The Paris Agreement outlines a series of measures for our society to adopt so that we can reduce greenhouse gas emissions and avoid the worst consequences brought upon by climate change.
However, in this master plan, many carbon dioxide-emitting practices, some of which being quite substantial, are overlooked. Take maritime transport for example, the industry that helps to mobilize global goods also leaves a giant carbon footprint. It could have been ranked among the top emitters if the entire sector is counted as a sovereign country.
So what can we possibly do about this? Many scientists and policymakers have their eyes on ammonia. The substance found in household cleaners and fertilizers could be a viable remedy to keep both the industry and our decarbonization roadmap healthy.
Currently, many shipping vessels rely on heavy fuel oil (HFO) as their main source of energy. Also known as residual fuel oil, HFO has a dense, tar-like consistency, because it is the remnant from the distillation and cracking process of crude oil. The inexpensive, energy-concentrated fuel contains aromatics, sulfur, and nitrogen, rendering dirtier combustion when compared to distillate-based fuels.
On the other hand, ammonia has a high compression rate and low flame temperature, comparable to high-performance gasoline fuel. Without any carbon in the molecule, ammonia produces water and nitrogen gas predominantly after combustion. What's more important, ammonia (NH3), a carrier of hydrogen, can be "cracked" open and releases hydrogen for fuel-cell consumption. The latter form of consumption gives ammonia a better edge in terms of energy density and energy output per unit volume than liquid methane.
Right now, the production of ammonia isn't nowhere close to be a "green" process. Similar to another promising clean fuel hydrogen, the current practice to produce ammonia involves methane reforming and emission of carbon dioxide. But new, sustainable methods to make ammonia are already here. Producing substrates such as hydrogen and nitrogen from processes powered by sustainable electricity is a popular and effective way to reduce the carbon footprint of manufacturing.
Ammonia—a renewable fuel made from sun, air, and water—could power the globe without carbon (Science Magazine)
Given its massive potential, many countries have already invested heavily in green ammonia projects. For example, the Australian Renewable Energy Agency (ARENA) has allocated 2.9 million Australian dollars to deliver feasibility studies at two ammonia plants in Queensland.
Before "green" ammonia become the mainstream, adopting "blue" ammonia – a production process that uses hydrogen from steam methane reforming with carbon capture and storage could be an interim solution. As "green" ammonia fuel becomes more available, it can be a game-changer for commercial shipping and other industries, allowing them to finally be a part of the global decarbonization effort.
Source: Physics World