The race to replace Southern California’s biggest polluter is on. It’s going to take science, time, money – and maybe an assist from Elon Musk.

At the ports of Los Angeles and Long Beach, an ambitious $14 billion clean-air plan calls for the elimination of dirty-burning diesel equipment by 2035 – $9 billion just to purchase and deploy trucks.

It’s not going to be easy or cheap to replace the iconic workhorse of the region’s economy. About 16,000 diesel trucks tote tons of cargo – nearly 40 percent of all goods imported into the country – from the ports to the warehouses and deployment centers of the Inland Empire.

“It’s going to be extremely expensive and the technology is not there,” Gene Seroka, executive director of the Port of Los Angeles, told his commissioners last week.

The plan relies on heavy-duty trucks producing zero and near-zero emissions. But that technology isn’t yet ready to carry the full burden of today’s goods movement, many say.

And already there are squabbles over which technology will be the best fit:

. Electric: These trucks promise to be robust and truly emission-free, but a wary trucking industry won’t believe a practical electric big-rig – one capable of towing 80,000 pounds of Reeboks, with a range beyond 200 to 300 miles, and a battery that can be easily recharged – until they see it.

. Natural gas: This technology is closer to ready than any of its competitors. But they don’t burn quite as clean as electric vehicles. And some truckers remain bitter about a disappointing past state program during which LNG trucks underperformed, despite considerable expense and hype.

. Hydrogen cells: This model is the furthest from full deployment, but is considered to have broad potential for range, quick fill-ups and clean water as its only byproduct. But, like your family SUV, they have a fuel tank to fill, so for these trucks to take to the road, a mammoth hydrogen-station infrastructure would have to pop up, too.

. Hybrid: A truck powered by both natural gas and electricity – or some other combination – might help the industry hit the sweet spot. This would resolve some of the sticky problems that each of the individual technologies pose, but would likely not achieve emissions-free status.

All of these solutions need to step up technologically, though natural gas-powered trucks are closest to that finish line.

Why not start there? Some are afraid to spend money on an “almost zero” solution that runs on a fossil fuel, only to replace it when cleaner options advance technologically.

Whichever new-tech trucks hit the road, experts agree that all promise to be much more expensive than their diesel-drinking peers – at least for now. Mass production of vehicles in the decades to come is expected to slash today’s prices.

The riddle doesn’t have to be solved today, but the clock is running and tighter emissions standards loom on the horizon.

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Why retire the diesel?

The romance of the open-road trucker behind the wheel of a hulking diesel big-rig is undeniable.

Perhaps the most common vehicle in American industry, they haul tons of cargo along the nation’s transit corridors. They are durable, reasonably cheap to run and easy to maintain and repair, their boosters declare.

An owner-operator can snag a bright-shiny new one for about $150,000 or a decent-running used model for $40,000 to $80,000.

Unfortunately, that iconic diesel can also leave behind a trail of smog-forming nitrogen oxide and lung-searing diesel-particulate matter, linked by researchers to asthma, various other respiratory ailments, and even cancer.

Diesel emissions in the logistics industry cause more than $20 billion in health impacts each year, according to the American Lung Association.

Though much science has been devoted to cleaner-running diesels, they still top the hit list for many environmentalists. So most plans for cleaning the nation’s air – especially along Southern California’s cargo corridor – include the deliberate disappearance of the diesel.

In the meantime, some fear smaller trucking companies forced to live up to the new standards might well be rocked financially.

“Near-zero emissions can be costly and limits some small fleets’ ability to get into the equipment,” said Matt Schrap, president of California Fleet Solutions, a transportation consulting firm. “But even more sophisticated, higher cost standards like zero-emission vehicles could price them out of the market,”

Go, diesels, go

The twin ports of Los Angeles and Long Beach – and the state’s air-quality regulators – have said it doesn’t matter how diesel is phased out, but it has to go. And they are willing to pour millions of dollars, maybe eventually billions, into incentive and test programs to assure it.

The air district has spent $40.9 million for demonstration projects showcasing 69 battery-electric, plug-in hybrid/electric and fuel-cell trucks.

Over the past seven years, the district also subsidized 6,000 big rig trucks that run on natural gas or cleaner-burning diesel, including 2,000 serving the port.

And with the mayors of Los Angeles and Long Beach calling for zero-emission ports, Seroka and others believe they can get there with the help of some deep-pocketed companies willing to invest in and grow the burgeoning market.

L.A. port chief Seroka worries that many of the major automotive players are loading their research dollars into autonomous vehicles rather than clean technology.

“We are going to bring the companies here and we are going to show them that they have a customer base ,” Seroka said, “that is worthy of consideration to invest in this technology.”

Major West Coast ports have united to send out an open request to engine manufacturers about current technology, hoping to signal that the region is open for the cleaner-burning business. They hope that the images of a hungry market will cut prices sooner rather than waiting years for the technology to become cheaper as production expands.

Zero? Almost

Proponents of natural gas and other fuels that burn cleaner than diesel argue their technology is ready to roll.

But some environmentalists counter that it would be better to invest in zero-emissions trucks later rather than spend on almost-zero-emitting vehicles now.

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“It’s frustrating because the warring factions have legitimate issues and points,” said Joe Lyou, president and CEO of Coalition for Clean Air and a member of the South Coast Air Quality Management District board.

