DIESEL PARTICULATE EMISSIONS: THE UNITED STATES,
EUROPE, AND JAPAN
by
Richard A. Rykowski, Senior Project Manager
and
Amy J. Brochu, Environmental Engineer
U.S. Environmental Protection Agency
Office of Mobile Sources
2565 Plymouth Road
Ann Arbor, MI 48105
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DIESEL PARTICULATE EMISSIONS: THE
UNITED STATES, EUROPE, AND JAPAN
INTRODUCTION
In recent years, the popularity of diesel-powered
motor vehicles has been steadily growing around the world,
primarily in response to rising gasoline prices. As
dieselization of the passenger car and light-duty truck
markets has occurred, and as the number of traditionally
diesel-powered line-haul trucks has increased, concern for
the environmental impact of particulate emissions from
diesel engines has also grown.
This paper presents an overview of the many and varied
aspects of the environmental assessment and regulation of
diesel particulate emissions, with primary focus on the
situation in the United States (since this is the locus of
the authors' personal experience), but with extrapolations
to both Europe and Japan. The first section briefly
summarizes some of the health and welfare concerns
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associated with diesel particulate emissions, including
both carcinogenic and non-cancer health risks, visibility
reduction, and soiling. Next, a review of U.S., European,
and Japanese regulation of diesel particulate is presented,
followed by estimated emissions inventories and ambient
concentrations of diesel particulate in selected areas.
The next section offers a comparison of dieselization in
various countries, with focus on trends in fuel prices.
The final section of the paper deals with techniques
available to control diesel particulate emissions,
including those related to the engine, the exhaust, and the
fuel.
HEALTH AND WELFARE EFFECTS OF DIESEL PARTICULATE EMISSIONS
As the diesel penetration of worldwide automobile and
truck markets increases, the health and welfare
consequences associated with diesel particulate emissions
grow as well. Potential health problems resulting from
exposure to diesel particulate, both carcinogenic and
non-cancerous in nature, are briefly reviewed in the first
two parts of this section. Next, the effect of ambient
particulate matter on visibility in urban areas is
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discussed. Finally, the soiling of materials (primarily
buildings) by diesel particulate is examined.
These health and welfare effects are examined in
greater detail in EPA's Diesel Particulate StudyCl], and in
the draft and final Regulatory Impact Analyses in support
of the heavy-duty diesel particulate standards published
March 15, 1985.[2,3] The following paragraphs are merely
brief overviews of the topics, and the reader is encouraged
to refer to the previous works for more detailed
information.
Cancer Risk Assessment
The carcinogenic potency of diesel particulate matter
is primarily associated with its soluble organic fraction
(SOF), particularly the heavier aromatic hydrocarbons with
high-temperature boiling points those with three or more
benzene rings. Included in this fraction is benzo-a-pyrene
(BaP), a poly-nuclear aromatic hydrocarbon known to cause
cancer in humans.
The potential risk of contracting lung cancer as a
result of exposure to diesel particulate has been evaluated
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through both epidemiological and clinical studies. Of
course, the most valuable is a long-term epidemiological
study tracing the health of people who have been exposed to
precisely, known concentrations of diesel particulate over a
period of time. One such study, conducted on London bus
garage workers, was reviewed by EPA and others and appears
to be somewhat flawed in its design (i.e., its results are
quite uncertain, statistically).[1] Another
epidemiological study this time on U.S. railroad workers
is currently being conducted by Harvard University for
EPA. Therefore, since human epidemiological data are
extremely limited at this time, clinical data on animals
and lower organisms must be relied upon in estimating the
carcinogenic potency of diesel particulate.
EPA is basing its current estimates of the cancer risk
associated with diesel particulate on a comparative potency
method[l], wherein the relative potency results of clinical
testing on lower organisms are extrapolated to humans.
This method involves the comparison of results of a number
of bioassays performed on diesel particulate with the
results of the same bioassays performed on human
carcinogens of known potency.
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In a recently published Regulatory Impact Analysis[3],
EPA estimated a "steady-state" cancer risk attributable to
diesel particulate exposure. In making this assessment,
EPA assumed that the average level of exposure to diesel
particulate estimated for the year 2000 based on
uncontrolled heavy-duty emissions in the U.S. would
continue over a number of decades. Then, using the
comparative potency method, the annual risk of contracting
cancer from lifetime exposure to these levels of diesel
particulate was estimated at up to eight individuals in a
million.
Non-Cancer Health Effects
Particulate matter in general has long been regarded
as hazardous to human health; in fact, EPA established an
NAAQS for total suspended particulate (TSP) as early as
1971. Recently, because of growing evidence that it is the
fraction of particles with diameters of 10 microns or less
(PMio) that is responsible for most of the human health
effects associated with TSP, EPA has proposed that the
primary NAAQS for TSP be revised to only include PMX0.
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Because diesel particulates are essentially "fine"
(less than 2.5 microns in diameter), they fall easily into
the PMj o category. From this small size stems one of the
basic concerns associated with inhalation of diesel
particulate its penetration of the deepest recesses of
the lungs, the alveoli, where the oxygen/carbon dioxide
exchange takes place with the circulatory system. The body
requires months or years to clear foreign matter from the
alveolar region, which is significantly longer than that
required for the upper respiratory tract. The second basic
concern is that diesel particulate may be composed of toxic
materials or may have hazardous materials adsorbed onto its
surface. [3]
The most obvious non-cancer health effect of an
inhalable particulate, such as that produced by diesels, is
injury to the surfaces of the respiratory system, which
could result in reduced lung function, bronchitis or
chronic respiratory symptoms. The hazardous chemicals that
may be associated with particulate matter (e.g., organic
compounds, lead, antimony, etc.) can either react with lung
tissue or be transported to other parts of the body by the
circulatory system. Particulate matter may also weaken the
resistance of the body to infection and there are
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indications that it reacts adversely in conjunction with
other atmospheric pollutants.[3]
Visibility Reduction
Probably the most apparent effect of diesel
particulate in urban areas, where traffic is generally most
concentrated, is reduced visibility. Because diesel
particles are of a diameter most effective in scattering
light and their carbon content of 65-80 percent produces a
high degree of light absorption, they are especially
effective in reducing visibility.[3]
The model used by EPA to determine the visibility
impact of a specified level of diesel particulate is a
fairly simple one based on Beer's Law, and requires inputs
such as the urban ambient diesel particulate concentration,
the extent (distance) of this concentration (assumed to be
the city radius), the extinction coefficient of diesel
particulate, and baseline visibility for the city being
modelled.[1] In the absence of heavy-duty vehicle
controls, EPA has projected that increased diesel
particulate levels would result in significantly reduced
urban visibility (compared to mid-1970's levels), ranging
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from a 22-percent reduction in
decreases of 4-9 percent in less
the year 2000.[3]
Soiling Effects
Soiling refers to the build-up of a layer of deposited
atmospheric particulates on an exposed surface, resulting
in a loss of reflectance of visual light by an opaque
material surface or a reduction in light transmission
through a transparent material.[1] Due to the
characteristics of diesel particulate its black color
and oily nature it may be more detrimental, in terms of
the amount of soiling per unit ambient concentration, than
other types of particulate matter. The black color would
make any buildup more apparent to the observer, and the oil
content may make cleaning more difficult. The net effect
is increased costs to the general public for more frequent
and more thorough cleaning of homes, vehicles, and public
buildings.[3]
REGULATION OF DIESEL EMISSIONS AND AIR QUALITY
Based on the adverse health and welfare effects
described in the previous section, control of diesel
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the largest cities, to
populous urban areas by
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particulate emissions has been warranted in the United
States. This section includes a review of regulatory
actions taken with respect to particulate emissions from
diesel vehicles and allowable levels of particulate matter
in the ambient air. First, the development of U.S.
particulate controls presently the most stringent in the
world are reviewed. Following this discussion, is a
brief overview of the limited controls currently enforced
in Europe and Japan.
