From food to clothes to electronics, most things consumers purchase are likely delivered on trucks. One could even call them the backbone of commerce.

But they are massive polluters. In Europe, heavy duty vehicles are responsible for 28% of transport emissions though they only make up 2% of vehicles on the road, according to the European Federation of Transport and Emission.

And as more and more freight is moved around, these emissions will keep increasing — unless truck manufacturers and governments take drastic action. 

How do we slash trucks' emissions? 

Truck producers' best bet is to make their new vehicles zero emissions by using electric motors. These can be powered with two options already familiar from the car industry: batteries or hydrogen fuel cells.

Batteries won the race to power passenger vehicles because they are cheaper. But trucks face a completely different set of challenges: They usually drive further and carry much heavier loads. That means truck companies are weighing their options. 

Are battery electric trucks even feasible? 

Just a few years ago, talk of a battery-powered truck might have gotten you "laughed out of a room," said Felipe Rodriguez, director for the Heavy-Duty Vehicles Program at the International Council on Clean Transportation (ICCT). 

"There were many preconceived notions about what batteries could do. They were too expensive, too heavy, too big," he said.

The idea was that big trucks would need massive batteries, which would compromise how much cargo the vehicle could carry. And transporting heavy loads would make them run out mid-journey, making drivers stop for hours of charging. Not a great choice for operators running on tight profit margins. 

"But what has happened in the last few years is mind-boggling," said Rodriguez. 

The price for lithium-ion batteries has plummeted in the last decade because raw materials and component prices have become cheaper. At the same time production capacity increased across the battery value chain. Part of the reason is government's high-scale investment in electric vehicles, or EVs, as they try to reduce emissions produced by passenger cars. 

"It's a whole automotive industry really bringing down the cost of batteries, but only a small industry working on engineering fuel cells and hydrogen delivery," said David Cebon, professor of mechanical engineering at Cambridge University in the UK.

Over the years, the energy density of batteries has also improved, meaning a truck can get much more range from the same size unit. 

And researchers are working on megawatt charging systems that could reduce battery-powered trucks' charging time from several hours to as little as 15 minutes. That would allow them to charge the vehicle during their mandated driving break. In the US and Europe, this break ranges from 30 to 45 minutes. 

What are the advantages of hydrogen fuel cell trucks? 

The major selling point of hydrogen trucks is that they can reduce emissions without compromising cargo or requiring long breaks.

That's because they use fuel cells. These devices essentially work like batteries, but instead of running on electricity, they run on hydrogen fuel and oxygen. The only by-products are heat and water. 

"Refueling a hydrogen truck is more or less the same as refueling your diesel truck,” said Volker Hasenberg who manages the hydrogen strategy at Daimler Truck. “You have a fueling station, you store your energy in the truck, and this takes a couple of minutes."

Fuel cell trucks are an especially attractive option to carry extremely heavy loads because battery-powered trucks run out of energy quicker the more cargo they carry. 

"Think about machines, construction — in general, what weighs a lot? When the threshold is the weight, not the space to be transported, then we have an advantage for hydrogen trucks," said Hasenberg. 

How do the technologies' emissions compare? 

Battery-powered trucks have a leg up when it comes to reducing emissions. 

According to the ICCT, they save about 65% in emissions compared to their diesel counterparts when they run on an electricity mix of fossil fuels and renewables. If they are powered by clean energy, they emit 92% less.

Meanwhile, fuel cell trucks only save up to 33% compared to diesel trucks. This figure goes up to 89% if they run on green hydrogen, which is produced with renewable energy. But this is barely happening. 

Which technology is cheaper? 

Battery electric trucks have a higher upfront cost than hydrogen trucks. But they are so efficient that they are much cheaper to operate — and ultimately more cost competitive.

When charging a fully electric truck, there are far fewer opportunities to lose energy along the way: The battery is charged at a station and then powers the motor. 

Compare that to a fuel cell truck where energy needs to be converted into hydrogen, transported to refueling stations and pumped into a fuel cell where it is then turned back into electricity.

Because of all these extra steps, a hydrogen-fueled vehicle needs about three times more energy than a battery-powered one. 

What is the future for these technologies? 

As batteries become cheaper and more efficient, most major truck manufacturers are opting for them instead of fuel cells.

Some companies, like Daimler and Volvo, are betting that batteries will never mature enough to carry very heavy loads though. So they are developing hydrogen trucks as well. 

"We can't really be sure that one technology will serve all our customers' needs,” said Hasenberg. "We stand better on two feet than one."

But projections show that fuel cell trucks likely won't make up more than 10% of the market share before 2050. The vast majority will be powered by batteries.

Edited by: Tamsin Walker