Many organisations see a real future for ammonia as a fuel. As an energy source, ammonia has nine times the energy of lithium-ion batteries and is 1.8 times more energy-dense than liquid hydrogen, and ammonia is easier to transport than liquid hydrogen.
Why are people talking about it?
“Green ammonia” is a term increasingly being heard in the ammonia industry and shipping circles these days. Interest in it has been spurred by global efforts to reduce carbon emissions over the coming decades. Whereas one tonne of conventional, or “brown” ammonia emits two tonnes of CO2, production of green ammonia would see it produced from renewable energy sources, emitting zero carbon.
Global ammonia production at present stands at 180mn t/yr, but its potential use as an energy source and energy carrier could see demand for it rise to a multi-billion tonne market for use in a range of applications. Ammonia is now one of the main fuels being considered by the maritime sector to enable the shipping industry to meet new CO2 reduction targets proposed by 2030 and 2050. Ammonia is also being seriously considered as a means to store renewable energy for delayed use, and as a carrier for hydrogen transportation.
Widespread use of ammonia in these sectors can be viable only if the CO2 emissions associated with its actual production are sharply reduced. This will require significant fresh investment in new technology and, based on current renewable energy prices, a rise in operating costs.
Green ammonia as a marine fuel
Following on from the introduction of IMO 2020, which imposed a cap on marine sulphur emissions, the next major regulatory change for the shipping industry is for vessels to sharply reduce CO2 emissions. The IMO’s initial strategy on this effort calls for CO2 emissions to be reduced by 40pc by 2030 and 70pc by 2050, compared with 2008 levels.
While efficiency gains and the substitution of hydrocarbon fuels can go a long way towards meeting the 2030 target, there is emerging consensus in the maritime industry that in order to meet IMO requirements, traditional fossil fuels will no longer be viable for use as a bunkering fuel after the 2050 deadline. A number of energy sources are being considered as replacements, and these include hydrogen and ammonia. Ammonia is gaining particular ground, both for combustion as a marine fuel and in fuel cells on ships. Ammonia has significant advantages over hydrogen in that it is significantly easier to store and handle, and is also seen as a safer way to transport hydrogen itself. Furthermore, ammonia is about 80pc more energy-dense than liquid hydrogen.
A number of ventures are already under way to test ammonia’s viability in the shipping sector, well in advance of the IMO limits. At the beginning of this year, Malaysia-based shipowner MISC, Samsung Heavy Industries (SHI), Lloyd’s Register and MAN Energy Solutions announced that they had joined forces to develop an ammonia-fueled tanker. While Norway’s oil firm, Equinor, has partnered with marine tech firm Eidesvik to retrofit the Viking Energy vessel to run on ammonia by 2024.
Nordic Innovation has announced funding for a number of clean maritime projects, including Nordic Green Ammonia Powered Ships (NoGaps), whose partners include shipowner Lauritzen Kosan and Yara International, and aim to launch an ammonia-powered ship by 2025.Interest from the maritime sector is not confined to bulk carriers either. The operators of the roll-on/roll-off passenger cruiser Color Fantasy, which operates between Oslo, Norway, and Kiel, Germany, have plans to pilot ammonia fuel.
Denmark’s Haldor Topsoe is in the process of compiling a report for the shipbuilding and operating industry that will outline a step-by-step guide as to what would be required to adopt ammonia as a marine fuel. It is also expected to highlight the current ammonia supply facilities already in place, such as ammonia storage tanks at potential bunker ports. The report is expected to be published later this year.
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Green ammonia – production challenges
Unlike conventional ammonia, which is typically produced using natural gas as feedstock, green ammonia is produced by using solar/wind/hydropower to produce electricity that then feeds an electrolyser to extract hydrogen from water, while nitrogen is separated from air using an air separation unit.
As an energy source, ammonia has nine times the energy of lithium-ion batteries and is 1.8 times more energy-dense than liquid hydrogen. Ammonia is easier to transport than liquid hydrogen using existing technology and infrastructure. This is why many organisations see a real future for ammonia as a fuel that can be used not only directly as an energy source, but also as a fuel that can be cracked for its hydrogen content, where hydrogen is required as the energy source.
Electrolyser-based ammonia using renewable energy is not a new concept, but technology is now being developed to considerably increase its energy efficiency. In the early 1900s, Norway’s Norsk Hydro was producing ammonia based on hydroelectric power. Significant research is now being conducted on green ammonia development, led by organisations in northwest Europe, with Japan also taking a notable lead.
There are no large-scale green ammonia plants today, but producers and technology companies are starting to pave the way to a greener approach. It is likely that any new green ammonia plants will need to be built in countries that have an abundance of solar, wind or hydropower, and ideally a combination of at least two of these resources, to mitigate intermittency issues and minimise operating costs. The sites ideally would be close to end-user markets, and countries such as Australia are being singled out as likely locations, based on renewable energy potential and proximity to an end-user market in east Asia.
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Developments in green ammonia technology
Existing leaders in the ammonia technology field are looking at ways to use renewable energy to produce ammonia, while addressing the crucial issues of maximising energy efficiency and reducing capital expenditure and operating costs.
