The Los Angeles County Metropolitan Transportation Authority's (LA Metro) governing board on Thursday voted to purchase 295 40-foot compressed natural gas (CNG) buses that would be fueled by renewable natural gas (RNG), or biomethane. The action follows increased calls for more transportation options by the state’s elected officials and climate change advocates.

Using RNG in combination with low-nitrogen oxide (NOx) engines, the buses are considered “cleaner” than electric-power versions using natural gas-fired generation, according to an analysis by the South Coast Air Quality Management District (SCAQMD).

LA Metro staff reportedly have confirmed in two separate reports prepared during the past 18 months for the board that low-NOx engine buses using 100% RNG are "zero-equivalent" vehicles that outperform the most efficient current electric vehicle (EV) technology. The nation's second largest transit system, which committed to move entirely away from diesel buses several years ago, has doubled down on RNG this year.

"We take our responsibility to both the environment and taxpayers very seriously," said LA Metro’s Cris Liban, environment and sustainability executive officer. "By using RNG, as well as other technologies, we will continue to exceed our environmental goals and ensure we provide the best transportation service to our region."

The combination of engine and fuel technologies in the natural gas vehicle (NGV) space would reduce LA Metro’s exhaust emissions by up to 98%, according to the California CNG Coalition. "When accounting for the amount of coal-fired electric generation in large areas of the grid where LA Metro operates, buses powered by RNG can register even lower emission levels than a 100% battery bus,” it said.

In addition to the CNG buses, LA Metro is retrofitting its older NGV buses with Cummins Westport low-NOx CNG engines. The new contract for nearly 300 buses also has an option to purchase 305 40-foot CNG buses. The transit board is slated to vote on another purchase in July.

Clean Energy Fuels Corp., which markets RNG, also has secured a five-year supply contract with LA Metro that includes fueling and station technology.

CNG fleet expansions are happening across North America, and interest has spread to Mexico with the opening of a CNG research center in Morelia in the state of Michoacan. The Center for Research, Engineering and Technology Manufacturing for the Advancement of CNG initially is to offer decompression, regulation and measurement stations for gas infrastructure; CNG loading and unloading equipment; and modular skid-mounted storage systems.

Mexico-based GNU Gas Natural opened the center, and it plans to focus on the Mexican market initially before eventually expanding into global markets. GNU's Daniel Cadenas, new business development director, said the 1,500-square-foot, $1.6 million facility is the first of its kind in the country.

Another emerging technology related to CNG, adsorbent natural gas (ANG), is being adopted by California and Colorado fleet operators. ANG developer Cenergy Solutions has ambitious plans to convert the fleets of Broomfield, CO-based The Gas Connection and Hayward, CA-based AAAA Generator Services Inc. The two companies asked Cenergy to convert their fleet NGVs to operate with low-pressure ANG tanks. AAAA Generator converted one of its fleet vehicles to ANG in December 2015, and it has been the most used vehicle in the fleet, the company said.

Cenergy is offering training on installing ANG tanks through its conversion partners throughout the United States and Mexico. According to Cenergy, the ANG technology may reduce fueling tank and operating costs for NGV fleets, as well as a more flexible, safer fueling system.