A group of researchers from Amsterdam University for the first time in history made a special focus on studying the benefits of using ammonia as marine fuel vs fuel oil for freight shipments. They wanted to understand is ammonia could really replace traditional bunker fuels.
The International Maritime Organization (IMO) has set the ambitious goals for the industry: at least 20% decrease of СО2 emissions by 2030 and 70 % decrease by 2040, carbon neutrality by 2050. At the same time about 99 % of marine fuel today is made from fossil feedstock. The service life of one vessel makes 25 years, hence, introduction of carbon-free or low-carbon technologies becomes relevant right now.
Ammonia is viewed as one of the potential fuels for switching to “clean” technologies. Different from hydrogen, it does not require storage under super-low temperatures, does not contain carbon and already is in the mass production — mainly for fertilizers. The idea of using ammonia as fuel is not at all new: back in the time of the 2nd World War it was used for fueling buses in Belgium when there was a shortage of oil. Since then, interest towards ammonia rose periodically, and it got stronger against the background of climate objectives adopted within the Paris Climate Agreement.
However, ammonia has its quite obvious disadvantages: it is toxic, its combustion temperature is low, its auto-ignition temperature is high and its flammability range is very narrow. On top of that, hazardous substance — nitrogen oxides (NOx), nitrous oxide (N₂O) and the remains of ammonia itself – may get into the atmosphere in case of its incomplete combustion. To improve its combustion performance, the scientists propose to use ammonia mixed with a small amount of diesel fuel or hydrogen within the dual fuel scheme.
In the process of their studies, the Dutch researchers explored two options of the on-board power plant fired by ammonia: the internal combustion engine, and its combination with a solid oxide fuel cell (SOC). The compared the full cost of ownership for such vehicle vs the vehicle using fuel oil with account of building costs, fuel costs and maintenance costs for 25 years of operation.
The results showed that even in the most optimistic scenario, i.e., given high performance of the engine (up to 55 %) and low ammonia prices, the cost of ownership for such vehicle will be 19–25 % more expensive vs the traditional one. The main reason is high fuel cost. The options with using fuel cells turned out to be even more expensive. They can be cost-effective only in case of extremely high fuel prices or poor performance of the internal combustion engine. At the same time, the share of CAPEX for the vessel or fuel tanks turned out rather small: practically all the rise in cost is connected with the ammonia price.
The researchers concluded that ammonia may be a robust alternative to the fuel oil only under two conditions: significant decrease in ammonia prices and introduction of high carbon tax. Without subsidies, the ammonia prices need to be below 28 cents per kilo, or the fuel oil prices need to double (up to USD 1.4 per kilo), but this is possible only in case the carbon tax is USD 200 per one ton of CO₂.
Hence, according to the Dutch researchers, ammonia applications remain an interesting decarbonization option, but practical use of this fuel will require not only a technological breakthrough, but also strict government regulation.
