Hydrogen: The grey area of guaranteeing green

Deep Dive

Hydrogen comes in a rainbow of colours: green, grey, blue, brown, yellow, turquoise, white and even pink. 

But only green hydrogen made by using clean electricity, white which forms naturally and pink made using nuclear power can be produced sustainably. However green is currently expensive, white requires drilling to be harvested at scale and the most popular way to ‘directly dispose’ of nuclear waste is to bury it in the Earth’s core. Potentially radioactive for 10,000-plus years it could pose an environmental risk beyond a next Ice age.

A white paper published last month by hybrid-electric propulsion developer, Ampaire entitled Why Hybrid-Electric? claims that hydrogen is actually a decarbonisation problem, not a solution. Over 98% of hydrogen produced globally is derived from fossil fuels, it said. Known as grey hydrogen, it is created from natural gas, or methane, using steam reformation and doesn’t capture the greenhouse gas emissions produced. Much of this hydrogen is used to produce products like fertiliser, whilst hydrogen could be one of the only means to decarbonise industrial processes like iron ore reduction in steelmaking. “Fossil hydrogen needs to be replaced by hydrogen produced with renewable electricity and there will be new industrial needs for hydrogen like steelmaking. Diverting our very limited supply of green hydrogen to transportation would be a significant mistake until weve replaced fossil fuel hydrogen and would only make sense if your goal was not in fact to replace fossil fuel hydrogen,” it stated.

The paper concludes it is “unsurprising” that hydrogen efforts in aviation are being funded and promoted to a “significant extent” by the fossil fuel industry. “Just like in ground vehicles where promises of green hydrogen ‘someday’ have, in reality, led to the use of fossil fuel-derived hydrogen and dubious carbon capture promises, there is a significant risk of a ‘bait and switch’ approach where hydrogen is promoted as aviation fuel.”

CEO Kevin Noertker tells Revolution.Aero the bait and switch is an old observation starting in the early 2000s with the first hydrogen economy hype. The pitch was that vehicles – at that time, the focus was mainly autos – would switch to hydrogen produced by 100% green electricity and possibly methane with carbon-capture. In the meantime, existing lower cost fossil hydrogen supplies would be used until green and blue became available. 

“However, what happened is that from the early 2000s until now, the ‘interim’ solution of fossil hydrogen is providing the vast majority of supply with very little green hydrogen (and even that hydrogen is produced inefficiently with largely fossil grid power, not 100% renewable electricity). The same is highly likely to happen with aircraft (and is already the case for early demos),” says Noertker.

Fossil fuel industry involvement 

While the fossil fuel industry has zero incentive to reduce its current fossil hydrogen production. The only cost-competitive means to do this is with fossil hydrogen, says the Ampaire CEO. “What is needed for the environment is not diverting our tiny precious supplies of green hydrogen to transportation, but rather replacing the applications of fossil hydrogen right now (fertiliser production, etc). Until we replace all existing fossil hydrogen for applications like fertiliser which have no other alternative than using green hydrogen, it is foolhardy to use any for transportation. But it makes a lot of sense as a bait and switch play.”

Ampaire, a hybrid-electric aviation propulsion system developer, is not objective. But the white paper does highlight a potential pitfall with the pursuit of hydrogen. The prevalence of the fossil fuel industry amongst the investors funding hydrogen aviation tech is easy to see. For example, the lead investor in Universal Hydrogen is American Airlines. American’s largest shareholder (11% share) is Vanguard Group, the world’s biggest investor in the coal industry and the worlds second-largest asset manager ($8.1trn). Shell Ventures has invested in both ZeroAvia’s venture and Series B rounds, although not as a lead investor. MTU Aero Engines, Germany’s biggest engine manufacturer, which again publicly backed liquid hydrogen fuel cell powertrains as a means to decarbonise commuter aircraft recently, is backed, amongst others, by Capital Research and Management (formerly E.ON’s largest shareholder) and Vanguard Group.

However, despite widespread interest hydrogen remains a small investment for the fossil fuel industry, bringing in at most a few billion dollars per year. Which is nothing compared with the predicted $200bn oil and gas is to invest in greenfields this year. According to Ian Palmer, author and former petroleum engineer, the oil and gas industry can portray its hydrogen investments as a serious contribution to meeting Paris Agreement climate goals. Which in turn they hope will reduce the climate focus on having to stop drilling and producing oil and gas. But even if the fossil fuel industry reached its overall energy target of 7% hydrogen, it would only save around the same percentage in emissions, said Palmer.

A niche for hydrogen?