U.S. Regulations
Clean Air Act
Section 202(a)(3)(A)(i i i) of the Clean Air Act, as
amended by the U.S. Congress in 1977, authorizes EPA's
Administrator to "prescribe regulations . . . applicable to
emissions of particulate matter from classes or categories
of vehicles manufactured during and after model year 1981
... ." This section specifically directs that particulate
control regulations "shall contain standards which reflect
the greatest degree of emission reduction achievable
through the application of technology ... available for the
model year to which such standards apply, giving
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appropriate consideration to the cost of applying such
technology . . . and to noise, energy, and safety factors
associated with the application of such technology." It is
this portion of the Clean Air Act that gave EPA the
authority and indeed the responsibility to set
exhaust particulate standards for on-highway diesel
vehicles and engines sold in the United States. (The
particulate standards currently in place are discussed
later in this section).
Section 109 of the Clean Air Act provides that
National Ambient Air Quality Standards (NAAQSs) be set
forth by the EPA. This section of the Act defines a
primary NAAQS as being that which is "requisite to protect
the public health", and the secondary standard as that
"level of air quality . . . (that) is requisite to protect
the public welfare."
Under these provisions, EPA established NAAQSs for
total suspended particulate matter (TSP) in a rulemaking
published November 25, 1971 (36 FR 22384); the same TSP
standards still apply today. The primary standards,
focusing on protection of human health, are 75 micrograms
per cubic meter (ug/mJ) as an annual geometric mean and
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260 ug/m1 as the maximum daily average concentration
(allowed to be exceeded only one day per year). The
secondary TSP standards, established in the interest of
public welfare, are an annual geometric mean of 60 ug/m1
and a second maximum 24-hour average of 150 ug/m1.
In an effort to further focus control on those
particulates most hazardous to human health, EPA has
proposed that an NAAQS on particles less than or equal to
10 microns in diameter (PMi0) be established to replace
the primary standard for TSP. The PMio alternatives
being considered, published on March 20, 1984 [49 FR
10408], range from 50-65 ug/m3 as an annual arithmetic
mean, and from 150-250 ug/m1 as the second maximum daily
average. Non-compliance with the proposed PMl0 standards
is expected to be almost as widespread as with the current
TSP standards between 105 and 329 non-attainment
counties with the primary PMl0 standard, compared to
300-525 counties projected to be in non-attainment of the
primary NAAQS for TSP in the 1987-89 timeframe.[3] This
projected degree of non-compliance calls for further
particulate emissions control and supports the Clean Air
Act's mandate for specific action with respect to diesel
particulate. The emissions standards currently in place in
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the U.S. designed to provide compliance with these
current and proposed ambient standards are discussed
below.
Passenger Car and Light-duty Truck Standards
The first exhaust diesel particulate standards for
cars and light trucks were established in an EPA rulemaking
published on March 5, 1980 [45 FR 14496] . This action set
a limit of 0.37 g/km (0.60 g/mi) for both diesel cars and
light-duty diesel trucks, to become effective with the 1982
model year. This rulemaking also established 1985
particulate standards of 0.12 g/km (0.20 g/mi) and 0.16
g/km (0.26 g/mi) for diesel automobiles and light trucks,
respectively.
In a subsequent rulemaking, published January 24, 1984
[49 FR 3021], EPA delayed the 1985 particulate standards
for cars and light trucks by two years. Therefore, the
0.37-g/km standard is applicable to model years 198,2
through ]986, and the 0.12/0.16-g/km standards (cars/light
trucks) come into effect with the 1987 model year. The
1987 standards will continue indefinitely until EPA
determines the need for revision.
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Because of California's more immediate need for
pollution control, the California Air Resources Board
adopted more stringent controls than those imposed for the
rest of the United States. California's particulate
standards for diesel passenger cars and light trucks are
0.25 g/km (0.40 g/mi) in 1985, 0.12 g/km (0.20 g/mi) in
1986, and 0.05 g/km (0.08 g/mi) in 1989.
Heavy-Duty Truck and Bus Standards
The very first particulate standards for heavy-duty
diesel engines were promulgated in a recent EPA rulemaking,
published March 15, 1985 [50 FR 10606]. This action
established particulate standards of 0.80 g/kWh (0.60
g/bhph) for engines of model years 1988 through 1990; 0.34
g/kWh (0.25 g/bhph) for model years 1991 through 1993
(except for urban bus engines of these model years, which
will be subject to a 0.13-g/kWh, or 0.10-g/bhph, standard);
and finally, 0.13 g/kWh (0.10 g/bhph) for all heavy-duty
diesel engines produced during model year 1994 and later.
The State of California has proposed a heavy-duty diesel
standard of 0.13 g/kWh (0.10 g/bhph) to be effective in
1990 (earlier than in the rest of the country).
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Pre-1988 heavy-duty diesel engines are not subject to
any particulate standards; however, exhaust smoke (opacity)
limits for heavy diesels were among the first emissions
standards set forth by the EPA. In a rulemaking
established June 4, 1968 [33 FR 8304], smoke standards were
promulgated and specified in terms of percent of light
allowed to be blocked by the smoke in the diesel exhaust
(as determined by a light extinction meter). Heavy-duty
diesel engines produced during model years 1970 through
1973 were allowed a light extinction of 40 percent during
the acceleration phase of the certification test and 20
percent during the lugging portion; 1974 and later model
years are subject to smoke opacity standards of 20 percent
during acceleration, 15 percent during lugging, and 50
percent at maximum power.
European and Japanese Regulations
Diesel Exhaust Standards
In Europe, the vehicle exhaust emissions standards
recommended by the United Nations-sponsored organization,
the Economic Commission for Europe (ECE), are generally
adopted in total by the common-market European Economic
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Community (EEC). In turn, member countries of the EEC are
bound by the organization's charter to adopt the emissions
regulations. With the exception of Sweden, all major
countries within Europe apply the ECE exhaust regulations
as national law.[4]
To date, the ECE has not developed any regulations
pertaining to particulate emissions from diesel cars or
trucks; however, no review of pending actions in Europe was
performed. The only exhaust standards currently imposed on
heavy-duty diesel engines in Europe are smoke limits. Due
to individual delays in adopting various amendments to the
ECE regulations, the stringency of the smoke standards
varies from country to country. West Germany's limits are
the most permissible in Europe, while the United Kingdom
and Denmark are two of the more stringent regulators of
diesel smoke. All European countries except Hungary,
Ireland, and Luxemburg (as of 1980) have adopted smoke
standards which are, on the whole, comparable to (or
slightly more stringent than) U.S. diesel smoke
regulat i ons. {4]
As in Europe, Japan does not currently regulate
exhaust particulate emissions from diesel engines.
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However, standards on diesel smoke levels have been
enfcreed on both new ar.d in-use vehicles since 19 72 and
1975, respectively. The maximum permissible limits for
both are 50-percent opacity levels[4]; however,the new
vehicle standard is the more stringent because smoke is
measured at full load, while in-use vehicles are required
to meet the standard under the less severe no-load
acceleration test.[5] Japan's smoke standard for new
vehicles is comparable to the U.S. standard of 50-percent
opacity at maximum power.
