Hydrogen fuel

Hydrogen is the lightest element in the universe and the most abundant, so on paper, hydrogen fuel has a lot going for it. Although it rarely exists on its own on Earth, it can be produced using clean energy to split essentially inexhaustible water molecules, producing only oxygen as a by-product.

However, 96 per cent of hydrogen today is made directly from fossil fuels – mostly natural gas, followed by coal and then oil. This overwhelmingly uses a process known as steam reformation that releases carbon dioxide.

Humanity produces around 70 million tonnes of hydrogen each year, mainly for use in making ammonia fertiliser and chemicals such as methanol, and to remove impurities during oil refining. Proponents of using hydrogen as a clean fuel think it could soon also play a vital role in decarbonising other sectors, including lorries, aviation, and heavy industry.

Hydrogen acts as a chemical energy carrier, rather like oil or gas, that can be piped or transported to where it is needed. It stores three times as much energy per unit of mass as conventional petrol, and when it “burns” in air – releasing that stored energy – it simply combines with oxygen to produce water again.

Different types of hydrogen production are labelled by colour. “Grey” hydrogen is made from fossil fuels using steam reformation. It costs about $1 a kilogram. “Blue” hydrogen also uses fossil fuels but captures and stores the CO2. Blue is about $2 per kilogram at the cheapest. Finally, there is “green” hydrogen, produced by water electrolysis running off renewable energy. For the most part, this costs upwards of $4 a kilogram.

There is a live debate in hydrogen technology over which production methods will win out. Green is the lowest carbon approach, because blue typically captures 85 to 90 per cent of the CO2 at best. While 10-15 per cent of lost CO2 emissions may not sound like a lot, it could have significant climate change ramifications if production is scaled up. Advocates of blue hydrogen contend it will play a key role because it is so much cheaper than green hydrogen.

A number of countries and blocs have launched hydrogen strategies in recent years, most notably the European Union’s strongly pro-green hydrogen plan in July 2020. Bringing down the cost of blue and green hydrogen to compete with polluting grey hydrogen will take many years of governments’ support, and huge investment ($150 billion over a decade, according to Bloomberg New Energy Finance).

Today, hydrogen’s potential new uses range from replacing coking coal in steel production to electricity generation, providing flexibility to help power grids cope with times of low wind and solar output. Some countries and companies think it could even play a big role in heating buildings, though others think ways of electrifying heating, such as heat pumps, are more likely to win out. Aerospace firm Airbus believes hydrogen holds more promise for decarbonising planes than batteries because of the energy it can store by weight. By modifying their existing internal combustion engines, they say they could use hydrogen to fuel their planes.

One stumbling block any hydrogen energy revolution faces is storage and transport. Hydrogen molecules are so small they can leak out of containers, meaning pipe networks previously used for methane may have to be upgraded before they are fit for hydrogen.