One of these companies, Haldor Topsoe, has devised a solid oxide electrolysis system, which runs on renewable energy and can produce ammonia synthesis feed-gas without the need for an air separation unit, significantly reducing capital expenditure. Although it remains in the pilot stage, the system will also require 10pc less energy than a conventional gas-powered ammonia plant, helping address the issue of prohibitively high operating costs for ammonia plants powered by renewable energy. As well as the considerable initial outlay required to build a plant, one of the major issues the green ammonia industry faces is the high cost and limited supply of renewable energy compared to widely abundant and inexpensive natural gas. In Europe, current energy costs mean that the cost of production for one tonne of green ammonia is around 200-300pc higher than that of conventional ammonia. In the longer term, it is estimated that falling renewable energy prices will bring the cost of production for green ammonia down to 50-150pc higher than that of conventional ammonia. An increase in the cost of carbon in Europe could help level the playing field further. The need to maximise energy efficiency and a reduction in renewable energy costs will prove key factors in developing green ammonia.
While acknowledging that the move towards green ammonia remains more a long time mission, Haldor Topsoe R&D director Pat Han says it is important to take the first steps. Haldor Topsoe is now moving from the research phase to the development phase as part of these first steps, and a pilot plant based on solid oxide electrolysis technology is now mechanically complete. The pilot, which was funded by a Danish consortium, has a green ammonia capacity of 180 t/yr. The next step after this demonstration plant will be to develop solid oxide electrolyser technology to the commercial phase. In future stages, Haldor Topsoe hopes to be able to offer conventional gas-powered plants the option to add solid oxide or other electrolyser technology to their existing plant set-ups in order to enable them to move a portion (perhaps initially 10pc, which can be implemented in steps) of their output to green ammonia production. In this hybrid set-up, there is no need to construct a new plant as producers can use their existing facilities, adding only the new electrolyser to partially upgrade to the green technology.
This approach may be of particular interest to west European producers, who can benefit from available renewable energy sources that allow them to produce green ammonia at the lowest cost. While there have been few new conventional ammonia plants built in western Europe in the last 30 years, Europe itself is likely to be a major driver for green ammonia production. Under the EU 2030 climate and energy framework, EU member states should target a greenhouse gas emission reduction of at least a 40pc by 2030 (compared with 1990).
Yara International has committed to a 10pc reduction in CO2 emissions by 2025 and aims for climate-neutral production by 2050. The producer has firm plans to replace 10pc of its ammonia production in the south of Norway with green production by 2022 and will fully convert to green ammonia production at its Porsgrunn site by 2050. Yara has partnered with local firm Nel Hydrogen to help it achieve is carbon-reduction goal.
Even companies with a large oil and gas focus are getting involved in the green ammonia process. Texas-based KBR’s K-GreeN solution is being developed to offer customers a complete green ammonia plant: from electrolyser to ammonia, or an add-on electrolyser that has no air separation unit or synthesis loop requirement.
A number of smaller organisations pioneering green ammonia in western Europe and the US are working on innovative ways to revolutionise the entire ammonia production process. Some of these new technologies are moving away from the traditional Haber-Bosch process altogether. Iceland-based Atmonia is working on a catalyst that works at ambient pressure and does not involve a separate hydrogen production in its process, but rather uses water directly. The electrocatalytic process emits no CO2 and Atmonia’s technology enables production to run intermittently, with relatively little cost associated with shutting down and restarting production. “This is a major advantage when relying on renewable energy, like solar and wind, for production,” Atmonia’s chief executive, Gudbjorg Rist, says. The company is currently building a prototype catalyst that will initially produce liquid ammonia for on-site fertilizer use, “but the end-goal will be to produce anhydrous ammonia”, Rist says.
In the US, Colorado-based Starfire Energy is developing modular systems to produce carbon-free ammonia. The organisation recognised a growing need for a renewable fuel that can be stored and used in transport and heat applications, and it believes ammonia is the ideal fuel.
Starfire Energy has moved away from the traditional Haber-Bosch system of production and has developed a system that requires lower pressures than conventional ammonia. The company has developed an ammonia reactor that can directly follow variations in output from wind and solar power and uses no fossil fuel in the production process. The company started with a Rapid Ramp NH3 prototype reactor that has a 3 kg/d capacity and has now built a 10 kg/d system that will form the foundation for its 100 kg/d modular pilot system. A second pilot system is planned for 1 t/d. After that system, the team will scale the technology to 50 t/d, which can be replicated so that a single site that can accommodate 10 units can potentially produce 500 t/d of ammonia. “The units will be 80pc factory-built, with the remaining 20pc built on site,” Jennifer Beach, Starfire Energy’s co-founder and chief operating officer, says.
Starfire Energy’s mission is to develop not just carbon-free ammonia production but also to provide the technology to tailor its end-use. The company is now developing a lower-temperature NH3 cracking catalyst that converts ammonia into nitrogen and hydrogen gas. The nitrogen and hydrogen can be used in combination at point of use, or the hydrogen can be used alone to power vehicles and plants that require high-pressure hydrogen for fuel cells.