These current smoke standards provide some degree of
emissions control; however, because they do not focus on
particulate levels over an average driving cycle and are
not particularly stringent, their effect on particulate
emissions is somewhat limited. This is evidenced by recent
U.S. regulation of heavy-duty diesels the particulate
standards recently promulgated represent an 85-percent
reduction from the emission rates existing under the
current smoke standards. Based on U.S. test data showing
current European diesel engines emitting basically the same
levels as in the U.S., diesel particulate emissions
throughout the world remain essentially uncontrolled at the
present time.
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Ambient Air Quality Standards
In addition to imposing vehicle exhaust regulations,
the EEC is also responsible for establishing ambient
standards for suspended particulate matter (SPM) in
European countries. Prior to development of the EEC
standards, member countries based their air quality
standards primarily on black smoke measurements; EEC's
standards are expressed two ways in terms of black smoke
and mass concentration. For purposes of comparison to U.S.
standards, the gravimetric-based EEC standards are
highlighted here.
Although direct comparison is somewhat difficult
because of the differing form of the standards, EEC's
current ambient SPM regulations appear to be less stringent
than the U.S. NAAQS for TSP. The European standards are an
annual arithmetic mean of 150 ug/m* (compared to the
U.S.'s annual geometric mean of 75 ug/m1) and 300 ug/mJ
as an annual 95th percentile of daily values in a year
(roughly speaking,, the eighteenth highest daily value,
compared to 260 ug/m1 as a second maximum daily average
in the U.S.).[6] Again, no pending regulations in Europe
were reviewed.
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In Japan, ambient standards have been established for
suspended particulate matter defined (by the Japanese)
as airborne particles of 10 microns or less in
diameter. [6] As this classification corresponds to the
definition of PM10 in the U.S., Japanese limits are most
appropriately compared to the EPA-proposed PMl0
standards. Japan allows a maximum daily average of 100
ug/m*, with hourly values not permitted to exceed 200
ug/m3.[5] Compared to the maximum allowable daily
average of 150-250 ug/m1 proposed by the U.S. EPA,
Japan's standard appears to be more stringent. However,
because the U.S. is also proposing an allowable annual mean
between 50 and 65 ug/m1, the U.S. standards may be
somewhat more stringent than those in Japan, where (by
nature of the daily standards) the annual mean could be as
high as 100 ug/m1 if the daily averages were very
consistent. Thus, a precise comparison of the U.S. and
Japanese standards cannot be made without using actual
monitoring data to simulate typical daily and seasonal
variations.
ENVIRONMENTAL IMPACT
The need for control (or further control) of diesel
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particulate is based primarily on estimates of the
environmental impact associated with a particular level of
emissions. Environmental impact is generally evaluated
both in terms of emissions inventories (tons of pollutant
per year) and ambient air quality (pollutant
concentrations) estimated for selected areas. This section
begins with a summary of diesel particulate emissions and
ambient concentrations for urban areas across the U.S.;
both current and future projections are shown. The
discussion on the U.S. is followed by estimated ambient
diesel particulate concentrations for selected cities in
Europe and Japan, based on methodologies used in the United
States.
United States
In support of the recently published particulate
standards for heavy-duty diesel engines for 1988 and later
model years, the U.S. EPA evaluated the current in-use
situation and made projections of future diesel particulate
emissions and ambient concentrations for the urban United
States. Future projections were based on two scenarios:
1) assuming uncontrolled heavy-duty diesel emissions (at
0.94 g/kWh), and 2) assuming the levels of control
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promulgated on March 15, 1985 (0.80, 0.34, and 0.13 g/kWh
in 1988, 1991, and 1994, respectively).[50 FR 10606]
Results of EPA's analysis were published in the final
Regulatory Impact Analysis for the NOx/particulate
rulemaking^], and are briefly reviewed below.
Emissions Inventories
Diesel particulate emissions inventories were
constructed for urban areas across the U.S. in aggregate;
estimates are shown in Tables I and II. Inventories are
broken down into various vehicle classes, designated as
follows: light-duty diesel vehicles (passenger cars) as
LDDV, light-duty diesel trucks (less than 8,500 pounds
rated gross vehicle weight, or GVW) as LDDT, and heavy-duty
diesel vehicles as HDDV. In Table II, the HDDV category is
further divided by weight classification, with Classes
2B-8A including trucks with GVWs between 8,500 and 50,000
pounds, Class 8B designating "line-haul" diesels over
50,000 pounds GVW (with trailer GVW, if applicable), and
buses. "Base" and "controlled" scenarios differ in the
future HDDV standards (as explained above), but both assume
the same LDV/LDT standards 0.12/0.16 g/km, beginning
with, the 1987 model year.
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As shown in Table I, diesel particulate emissions in
the urban U.S. were expected to grow to twice the current
level by the year 2000 if no further HDDV control had been
imposed. It is the HDDV category that makes up the
majority of total emissions, currently representing over 80
percent; Table II shows that line-haul diesels (Class 8B)
are the largest contributor of all, accounting for 50
percent of current HDDV emissions, or over 40 percent of
total diesel particulate emissions in 1984.
The effect of HDDV control (including the more
stringent control on urban buses) is significant, with the
combined 1988/91/94 standards bringing about an estimated
46 percent decrease from the base (uncontrolled) case in
the year 2000. This level of control essentially prevents
significant growth beyond current levels, with about an
11-percent increase projected between 1984 and 2000.
Air Quality
Because it is difficult (if not impossible) to
distinguish diesel particulates from the other particles
collected at ambient monitors, a surrogate method of
estimating ambient concentrations of diesel particulate
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alone was used. The most commonly used surrogate for
diesel particulate matter is lead, since motor vehicle
emissions represent the primary source of lead in the
atmosphere. (Of course, the lead surrogate method is not
valid for cities in which lead smelting operations are
found.) Carbon monoxide has also been used as a surrogate
by EPA, particularly in estimating average urban exposure
in determining cancer risk.[l]
The lead surrogate method uses historical ambient lead
concentrations in urban areas as indices of mobile source
pollutant levels. Both the automotive fleet's lead
emission factor for the year in which the ambient lead
measurements were made and the expected diesel particulate
emission factor for the year of projection are estimated
and assumed to have a proportional effect on ambient
concentrations. Taking into account future growth in
vehicle miles travelled (VMT) and the differing dispersion
characteristics of lead and diesel particulate, ambient
concentrations of diesel particulate are estimated. (For
more details on the methodology used in EPA's projections,
see the Diesel Particulate Studytl].)
The EPA's lead-based projections of current and future
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ambient diesel particulate concentrations for urban areas
in the U.S. are presented in Table III. (The future
scenarios shown are the same as those presented earlier.)
As indicated, the impact of growth in diesel particulate
emissions on urban air quality is significant. Current
ambient diesel particulate concentrations in large U.S.
cities are projected to grow from an average of 1-3 ug/mJ
to levels of 3-7 ug/raJ by the year 2000 with no control
on HDDVs. With the HDDV standards recently promulgated,
diesel particulate concentrations in large cities will be
lowered to 1.5-4 ug/mJ, a reduction to almost half of
baseline concentrations in the year 2000.
Europe and Japan
Background and Methodology
Information on levels of diesel particulate emissions
and ambient concentrations outside of the U.S. was rather
limited. However, for selected cities in Europe and Japan,
a review of the, American literature provided adequate
information to allow use of the lead surrogate model to
roughly estimate recent (1982) ambient diesel particulate
levels, which is the same approach used by the EPA to
project concentrations in U.S. cities.
