For the other biggest polluter in the transportation sector, aviation, the path forward doesn't seem entirely clear yet. What seems certain is that, regardless of the shape and size they'll take in the future, or the fuel they'll use, aircraft engines will continue to rely on the combustion of some sort of harmful substance to operate.
There are organizations presently engaged in trying to come up with battery-based electric systems to power aircraft, but it's unlikely that we'll get to see such a thing applied to a commercial airliner anytime soon.
But ZeroAvia has a mildly different approach. It not only keeps the traditional way of burning fuel for generating power in use, but also makes the new solution easy to adapt to existing aircraft. The difference is the fuel being burned, which is the benign hydrogen.
The company's take on the matter is to develop a hydrogen powerplant that could be easily installed on existing aircraft, by simply taking the original engines out. The crew has already done this, as it fitted hydrogen engines called ZA600 (600 stands for the engine's output in kW) on a Dornier 228 passenger aircraft.
On the ZeroAvia test aircraft the propellers are still there, only they're not spun by regular aircraft engines, but by the ZA600 solution. The exact specs for this engine are not entirely public, but the thing has flown eight times so far, so we do know a thing or two about its capabilities.
During the last test flight, which took place in May 2023, the Dornier took off from the Cotswold Airport in Gloucestershire, the UK. It climbed to an altitude of 4,000 feet (1,219 meters), which makes the plane "the highest flying commercial-scale aircraft powered by fuel cells." Also, the mission lasted for 22 minutes, which is the "longest duration flight yet" for the plane.
The company plans to offer this engine as a replacement for the ones on existing planes, with capabilities growing exponentially over the next few decades. By 2025, the range of Dornier-like aircraft powered by the ZA600 should grow to a total of 345 miles (555 km).
In 2027, the engine should be ready to support airplanes with up to 80 seats for distances as long as 1,150 miles (1,852 km). Two years after that, 200 passengers should be able to fly for 2,300 miles (3,700 km).
The ultimate target is that by 2040, airplanes with over 200 seats to be able to fly using the ZA600 (its successors, actually) for an incredible 5,700 miles (9,200 km).
Hydrogen also has a tendency to dissipate a lot faster than liquid fuel vapors when released into the air - up to 14 times faster. Because it needs at least 18 times more oxygen concentration to ignite when compared to gasoline, it's also a lot safer.
Compared to lithium-ion batteries, hydrogen provides 30 times more specific energy and much lower cost (by up to 60 percent) compared to turbines, making ZeroAvia confident the gas is "the only viable, scalable solution for zero-emission aviation."
As for the approach to simply swap the old engines on fixed-wing aircraft for the ZA600-derived ones, it does have clear advantages over designing a hydrogen aircraft from scratch, the most important being the much faster clearance of regulatory hurdles.
There is, of course, a lot of work ahead before this idea becomes widespread. If it succeeds, it will clearly change the way people look at aviation. And, who knows, maybe even the auto industry's greats will come to their senses and see hydrogen as a better source of power for cars than electricity produced in conventional ways.
Aside for the Dornier and the Natilus Kona, there is no other plane that we know of waiting in line to be fitted with the ZA600 engine.