Low-Carbon Ammonia Technology: Blue, Green, and Beyond

As the world intensifies efforts to combat climate change, several industries are focusing on the development of sustainable manufacturing processes for high-impact products like ammonia. Primarily used as an agricultural fertilizer, ammonia and other ammonia-based fertilizers are essential for providing nitrogen to crops. Conventional ammonia production methods are carbon-intensive, relying heavily on fossil fuels, and thus, alternative low-carbon pathways to produce ammonia are under development, offering promising solutions to decarbonize ammonia production.

Ammonia production technologies generally fall under two categories: those that utilize the Haber-Bosch (HB) process, and those that are more novel. The Haber-Bosch process is the method by which hydrogen and nitrogen are converted into ammonia (NH₃) through the use of a high-pressure, high-temperature reactor and a chemical catalyst. Utilized in industry since the early 1900s, HB is already a mature technology. However, while nitrogen is sourced from the air, hydrogen is conventionally sourced from natural gas (methane) through a process called Steam-Methane Reforming (SMR) which releases significant amounts of carbon dioxide (CO₂), accounting for over 1 percent of global greenhouse gas (GHG) emissions. By capturing the carbon emitted or by sourcing the hydrogen from other feedstocks like water (H₂O), the ammonia production process can become much less carbon intensive.

Promising low-carbon ammonia technologies

1. Conventional Haber-Bosch with CCS, aka Blue Ammonia
   Blue ammonia production captures and stores (or utilizes) the CO₂ emissions generated from natural gas-based hydrogen production. This approach combines the conventional SMR process with carbon capture and storage (CCS) technology and then utilizes the Haber-Bosch process to combine the “blue hydrogen” and nitrogen to create ammonia. Blue ammonia can significantly reduce emissions depending on the capture efficiency.
   • Hydrogen Feedstock: Natural gas/methane (CH₄)
   • Key Technologies: Steam methane reforming (SMR) or autothermal reforming (ATR) to produce hydrogen from natural gas, coupled with CCS
   • Advantages: Utilizes established infrastructure; CCS reduces CO₂ emissions
   • Challenges: High cost and energy requirements for CCS; concerns about CO₂ leakage over time; requires access to geologic sites for CO₂ sequestration
   • Commercial Readiness: Commercial-scale SMR+CCS plants have been demonstrated around the world; over 20 ammonia facilities with CCS integration are under development
2. Electrolysis-Based Ammonia Production, aka Green Ammonia
   Green ammonia is produced using renewable electricity (e.g., from wind or solar) to electrolyze water, producing hydrogen from water in a zero-carbon process. then combined with nitrogen to synthesize ammonia. Green ammonia is viewed as the most sustainable option, achieving near-zero emissions in production.
   • Hydrogen Feedstock: Water (H₂O)
   • Key Technologies: Electrolysis (alkaline, PEM, or solid-oxide electrolysis), Haber-Bosch synthesis powered by renewable energy
   • Advantages: No CO₂ emissions; uses abundant renewable resources; decoupling from natural gas pricing and supply chain risks; suitable for small-scale/localized ammonia fertilizer production
   • Challenges: High cost of renewable hydrogen; flexible system design required for intermittent renewable energy supply may impact scalability and costs
   • Commercial Readiness: Electrolysis technology is well developed and demonstrated in commercial environments; one fully renewable electrolysis-based ammonia facility deployed in the US
3. Electrochemical Ammonia
   Electrochemical ammonia is a promising alternative to the Haber-Bosch process that can operate in a low-pressure environment. By running an electric current through an electrochemical cell containing a source of hydrogen and nitrogen, a single-step nitrogen reduction reaction (NRR) can occur.
   • Hydrogen Feedstock: Water (H₂O)
   • Key Technologies: Electrochemical cell
   • Advantages: No CO₂ emissions; low-pressure ammonia synthesis; single-step process simplicity; suitable for small-scale/localized ammonia fertilizer production
   • Challenges: low ammonia synthesis performance results at the research level; high energy requirements; reactor catalyst optimization
   • Commercial Readiness: Lab-scale prototyping phase
4. Plasma-Catalysis Ammonia Recent advancements in non-thermal plasma (NTP) ammonia have proven it to be a likely competitor of small-scale electrolysis systems as it can be used for on-farm ammonia fertilizer production. The low-temperature and low-pressure plasma reactors can produce nitrogen-based fertilizers such as nitric acid and ammonia, and this method does not require the Haber-Bosch process.
   • Hydrogen Feedstock: Water (H₂O)
   • Key Technologies: NTP reactor
   • Advantages: No CO₂ emissions; low-pressure, low-temperature ammonia synthesis; suitable for small-scale/localized ammonia fertilizer production
   • Challenges: low energy efficiency; reactor catalyst optimization
   • Commercial Readiness: Emerging from lab-scale to pilot-scale project phase

Recent innovations in ammonia technology have shown the potential for sustainable methods of ammonia production as well as alternatives to the Haber Bosh process altogether. As ammonia’s role in the energy transition continues to grow, reducing fossil fuel dependence and supporting technology innovation will become even more important in the near future. The path to a low-carbon ammonia industry will require multi-pronged investments in technology, infrastructure, and policy support. Collaborations across industries, governments, and academia are essential to advance these technologies, drive down costs, and scale production to meet global demand.

Within the next few decades, the convergence of renewable energy advancements, carbon capture improvements, and innovative reactor designs will create a portfolio of ammonia production technologies that not only meet the world’s fertilizer needs but also contribute to a low-carbon, sustainable future.