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The three European and nine Japanese cities included
in this part of the study were chosen based on the
availability (in the American literature) of information on
local ambient lead levels in any base year; in this
analysis, base years range from 1975 to 1981, depending on
the area. Given this, the remaining factors necessary for
calculation of ambient diesel particulate levels for these
cities were: 1) a fleet-wide lead emission factor for the
base year, 2) a fleet-wide diesel particulate emission
factor for the year of projection (1982), 3) estimated VMT
growth between the base year and year of projection, and
4) the ratio of diesel particulate dispersion to lead
dispersion. This dispersion ratio was estimated at 1.00 to
0.43 in the Diesel Particulate Study.[1] The other three
factors had to be calculated for each area using data
available in the American literature; because this
information was usually not provided for a specific city,
data for the appropriate countries were used. The three
factors calculated for each of the five countries examined
are shown in Table IV, along with monitored ambient lead
concentrations; the approaches used to determine the
various factors are described below. (The table includes
U.S. factors for comparison.)
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Before the fleet-wide composite lead and diesel
particulate emission factors could be calculated, the VMT
breakdown by vehicle class to be used in weighting the
class-specific emission factors had to be estimated for the
two years of interest. If such a breakdown was not already
provided in the literature, data on per-vehicle annual VMT,
annual fleet registrations and fleet diesel penetrations
were used to estimate the percentage of travel by each of
the four classes: gasoline-fueled cars, diesel-powered
cars, gasoline-fueled trucks, and diesel-powered trucks.
(If possible, the gasoline and diesel truck classes were
further broken down into light-duty trucks, heavy-duty
trucks, and buses.)
Next, base-year lead emission factors were estimated
for the gasoline-fueled car and truck classes, using the
lead content of gasoline and the manufacturer-weighted
average fuel consumption value for the appropriate
country. Assuming that 75 percent of the lead contained in
the gasoline is eventually emitted with the exhaust[l], the
estimated class-specific lead factors (in g/km) were
averaged for the fleet using the VMT breakdown calculated
above. (Of course, the lead emission factors for the
diesel-powered vehicles and trucks were zero.)
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The fleet-wide diesel particulate emission factor for
the year of projection was calculated using estimates of
uncontrolled emissions from each of the vehicle, classes.
Based on relative engine sizes, diesel cars and light
trucks were assumed to emit 0.31 g/km (0.50 g/mi) in the
European countries and 0.22 g/km (0.35 g/mi) in Japan. All
heavy-duty diesel truck and bus emissions were estimated at
0.94 g/kwh, which was converted to g/km using factors
developed in an EPA technical report.[7] Again using the
VMT breakdown calculated earlier, these class-specific
estimates were averaged to yield the fleet-wide diesel
particulate emission factor for 1982.
Finally, growth in VMT between the base year and year
of projection (which vary with available data) was
estimated for each of the areas being examined. Because
Japan's annual compound growth rate was calculated between
1975 and 1982, instead of during the economically depressed
1980-82 period used for the European countries, Japan's
rate is significantly higher than the others.
Combining all of the above factors, and multiplying by
0.9 to account for the estimated mobile source contribution
to total lead emissions! 1], ambient diesel particulate
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concentrations were calculated for the selected European
and Japanese cities. Lead-based estimates are shown in
Tables V and VI for cities in Europe and Japan,
respectively.
Europe
As indicated in Table V, 1982 levels of ambient diesel
particulate in European cities appear to be significantly
higher than current estimates for U.S. cities. Within
urbanized portions of Naples, Birmingham, and Stockholm,
estimated concentrations range from 2.5-35.1 ug/mJ,
compared to 1.3-3.0 um/m1 in the largest U.S. cities.
This relationship is expected for two reasons: 1) lack of
any controls on diesel particulate emissions in European
countries and 2) significantly higher diesel penetration
of European passenger car and light truck markets (to be
discussed in further detail in the next major section).
Of the three European cities examined, Naples has the
highest estimated artibient concentrations;, again, this seems
reasonable in view of the significantly high diesel
penetration of Italian markets in comparison to English
and Swedish sales among the lowest diesel penetrations
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in Europe. As countries with the lowest and highest diesel
sales fractions in Europe are represented in Table V,
ambient diesel particulate concentrations in other European
cities could be very roughly estimated using relative
gasoline prices and gasoline/diesel price differentials (to
be analyzed in the next major section).
Japan
Lead-based estimates of ambient diesel particulate in
selected Japanese cities are presented in Table VI. The
nine cities are ranked according to population; as in the
U.S., in general, the most heavily-populated cities tend to
have the higher concentrations due to higher levels of
motor vehicle activity. In Japan, cities with populations
over 1,000,000 are estimated to have ambient diesel
particulate levels ranging from 1.4 to 10.2 ug/mJ,
compared to the estimate of 1.3-3.0 ug/m1 for the largest
U.S. cities. As in Europe, the higher diesel particulate
levels in Japan (as compared to the U.S.) are expected due
to higher diesel penetration and lack of diesel particulate
controls.
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WORLDWIDE DIESEL PENETRATION PRESENT AND FUTURE
Over the past decade, rising fuel prices in the United
States and abroad have enhanced the popularity of the
diesel engine as a fuel-saving technology. In the early
1970's, the use of diesel engines formerly only found in
the heavier trucks spread into the passenger car and
lighter truck markets. Because the popularity of
diesel-powered vehicles is naturally linked to fuel prices,
the first part of this section focuses on the price of
gasoline versus that of diesel fuel in the U.S., Europe,
and Japan. Following this, the relative fuel prices are
compared to trends in diesel penetration of the automobile
and truck markets in the countries examined.
Gasoline versus Diesel Fuel Prices
In comparison to European countries and Japan, the
U.S. traditionally has significantly lower prices for both
gasoline and diesel fuel, with U.S. pump prices at times
less than half the cost of fuel abroad. As Table VII
shows[6,8,9], of the countries examined, Italy has recorded
the highest gasoline prices in recent years, with the cost
i
over $3/gallon at times during 1983. Japan's gasoline
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prices have come down since 1980 (when they were comparable
to Italy's high rate), but have been surpassed in price by
only one to two European countries in more recent years.
As relevant as the absolute cost of gasoline is the
price differential between gasoline and diesel fuel, since
it is the traditional price advantage of diesel fuel that
helps make diesel-powered vehicles more attractive to
consumers. Although gasoline prices in Italy are high, the
price of Italy's diesel fuel tends to be among the lowest
in Europe; therefore, consumers in Italy are offered a more
substantial diesel price advantage than that available in
the other countries examined. As indicated in Table VII,
gasoline prices in Italy tend to be roughly double the cost
of diesel fuel, while the U.S. price differential over the
last decade has been only 25-30 percent (i.e., the ratio of
gasoline price to diesel fuel price was between 1.25 and
1.30, as shown in the table). However, recently, the price
differential in the U.S. has become even smaller. . In
Japan, gasoline has been priced roughly 40 percent more
than diesel fuel. The advantage of diesel.fuel is smallest
in the United Kingdom and West Germany with
differentials of less than 10 percent and Switzerland,
where diesel fuel actually costs more than gasoline.
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Diesel Penetration of the Automobile and Truck Markets
As one would expect, sales of diesel-powered
automobiles tend to be highest in those countries' that
offer the greatest price advantage with diesel fuel and the
highest gasoline prices. As Table VIII shows[8,9,10],
diesel penetration of the passenger car market in recent
model years has been highest in Belgium, Italy, and Spain,
where roughly one in every four new cars sold is equipped
with a diesel engine. As shown previously in Table VII,
Italy has traditionally offered the greatest pump price
advantage, selling diesel fuel for roughly half the cost of
gasoline. Although Belgium's fuel price differential is
lower than Italy's and Spain's, and even lower than that in
Sweden and the Netherlands, diesel-powered cars have been
more popular in Belgium than in any other European country
since the late 1970's. This is primarily due to the
relatively high cost of gasoline in Belgium. Of the
countries examined, diesel vehicles have traditionally been
the least popular in the United Kingdom and Switzerland,
where diesel fuel costs roughly , the same or even more than
gasoline.
