Ammonia has been considered a fuel of the future because of its big potential, but most manufacturing methods make it a dirty source of energy. A new method introduced by researchers at MIT could derive the compound using the Earth’s rocks and natural heat cleans it up considerably.
The idea comes from a well in Mali, West Africa which was found to be full of hydrogen gas streams in the 1980s, which was coming from a reaction deep below the Earth’s surface between chemicals in the rock and the water, also known as an ‘aha’ moment.
The MIT scientists built a model system that allowed them to inject nitrogen-enhanced water into synthetic iron-rich minerals to mimic those that are found beneath the Earth’s surface. The process generated ammonia without producing any CO2 or needing any outside energy to encourage the chemical process.
Then, they replaced the synthetic iron with olivine, an iron-rich rock found in nature. They also added a copper catalyst and heated the system to 300 °C (572 °F) to simulate the temperatures found miles beneath the Earth’s surface.
As a result, the nitrogen in the water reacted with the iron to create clean hydrogen, which then reacted with the nitrogen to create ammonia. The process produced 1.8 kg (4 lb) of ammonia per ton of olivine.
According to the study senior author Iwnetim Abate, the method could be adapted widely across the globe as these olivine rocks are available all over the world.
However, there are also some other complexities such as the problems that might arise when they drill deep into the Earth or inject nitrogen-enhanced water. In addition, they also might have to deal with the ways in which the liquids and gases produced interact with bedrock.
Ammonia is currently the second-most produced chemical in the world, where about 80% of it is used as agricultural fertilizer. Additionally, being a combination of nitrogen and hydrogen gives it enormous potential in the power sector as it can store more than 20 times as much energy by weight as current lithium batteries.
Therefore, green ammonia production could go a long way toward servicing energy demands as well as reducing carbon emissions. MIT’s technique is expected to open another pathway to producing green ammonia and will be tested in the real world within a year or two.
