Energy companies are fighting part of a proposed clean air plan for the ports of Long Beach and Los Angeles that would demand zero-tolerance for truck emissions by 2035.

Proponents of natural gas and other fuels that are cleaner than diesel argued at a Long Beach Harbor Commission meeting Monday night they can accomplish near zero-emission using energy that is already available, getting the port closer to its goal quicker.

But environmentalists want no trace of harmful exhaust being emitted into the air and prefer electric-powered vehicles that do not produce emissions.

The debate over tailpipe truck emissions is at the center of a decade-old clean air plan that the two ports are updating. On Monday, more than a dozen natural gas advocates, environmentalists and community groups showed up to stake out their position.

Heather Tomley, director of environmental planning for the Port of Long Beach, told the commission the two ports have been weighing industry concerns with the environmental aspirations, and she expects to release a revised plan in May that will include a cost benefit analysis of various options.

“We have to focus immediately on proven cost effective technologies,” said Rich Dines, a harbor commissioner who is also a dockworker at the ports. “(Natural gas) seems to be cost effective, although I understand the long-term goal is zero emission.

“There’s a way we can all work together to achieve our goals, and that’s to protect the health of the community,” he said.

The argument environmentalists make for electric trucks doesn’t consider how electricity is produced, said Greg Roche, vice president of sustainable trucking at the fuel company Clean Energy.

“There is a lot of (electric) power generation from natural gas and coal,” he said. “When you look at the total emissions of a renewable natural gas and an electric battery truck, they are about the same.”

With 570 fueling stations – including one at the Port of Long Beach – Clean Energy is the largest provider of natural gas transportation fuel in the U.S. and North America and would benefit from expanded use at the port. The fuel consists of methane gas that is captured from landfills and dairy and sewage plants. This form of energy fuels about 700 port trucks.

Leaders have been struggling to balance their goals with the multibillion cost of implementing zero-emission technology.

Natural gas has been pitched by the industry as an alternative. Roche said recent studies from UC Riverside show the fuel produces about 0.002 percent of smog-forming nitrogen oxide.

But Jesse Marquez, executive director of Coalition for a Safe Environment, advocates electric-powered vehicles, saying they don’t release nitrogen oxide that can ultimately be harmful to the community.

“We don’t need to be investing any further in natural gas,” he said.

Truck operators, meanwhile, have argued electric vehicles cost three times the amount of the dirtier diesel-powered big rigs.