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Although the price differential between gasoline and
diesel fuel in the U.S. is comparable to that in France (as
shown in Table VII), the absolute cost of gasoline in the
U.S. is roughly half that in France and other European
countries. Therefore, it is not surprising that U.S.
diesel sales fractions have always been significantly lower
than those in the majority of the European countries (see
Table VIII). The popularity of diesel automobiles in the
U.S. peaked in 1981, when 6 percent of new car sales were
diesels. Since then, the figures have declined and are
currently comparable to diesel fractions in the United
Kingdom and Switzerland, which are the lowest in Europe.
This decline in U.S. diesel penetration has followed the
recent reduction in the gasoline/diesel . price
differential. Even though several American auto
manufacturers have reduced their diesel sales projections,
some growth in diesel share is still projected both by
manufacturers and EPA. In its air quality projections in
support of the recently published diesel particulate
standards for heavy-duty vehicles [50 FR 10606, March 15,
1985], EPA assumed, a 5-percent diesel penetration of new
automobile sales by 1990; General Motors also predicts
diesel growth, but estimates that the 5-percent level will
not be reached until 1995.[3]
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Limited data (from American literature) on the diesel
fraction of new car sales in Japan[8], presented in Table
VIII, indicate that diesels are slightly more popular in
Japan than in the U.S., but are less popular than in most
of Europe. This trend is supported by the relative fuel
price advantages shown in Table VII gasoline in Japan
costs roughly double that in the U.S., and Japan currently
has a significantly larger price differential between
gasoline and diesel fuel. Because information on new
diesel car sales in Japan was limited, available data on
the diesel fraction of the in-use automobile fleet in Japan
was examined as well. These in-use registration data
confirmed the trend cited above diesel penetration of
Japan's passenger car fleet in 1982 was at roughly 2.6
percent[5], compared to a 1.8-percent diesel penetration of
the U.S. fleet in the same year[11]. Future projections
for both countries are consistent with historic trends;
Japan predicts a 10-percent diesel penetration of the fleet
by 1992 [ 8 ] , compared to a U.S. estimate of 4 percent for
the same year [12].
Because dieselization of the heaviest truck fleet
began decades before diesel-powered passenger cars became
popular, and because heavy-duty dieselization is less in a
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state of flux, there generally tends to. be limited
information published on the diesel penetration of the
heavy-duty fleet. This is particularly true in European
countries, where heavy-duty vehicles represent a relatively
small fraction of road vehicles (compared to Japan or the
U.S.).[8] However, diesel penetration of the light-duty
truck market is changing almost as rapidly as with
automobiles; but, unfortunately, light-duty and heavy-duty
trucks are often reported within the same general category
of "trucks", making it difficult to separate the two.
Adequate information on the current diesel penetration
of new light-duty truck sales was available in the American
literature only for the U.S., where diesels presently
account for approximately 8 percent of new light trucks.
This figure is projected to grow to 15 percent of new sales
by 1990, according to the EPA.[3] The only Japanese
projection found estimated that, by 1992, 50 percent of the
in-use light-duty truck fleet in Japan will be
diesels.[12] This figure compares to a U.S. projection of
10-percent penetration of the in-use fleet by 1992.[11]
Based on this, the same trend noted for passenger cars
seems to hold true for light-duty passenger trucks as well
due to higher Japanese gasoline prices and diesel price
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advantages, diesels appear to be more popular in Japan than
in the United States.
Based on the relative trends in diesel penetration
shown in Table VIII, it is not surprising that current
ambient diesel particulate concentrations in European and
Japanese cities are estimated to be significantly higher
than in the United States. Even though the popularity of
diesel engines in cars and light trucks is lower in the
U.S., EPA has determined that there is a substantial need
to regulate diesel particulate emissions in the future. In
view of current ambient particulate levels and the growing
popularity of diesel engines in Europe and Japan, it
appears that the environmental need to control particulate
emissions from diesel vehicles in these countries is
perhaps even greater than in the United States. The final
section of this analysis focuses on various techniques
available to control these particulate emissions, including
approaches already being implemented and those under
consideration in the United States.
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DIESEL PARTICULATE CONTROL TECHNIQUES
Particulate emissions from diesel-powered vehicles can
be controlled using various techniques, involving either
reduction of the actual formation of particulate or the use
of exhaust treatment to reduce levels allowed to reach the
atmosphere. Three basic approaches to controlling diesel
particulate emissions will be discussed in this section,
beginning with engine modifications to reduce emissions of
unburned particles from the engine. The second approach
reviewed is exhaust aftertreatment, primarily the use of
trap-oxidizer systems to capture particulate and combust it
periodically. Finally, the third approach reviewed is to
modify the fuel to reduce particle formation either in the
engine or exhaust.
Engine Modifications
Diesel combustion occurs around the surface of tiny
fuel droplets where the fuel-air ratio is quite rich. The
rate, and extent of . combustion is quite sensitive to
numerous parameters, such as combustion chamber geometry,
piston bowl or prechamber design, injector design, and
injection pressure and timing. Because diesel particulate
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is comprised mainly of the carbon residue of unburned fuel
droplets, any modifications to the parameters described
above are likely to have an effect on particulate
emissions. However, as each manufacturer's engine design
is somewhat unique, beneficial modifications for one engine
do not always translate to another and assessments of the
benefits of engine modifications are difficult to perform
generically. Suffice it to say that nearly all of the
techniques attempt to enhance complete combustion of each
fuel droplet. This can be done by increasing the amount of
oxygen present via turbocharging, decreasing the amount of
fuel available (fuel governing), increasing the amount of
time available for combustion (advanced injection timing),
or increasing fuel-air mixing (increased swirl, higher
injector pressure).
Unfortunately, most of these techniques also increase
nitrogen oxides (NOx) emissions, which represent another
significant environmental impact of diesel engines.[3] The
use of engine modifications must be balanced to obtain
reductions of both pollutants. Electronic controls are
very useful in. performing this balance because of their
flexibility and precision. In addition, general reductions
in brake-specific fuel consumption also lead to
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commensurate reductions in both particulate and NOx
emissions, since fuel-specific emissions tend to be
constant under these conditions.[3]
On small (1.6-2.5-liter) LDDVs, engine controls have
reduced emissions to levels below 0.12 g/km particulate and
less than 0.62 g/km NOx. On larger LDDVs (4.3-5.7-liter
engines), engine controls have achieved levels of 0.16-0.22
g/km particulate at NOx levels of 0.62-0.93 g/km.[1,13].
With respect to HDDVs, EPA projects that engine controls
can achieve 0.80 g/kWh particulate and 8.0 g/kWh NOx by the
1988 model year. By 1991, engine-out emission levels of
0.67 g/kWh particulate and 6.7 g/kWh NOx are projected to
be achievable.
In the longer term, adiabatic or heat-retaining
combustion techniques may hold great promise for
particulate control. Early testing has shown dramatic
particulate reductions at constant NOx emissions. However,
there is some doubt about whether these results will be
indicative of production technology.[3]
The cost of engine-related particulate controls tends
to be small since the modifications are usually integral to
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the engine itself and involve no new hardware. Electronic
controls and turbocharging are .the exceptions. However,
many manufacturers, especially those of heavy-duty diesel
engines, are moving to these technologies for reasons other
than emission control (i.e., fuel economy), so even here
the cost attributable to emission control may be small.
