The transient test cycle is a
fairly lightly loaded cycle. Over the steady-state
cycle, the dual-fuel Volvo and pure methanol M.A.&.
engines were both 10 percent less efficient than the
conventional Volvo diesel engine. The energy
efficiency comparisons between the M.A.N, engine and
the Volvo engine configurations must be qualified in
view of the significant design differences between the
engines. The much higher efficiency of the Volvo
diesel engine compared to the pure methanol M.A.N,
engine may not be due exclusively to the different
fuels used. There is some evidence in the literature
that methanol is less efficient than diesel fuel at
lower loads but equal to or more efficient at heavier
loads, though it must be noted that this is based
predominantly on dual-fuel engines and steady-state
testing. (1)(24)(25)(27)
Summary of Heavy-Duty Engine Test Program
Table 7 summarizes the average emission and energy
efficiency data over the EPA transient test cycle for
the four heavy-duty engine configurations evaluated in
this program. The conventional Volvo diesel engine
produced results typical of heavy-duty diesel engines;
fairly low organic and CO emissions, fairly high NOx,
particulate, and smoke values, measurable amounts of
benzo
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29
amounts of hydrocarbons were also detected. CO
emissions were over twice as high, but significant
reductions of NOx, particulate, smoke, and
benzo(a)pyrene levels were found* Fuel consumption, on
an energy equivalent basis, was slightly higher for the
dual-fuel engine than for the Volvo diesel engine*
Addition of an oxidation catalyst to the
dual-injection Volvo engine reduced organic emissions
by a factor of four, and resulted in total organic
levels similar to those of the diesel engine. The
organics were composed almost entirely of unburned
methanol and aldehydes. The catalyst reduced CO levels
below those of the diesel engine, and reduced smoke and
benzo(a)pyrene values even further. NOx, particulate,
and energy efficiency were not affected much by the
catalyst.
The emissions from the pure methanol,
spark-ignited M.A.N. engine with catalyst were
generally much lower than the emissions from the other
three engine/catalyst configurations. Total organic
emissions were lower than those from the diesel engine,
and were nearly all unburned methanol with only trace
amounts of aldehydes during transient operation.
Somewhat greater amounts of aldehydes were observed
during steady-state testing. CO values were very low,
nearly a 90 percent reduction compared to the diesel
engine. NOx emissions were lower than from the diesel
engine, but somewhat higher than from the dual-fuel
engine. Particulate, smoke, and benzo(a)pyrene values
were all zero or near zero. However, the energy
efficiency of the M.A.N, engine was 13 percent lower
over transient operation and 10 percent lower during
steady-state testing compared to the diesel engine. A
more detailed presentation of the data from the
heavy-duty testing programs is available elsewhere. (23)
CONCLUSIONS
Light-Duty Program
At this time it is not possible to conclude
whether methanol-fueled passenger cars would be
environmentally preferable to current gasoline-fueled
models. EPA's testing of two of the more advanced
methanol-fueled designs produced mixed results. Total
organic emissions were higher from the methanol-fueled
Escort and Rabbit compared to their gasoline-fueled
counterparts, although the overall impacts on urban
atmosphere photochemical reactivities cannot be
predicted because of the different compounds emitted.
The methanol-fueled vehicles emitted primarily unburned
methanol and formaldehyde while the gasoline-fueled
vehicles produced almost exclusively hydrocarbons.
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30
More research is needed to determine the relative
public health impacts of these various pollutants.
Because of its high photochemical reactivity and
possible human carcinogenicity, formaldehyde emission
is probably the most critical public health issue
associated with widespread methanol-fueled vehicle
introduction. CO and NOx emission results were mixed
in this program, though there is good agreement in the
literature that methanol combustion should reduce NOx
formation* Particulate and unregulated pollutant
emissions were consistently lower for the
methanol-fueled vehicles. The two Escorts had similar
energy efficiencies, while the methanol-fueled Rabbit
was about 15 percent more efficient than its
gasoline-fueled counterpart. Many researchers have
predicted even greater energy efficiency improvements.
Although conclusions at this time would be
premature, some comments on the results of this program
can be made. First, it must be noted that one of the
two vehicles used in this program for comparative
purposes, the gasoline-fueled Volkswagen Rabbit, is one
of the lowest emitting vehicles on the market today.
