A compound made of three atoms
of hydrogen and one of nitrogen, ammonia is typically known as the
foul-smelling base for cleaning chemicals, or as a heavily toxic fertilizer. It
is also used as a base for explosives, refrigerants and textile products, for
example.
But in the last few years, scientists have found yet another
— and potentially groundbreaking — use for ammonia: energy. In fact, some
scientists say the compound has huge potential to replace fossil fuels in all their
applications. There’s even talk of a future “ammonia economy.” Others call it
the “missing link” to make decarbonization a reality.
As companies and researchers
around the world work to fulfil ammonia’s potential, here’s a tour of the main
ideas and challenges in the pipeline:
Pocket hydrogen
Hydrogen has long been talked
about as a potential carbon-free replacement for fossil fuels, but its use has
been hampered by how difficult it is to store and transport. Because ammonia is
rich in hydrogen, with some saying the compound is made of “hydrogen and air,”
it is gathering momentum as a solution to the technical challenges presented by
hydrogen:
- Easier to liquify: Hydrogen normally exists in the world in gas form, and has to reach cryogenic temperatures of less than -253 °C to be transported as a liquid. The process alone would use up energy equivalent to one-third of the total output of the liquified hydrogen. In contrast, ammonia liquefies at -10 °C under only mild pressures.
- Infrastructure already exists: Because of that, transporting and storing hydrogen requires technology-intensive facilities and worldwide infrastructure that, simply put, does not yet exist. But ammonia is already shipped across the world in large quantities, and many ports are already able to store it and process it safely.
- Cutting out fossil fuels: Converting ammonia into hydrogen normally requires high amounts of thermal energy from fossil fuels, which defeats the purpose of using the compound. But in November 2020, Northwestern University researchers announced they had developed an efficient process to make the conversion using only renewable electricity.
- Cars: The development could allow owners of hydrogen cars to drive to a fuel station and get pressurized hydrogen on the spot, solving a logistical problem that has long given battery-powered cars an edge in the carbon-free vehicles market.
Alternative fuel
- Easy adoption: Some believe that using ammonia as a fuel itself — without converting it into hydrogen — might be even more efficient. Ammonia can be burned in conventional internal combustion engines and gas turbines with only minor modifications, making it easier for industries to transition to its use.
- Shipping has the head-start: Responsible for about 2% of global carbon emissions — about the same as the entire German economy — the shipping industry is under real pressure to decarbonize. But running ships on hydrogen is unrealistic because storing the fuel would take up too much space. Ammonia takes up far less space. “Ammonia is the only zero-carbon fuel that will get you across the oceans,” Professor Bill David, who authored a study on the subject for the British Royal Society, told the BBC. MAN Energy Solutions, a manufacturer of marine engines, announced that its first ammonia engine could be in operation as early as 2022.
- Other uses: If ammonia proves successful in shipping, new opportunities could also open up as green fuel for trains, heavy-duty freight and perhaps even aviation. Japan has vowed to use ammonia for shipping starting in the late 2020s, and has already started burning the compound in thermal power stations.
- Competitive cost: MAN Energy Solutions, the marine engines company, expects that as time goes on the compound will be competitive price wise with other alternative fuels such as liquefied petroleum gas, liquefied natural gas or methanol in the future.
- How green exactly? Ammonia does not emit carbon, and for a simple reason: It doesn’t contain any. But that doesn’t mean it is risk-free. Critics warn that burning ammonia can release nitrogen and nitrates, whose cycle is not as well-studied as the carbon cycle. Also, ammonia is traditionally mass-produced using methane, so the environmental impact of burning ammonia depends on whether it can be replaced with renewable energy at a large scale. Several companies, such as CF Industries in the U.S., have announced plans to scale up their production of green ammonia.
Fuel cells
- Nitrogen in, ammonia out: Chemist Douglas MacFarlane and his team at Australia’s Monash University have developed a way to use ammonia to store solar and wind power into fuel cells. With the supply of electricity, water and nitrogen, the device produces ammonia, which can then be burned or converted to hydrogen.
- Shipping renewables: The development could make ammonia the only viable way to export large quantities of renewable energy — an important development for countries like Australia, which are rich in renewables, but unable to export the energy because of their geographical isolation. “Ammonia is the only way to store zero-carbon fuel from renewables for days, months and years,” says Professor MacFarlane.
ENGIE Expert Eye
Camel Makhloufi and Nouaamane
Kezibri, research engineers at ENGIE Lab CRIGEN’s Hydrogen Lab: “There are
still many technological obstacles to the integration of green ammonia, in
particular regarding the management of the intermittence of the renewable
source, and the improvement of the efficiency and reliability of the process.
Also, the high costs associated with this solution mean that, for the moment,
it still cannot compete with other, more conventional methods.
Finally, the regulatory
framework plays an important role in the deployment of such a solution. If in
North America the use of ammonia fertilizer is a common practice (accounting
for more than 27% of the market), this is far from being the case in the rest
of the world — even less in Europe. As a matter of fact, the uncontrolled use
of ammonia can have negative consequences on the environment and on air
quality. Europe is committed to reducing ammonia emissions by 21% by 2030.Thus
green ammonia intended for agricultural application will certainly take other
forms that are more in line with the European market, such as nitrates or
urea.”
