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Reducing Emissions from Shuttle Buses
W-
at Can
Shuttle Bus Fleet
Operators Do?
Buses play an important role in transporting
people from place to place. They are a key
element of public transportation and tourism
by making travel convenient and affordable.
There is growing concern, however, about
the health effects associated with exposure to
diesel exhaust. Like other vehicles on the
road, buses emit significant amounts of
pollution, including carbon dioxide, nitrogen
oxides (NOx), poisonous carbon monoxide,
particulate matter (PM) and air toxics. Not
only do these emissions contribute to the
formation of ozone smog, acid rain, and
global climate change, they also contribute
to asthma, heart disease, lung damage, and
possibly cancer. This pollution affects
everyone, including bus drivers.
Although new emission standards and
technology for the diesel and gasoline
vehicles of the future will dramatically reduce
these health risks, there are three main actions
that shuttle bus fleet operators can take now
to now to use less fuel, save money, and
reduce pollution.
Reduce Engine Idling
Idling vehicles emit pollution and waste fuel.
Recent studies found that fuel consumption
during engine start-up is equal to about 30
seconds of engine idling, if the engine is
within normal operating temperature.
Therefore, it is more fuel efficient for drivers
to turn off the motor than to idle the engine.
An idling bus consumes about one gallon of
fuel per hour. If a company operates 50 buses
and reduces the idling time of each bus by 30
minutes per day, at $2.00 per gallon of diesel
fuel, the company would save over $18,000
per year in fuel costs.
In addition to saving fuel and reducing
emissions, there are legal reasons not to idle.
Massachusetts' law prohibits unnecessary
idling of all motor vehicles that are stopped
for a foreseeable period of time over five
minutes. Find out more at: www.mass.gov/
legis/laws/mgl/90-16a.htm
Use Cleaner Fuels
Burning cleaner diesel fuel, or alternative
fuels, helps reduce vehicle pollution. Some
fuels can be used in a standard diesel engine
without any modifications. Others require
engine modifications. Some examples of
cleaner fuels available in the Boston
metropolitan area include:
Biodiesel
• Biodiesel is a domestically produced,
renewable fuel that can be manufactured
from new and used vegetable oils and
animal fats. It is safe, biodegradable, and
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better
reduces air pollutants such as fine
particles, poisonous carbon monoxide,
smog forming hydrocarbons, and air
toxics. However, nitrogen oxides
emissions increase slightly with the
concentration of biodiesel in the fuel.
Some biodiesel produces more nitrogen
oxide emissions than others, and some
additives have shown promise in reducing
these increases.
•Blends of 20% biodiesel with 80%
petroleum diesel (B20) can be used in
regular diesel engines. Biodiesel can be
used in its pure form (B100), but may
require minor engine modifications to
avoid maintenance and performance
problems. Pure blends of biodiesel are not
suitable for cold climates.
• B20 costs about 20 to 30 cents more per
gallon than regular diesel fuel, and
reduces emissions of fine particles by
about 10 percent. It also reduces emissions
of hydrocarbons by more than 20 percent.
Boston Coach has
established a strong anti-
idling policy for its drivers.
To reduce winter warm up
time, Boston Coach also
created garage space to park
their vehicles. By establishing
a program to inform your
drivers about the
Massachusetts Anti-Idling
rule and ensuring full
compliance with the rule,
you can reduce air pollution
and save money
in fuel costs.
4>EPA
United States
Environmental Protection
Agency New England
EPA-901-F-04-013
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Emulsified Diesel
Emulsified diesel is a blended
mixture of diesel fuel, water, and
other additives that reduces both
fine particle and nitrogen oxide
emissions. Emulsified diesel can be
used in any diesel engine, but the
addition of water reduces the
energy content of the fuel, so
some reduction in power and fuel
economy can be expected. Case
studies suggest that emulsified
diesel can reduce emissions of
smog-causing nitrogen oxides
between 10-20 percent and fine
particles between 50 - 60 percent.
Emulsified diesel costs roughly 20
cents more per gallon than regular
diesel fuel.
Ultra Low Sulfur Diesel Fuel
Ultra Low Sulfur Diesel Fuel
(ULSD) will be available
nationwide in June 2006, but
currently is available in certain
parts of the country, including the
Boston area. ULSD reduces fine
particle emissions between 5 and 9
percent. The combination of
ULSD with advanced pollution
control technology, such as a
diesel particulate matter filter
(DPF), reduces fine particle
emissions by more than 90
percent. ULSD currently costs
between 5-20 cents per gallon
more than regular highway diesel fuel. In
2006, when ULSD is available nationwide,
the cost differential will disappear.
Compressed Natural Gas
Compressed natural gas (CNG) buses
equipped with an oxidation catalyst can
A
number of fleets in the Boston area are operating buses
equipped with diesel
particulate matter filters:
MBTA: Currently, the MBTA is using ULSD
in all of its diesel buses and has committed
to retrofit all of its existing and new diesel
buses with particulate matter filters. The
entire diesel fleet will be equipped with
particulate matter filters by the end of 2004.
Medical Academic and Scientific
Community Organization (MASCO):
In 2003, MASCO, owners of the shuttle buses that serve the Longwood Medical
area in Boston, became the first private fleet in New England to install diesel
particulate matter filters and use ULSD fuel in their entire fleet of 17 buses.
Old Town and Beantown Trolley Tour Buses: The 34 diesel powered tourist
trolleys operating in downtown Boston are equipped with diesel oxidation
catalysts and 20 of them are using ULSD fuel.
Two notable fleets in the Boston area operate CNG buses:
Massport: Logan airport is an ideal location for CNG buses, since buses are
centrally fueled on site. The 32 shuttle buses at Logan Airport that transport
airport passengers and employees among the terminals and to the Massachusetts
Bay Transportation Authority (MBTA) Airport Station run on CNG.
MBTA: 358 of the MBTA's approximately 1000 buses are fueled with CNG.
Three of the MBTA's garages are equipped with CNG refueling and
maintenance facilities.
Several fleets in the
Boston area use biodiesel,
including all of Harvard
University's diesel
vehicles, which currently
operate on B20.
reduce fine particle emissions between 70 to
90 percent, compared to an uncontrolled
diesel bus. New CNG buses cost about
$30,000 more than a comparable diesel
bus. They also require special refueling
and maintenance facilities. Overall the cost
of natural gas and diesel fuel are very
similar but in some areas of the country
natural gas fuel may be more economical.
Install Pollution Control
Equipment
Adding pollution control equipment such
as a diesel oxidation catalyst or a
particulate matter filter is another way to
reduce emissions from buses. These
devices are installed in the exhaust system
of an existing diesel engine.
• Diesel Oxidation Catalysts
Diesel oxidation catalysts are similar to
the catalytic converter in your car and
can reduce emissions of PM by between
20 and 50 percent (in certain types of
vehicles), hydrocarbons (HC) by 50
percent, and carbon monoxide (CO) by
approximately 40 percent. Oxidation
catalysts cost between $1,000 and $2,000,
can be installed on any new or used
bus, and run on regular diesel fuel.
' Diesel Particulate Matter Filters
Diesel particulate matter filters are
ceramic devices that collect PM in the
exhaust stream. The high temperature of
the exhaust heats the ceramic structure
and allows the particles inside to break
down (or oxidize) into less harmful
components. They cost between $5,000
and $10,000, and can be installed on
buses built after 1995. To ensure that the
filter will work properly, it is necessary to
use ULSD fuel with a sulfur content of
less than 15 parts per million.
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