Ammonia - a colorless gas turning green
Ammonia - a colorless gas turning green
Exploring pathways from brown to green and blue ammonia
Ammonia, a sharp-smelling gas made from nitrogen and hydrogen, plays a crucial role in producing fertilizers that sustain global agriculture. Beyond its agricultural applications, ammonia is also used in manufacturing synthetic fibers, explosives, dyes, and pharmaceuticals. Currently, global ammonia production stands at approximately 175 million tons per year, with the traditional Haber-Bosch process consuming up to 2% of the world’s total energy and contributing significantly to greenhouse gas emissions.1
The conventional method for producing ammonia is not environmentally friendly. It involves steam methane reforming (SMR) to produce hydrogen from methane, which, when combined with nitrogen from the air in the Haber-Bosch process, produces ammonia (NH3). This method is energy-intensive and results in about 1.8% of global carbon dioxide emissions, with approximately 90% of these emissions coming from the SMR process itself.
As the world confronts climate change, the ammonia industry faces increasing pressure to reduce its carbon footprint. In the future, the world will need more ammonia but with fewer emissions. The World Economic Forum's Net-Zero Industry Tracker 2023 outlines ambitious goals for the industry, aiming for a 27% reduction in emissions intensity by 2030 and a 96% reduction by 2050.2 Green ammonia, produced from air, water, and renewable energy, emerges as a key solution for decarbonizing the industry and meeting these targets.
Fig 1: Projected emissions from existing ammonia plants under different lifetime assumptions, 2020-2070; IEA (2024)
From brown to blue and green
The shift from brown to blue and green ammonia represents a significant advance in sustainable production. Originally, the Haber-Bosch process for producing brown ammonia combined nitrogen from the air with hydrogen from natural gas. Modifications that include carbon capture have led to the production of blue ammonia, which significantly reduces emissions. As another approach, green ammonia is produced powered by renewable energy. This method is not only cleaner, but also supports the development of milder production conditions and flexible plant designs to accommodate the variability of renewable energy sources.3
Fig 2: Overview of production processes of brown, blue and green ammonia
Green ammonia is synthesized by combining hydrogen—produced through renewable energy-driven electrolysis—with nitrogen from the air.4 This process contrasts with the conventional method, which relies on natural gas. In the most commonly used process, electrolysis splits water into hydrogen and oxygen using clean energy sources like wind or solar. The hydrogen is then combined with nitrogen to produce ammonia. But this is just the tip of the iceberg.
Several approaches to green ammonia production are currently being explored. Electrochemical methods like water electrolysis and direct electrochemical synthesis are advancing rapidly. Photocatalytic methods, still in the research phase, use light to drive the chemical reactions needed to produce ammonia. Biocatalytic methods leverage bacteria that naturally produce ammonia using an enzyme called nitrogenase. Chemical looping processes involve a series of chemical reactions where core reaction chemicals are recycled, producing ammonia as a by-product. Innovative approaches, such as atmospheric plasma in liquid (PiL), use plasma in liquid starting materials to generate catalyst suspensions quickly.
Beyond Fertilizers
Green ammonia's potential extends beyond fertilizers, holding promise as a sustainable energy carrier due to its flexibility and transport efficiency. It can be shipped from regions like Australia to Japan for power generation or hydrogen production. With a higher energy density than hydrogen, ammonia is easier to transport and store, making it suitable for transferring green hydrogen over long distances. Some experts are forecasting that the maritime industry is likely to adopt green ammonia early on, replacing fuel oil in marine engines, providing a zero-emission alternative to fossil fuels.5 Green ammonia can be used in gas turbines, ship engines, and fuel cells to produce electricity. Its ability to be stored in bulk and used as an effective hydrogen carrier further enhances its utility.
Fig 3: From production to end-use, green ammonia can be used as an efficient energy source in numerous industries.
A green highway
Near-zero-emission ammonia production requires new infrastructure, innovation, and investment. Several well-funded startups and established companies are making significant progress. In the USA, Monolith leads with $364.3M for clean hydrogen and ammonia production, followed by Amogy with $219.3M for ammonia-based energy systems. C-Zero has received $45.5M to convert natural gas into cleaner hydrogen and ammonia. Other notable efforts include Starfire Energy ($34.3M) for sustainable energy tech, Clean Hydrogen Works ($30M) for hydrogen-ammonia plants, and Israel's NitroFix with $3.6M to eliminate carbon emissions in ammonia generation. Globally, ENGIE and Mitsui are advancing industrial-scale hydrogen projects for Yara's Western Australia plants, while ThyssenKrupp is producing green ammonia in Germany using alkaline water electrolysis.
Further, governments play a central role with policies and incentives such as the EU Hydrogen Strategy, the REPowerEU plan, and the US Regional Clean Hydrogen Hubs. The private sector is racing to scale up production, with BloombergNEF estimating a need for $150 billion in subsidies by 2030. If developed, the hydrogen economy could become a $12 trillion market.6 Countries like Germany, Korea, Japan, and regions like the Middle East are leading investments in green hydrogen.
The difficulties
However, the green ammonia sector faces hurdles in cost, efficiency, and scalability. Current production costs exceed $900 per ton, with optimistic reductions to about $600 per ton. Technologically, the energy conversion efficiency is low, with up to 83% energy loss, raising concerns about its viability.7 Additionally, while green ammonia avoids CO2 emissions, it can produce harmful nitrogen oxides, requiring effective abatement technologies. Economically, the sector must become cost-competitive with traditional ammonia and other renewable energy sources. Infrastructure development for hydrogen and CCS is crucial, and challenges with the grid, land permits, and labor for installation remain.8
The progress by startups and industrial players shows the growing momentum behind green ammonia as a sustainable solution. With supportive policies and technological advancements, green ammonia is poised to play a significant role in the transition to a greener future.
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Fletcher, A., Nguyen, H., Salmon, N., Spencer, N., Wild, P., & Bañares-Alcántara, R. (2023). Queensland green ammonia value chain: Decarbonising hard-to-abate sectors and the NEM; Main Report. Centre for Applied Energy Economics & Policy Research: Working Paper Series 2023-16.
Salmon, N., & Bañares-Alcántara, R. (2021). Green ammonia as a spatial energy vector: a review. Sustainable Energy & Fuels, 5(11), 2814-2839.
Machaj, K., et al. (2022). "Ammonia as a potential marine fuel: A review." Energy Strategy Reviews 44. 100926.