Lyou eventually would like to see all zero-emission trucks on the road some day – although he’s pleased to have low-emitting natural gas vehicles taking up lanes now.

To be fair, natural gas-powered vehicles do cut air pollution radically. And next year, the heavy-duty natural-gas engines are expected to get certified by the state’s air regulators, making them easier to purchase widely. Their engines emit 90 percent less of the smog-forming nitrogen oxide than even the cleanest diesel trucks. Plus, there’s no diesel particulate matter, a toxic responsible for many of the trucks’ damaging health effects.

“There is not a one-size-fits-all solution for the entire basin,” said Fred Minassian, who works on research and development at the air district. “We cannot wait five or 10 years or so for the perfect electric fuel-cell to be a fit for all.”

The fossil-fuel feud

Natural gas vehicles are clean, getting cheaper and are more plentiful each day, its proponents say. The trucks that run on compressed (CNG) or liquified (LNG) natural gas are pricier than diesel, costing as much as $225,000, but they’re cheaper than the next wave of other zero-emissions options, experts say.

And don’t expect a shortage of natural gas, they say. There’s so much of it, the industry sells more to overseas buyers each year. Since 2015, seven new LNG facilities have launched production, according to Forbes magazine, and another 15 are under construction.

Increasingly, the fuel is what the industry calls renewable, with more produced from waste at landfills and dairy farms.

Nonetheless, it’s still considered a fossil fuel. And it shouldn’t shift focus away from pollution-free technology, some environmentalists say.

“This notion that we can further our dependency on fossil fuels and we can get to long-term air quality is wrong,” said Evan Gillespie, who directs the Sierra Club’s campaign for clean energy.

“One of the things you do when you invest (in natural gas) is you lock in a fossil fuel for a long time,” Gillespie said. “We can’t afford to do that.”

Forgiving LNG

Many in the trucking industry just don’t trust natural-gas vehicles.

“There is a huge stigma with natural gas,” said Weston LaBar, executive director at Harbor Trucking Association.

A decade ago, the port promoted them as the best alternative to diesel – and they partnered with AQMD to sink millions of dollars into subsidizing LNG-fueled trucks as part of their first clean-air plan.

Those trucks soon proved to be a bust, truckers say. Amid all the spending and environmental hype, the trucks developed mechanical problems and weren’t powerful enough to carry the heaviest of loads.

“When natural gas was imposed by the ports as part of the first clean-trucks program, the technology wasn’t ready for the job it was supposed to do and many drivers had bad experiences,” LaBar said. “They have no interest in using it again.”

But, he said, “natural gas works.”

The biggest hurdle, he said, is the stigma associated with that first program. “They have to win back the hearts and minds of the trucking community,” LaBar said.

Plugged in, progressing

You don’t have to sell environmentalists on electric trucks.

With the roads packed with fuel-cell hybrid family cars and Tesla’s vow to reinvent the affordable rechargeable with the arrival of the Model 3, electric vehicles are no longer an impractical, however responsible, dream.

Electric trucks, however, aren’t as ready.

The ports of Los Angeles and Long Beach successfully use electric-powered forklifts and cranes, but electric-powered vehicles can’t be run for more than 140 miles without a charge.

Also, the heavier the loads, the smaller the range. At this point, a truck hauling 80,000 pounds can only go 80 miles.

Electric big-rigs range in price from $300,000 to $400,000.

Charging stations for family cars are growing increasingly common. But armies of electric trucks would call for more stations and more power lines. The infrastructure to power up trucks would prove pricey, especially along remote roadways. And worse, they can’t run a 24-hour cycle.

However, some believe battery exchanges – swapping out a fully charged battery for a spent one – could eliminate that problem.

The landscape is changing rapidly.

Iconic heavyweights in the truck industry and startups alike are introducing one advance after another.

And Musk – with his own brand of enigmatic chutzpah – promises to single-handedly reinvent the electric truck industry when he reveals his company’s Tesla Semi in September. Musk owns rocket builder SpaceX in Hawthorne and operates a Tesla design center in the city.

His truck rides like a sports car, he says.

High hopes for hydrogen

In the end, hydrogen-fueled trucks may prove a superior option to electric because there’s no charging lag time.

When the liquid fuel is combined with air in the fuel cell, it creates electricity to power the vehicle and releases only clear H2O.

But hydrogen trucks are the most costly of the clean-burning options – about $480,000 to $640,000 per vehicle. These trucks are furthest away from mass production, which is expected to drive down vehicle cost.

They run on hydrogen, often derived from compressed natural gas. Yes, that’s a fossil fuel, but it can also be created by a solar-energy process.

“It looks promising from the standpoint that it’s proving reliable and efficient,” said Frank Falcone, vice president of powertrain engineering at Transpower, a company that refits trucks to run on clean-burning energy. The Escondido-based firm just commissioned its first version of the hydrogen fueled big rig and is working toward commercialization.

However these technologies play out, it’s possible that hybrid versions of each – electric-battery-plus-liquid-fuel trucks, like a large-duty version of the Toyota Prius or other family vehicle – could prove popular.

“We don’t know what technology is going to become dominant or we wouldn’t be doing all of this,” he said, “but I am confident that electrification will be part of the final solution.”