Trap-Oxidizeir Systems
The second type of particulate control is exhaust
aftertreatment, with the primary technique being a
trap-oxidizer system. This device, placed at the end of
the exhaust manifold, serves as a "filter", removing solid
particles from the exhaust flow. Periodically, the trap
undergoes regeneration, during which the particulate matter
captured is burned off, since space is not available to
capture a lifetime supply of particulate. The most common
filter media used to date is a porous ceramic material,
usually an automotive catalyst substrate with alternate
ends of each channel plugged to force exhaust flow through
the thin ceramic wall; stainless wire-mesh or steel-wool,
traps are also being researched.[2,3]
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The particulate reductions achievable via trap
oxidizers are substantially greater than those possible
with engine modifications alone. In tests performed on
various makes of diesel-powered passenger cars equipped
with ceramic traps, an average of 80 percent of the total
particulate matter generated was captured by the trap.
Removal of the soluble organic fraction (SOF) of the
particulate emissions, which is the portion regarded as the
most carcinogenic, was just slightly less efficient at 70
percent. Limited data on heavy-duty vehicles equipped with
ceramic traps produced roughly the same results.[1]
Wire-mesh traps are generally less efficient with respect
to total particulate (a rough average of 65-percent
removal), but can be somewhat more efficient with respect
to the SOF.[1]
Regeneration techniques aim at either raising the
exhaust temperature or lowering the temperature of particle
combustion, since typical exhaust temperatures alone are
not sufficient. Fuel burners and electrical heaters are
the most popular among the former, and catalysts either
on the filter material, in the fuel or injected into the
exhaust are prominent among the latter. Catalytic fuel
additives, while appearing to be the most effective, are
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potentially an environmental concern themselves if they
contain toxic metals which reach the atmosphere. Their
potential use is being watched carefully by EPA.
Particulate traps are currently installed on only one
model sold in the United States a 1985 Mercedes 300D
sold in California and other western states (so equipped to
meet California's particulate standard). However, the
diesel particulate emission standards that EPA has
promulgated for future model years are technology-forcing
and traps will be .necessary on some, 1987 and later model
year passenger cars and light trucks and on most 1991 and
later model year HDDVs. As substantial research and
development of traps suitable for the light-duty vehicles
have already been performed, manufacturers are expected to
have little difficulty meeting. these standards.
Development of traps for heavy-duty vehicles is not as far
along, but since the first trap-based standards for this
heavy class (0.34 g/kWh for trucks and 0.13 g/kWh for urban
buses) are not effective until 1991, additional time exists
for proper development-.
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EPA has estimated the cost and cost-effectiveness
associated with the trap-forcing standards promulgated for
the various vehicle classes.[1,3] For 1987 and later
diesel passenger cars and light trucks, the lifetime
consumer cost associated with reducing a vehicle's emission
rate from 0.37 to 0.12 g/km (via a trap) is approximately
$250-270, or an annualized cost of roughly $40. Because
averaging is permitted in meeting this standard, traps will
be installed only on a portion of each manufacturer's
sales. Based on the fleet cost at appropriate trap usage
rates and the estimated reductions in emissions reisulting
from the 0.12-g/km standard, the cost-effectiveness of this
technique is approximately $13,500/Mg.[1]
. Depending on engine size, heavy-duty traps are
projected to cost $580-1850 (including a fuel economy
penalty of 1.0-1.5 percent); these estimates represent
lifetime costs discounted to the year of vehicle purchase
at a rate of 10 percent per annum.. In order to meet the
1991 heavy-duty particulate standards of 0.34 g/kWh for
trucks and 0.13 g/kWh for urban buses, both of which permit
averaging, approximately 60 percent of the trucks and 100
percent of the urban buses will likely require traps.
Based on the emissions reductions projected, the
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cost-effectiveness associated with the 1991 trap standards
is approximately $11,900-13,900/Mg.[3]
In 1994, heavy-duty truck engines are required to meet
a 0.13-g/kWh standard (with averaging), which represents a
long-term trap-usage rate of 90 percent; urban buses will
still be subject to the 0.13-g/kWh standard set for 1991,
requiring 100 percent of the buses to be equipped with
traps. Based on these trap-usage rates, the
cost-effectiveness of the additional emissions benefit
associated with the 1994 standard is between $17,000 and
$20,000/Mg.[3]
Fuel Variations
A number of recent studies have focused on the impact
of fuel characteristics on diesel particulate emissions.
Initial published findings on the effect of variations in
such diesel fuel parameters as aromatics content,
90-percent distillation temperature, and sulfur content are
briefly summarized in the first section below. The second
section reviews recent tests on the conversion of diesel
engines to methanol fuel.
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Diesel Fuel Modifications
Recent research has identified the following three
fuel parameters as those having the greatest impact on the
level and composition of particulate emissions from diesel
engines: 1) sulfur content, 2) aromatics content, and 3)
back-end volatility (90-percent distillation temperature).
Fuel sulfur contributes to particulate emissions through
the formation of sulfate and associated bound water, and
also by increasing the amount of soluble organic material
absorbed on the carboneous particles. Aromatics and
volatility (T90) affect the amount of carboneous material
formed.[14]
Chevron's steady-state tests on a heavy-duty diesel
engine showed that an 88-percent decrease in fuel sulfur
content (from 0.4 percent to 0.05 percent) resulted in a
36-percent reduction in particulate emissions. A
two-thirds reduction in aromatics content (from 30 percent
to 10 percent) resulted in an additional particulate
decrease of 16 percent. And, finally, an 18-percent,
decrease in T90 (from 316° C to 260° C) lowered
particulate emissions by another 8 percent.[14]
Unfortunately, such changes in diesel fuel composition
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appear to be prohibitively expensive, though they are
currently being evaluated in greater detail.
Fuel sulfur, unlike the other two properties, also
influences the composition of diesel particulate, primarily
by increasing the amounts of sulfate, bound water, and
soluble organics. However, the change in solid carboneous
material formed is not significantly affected by a change
in sulfur. Chevron's test results show that an increase in
fuel sulfur content from 0.20 percent to 0.55 percent
caused the following: 1) a three-fold increase in the
amount of sulfate and bound water produced, 2) more than
double the amount of soluble organics collected on the
particulate, and 3) only an 8-percent increase in solid
carboneous material produced. The overall effect of the
increased fuel sulfur content was a 63-percent increase in
the level of diesel particulate emitted.[14]
Data published in a 1979 EPA report suggest that the
impact of certain fuel parameters aromatics content, in
particular on particular.- emissions may be greater for
light-duty diesel vehicles (cars) than that demonstrated
with the heavy-duty engines. Test results show that a
two-thirds reduction in aromatics content resulted in a
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decrease in particulate ranging from 21 to 54 percent.[15]
Using the same reduction in aromatics, these figures can be
compared to Chevron's heavy-duty results lower at a
16-percent decrease in particulate. The noted difference
between the light-duty and heavy-duty results is not
particularly surprising in view of the contrast in
combustion chamber design between the two classes.
However, part of the difference may also be due to the fact
that EPA's light-duty testing involved transient operation
(a known source of high particulate emissions), while
Chevron's heavy-duty study only involved steady-state
testing. Thus, the heavy-duty test results must be used
with some caution since they may or may not be indicative
of emission trends under more realistic conditions.
Conversion to Methanol
While modifications to diesel fuel are limited by both
cost and refinery capacity, the use of an entirely
different fuel methanol in converted diesel engines
appears to hold great promise for emission control.
