July 3, 2017
The Los Angeles County Metropolitan Transportation Authority is buying hundreds of new natural gas buses and shifting to RNG as the most cost-effective way to continue driving down emissions on all of its routes.
The LA Metro board voted on June 22 to purchase 295 40-foot CNG buses equipped with Cummins Westport ISL G Near Zero 8.9-liter engines.
“This purchase of 295 CNG buses is a routine replacement for us—this year, we’ll buy a total of 450 buses and more than 350 of them will be natural gas,” said John Drayton, LA Metro’s director of vehicle technology. “The buses we’re replacing have expiring CNG tanks, so it’s a good time to replace them with new buses using the Cummins Westport Near Zero low-NOx emissions engines.”
LA Metro’s goal is to have a zero-emission fleet by 2030, and it has been a clean-fleet pioneer since 1998, when it began adding natural gas buses. The agency continues to add hundreds of new CNG buses each year and participates in cleaner-engine research projects. So far, the agency has bought more than 2,300 NGVs.
“There’s no magic to it,” Drayton said. “The CNG buses run well, the fuel is inexpensive and clean, and the technology is only getting better.”
The agency is also committing to the big change of transitioning from CNG to RNG. Under a contract with Clean Energy Fuels, LA Metro has agreed to buy Redeem RNG for 10 percent of its NGV refueling needs during the first year of the five-year contract, and it will move to 100 percent RNG as quickly as possible within the next few years.
“LA Metro’s CNG cost is one-third the cost of diesel fuel on a cost-per-mile basis, and RNG will make our fuel even less expensive, due to LCFS credits. Moving to RNG will drop our greenhouse gas footprint 70 to 80 percent,” said Drayton.
NGV Engines Beat Lowest Certification Standard
CARB recently borrowed one of LA Metro’s CNG buses running RNG to test its NOx emissions in real-world transit operations. Preliminary test data shows that the Cummins Westport ISL G engine certified at 0.02 grams per brake horsepower-hour NOx runs well below that level in all transient conditions.
These early results echo data that Southwest Research Institute recently published from tests on an Orange County Transportation Authority natural gas bus. Researchers modified the baseline CNG engine—a 2014 Cummins ISXI 2-G engine compliant with 2010 emissions standards—with readily available advanced air-fuel control technologies, a close-coupled three-way catalyst, and conventional under-floor three-way conversion.
They found 0.00 g/bhp-hr NOx emissions on the OCTA bus in low-load vocational and heavily transient operation test cycles. In addition to recording zero tailpipe NOx emissions in these two testing conditions, the modified engine significantly reduced methane and non-methane hydrocarbon emissions.
LA Metro Green Fleet Will Continue to Expand
LA Metro plans to continue expanding its fleet with both natural gas and battery electric buses, using each technology where it makes the most sense. Drayton said that battery electric vehicles, although expensive, work well for certain types of service, such as on bus rapid transit routes. LA Metro is preparing to operate electric buses on two BRT lines in heavily trafficked, dedicated right-of-way corridors that can have charging stations at each end. For the majority of LA Metro’s 170 operating lines, however, natural gas is currently a more flexible and cost-effective choice, he said.
The transit agency will vote on a similar purchase at its July board meeting; its current contract with ElDorado National-California in Riverside includes an option to purchase 305 additional CNG buses.
“Going forward, we will assess the tech choices that keep us on the cutting edge,” said Drayton. “We’ll build up the CNG fleet with RNG buses and will also use electric vehicles to complement them. We’ve driven almost 2 billion miles on natural gas buses, and we’ll continue to push that number higher.”
Photo: James Cuevas Jr.