New Natural Gas Buses are Zero Emissions Equivalent
Natural gas buses today reduce harmful emissions of
nitrogen oxides (NOx) and particulate matter (PM) by more
than 95 percent compared to transit buses built prior to 2010,
thus the emission difference between new natural gas buses
and electric buses, which have no tailpipe emissions but do
have particulate matter emissions associated with tire wear
and braking, are miniscule. Importantly, natural gas buses
produce these emission reductions without relying upon
costly and cumbersome emission control equipment.
Fueling transit buses with conventional (geologic) natural gas
reduces greenhouse gas emissions (GHG) by about 12
percent compared to diesel. But according to the California
Air Resources Board, fueling buses with renewable natural
gas (biomethane) collected at local landfills, wastewater
treatment plants, commercial food waste facilities, and
agricultural digesters can yield a carbon-negative lifecycle
emissions result. According to CARB data, renewable natural
gas (RNG) holds the lowest carbon intensity of any on-road
vehicle fuel, including fully renewable electric. On-road
natural gas fueling trends show increasing adoption of RNG.
According to data from the U.S. Energy Information
Administration (EIA) and U.S. Environmental Protection
Agency (EPA) Renewable Fuel Standard reporting, 39
percent of all on-road natural gas fuel in 2019 was RNG. In
California, 77 percent of all on-road natural gas fuel in 2019
was RNG.
When you add it all up, natural gas provides a winning
solution for transit agencies looking to lower costs and
reduce emissions. As estimated in this report, it could cost
billions – as much as $24 billion more – to switch the majority
of the U.S. larger bus fleets to an all-electric fleet. Switching
the majority of the U.S. bus fleet to an all-CNG fleet powered
by RNG would not only save significant capital and operating
amounts of money but also would generate much greater
annual emission reductions: 10,000 tons of GHG, 25 tons of
NOx, and 6.26 tons of PM2.5
Grid Upgrades
Electric bus advocates fail to evaluate the cost and extent of
major utility upgrades needed to accommodate an
expected surge in electricity transmission and demand for
electric buses, upgrades not needed to fuel natural gas
buses. These factors are easily overlooked in the case of
demonstration projects involving only a limited number of
buses but can quickly become overwhelming when
converting an entire fleet to electricity. This is not an issue for
natural gas as many bus facilities around the country have
been converted entirely or almost entirely to natural gas with
hundreds of buses fueling at a single depot. Nearly 100
transit agencies currently operate more than 10,000 natural
gas buses with additional natural gas buses successfully in
service at many other facilities such as airports and colleges
across the United States.
Reliability
In the reports evaluated by NGVAmerica, natural gas buses
have demonstrated that they are more reliable than electric
buses, accumulating far more service miles, spending fewer
days out of service and under-repair than electric buses. A
key factor of reliability is availability for pull out. In the studies
prepared by NREL evaluating real-world bus fleets, natural
gas buses morethan exceed the expected rate of 85 percent
availability while electric buses struggle to meet the
requirement. In the Foothill fleet, during the most recent
evaluation period the twelve 35-foot electric buses had an
average availability rate of 63 percent.
The availability for electric buses was as low as 46 percent during
the first half of 2019. In contrast, CNG buses had an
availability rate of 93 percent for the same period and an
overall availability rate of 96 percent.4
Once out on route, CNG buses had far fewer road calls, or
revenue vehicle system failures, than their electric
counterparts in the Foothill study. Such incidents require a
bus to be replaced on route and/or cause a significant
schedule delay affecting system operations. Such reliability
in the transit industry is measured in mean distance (miles)
between failures (road calls), or MBRC. At Foothill, the
average miles between road calls for natural gas buses
exceeds that of the BEBs by between 18,000 to almost
20,000 miles.5
Fuel Efficiency
Much attention is given to the efficiency of electric buses but
very few studies or reports acknowledge efficiency losses
associated with charging infrastructure which can increase
energy consumption by 10 – 15 percent. And when
determining the overall energy efficiency of electric bus
transit operations, it is important to consider that more than
60 percent of energy used to generate electricity is lost in
conversion. According to the U.S. Department of Energy,
U.S. utility-scale generation facilities consumed 38 quadrillion
British thermal units (quads) of energy to produce only 14
quads of electricity last year.6
Efficiency claims also almost never acknowledge the tradeoffs associated with heating and cooling of buses, which is
not accounted for in the test cycles used to determine
efficiency ratings of transit buses. Another fact that is often
omitted is the large percentage of electric buses that are
equipped with fossil fueled heaters to reduce the need to
draw on electricity to provide heat. Such heaters can be a
significant emission source that are not at all considered.
If you would like a no cost obligation in regard to Bus Fleet Options. Please contact us for a consultation.
NGV Global Group Inc.
10733 Spangler Rd,
Dallas, TX 75220 USA
Phone: +1 (214) 630-1000
Mail: info@ngvglobalgroup.com