Fueling a FCEV isn't the same as pumping your own gas, but there are lots of similarities. With the Mirai, you need to open the fuel cap, pull off the safety cork and push on the fueling nozzle, pulling the handle to create a seal. A gentle tug, to make sure it's on tight, and you can wander over to the pump itself. Tell it at what pressure you want your hydrogen delivered and hit the start button. The system will run an initial safety check before filling your tank up to the brim with sweet, sweet H2.

Your favorite is problematic Hydrogen and batteries both carry an environmental cost that means neither can be called entirely green. For all the piety surrounding BEVs, current battery-manufacturing processes mean that, during construction, they're almost as bad for the environment as traditional cars. It's only when they're out on the road that the situation begins to improve. The majority of hydrogen is not created using renewables, either, but is mass-produced with steam-methane reforming. The system uses natural gas (not renewable) and high-temperature steam to create carbon monoxide and hydrogen. Steam reforming means that you're left with a big pile of carbon monoxide to deal with, but that methane also has a tendency to leak. It can escape from both the factory, when it is created, and from the pipelines used to transport it, and methane is one hundred times more damaging to the climate than CO2. Decarbonizing the economy will be for nothing if these leaks aren't brought under control or stopped completely. With that in mind, Shell is building an electrolysis plant on the side of an existing steam-methane reformer. The company is aiming to get a 50/50 split on the balance of green hydrogen it can produce, although van Els hopes that figure can reach 80 percent in the longer term. The problem "has to be dealt with," said Thomas Hwan Jensen, a policy adviser at Energinet, the body that owns Denmark's gas and electricity transmission system. "Methane leakage is being addressed," he added, showing that the energy companies at least understand the issue. If there are positives, it's that there are systems in place that could mitigate some of the damage caused by carbon dioxide. Denmark's BioCat Project (pictured), for instance, uses a biological process to turn carbon dioxide and hydrogen into synthetic natural gas for use in power stations. It's still emissions-heavy, but, if powered by renewable energy, it could be a better way to generate power than, say, more coal-fired stations. Of course, any solution that doesn't involve burning fossil fuels is better for the environment; this isn't any defense of the oil industry. It's just important to understand that there is no wonder fuel that is entirely free from downsides.

Hydrogen's ideal place seems to be in medium-size vehicles, where the trips are long and the loads are heavy. Fleet vehicles, mid-range sedans, SUVs, vans, trucks and trains could all benefit from a shift in fuel. After all, it can be stored similarly to gasoline, with a better energy density, and is theoretically cheaper than bulky batteries. Alstom is working on a hydrogen train that could replace diesel-powered fleets across the globe as a far cheaper alternative to rail electrification.

Toyota is already running a hydrogen-powered big rig out of the port of Los Angeles, called Project Portal. NEL Hydrogen's Lars Jacobsen said that the fuel cell technology is "mature" enough for use in heavier industry. He added that, while "cars are fantastic, they don't make the business case" (for it). It's his belief that it's in trucking that hydrogen will make the biggest initial impact, and his company is already working with Nikola Motors.

Nikola has secured a pretty extraordinary deal with brewer Anheuser-Busch, which has pre-ordered $9 billion worth of hydrogen trucks. Eight hundred vehicles are expected to be pressed into service, starting in 2020, each one capable of traveling 1,200 miles before refueling. The trucks could serve as the catalyst for a new, America-wide hydrogen-refueling network, with 700 stations anticipated, which would hopefully encourage the production of more hydrogen-powered consumer vehicles.

Meanwhile, is there a place for hydrogen in the aerospace industry? The image of the Hindenburg engulfed in flames remains a powerful one, even today. Hamburg's Center of Applied Aeronautical Research has already found that it would be feasible to build a drone plane fueled by hydrogen. Airbus, too, is looking at ways to incorporate hydrogen into the aircraft of the future, in place of kerosene, although such a decision would require all aircraft to be radically redesigned.

At present, it has built a demonstration "imponator" (pictured), a 3D-printed model of a fuel cell that could replace an aircraft's kerosene-driven auxiliary power unit. This system traditionally drives the plane's air conditioner while in flight, but it's not likely to reach service in this half of the century. The company's Jörg Tappermann said that in the airline industry, the "relevance of a decision can take between 60 and 95 years." Choices that are made now will have a lasting impact in the centuries that follow, so there's reluctance to make a mistake.

Shell's German communications chief, Axel Pommeraenke, believes that "for the foreseeable future, all fuels will be needed," especially with a growing global population. The company's Stijn van Els said he is often asked which -- EVs or FCEVs -- "is going to win," and his response is that he "doesn't know" but that Shell will do its best to sell the power to make them go. "We need these fuels to be a success," said van Els, "because we want people to buy energy from Shell, and we want to be around by 2050."

There is a sense that every company is trying to avoid another HD DVD vs. Blu-ray scenario (or VHS vs. Beta, if you're older). Although the comparison isn't necessarily apt, because what Toyota is going to great pains to show is that there won't be a single winner. There can't be. Instead, the hope is that we'll be able to choose the energy that best suits the requirements of the job, rather than being chained to the altar of oil. And, of course, we need to move away from oil as quickly as possible, if only to avoid an ecological catastrophe.

Theory, however, is only half of the problem: Toyota has proved that it can build an FCEV, and on May 24th the company pledged to ramp up production. The company says that if not by 2020, then shortly after it, it will have produced 30,000 fuel cell electric vehicles. (For comparison, in 2017, Toyota sold 1.52 million "electrified vehicles," which includes hybrids.) Now it has to show that it has a compelling enough case that consumers will open their hearts, and wallets, in practice.