“When I first started hearing about blue hydrogen, let alone blue ammonia, it seemed like a scam, quite frankly,” Robert Howarth, Professor of Ecology and Environmental Biology at Cornell University, states. “In some ways, it is.”
However the president of COP28 in the United Arab Emirates, Sultan Al Jaber, praises blue ammonia as a 'low-carbon product'.
As well as leading the world’s key conference on fighting climate change, Al Jaber is the UAE’s Minister of Industry and Advanced Technology and CEO of the Abu Dhabi National Oil Company (ADNOC).
ADNOC has been developing its capacity for blue ammonia exports as part of an effort to present itself as a 'greener' company.
What is blue ammonia?
Ammonia is a colourless gas made up of hydrogen and nitrogen that acts as a carrier fuel for hydrogen. It allows for safer and more efficient storage of hydrogen, an energy carrier which many industry experts lauded as a decarbonisation solution. Blue ammonia is achieved by capturing carbon dioxide emissions from its production.
The first cargo of blue ammonia left the UAE in 2021 headed for Japan. Fertiglobe, a joint venture between ADNOC and Dutch chemical company OCI, produced the blue ammonia in the Ruwais Industrial Complex in Abu Dhabi. Fertiglobe sold further shipments to customers in Germany and South Korea. Plans are underway to build a commercial-scale blue ammonia factory in Ruwais.
A closer look at the greenhouse gas footprint of blue ammonia reveals that it is not a 'low-carbon product' at all. Its production can emit three times more greenhouse gases than diesel, and two-and-a-half times more than coal or natural gas.
This high number mainly comes from methane leakage in the production process, compounded by inefficiencies in converting hydrogen into ammonia and back. Besides, ADNOC uses the CO₂ it captures to pump more oil in a process called enhanced oil recovery (EOR).
How does blue ammonia help fulfil hydrogen’s promise?
The hype is not really about ammonia. The industry heralded hydrogen as a way to decarbonise the energy system, especially in sectors with hard-to-abate emissions, such as transport or power generation. Ammonia enables hydrogen to be stored and transported in safer and more efficient conditions.
In contrast to fossil fuels, which are themselves burned for energy, hydrogen is an energy carrier. That is because hydrogen itself - unlike oil or fossil gas - has to be produced, either from water with electricity or from gas.
Depending on its production, hydrogen is divided into three main types: green, grey, and blue. Only green hydrogen is truly carbon-free as it comes from renewably generated electricity. Grey hydrogen is produced from natural gas, with all the associated greenhouse gas emissions. And blue hydrogen is what is produced when a hydrogen plant applies carbon capture and storage (CCS) to capture the carbon dioxide emissions from production.
This is the type that ADNOC and OCI produced. Fertiglobe fitted its ammonia factory with temporary liquefaction units, which allowed it to transfer and inject CO₂ into the underground reservoirs in Al Reyadah, ADNOC’s carbon capture and storage plant near Abu Dhabi. Applying the CCS technology prompted Al Jaber’s claim that the ammonia is 'low-carbon'.
As a very small and explosive molecule, hydrogen is hard to store and transport. Therefore, “blue ammonia is simply taking blue hydrogen, converting it to ammonia to transport, and then converting the ammonia back to hydrogen,” Howarth explains.
The forgotten methane from blue hydrogen
Producing blue hydrogen requires more natural gas than grey hydrogen, which leads to higher methane emissions. Both types are produced from fossil fuels, but for blue hydrogen, natural gas is also used to power the CCS technology.
Carbon dioxide emissions from the production are indeed lower - but not methane emissions. This powerful greenhouse gas is responsible for one-third of global warming that has occurred since 1900 but it is rarely counted in assessments of climate impacts.
When taken into account, ”the overall greenhouse gas footprint of blue hydrogen is significantly larger than that of either coal or natural gas,” Howarth explains. He estimates that the energy carrier’s greenhouse gas footprint is 20 per cent greater than burning natural gas or coal for heat, and 60 per cent greater than burning diesel.
”And we're not going to blue ammonia yet, just blue hydrogen,” Howarth adds.
Currently, it takes more energy to produce hydrogen than the energy carrier provides. This means that some of the produced hydrogen will get lost in conversion inefficiencies, increasing methane emissions.