Second, it would appear that much optimization is
possible for methanol-fueled vehicles. Until now, the
methanol-fueled vehicles which have been developed have
involved modifications of designs intended and
optimized for gasoline fuel. Emissions and fuel
economy of gasoline-fueled vehicles have been studied
for many years. It is plausible that continued
research and development will lead to future
methanol-fueled vehicles which will provide both
emissions and energy efficiency improvements.
Heavy-Duty Program
Compared to the conventional diesel Volvo engine,
the dual-fuel Volvo engine, which utilized
approximately 80 percent methanol fuel, produced mixed
emission results. Without an oxidation catalyst, the
dual-fuel Volvo emitted much more organic and CO
emissions, but considerably less NOx, particulate,
smoke, and benzo(a)pyrene emissions. The addition of
catalytic aftertreatment reduced the organic and CO
emissions to levels similar to those of the
conventional diesel engine, and maintained the lower
NOx, particulate, smoke, and benzo(a)pyrene values.
The organic emissions from the dual-fuel engine
configurations were mostly unburned methanol and
aldehydes, while the diesel engine emissions were
largely hydrocarbons. The energy efficiencies of the
dual-fuel engine configurations were slightly less than
that of the conventional diesel engine. These results
generally compare well with results reported in the
literature.
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31
The pure methanol, spark-ignited M.A.N. engine,
with catalyst, emitted zero or near zero CO,
particulate, smoke, and benzo(a)pyrene. It also
emitted less NOx and organic emissions than the
conventional diesel engine, with the organics being
composed almost exclusively of unburned methanol and
very low levels of aldehydes. The energy efficiency of
the M.A.N, engine was 10 to 13 percent less than that
of the conventional diesel engine, although the design
differences between the M.A.N, and Volvo engines may
account for part of the latter's efficiency advantage.
These results, and data reported in the literature,
indicate that methanol utilization in heavy-duty diesel
engines would produce significant environmental
benefits, especially with respect to NOx and
particulate emissions which are particularly difficult
to control from diesel engines. The primary concern
involves energy efficiency, which is critical in the
trucking industry. Again, it is possible that further
research will result in improvements with respect to
the energy efficiency of methanol-fueled heavy-duty
engines.
ACKNOWLEDGEMENTS
The results discussed in this paper were obtained
from test programs performed by Southwest Research
Institute (SwRI) and sponsored by the Environmental
Protection Agency (EPA) under Contracts 68-03-2884,
68-03-3072, and 68-03-3073. The authors wish to thank
the many individuals from SwRI and EPA who participated
in the programs, as well as the following organizations
which provided test vehicles; Ford Motor Company,
Volkswagen of America, Volkswagenwerk AG of Germany,
California Energy Commission, Los Angeles County
Mechanical Department, Volvo Truck Corporation, and
M.A.N, of Germany.
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32
REFERENCES CITED
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"The Utilization of Different Fuels in a Diesel
Engine with Two Separate Injection Systems,"
Paper 11-29, Third International Symposium on
Alcohol Fuels Technology, Asilomar, California,
May 29-31, 1979.
2. Neitz, A., and Chmela, F., "Results of M.A.N.-FM
Diesel Engines Operating on Straight Alcohol
Fuels," Fourth International Symposium on Alcohol
Fuels Technology, Paper B-56, October 5-8, 1980.
3. "Senate Bill 620i Alcohol Fleet Test Program,"
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December 1981.
4. Code of Federal Regulations, Title AO, Chapter 1,
Part 86, Subpart B, Sections 86.113-78 and
86.113-79.
5. Code of Federal Regulations, Title 40, Chapter 1,
Part 86, Subpart B, sections applicable to 1981
Model-Year Light-Duty Vehicles.
6. Federal Register, Vol. 41, No. 100, May 21 , 1976,
Appendix I: Highway Fuel Economy Driving Schedule.
7. Federal Register, Thursday, September 8, 1977,
"Heavy-Duty Engines for 1979 and Later Model
Years."
8. Federal Register, Vol. 45, No. 14, January 21,
1980, "Gaseous Emission Regulations for 1984 and
Later Model Year Heavy-Duty Engines."
9. Federal Register, Wednesday, January 7, 1981,
"Control of Air Pollution from New Motor Vehicles
and New Motor Vehicle Engines; Particulate
Regulation for Heavy-Duty Diesel Engines."
10. Code of Federal Regulations, Title 40, Chapter 1,
Part 86, Subpart D, sections applicable to
heavy-duty diesel engines.
