In recent years, governments and automakers have been busy trying to develop and deliver new cars to consumers that will minimize their impact on our planet’s climate and environment at large.

With estimates of the ‘proved reserves’ of oil suggesting that we now have about 50 years-worth left, the hunt is on for some other – more sustainable – fuel for the cars of the future (and, indeed, the present).

Thankfully, car buyers already have options.

Propane – also known as liquefied petroleum gas (LPG), or propane autogas – has been around for decades, with its use in the U.S. growing at the start of the decade and likely to increase for fleet users over the next few years. It’s available from over 2,500 fueling stations across the U.S. and the price averages $1 less per gallon than regular unleaded gasoline, according to Autogas for America.

Another option is renewable natural gas (RNG) and conventional natural gas, which is compressed (CNG) or liquefied (LNG) for use in vehicles. Again, mostly used by fleets and trucks, it can nonetheless be an alternative to gas.

However, the fuel with the brightest future seems to be hydrogen, used in fuel cell vehicles (FCVs), which are seen by many as the answer to a sustainable mobility future.

Honda, Hyundai, and Toyota are currently selling vehicles that use this new technology. The Clarity, ix35 and Mirai models are the first to offer consumers a taste of hydrogen-powered motoring.

The Hyundai ix35 Fuel Cell and the Toyota Mirai, in particular, offer a surprisingly familiar feel in many ways. Their whisper-quiet operation is unlike a car with a gasoline engine and has more in common with an electric vehicle (EV), but there’s none of the “range anxiety” that comes with an electric car, thanks to ranges of over 300 miles. Apart from that though, they are much like any of the compact SUV or sedans that you’d find on the market.

So how does hydrogen power a car?

The hydrogen stored in the fuel tanks is combined with oxygen from the air in the fuel cell – an electrochemical energy conversion device where a chemical reaction takes place that produces electricity. This electricity powers a motor to drive the vehicle’s wheels, as in an EV.

Test drives of the current FCVs on sale prove that they can be a viable form of transport, but how close are we really to them being a practical alternative to gas-powered cars?

Hydrogen cars certainly offer a number of advantages, but least of which is the fact that hydrogen, as a substance, is all around us, in the water that covers 71% of planet Earth, and also in natural gas.

But it’s also been calculated that hydrogen is three times more energy efficient than gasoline: conventional engines use approximately 20% of the chemical energy in gas, while fuel cells can access up to 60% of the hydrogen’s energy.

There are also no harmful emissions, either when hydrogen is produced using electrolysis (using electricity from renewable sources such as solar or wind power) or after its use in a fuel cell – water is the only tailpipe emission.

There are, of course, downsides. Even if we ignore the massive development costs that will be required to make hydrogen a viable energy alternative (and who’s going to make that investment), there are other questions.

Take the production of hydrogen, for one. Hydrogen, the actual chemical element, isn’t the same as hydrogen the fuel: the atom itself is everywhere, but the fuel has to be produced. At the moment, approximately 50 million tons of hydrogen are produced every year, mostly via a process called steam-methane reforming. This is expensive and not particularly good for the environment. A better alternative would be integrated wind-to-hydrogen plants, which would “electrolyze” water (extracting the hydrogen from water), though the investment required to get enough produced for the world’s passenger cars is enormous.

The biggest obstacle, however, is the question of why we need to spend billions on developing a hydrogen economy which produces electricity for a vehicle, when battery-powered EVs can plug into existing sources of electricity? And why take renewable energy from things such as solar panels to create hydrogen, when it can be used to directly charge EVs?

At the same time, battery technology is improving rapidly – enabling EVs to increase in range – so it might arguably overtake the development of hydrogen as a fuel in the next 10 to 20 years.

Whatever the answer to our future fueling options, it’s unlikely to emerge for quite some time – with plenty of gas being pumped while we wait to see what will replace it.

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