Alchemist Theophrastus Bombast, better known as Paracelsus, was the first to talk about hydrogen (H2). That was in the 16th century. Since then, the first element of the periodic table has been in the spotlight many times and today it comes in several "colors" depending on how it is made.

The most recent hype occurred in the 1990s when Japan and South Korea invested heavily in creating a hydrogen economy, producing the gas mostly from fossil fuels.

"The decarbonization impact depends on how hydrogen is produced, where it is sourced and where the consumer is situated," IRENA Director-General Francesco La Camera told DW. "The use of hydrogen does not emit CO2, but its production and transportation can."

The International Renewable Energy Agency (IRENA) is an intergovernmental organization mandated to promote the sustainable use of renewable energy among its 160 member states.

Hydrogen: From grey to green

Hydrogen was first produced via the gasification of lignite (brown coal hydrogen) and bituminous coal (black coal).

Most recently, it's been retrieved from natural gas via a process called steam reforming. This process also produces CO2. If the carbon dioxide ends up in the atmosphere, the hydrogen is called grey; if the CO2 is captured and put underground through experimental systems called CCS, the hydrogen is labeled blue.

Hydrogen can also be produced from water, using electricity to separate H2 from oxygen through water electrolysis. In this case, the emissions depend on the source of the electricity. If nuclear energy is the source, the resulting hydrogen is pink, yellow if it comes from mixed sources and green when made from renewable sources.

Over the past two years, the European Union has focused its attention on green hydrogen, which is currently only a tiny fraction of total hydrogen production (just 5% globally). Investment plans are promising, though.

Certification requirements

"Hydrogen produced from renewables can play an important role in the energy transition, complementing electrification and energy efficiency as key pillars in the race to a climate-safe future," said La Camera. "Our 1.5 degree Celsius scenario projects that hydrogen and its derivatives could account for around 12% of total final energy consumption in 2050."

Accordingly, institutions are working on a certification system to clarify how hydrogen is made. "Certification is also a key component of global trade since most of the CO2 emissions would take place outside the importing country or region," La Camera pointed out.

The hydrogen price issue

Prices are a crucial element for the future of hydrogen. "So far, H2 is more expensive than currently used fuels and a successful energy transition would only be possible if the switch is in favor of a better and cheaper fuel," Thierry Bros, a professor at Sciences Po Paris, told DW. 

"This is why the best way to grow the H2 supply and demand is to allow all hydrogen under a certain threshold (in tCO2/tH2) to be produced. So far, H2 has only been used as a chemical product in refineries, not as an energy vector. So we are in unchartered territories," he added.

An energy vector is a human-made form of energy, resulting from the conversion of energy available naturally.

Bros thinks that countries relying on oil and gas revenues would put up a fight by making sure prices stay low enough to delay any energy transition.

Hydrogen could also meet with public and political opposition. Prices and safety will be decisive. "Today we have a hydrogen hype but we have to make this a resilient and low-cost solution. If not, H2 will lack the popular support it needs to become a fuel of choice," said Bros.

Green hydrogen has two major cost components: electricity and electrolyzes, which are systems to separate hydrogen from oxygen. Prices for both are falling because of significant investments in economies of scale.

"IRENA studies show that green hydrogen can become cost-competitive with fossil-based hydrogen within the next decade, providing nearly 70% of all hydrogen consumed by 2050," said La Camera.

Growing potential

Hydrogen can have a future in some sectors like heavy industry, aviation and shipping, but also beyond.

"Hydrogen can complement or even replace natural gas in pipeline systems, thus enabling carbon mitigation in buildings and industrial heating systems," said La Camera.

"While low-cost natural gas might favor blue hydrogen, environmental concerns remain regarding the upstream methane emissions as well as the CO2 storage efficiency," he reasoned, adding that blue hydrogen projects would need to prove their carbon neutrality while green hydrogen represented a paradigm shift.

At the same time, the current hype may also lead to more refined categories not based on colors. 

"Colors make little sense as the only metric that should be used is a climate-related one," said Bros. "We therefore need to rank produced H2 according to its full-cycle emissions."