11. Dietzmann, H. E., et al., "Analytical Procedures
for Characterizing Unregulated Pollutant Emissions
from Motor Vehicles," EPA 600/2-7 9-017, February
1979 .
12. Smith, L., et al., "Analytical Procedures for
Characterizing Unregulated Emissions from Vehicles
Using Middle-Distillate Fuels," EPA 600/2-80-068,
April 1980.
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13. Ingamells, J. C. and Lindquest, R. H., "Methanol
as a Motor Fuel or a Gasoline Blending
Component," SAE Paper No. 750123.
14. Hilden, D. L. and Parks, F. B., "A Single-Cylinder
Engine Study of Methanol Fuel—Emphasis on Organic
Emissions," SAE Paper No. 760378.
15. Menrad, H., Lee, W., and Bernhardt, W.,
"Development of a Pure Methanol Fuel Car," SAE
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16. Brinkman, N. D., "Vehicle Evaluation of Neat
Methanol— Compromises Among Exhaust Emissions,
Fuel Economy, and Driveability, " Energy Research,
Vol. 3, 1979.
17. Bechtold, R. and Pullman, J. B«, "Driving Cycle
Economy, Emissions, and Photochemical Reactivity
Using Alcohol Fuels and Gasoline," SAE Paper No.
800260.
18. Baisley, W. H. and Edwards, C. F., "Emission and
Wear Characteristics of an Alcohol Fueled Fleet
Using Feedback Carburetion and Three-Way
Catalysts," Fourth International Symposium on
Alcohol Fuels Technology, Brazil, October 5-8,
1980.
19. Pischinger, F. F. and Kramer, K., "The Influence
of Engine Parameters on the Aldehyde Emissions of
a Methanol Operated Four-Stroke Otto Cycle
Engine," Paper 11-25, Third International
Symposium on Alcohol Fuels Technology, Asilomar,
California, May 29-31, 1979.
20. Smith, L. R., Urban, C. M., and Baines, T. M.,
"Unregulated Exhaust Emissions from
Methanol-Fueled Cars," SAE Paper No. 820967.
21. Menrad, H.} "A Motor Vehicle Powerplant for
Ethanol and Methanol Operation," Paper 11-26,
Third International Symposium on Alcohol Fuels
Technology, Asilomar, California, May 29-31, 1979.
22. Smith, L. R. and Black, F. M., "Characterization
of Exhaust Emissions from Passenger Cars Equipped
with Three-Way Catalyst Control Systems," SAE
Paper No. 8008 22.
23. Ullman, T. M., Hare, C. T., and Baines, T. M.,
"Emissions from Direct-Injected Heavy-Duty
Methanol-Fueled Engines (One Dual-Injection and
One Spark-Ignited) and a Comparable Diesel
Engine," SAE Paper No. 820966.
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24. Pischinger, F. F. and Havenith, C., "A New Way of
Direct Injection of Methanol in a Diesel Engine,"
Paper 11-28, Third International Symposium on
Alcohol Fuels Technology, Asilomar, California,
May 29-31, 1979.
25. Bro, K. and Pedersen, P. S., "Alternative Diesel
Engine Fuels: An Experimental Investigation of
Methanol, Ethanol, Methane, and Ammonia in a D. I.
Diesel Engine with Pilot Injection," SAE Paper No.
7 7 0794.
26. Adelman, H., "Alcohols in Diesel Engines--A
Review," SAE Paper No. 790956.
27. "Use of Glow-Plugs in Order to Obtain Multifuel
Capability of Diesel Engines," Instituto Maua de
Tecnologia, Fourth International Symposium on
Alcohol Fuels Technology, Brazil, October 5-8,
1980.
28. "Formaldehyde Health Effects," EPA Report
460/3-81-033, NTIS PB 82-162397, p.175.
29. Hagen, D. L., "Methanol as a Fuel; A Review with
Bibliography," SAE Paper No. 770792.
30. Bradow, R. L. and Moran, J. B., "Sulfate Emissions
from Catalyst Cars--A Review," SAE Paper No.
750090.
31. Peter W. Jones and Philip Leber, editors,
"Polynuclear Aromatic Hydrocarbons," Third
International Symposium on Chemistry and
Biology—Carcinogenesis and Mutagenesis, 1979.
32. Letter from M.A.N, to Charles L. Gray, EPA, July
21, 1982.
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