Available data from tests conducted on two types of diesel
bus engines modified to operate on neat methanol show
methanol to be significantly cleaner-burning than diesel
fuel, without use of a trap-oxidizer.
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The two methanol-fueled engines were developed by
M.A.N, of Germany and General Motors of the U.S. and both
are currently being used in public transit buses in the San
Francisco area.[16] The M.A.N, engine (equipped with a
catalyst) was tested over the transient cycle for EPA at
Southwest Research Institute and found to have emissions of
0.06 g/kWh (0.04 g/bhph) particulate and 8.9 g/kWh (6.6
g/bhph) NOx.[17] GM's steady-state (13-mode) tests of
their engine without a catalyst showed emissions of 0.23
g/kWh (0.17 g/bhph) particulate and 2.9 g/kWh (2.2 g/bhph>
NOx.[18] Transient testing of an aftermarket conversion of
a GM diesel bus engine equipped with a catalyst showed
emissions of 0.08 g/kWh (0.06 g/bhph) particulate and 2.8
g/kWh (2.1 g/bhph) NOx; steady-state (13-mode) tests on the
same engine indicate emissions of 0.03 g/kWh (0.02 g/bhph)
particulate with 4.0 g/kWh (3.0 g/bhph) NOx.[19,20]
Although particulate and NOx data on methanol-fueled
diesel engines are limited, the results to date appear very
promising as typical emissions from these engines are
0.7-0.9 g/kWh (0.5-0.7 g/bhph) particulate and 9-12 g/kWh
(7-9 g/bhph) NOx. Of course, such factors as the
cost-effectiveness of methanol fuel and the practicality of
converting diesel engines to methanol operation must be
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considered in evaluating this approach as a viable diesel
particulate control technique. However, for transit buses,
their use of a central fuel depot makes distribution of
methanol quite simple and their extensive use in crowded
urban areas makes the control of their emissions a
number-one priority.
CONCLUSIONS
The environmental impact of diesel particulate
emissions is a prime concern in the United States. Both
health (carcinogenic and non-carcinogenic) and welfare
(visibility and soiling) effects are significant.
Legislative action has mandated stringent control and EPA
has followed with regulations requiring up to an 85-percent
reduction from uncontrolled levels, holding year 2000
particulate levels at only slightly greater than 1982
levels, despite the projected large growth in diesel
usage. Traditional engine-related controls provide only a
small part of this reduction. Rapidly developing
trap-oxidizer technology is expected to provide the lion's
share. The use of methanol in specially designed diesel
engines also appears capable of providing this substantial
degree of reduction.
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The current environmental impact of diesel particulate
in-Europe and Japan appears to generally exceed that in the
United States. Given that gasoline prices are much higher
in Europe and Japan than in the United States, making
diesels more popular, diesel particulate levels in the
future can be expected to increase in these areas even
faster than in the United States. To date, however, no
particulate emission standards have been implemented in
Europe and Japan (only smoke standards of very limited
effectiveness), and emission levels are generally analogous
to those in the United States prior to regulation. The
technology to significantly reduce these emissions is now
or will soon be available. Thus, worldwide reduction of
the environmental impacts of diesel-powered motor vehicles
awaits only a decision to act.
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REFERENCES
1. "Diesel Particulate Study," U.S. Environmental
Protection Agency, Office of Air and Radiation, Office
of Mobile Sources, Emission Control Technology
Division, Standards Development and Support Branch
(October 1983).
2. "Draft Regulatory Impact Analysis and Oxides of
Nitrogen Pollutant Specific Study (in support of)...
Particulate Emission Regulations for 1987 and Later
Model Year Heavy-Duty Diesel Engines," U.S.
Environmental Protection Agency, Office of Air and
Radiation, Office of Mobile Sources (October 1984) .
3. "Regulatory Impact Analysis, Oxides of Nitrogen
Pollutant Specific Study and Summary and Analysis of
Comments (in support of) Particulate Emission
Regulations for 1988 arid Later Model Year Heavy-Duty
Diesel Engines)," U.S. Environmental Protection
Agency, Office of Air and Radiation, Office of Mobile
Sources (March 1985).
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Rykowski, Brochu
4. "Summary, International Regulations" (1980).
5. "Motor Vehicle Pollution Control," Environment Agency
(of Japan), Air Quality Bureau, Automotive Pollution
Control Division (April 1984).
6. Report of the Ad-Hoc Group "Eqra-Air Pollution"
(Brussels: Commission of the European Communities,
August 1983).
7. Smith, M.C. "Heavy-Duty Vehicle Emission Conversion
Factors/ 1962-1997," U.S. EPA Report EPA-AA-SDSB-84-1
(August 1984).
8. "Environment Implications of Energy Use in
Transportation," Environment Committee, Group on
Energy and Environment, Paris (drafted August 9, 1984).
9. Feast, R. "1984 Diesel Sales Top 1.2 Million, Popular
Engine :Sets Sales Record, in Europe," Automotive World
News (February 25, 1985), p. 41.
10. World Motor Vehicle Data (Detroit: Motor Vehicle
Manufacturers Association of the United States, Inc.,
1984).
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Rykowski, Brochu
11. Unpublished results, output from draft M0BILE3 Fuel
Consumption Model, U.S. Environmental Protection
Agency, Office of Air and Radiation, Office of Mobile
Sources, Emission Control Technology' Division, Testing
and Evaluations Branch (January 21, 1985).
12. Cole, R.E., and T. Yakushihi. The American and
Japanese Auto Industries in Transition (U.S.:
University of Michigan, Center for Japanese Studies,
Ann Arbor, Michigan, and Technova, Inc., Tokyo, Japan,
1984).
13. Kanner, R. "An Evaluation of the Particulate Levels
Occurring Under 1.0/1.2 g/mi NOx Standards for LDDVs
and LDDTs," U.S. EPA Report EPA-AA-SDSB-84-2 (May
1984).
14. Wall, J.C., and S.K. Hoekman. "Fuel Composition
Effects on Heavy-Duty Diesel Particulate Emissions,"
SAE Paper No. 841364 (October 1984).
15. "Characterization of Gaseous and. Particulate Emissions
from Light-Duty Diesels Operated on Various Fuels,"
U.S. EPA Report No. EPA-460/3-79-008 (June 1979) .
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Rykowski, Brochu
16. Jackson, M.D., S. Unnasch, C. Sullivan, and R.A.
Renner. "Transit Bus Operation with Methanol Fuel,"
SAE Paper No. 850216 (January 1985).
17. "Emission Characterization of a Spark-Ignited,
Heavy-Duty, Direct-Injected Methanol Engine," U.S. EPA
Report EPA-460/3-82-003 (November 1982), p. 4.
18. Toepel, R.R., J.E. Bennethum, and R.E. Heruth.
"Development of Detroit Diesel Allison 6V-92TA
Methanol Fueled Coach Engine," SAE Paper No. 83174 4
(October 1983).
19. "First DDA 6V-71 Engine Conversion and Test Report,"
in support of the Methanol Transit Bus Development and
Demonstration Program, Booz-Allen and Hamilton, Inc.,
for Florida Department of Transportation (drafted
March 1985).
20. Kidd, C.A., and R.M. Kreeb. "Conversion of a
Two-Stroke Diesel Bus Engine to Methanol FuelSAE
Paper No. 841687 (December 1984).
