There’s a major push now to find energy sources with smaller carbon footprints. The maritime shipping industry, according to IEEE Spectrum, is going towards ammonia. Burning ammonia produces no CO2 and it isn’t hard to make. It doesn’t require special storage techniques as hydrogen does and it has ten times the energy density of a modern lithium-ion battery.
You can burn ammonia for internal combustion or use it in a fuel cell. However, there are two problems. First, no ships are currently using the fuel and second most ammonia today is made using a very carbon-intensive process. However it is possible to create “green” ammonia, and projects in Finland, Germany, and Norway are on schedule to start using ammonia-powered ships over the next couple of years.
Switching over, though, will be an infrastructure challenge. Ships consume about 300 million tons of fuel each year, and most of that is diesel which has twice the energy density of ammonia. Ports will need storage and filling equipment to make the switch practical.
To make ammonia takes hydrogen and nitrogen. Most commercial hydrogen is made by reacting methane which releases carbon as a byproduct. However, hydrogen can be split from water using green energy, too, and that will be another key factor in making ammonia fuel work for companies trying to reduce carbon emissions.
You might think this is a new idea, but Germany used ammonia in 1942 to fuel public buses in occupied Belgium. The buses used an internal combustion engine that ran on a combination of ammonia and coal gas. The X-15 aircraft also used ammonia as one component in the fuel that powered its rocket engines.