Converting hydrogen into ammonia and back takes energy, too. Howarth estimates that the hydrogen-ammonia-hydrogen switch ends up with a 1.93 times greater greenhouse gas footprint than producing blue hydrogen.
The methane emissions from blue hydrogen production, compounded by losses from conversion, mean that in total, blue ammonia emits 2.5 to 3 times more greenhouse gases than 'regular' fuels such as coal, natural gas, or diesel. This estimation is without transportation, which, according to Howarth, would add another 5-10 per cent emissions depending on the tanker type.
How efficient is carbon capture and storage?
Researchers have serious doubts about the efficiency of the backbone of blue ammonia’s 'cleanliness': the CCS technology. Clark Williams-Derry from the Institute of Energy Economics and Financial Analysis (IEEFA) explains that CO₂ capture rates vary depending on “whether you’re trying to paint a realistic picture of CCS operations, or if you are trying to make CCS look good. The more realistic figures are pretty depressing.”
CCS plants usually capture much less CO₂ than claimed. Williams-Derry points to the Petra Nova CCS plant in the United States, which claimed to capture 90 per cent of CO₂. Reported emissions around the plant, plus accounting for emissions caused by the CCS technology, put the actual figure at 55-58 per cent.
There is no publicly available information on the capture rates of the Al Reyadah CCS plant in Abu Dhabi. Expert calculations vary from 17 to 36 per cent. The upper limit is a conservative estimate because in 2022, the only year for which a CO₂ capture rate is available, the plant only captured 30 per cent of the CO₂.
Apart from the capture rates, some of the injected CO₂ may leak back into the atmosphere. Schlissel talks of a "real risk" that a portion of the injected CO₂ may find its way back to the surface without being recaptured.
The volume of the gas moving back up from its underground storage depends on the type of geological formation where it is stored, and how many unplugged oil and gas wells the basin stores. “It could be awfully hard to store CO₂ in reservoirs that resemble pincushions,” says Williams-Derry.
How blue ammonia is used to capture more oil
Finally, the CO₂ captured from 'low-carbon' blue ammonia production ends up producing more oil for ADNOC, in a process called enhanced oil recovery (EOR). EOR means injecting CO₂ into a nearly depleted oil field. The pressure makes more oil reach the well.
The Al Reyadah plant captures up to 800,000 tonnes of CO₂, which is then compressed, dehydrated, and transported to the Bab and Rumaitha oil fields for EOR.
Injecting the captured CO₂ improved ADNOC’s oil recovery by 10 per cent.
Schlissel from the IEEFA estimates that a metric tonne of CO₂ used for EOR produces between two to four new barrels of oil.
“When burned, a barrel of oil emits about 440 kg of CO₂,” Schlissel explains. “Thus, if you assume that using one tonne of CO₂ produces even 2.5 barrels of oil, the net result of using captured CO₂ for EOR is higher emissions than if the CO₂ were never captured in the first place.”
Filip Johnsson from the Chalmers University of Technology adds: “Blue ammonia can only be claimed when the CO₂ is stored permanently in geological formations and when it is not associated with EOR. Injecting CO₂ as part of an EOR scheme also raises the question of what would have happened with the newly produced oil if the CO₂ had not been available.”
Furthermore, CO₂ also leaks during EOR, although the numbers are again unknown. “No one measures how much CO₂ leaks back into the atmosphere from an EOR injection well,” Schlissel explains.
Yet, the fact that it happens is undisputed. 'CO₂ recycling' - capturing the gas that migrates up - is a way to counter this negative impact. ADNOC spokesperson Philip Robinson stated that the company deploys “closed-loop CO₂ capture and reinjection technology at the well site.”
Blue ammonia represents a ‘dangerous approach’
Given the negative climate impacts of blue ammonia, “I would politely disagree with the president of COP28 that we can make it work with these technical solutions and fossil fuels,” says Howarth.
He highlights that we need to stop using fossil fuels and that we have the solutions to do so, such as renewable energy sources, high-efficiency heat pumps, and electric vehicles.
“The industry has these dreams that they can continue to use fossil fuels and somehow make it work by capturing the carbon and doing other complicated technical things, which are extraordinarily difficult and have not been successfully done in the past. I think it is a very dangerous approach.”
Despite previous communication on blue ammonia, ADNOC did not respond to a request for comment on the claims in the article.