Ammonia

H2 has the highest energy content of all chemical fuels when measured by mass at 120.2 MJ/kg, compared to heavy fuel oil at 40.2, ammonia at 22.5 (about 6x less than H2), and methanol at 19.9 [PS, 2022].  The drawback - and it's a big one - is that H2 has a very low energy density per volume.

  

Current H2 use is centered around oil refining and ammonia & methanol production, which are the main candidates to deliver zero-emission shipping.  Also, ammonia & methanol could be attractive options as hydrogen carriers at a large scale because of their compatibility with existing liquid fuel infrastructure.

  

Ammonia - NH3

  

Ammonia (NH3) is a bulk chemical normally synthesized from natural gas (NG) and mainly used as chemical feed-stock, e.g. in fertilizer production [RB, 2021].  It is the most popular substance as a green hydrogen (GH2) carrier because it does not carry carbon atoms.

  

Ammonia gas can be stored as a liquid at room temperature under a pressure of just 10 bar (147 psi), or under atmosphere pressure at -33 °C [EN, 2022].  Liquid ammonia is non-corrosive, so internal pipeline corrosion is extremely unlikely.  Current ammonia production of 235 Mt is mostly used for agricultural purposes.  The total H2 content of ammonia is higher than other fuels (5,7 kg of NH3 carries 1 kg of H2), and is thus suitable to (re)convert to hydrogen.

  

Advantages & disadvantages

  

dvantages of ammonia as a fuel include a relatively high power-to-fuel-to-power (PFP) efficiency, a high technological maturity, a large-scale distribution infra that is already in place, a high-octane rating of 110–130, and a narrow flammability range, making it relatively safe in terms of explosion risks [SD, 2022].

  

But, due to the safety concerns (toxicity), it is questionable whether authorities would permit the transportation and use of ammonia in populated areas.  Although no ammonia-powered demonstration vessel has yet sailed, several shipping-related consortia have initiated projects that should lead to ammonia-powered vessel demonstrations by 2023/2024.

  

Synthesis & applications/market

 

Synthesis of ammonia has been carried out by Haber-Bosch process since the beginning of the 20th century, which converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with H2 using a metal catalyst (typically an iron oxide - Fe3O4) under high temperatures & pressures, as shown in Figure 1.

  

Traditionally used in the production of nitrogen fertilizers or as industrial refrigerant, ammonia now finds new uses riding the energy transition wave.  Figure 2 shows some new ammonia applications.

  

Market size was valued at USD 68.69 Bi in 2021 and is projected to reach USD 123.12 Bi by 2030, growing at a CAGR of 6.82% from 2023 to 2030 [VMR, 2023].  Ammonia will likely have a lower initial uptake than e-methanol until 2040, but then scale faster from 1,100 PJ (8% of the shipping fuel mix) in 2040 to 4,500 PJ (35%) in 2050 [DNV, 2022].