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Table I. Current and Future Diesel Particulate Emissions
in Urban Areas of the United States (Mq/year)[6]*
1995 HDDV
Scenarios
2000 HDDV
Scenarios
Vehicle
Classes
1984
Levels
Base
(0.70)
Controlled
(0.60/.25/.10)
Base. Controlled
(0.70) (0.60/.25/.10)
LDDV
5,181 {11%)**
12,175 (15%)
12,175 (23%)
17,909 (18%)
17,909 (33%)
LDDT
2,265 (5%)
11,884 (15%)
11,884 (23%)
18,830 (19%)
18,830 (35%)
HDDV
40,925 (84%)
55,895 (70%)
27,970 (54%)
62,298 (63%)
17,185 (32%)
Total
48,371(100%)
79,954(100%)
52,029(100%)
99,037(100%)
53,924(100%)
* Mg = Metric ton.
** Figures in parentheses indicate percent of total.
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Table II. Breakdown of HDDV Emissions in the Urban Areas of the
United States (Mq/year>[6]*
1995 HDDV
Scenarios
2000 HDDV Scenarios
Vehicle
1984 .
Base
Controlled
Base
Controlled
Classes
Levels
(0.70)
(0.60/.25/.10)
(0.70)
(0.60/.25/.10)
2B-8A
14,025 {34%)**
21,875 (39%)
11,232 (40%)
24,857 (40%)
6,855 (40%)
8B
19,828 (49%)
24,282 (44%)
12,536 (45%)
26,281 (42%)
7,405 (43%)
Buses
7,073 (17%)
9,739 (17%)
4,202 (15%)
11,160 (18%)
2,924 (17%)
Total
40,926(100%)
55,896(100%)
27,970(100%)
62,298(100%)
17,184(100%)
Mg = Metric ton.
Figures in parentheses indicate percent of total.
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Table III. Current and Future Ambient Concentrations of Diesel Particulate
in U.S. Cities (micrograms per cubic meter)[6]
1995 2000
U.S. City Population 1984 Base Controlled Base Controlled
Greater than 1,000,000 1.3-3.0 2.3-5.5 1.5-3.6 2.9-6.8 1.6-3.7
500,000-1,000,000 0.8-2.0 1.5-3.6 1.0-2.4 2.0^-4.6 1.1-2.5
250,000-500,000 1.0-1.6 1.8-3.0 1.2-2.0 2.2-3.7 1.2-2.0
100,000-250,000 0.7-1.7 1.2-3.2 0.8-2.1 1.5-4.0 0.8-2.2
* Ranges are average values plus and minus one standard deviation.
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Table IV. Inputs to the Lead Surrogate Model
Fleetwide EF (q/km)
Country
Lead*
Diesel
Particulate**
VMT Growth
(VYear)
Ambient Lead
Concentration (uq/m3)
U.S.
.079
.035
2.5
0.29-3.03 (1975)
Italy
.026
.080
2.0
0.52-5.12 (1980)
U.K.
.047
.069
1.0
0.16-1.75 (1980)
Sweden
.015
.089
1.0
0.20-1.30 (1981)
Japan
.025
.182
4.0
0.03-0.50 (1975)
* Lead emission factors (EFs) were calculated for the base year in
which ambient lead data were taken (shown in parentheses in last
column).
** Diesel particulate EFs were calculated for year of projection (1984
for U.S.; 1982 for other countries).
*** Annual compound VMT growth rates were calculated between the base
year and year of projection (vary with area).
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Table V. Estimated Ambient Diesel Particulate
. Concentrations in Selected European Cities*
Location 1982 Concentration (uq/m3)
Naples, Italy
-urban 7.2 - 35.1
-industrial 3.6 - 31.0
Birmingham, England
-urban- 3.2 - 20.3
-rural 0.5
-university campus 0.8 - 5.5
Stockholm, Sweden
-inner city 2.5 - 16.4
Estimates based on lead surrogate method.
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Table VI. Estimated Ambient Diesel Particulate
Concentrations in Selected Japanese Cities*
City Population 1982 Concentration (uq/m3)
Tokyo 8,350,000 10.2
Osaka 2,648,000 6.6
Nagoya 2,086,000 3.9
Sapporo 1,337,000 1.4
Sendai 617,000 2.1
Amagasaki 536,500 4.1
Ichihara 207,000 1.6
Ube 166,392 2.1
Matsue 133,000 0.6
* Estimates based on lead surrogate method.
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Table VII. Worldwide Fuel Prices (U.S. Dollars/Gallon)[6,8,9]
1982* 1983* 1985*
Country
Gas
Diesel
(Ratio)** Gas
Diesel
(Ratio)**
Gas
Diesel
(Ratio)**
U.S.
1.26
1
.01
(1.25)
1.15
0.89
(1.29)
-
-
-
Japan
2.46
1
.74
(1.41)
2.70
1.92
(1.41)
-
-
U.K.
2.46
-
-
-
1.76
1.75
(1.00)
France
2.24
1
.83
(1.22)
2.51
2.07
(1.21)
2.26
1.70
(1.33)
W. Germany
2.04
2
.00
(1.02)
2.14
2.12
(1.01)
1.69
1.58
(1.07)
Italy
2.65
1
.35
(1.96)
3.16
1.64
(1.93)
2.51
1.32
(1.90)
Sweden
2.35
1
.42
(1.65)
2.18
1.35
(1.61)
1.94
1.25
(1.55)
Switzerland
-
-
2.29
2.42
(0.95)
1.74
1.93
(0.90)
Netherlands
2.47
1
.65
(1.50)
2.36
1.73
(1.36)
1.97
1.34
(1.47)
Belgium
2.64
1
.85
(1.43)
2.53
1.98
(1.28)
2.01
1.48
(1.36)
Spain
2.22
1
.47
(1.51)
2.38
1.57
(1.52)
-
-
-
1982 figures for July; 1983 and 1985 for January.
Ratio equals gasoline price divided by diesel fuel price.
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Table VIII. Worldwide Diesel Penetration of New Car Sales of Total Sales)f8,9,10]
Model Country
Year
U.S.
Japan
U.K.
France
Germ.
Italy
Swed.
Switz.
Nether.
Belq.
Spain
1970
0.1
0.1
1.8
2.8
0.4
4.1
0.1
0.9
1.6
1971
0.1
-
0.1
2.1
2.8
0.6
4.5
0.1
1.2
1.9
-
1972
0.1
-
0.1
2.4
3.4
0.8
4.2
0.1
1.6
2.1
-
1973
0.1
-
0.1
2.0
3.7
1.2
3.2
0.1
1.6
3.3
-
1974
0.2
-
0.1
3.3
4.6
1.6
4.5
0.1
2.2
4.3
-
1975
0.3
-
0.5
4.5
4.3
2.5
3.9
0.2
2.2
4.3
-
1976
0.2
0.4
0.5
4.3
3.8
2.9
4.4
0.1
2.1
3.9
1977
0.4
1.1
0.5
6.4
4.7
4.0
3.7
0.2
3.6
4.9
1978
1.1
1.5
0.4
6.5
5.8
4.4
4.1
0.1
3.7
7.6
-
1979
2.6
2.0
0.5
7.3
7.0
-
6.5
0.6
6.4
11.0
-
1980
4.3
-
0.4
9.9
8.0
-
7.2
0.8
6.0
12.3
-
1981
6.1
-
0.7
11.7 .
14.3
14.8
6.7
-
9.5
17.3
-
1982
3.9
-
-
-
-
-
-
-
-
-
1983
1.9
-
1.4
9.6
11.0
18.5
5.4
1.7
9.5
23.7
15.1
1984
2.3*
*
2.4
12.6
12.5
24.1
4.4
2.4
12.6
25.7
24.0
EPA best estimate.
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