Decarbonization is a pressing global challenge. Resources like wind and solar generate clean energy, but the supply is inconsistent. Finding a reliable method to store low-carbon power for on-demand use is essential for meeting net zero goals.
Hydrogen is an abundant element that can store renewable energy; however, hydrogen is difficult to manage. Using ammonia as a hydrogen carrier and then “cracking” it — that is, decomposing the ammonia to obtain hydrogen at the point of end use — presents a possible solution for overcoming some of hydrogen’s storage and transportation challenges. Several pilot projects involving ammonia cracking are already underway in Belgium and Germany.
Ammonia could play a key role in the transition to new energy, with cracked ammonia set to become part of the future energy landscape. Read on to explore the intricacies of ammonia decomposition, its transformative potential and the solutions required to speed up hydrogen’s use as a clean energy source.
The Basics: Clean Hydrogen from Cracked Ammonia
The Haber-Bosch process is the most common way to make ammonia today. It involves mixing nitrogen, hydrogen and iron catalysts at high temperatures and pressures to create ammonia.
The energy for Haber-Bosch is typically generated by burning fossil fuels — a practice that produces significant carbon dioxide emissions. In today's new energy era, it's essential to create clean hydrogen (or clean ammonia) using alternative methods that lower carbon emissions.
Decarbonizing Ammonia Production
Industry can reduce ammonia production emissions by leveraging technologies such as carbon capture, utilization and storage (CCUS) to divert CO2 from the atmosphere. Further carbon reductions can be accomplished by supporting Haber-Bosch with zero-carbon energy from wind turbines and solar photovoltaic cells.
Researchers are currently developing another process for creating low-emissions ammonia as an alternative to Haber-Bosch. Akin to operating a fuel cell in reverse, the system consumes electricity to combine hydrogen (from water) and nitrogen (from air) to make ammonia. Renewable electricity would make this process environmentally friendly; however, this technology has not yet proven feasible at scale.
No matter the method, once ammonia is produced, it can be directly used as a fuel or “cracked” for its hydrogen. One of the steps to decarbonizing the energy sector involves scaling up the production of low-carbon ammonia using renewable resources and then transporting it for cracking to locations where clean-burning hydrogen energy is required.
Cracked Ammonia
Ammonia, or NH3, is a composition of nitrogen and hydrogen. Cracking ammonia breaks the compound into its base elements, nitrogen (N2) and hydrogen (H2). There are two primary processes for separating ammonia. Understanding the fundamentals of these techniques will help clarify ammonia’s potential and shortfalls as a hydrogen energy carrier.
Thermal Ammonia Cracking
When exposed to extremely high temperatures, ammonia breaks into nitrogen and hydrogen. Typically, a fuel like natural gas or propane is burned to bring the interior of a reaction chamber — aka, the cracking chamber — to a critical temperature where the ammonia separates.
Thermal cracking, which uses only heat, is straightforward, slow and inefficient. Adding a catalyst lowers the required temperature and stimulates reaction rates. This makes catalytic cracking more efficient and more popular for decomposing ammonia.
Catalytic Ammonia Cracking
As the name suggests, catalytic cracking involves a catalyst, which enables the separation of ammonia at a lower temperature and speeds up the reaction that breaks ammonia into N2 and H2.
Today, nickel-based catalysts are the most commonly available; they facilitate ammonia cracking at 900°C (1650°F), which is considered high-temperature cracking. Low-temperature alternatives, or catalysts made of rare metals, are being developed for decomposing ammonia at a heat of 500°C (930°F).
Ammonia’s Potential: Where NH3 Fits into a Hydrogen Economy
The term “hydrogen economy” refers to the overall framework for transitioning to low-carbon hydrogen for clean energy. As the International Energy Agency explains, “Hydrogen is an increasingly important piece of the net zero emissions by 2050 puzzle.”
The path to net zero hydrogen uses clean production methods based on renewable power. However, the intermittent nature of solar and wind makes them unsuitable for applications that require an uninterrupted energy supply. Efforts to overcome this challenge have triggered interest in energy storage solutions.
Hydrogen is a promising option for capturing renewable energy. H2 is abundantly available and can be produced using emission-free technology. However, hydrogen storage and transportation pose key challenges.