Palmer does however believe there is a “niche” hydrogen market for aviation and shipping fuel, and manufacture of metals and chemicals. If there is a market for hydrogen-powered aircraft then it has to be sustainable, otherwise the use of fossil-derived hydrogen could increase both emissions and cost relative to just burning the fossil fuel directly as per today. (And the tipping point to cost-effectiveness remains some way off). Today, grey hydrogen is less than half the price of green hydrogen; however, prices are expected to turn around by 2030, driven by lower renewable energy costs and cheaper electrolysers. Whilst, grey hydrogen prices will suffer as a result of increasing penalties for carbon dioxide emissions.

Michael Winter, principal fellow, Advanced Technology, Pratt & Whitney, says: Somewhere there is likely to be a role for hydrogen and we will be ready, but hydrogen will be really hard. Not insurmountable, but really hard.” Pratt & Whitney has been developing hydrogen aviation technology since it took part in a US military and Lockheed Martin Skunkworks project in the 1950s. “Hydrogen fuel, possessing no carbon atom, could enable zero carbon dioxide emissions flight for a range of aircraft applications, including short and medium range passenger aircraft. To make hydrogen economically viable for operators, we believe it will be essential to develop propulsion technologies that are optimised to take full advantage of the cryogenic properties of the liquified fuel,” Winter tells Revolution.Aero.

On an energy basis, operating 10% of the aircraft flown in 2019 would require 90% of global hydrogen production in that year – most of which is used in the production of agricultural fertiliser required for food production, as Noertker referenced. Considering also that many other sectors, such as heavy industry, marine and ground transportation, are looking at hydrogen as a solution to their decarbonisation challenges – aviation faces considerable competition on accessing hydrogen as a scarce resource, according to Winter. 

One way for hydrogen to be truly green, it should be produced from electrolysing water using electricity generated from low-cost, sustainable energy sources such as wind and solar. Another solution is carbon capture and storage technology, which would sequester carbon emissions resulting from hydrogen production, and thereby achieve emissions neutrality, but this technology is still in its infancy and will also rely on significant investment,” says Winter.

California’s green hydrogen production

California – home to firms like Heliogen and Equatic – is a leading light in the scaling of green hydrogen. The California Hydrogen Action Plan, released in 2019, set a goal of achieving 1.5mt of annual green hydrogen production by 2030. “In fact most of the local fuelling stations in Los Angeles are 100% green hydrogen,” Dr Anita Sengupta, founder and CEO, Hydroplane tells Revolution.Aero. [However] We need to increase supply, demand, and add incentives and subsidies for end users to keep the price affordable.” A Federal law passed in 2021 saw a further $8bn invested in the development of regional clean hydrogen hubs – California is one of the states selected. Also, in 2022, Assembly Bill 1550 passed, requiring all hydrogen produced and used in California for the generation of electricity or fuelling of vehicles to be green by 2045.

Equatic is a carbon removal company developing a combined carbon dioxide removal and carbon-negative hydrogen generation technology using a patented seawater electrolysis process. Pioneered at the UCLA Samueli School of Engineerings Institute for Carbon Management, the process uses four inputs: seawater, renewable electricity, rock and atmospheric air. With pilots in Los Angeles and Singapore, in May, Equatic signed a pre-purchase option agreement with Boeing. The deal will see it remove 62,000t  of carbon dioxide and deliver 2,100t of carbon-negative hydrogen to the aviation giant. Purported to cost $100/t to produce at scale, Equatic executives said the technology is cheap enough “to allow unprecedented scaling and adoption globally.” 

Chief operating officer, Edward Sanders, tells Revolution.Aero: “There are no net carbon dioxide emissions from producing hydrogen using the Equatic technology. On the contrary, we remove 29 tonnes of carbon dioxide for every one tonne of H2 produced. Other methods of producing hydrogen do not remove carbon dioxide.” Sanders says technology is scalable because of the vastness of the ocean reservoir as a source of divalent cations and, ultimately, a storage of dissolved inorganic carbon. “Operating both carbon dioxide removal and hydrogen production using the same plant infrastructure reduces our capex and provides two major revenue streams (CDR, H2), enabling rapid scale-out,” he explains.

But the world must work on multiple technologies to address climate change, according to Sanders. “We do not want to repeat the mistakes of the past and ‘lock-in’ a fuel source to the detriment of investments in other, more efficient and/or less carbon intensive technologies. We are developing the Equatic technology because it both takes out atmospheric carbon and provides a clean fuel to eliminate future emissions.”


On one hand, investment from any industry – oil and gas is no different – is welcome if it boosts the production of green hydrogen and, in aviation’s case, furthers startups along their path to certification. But on the other, simply being hydrogen technology does not guarantee it is environmentally friendly. Which makes source provenance key.  

Broad market application is now unlikely and probably too expensive (even for oil and gas), said Palmer. Taking the EV industry as measurement, battery use has exploded past hydrogen in recent years – there are over 130,000 public EV chargers in the US and around 100 hydrogen filling stations. This means all colours of hydrogen are set to stay expensive compared with  today’s fuel for some time. And anyone using it needs to do some due diligence on the source.

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