Toyota city, Aichi Prefecture, Japan – 30 October 2017

1. Wide of hydrogen tank being placed into Mirai vehicle on assembly line

2. Close of workers fixing the tank

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Tokyo, Japan – 18 November 2014

3. Various of the first model of Mirai on test run

4. Various of the display of how hydrogen works inside Mirai

Toyota city, Aichi Prefecture, Japan – 30 October 2017

5. Wide of Takeshi Uchiyamada looking at manufacturing process of Mirai

6. Close of the shirt of a worker, reading: (English) "Challenge Zero Emission 2050"

7. SOUNDBITE (Japanese) Takeshi Uchiyamada, Chairman, Toyota Motor Corp.:

"Upon thinking of what will become the energy of the future, we have been debating both within Japan and internationally about what kind of energy should be our option. There are two main points we need to consider. First, how to realize a low-carbon society to create a society with less CO2 emissions. The second point is to ensure a stable energy supply for the future. In this light, hydrogen holds tremendous potential."

8. Wide of hydrogen tank being towed inside the plant

9. Mid of hydrogen tank being filled

10. SOUNDBITE (Japanese) Takeshi Uchiyamada, Chairman, Toyota Motor Corp.: ++audio as incoming++

"It (Hydrogen FCV) certainly has more convenience for users (in comparison to electric vehicles), meaning driving range is much longer and there is not much of difference in time to fill in hydrogen with the conventional gasoline cars. I think that is one of the major features (for hydrogen fuel cell vehicles)."

Tokyo, Japan – 25 October 2017

11. Setup shot of Joseph Capparella, Car and Driver magazine

12. SOUNDBITE (English) Joseph Capparella, Car and Driver magazine:

"I think it will depend a lot on if automakers are able to get the cost down because right now the technology is very expensive and difficult to develop. But, I think it's in its early stages. So, you know, it seems to be possible if it could be streamlined into a more affordable and mass producible technology then, it might be able to catch on but it's hard to say because our society is so deeply entrenched in, what we already know, which is gasoline and electric. So, to enact such a broad shift in the mind of consumers, I think it's a difficult obstacle."

Toyota city, Aichi Prefecture, Japan – 30 October 2017

13. Assembly line worker

14. SOUNDBITE (Japanese) Takeshi Uchiyamada, Chairman, Toyota Motor Corp.

"Hydrogen society is something all the players need to work together in order to create it. So, it will need lots of fathers and mothers."

Tokyo, Japan – 14 November 2017

15. Various of Mirai being filled up at Hydrogen station

At the Motomachi car factory in this city named after Toyota, the usual robots with their swinging arms are missing.

Instead, workers intently fit parts into place by hand with craftsmanship-like care.

The big moment on the assembly line comes when bulbous yellow tanks of hydrogen are rolled over and delicately fitted into each car's underside.

While much of the world is going gung-ho for electric vehicles to help get rid of auto emissions and end reliance on fossil fuels, Japan's top automaker Toyota Motor Corp. is banking on hydrogen.

Toyota sells about 10 million vehicles a year around the world. It has sold only about 4,000 Mirai fuel cell vehicles since late 2014, roughly half of them outside Japan.

The Mirai, which means "future," is not cheap at 57,500 US dollars but Toyota loses money on each one. Still, the company's goal is to sell 30,000 fuel-cell vehicles a year by about 2020.

Toyota's chairman, Takeshi Uchiyamada, believes hydrogen is an ideal, stable fuel for a future low-carbon society.

"Upon thinking of what will become the energy of the future, we have been debating both within Japan and internationally about what kind of energy should be our option. There are two main points we need to consider. First, how to realize a low-carbon society to create a society with less CO2 emissions. The second point is to ensure a stable energy supply for the future. In this light, hydrogen holds tremendous potential," says Uchiyamada, known as "the father of the Prius," the world's top-selling hybrid car.

The Prius turned out to be a good bet for Toyota. The Mirai could be the same.

Hydrogen fuel cells don't suffer from limited range drawbacks of many electric vehicles. The Mirai can run for 312 miles (502 kilometers) per fuelling, under U.S. EPA conditions, and fuels as quickly as a regular car.

"It (Hydrogen FCV) certainly has more convenience for users (in comparison to electric vehicles), meaning driving range is much longer and there is not much of difference in time to fill in hydrogen with the conventional gasoline cars. I think that is one of the major features (for hydrogen fuel cell vehicles)," says Uchiyamada.

A fuel cell mixes hydrogen with the oxygen in the air to generate electricity that can power a motor.

Producing the highly flammable gas and getting it into the vehicles requires energy. Ultimately, the idea is to convert energy from renewables like wind and solar power into hydrogen, or even make hydrogen from sewage waste.

Unlike a gas-powered internal combustion engine, the only byproducts from a fuel cell are electricity, heat and water. There are no emissions of pollutants that can cause global warming. Yet the energy unleashed is powerful: Hydrogen is the fuel that sends NASA rockets into space.

So fuel cells could be used to power cars, trains, buses, trucks and forklifts, and to provide electricity and heat for homes.

Detroit-based General Motors Co., Mercedes-Benz of Germany, Japan's Honda Motor Co. and Hyundai of South Korea have also developed fuel cell vehicles that are on the roads in extremely limited numbers.

The global stock of electric vehicles will soon surpass 2 million, according to the International Energy Agency. It's projected to climb to between 9 million-20 million by 2020. Fuel cell vehicles are scarcely a presence.

The Hydrogen Council, made up of 28 companies that are promoting hydrogen fuel, said in a report this week that it expects hydrogen to power about 10 to 15 million cars and 500,000 trucks by 2030. It also forecasts it will be widely used for industries, heating and power and power storage.

The group met this week in Bonn, on the sidelines of the COP23 U.N. meeting on the environment.

Joseph Capparella, a reporter from Car and Driver magazine covered Toyota's concept fuel cell vehicle at the Tokyo Motor Show last month.

He says the concept seems "possible" if the costs are reduced and the technology can be mass produced.

"So, you know, it seems to be possible if it could be streamlined into a more affordable and mass producible technology then, it might be able to catch on but it's hard to say because our society is so deeply entrenched in, what we already know, which is gasoline and electric. So, to enact such a broad shift in the mind of consumers, I think it's a difficult obstacle," says Capparella.

Toyota and other manufacturers pursuing hydrogen fuel cells face some significant hurdles. Japan has an ample 28,000 EV (electric vehicle) charging stations but only 92 hydrogen fuelling stations, and they are costly to build.

"Hydrogen society is something all the players need to work together in order to create it. So, it will need lots of fathers and mothers," says Uchiyamada.

For many automakers, fuel cells are an area just for research, while EVs already are commercialised.

But Toyota's push towards hydrogen power could drive the technology to one day become mainstream.