Liquid hydrogen is energy dense, enabling storage of a large amount of energy in a small volume, but maintaining a liquid state requires cryogenic temperatures below -253°C (-423°F). Gaseous hydrogen has a relatively low density, meaning it takes up a lot of space unless compressed; vessels must withstand high pressures up to 700 times greater than atmospheric. Both systems are impractical at scale.
Ammonia offers a possible solution to these challenges. NH3 contains a high proportion of hydrogen, roughly 17.6% by weight, and ammonia is easily stored and transported. Unlike liquid hydrogen, which requires cryogenic conditions, ammonia liquifies at a mere -33°C (-27°F), reducing the demands for supporting infrastructure throughout the supply chain.
To underscore ammonia’s potential as a hydrogen carrier, it’s helpful to consider how it is utilized today:
- Ammonia is an in-demand commodity. As one of the world’s most useful compounds, ammonia supports industry use as a fertilizer and a chemical. Ammonia producers can leverage its role as both a hydrogen energy carrier and a feedstock for other industries, thus lowering investment risk.
- It’s available in today’s marketplace. Ammonia is readily available via an established supply chain for innovative enterprises transitioning to new energy. A customer can easily purchase ammonia to test it with new technologies.
- There’s infrastructure in place. Ammonia’s extensive use in agriculture means a global supply chain for bulk transportation and utilization already exists. The technical expertise, equipment and safety standards for ammonia are well established. The fertilizer industry could champion ammonia’s use as a hydrogen carrier, accelerating access across various regions and industries.
- Nitrogen also adds value. Cracking yields hydrogen and nitrogen. In the new energy economy, H2 would provide clean power, while N2 has the potential to support a range of industrial applications. For example, steel production uses nitrogen gas for deoxidization, and in the food-packing industry, it preserves freshness.
In the foreseeable future, it will be feasible to produce hydrogen at renewable-rich locations, convert it to ammonia and then ship the NH3 for cracking to any location where clean energy is needed. Using ammonia as a hydrogen carrier could fast-track the new energy economy; however, there are obstacles to overcome before global adoption is possible.
Industry Challenges: Innovations to Accelerate Adoption
Although the ammonia industry has storage and transportation infrastructure, scaling up to expedite a transition to ammonia as a hydrogen carrier poses several challenges.
Improving Energy Efficiency
Producing ammonia is energy intensive. Likewise, cracking ammonia demands exceptionally hot temperatures. This need for energy affects the round-trip efficiency of ammonia as a hydrogen carrier; to become economically viable, the efficiency of both processes must improve.
With current technologies, using ammonia as a vector for hydrogen is only practical in specific scenarios. Meeting net zero goals will require investment and government support to improve ammonia production and cracking techniques.
Transitioning to Near-Zero Emissions Hydrogen Production
Today, the hydrogen used to create ammonia is mainly produced via steam methane reforming (SMR), an unsustainable fossil fuel-reliant process. Alternative hydrogen generation methods, such as electrolysis, could enable net zero production when powered by a renewable source.
However, significant scaling up of electrolysis infrastructure will be required to support a global energy transition. In the Net Zero Emissions by 2050 Scenario, natural gas-based SMR with CCUS would be reduced to around 20% of total production, and electrolysis would make up more than 40%, according to the IEA.
Increasing Safety
Reducing safety hazards is paramount for ammonia distribution in populated areas like the urban core. Ammonia’s hazards include inhaled toxicity and potential air-mix flammability.
Ammonia has a distinctive smell, making leaks easily detectable. Even so, using proper sealing technology and employing a robust preventive maintenance program can practically eliminate leaks.
Next Steps: Exploring Ammonia’s Potential with John Crane
A global low-carbon energy future requires leveraging various solutions, including cracked ammonia. The energy transition will take skill and experience; choosing strategic partners is essential. At John Crane, we’re known for our advanced sealing technologies. We already have experience delivering solutions throughout the ammonia industry, from traditional production to renewables to navigating the complexities of co-fired power plants.
As leaders in the energy and process industries, we serve many of today’s major corporations. Yet, we support a wide range of decarbonization initiatives, including smaller projects led by pioneering newcomers. We have a range of services tailored to those on new journeys: top-of-class sealing systems, and asset management, remote monitoring and field support programs, to name a few.
Transforming ammonia into hydrogen has the potential to accelerate the transition to new energy. We’re excited to join innovative projects and apply our sealing expertise to every link of the ammonia value chain. Consider our experts your catalyst for success.
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