Ammonia’s potential as a zero-carbon fuel

WHAT IS AMMONIA AND WHAT ARE THE ISSUES WITH IT?

Ammonia is a chemical we have used to improve the yields of our crops for over 100 years. The main method of ammonia production involves releasing hydrogen and carbon dioxide (CO2) from natural gas (a fossil fuel). The hydrogen is then made into ammonia using a method called the Haber-Bosch process.

Ammonia is extremely important and useful. Without it, we would not be able to grow enough food to feed the world. However, ammonia production currently accounts for a significant portion of global greenhouse gas emissions, which contributes to the climate emergency.

HOW COULD WE MAKE ‘GREEN’ AMONIA?

‘Green’ ammonia is made without releasing any CO2. It could be made by using electricity to split water into hydrogen and oxygen, rather than getting the hydrogen from fossil fuels. This electricity could be obtained from renewable energy sources such as solar and wind power.

Another possibility is known as ‘carbon capture and storage’. This involves capturing the CO2 when it is released, and storing it underground so it never gets into the atmosphere. This is cheaper than the water method but would not be able to reduce CO2 emissions to zero.

WHAT COULD GREEN AMONIA BE USED FOR?

Ammonia is used in more than just fertiliser. It is becoming widely accepted that it could be a great way to store and transport energy. As already mentioned, we can get sustainable energy from sources such as wind and solar power, but they are intermittent. This means that they cannot provide a constant source of energy. For example, solar panels only make energy during the day. We need energy at night as well, and we also need to be able to transport the energy from where it is made to where it is needed, such as cities. This is where ammonia comes in.

The sustainable electricity from solar power could be used to make ammonia, which is a flexible energy source. It can either be burned in an engine, or it can be allowed to react with oxygen to make electricity to power motors in all sorts of machines. Because we use ammonia in farming, we already have the transportation and storage set-ups needed to effectively use ammonia as a fuel.

One of the industries ammonia could be particularly important in is international shipping. Large shipping vessels run on oil, a fossil fuel, but in the future could run on ammonia instead. The International Maritime Organisation has committed to zero carbon emissions by 2050 and has recognised ammonia as a possible way of achieving this.

DISADVANTAGES OF AMMONIA

As with any fuel source, ammonia has certain disadvantages. If it leaks out into the environment, it can cause acid rain and smog, so we need to have precautions in place to prevent this. Additionally, making hydrogen to generate ammonia is expensive. Finally, ammonia isn’t suitable for use in high-speed engines. Chemical additives have to be used, but there are environmentally friendly options available.

EMILIE RAPPORT MUNRO

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