SCEINCE

Lack of CO2 can lead to empty shelves


In terms of the environment, carbon dioxide is probably the number one public enemy. This makes it even more ironic that Britain is currently suffering from a gas shortage, which experts warn will affect various industries, especially food and beverages.

With the right setting, CO₂ is an extremely useful gas. When added to drinks, it gives them soda. Catch it in high pressure bubbles in cakes and you will get candy popping. Compress it in a cylinder and you have a fire extinguisher. Freeze it and produce dry ice, which is used to store medical supplies (including vaccines against COVID) cooled during transportation.

The microbial organisms that cause food death need oxygen to survive, so wrapping lettuce leaves with CO₂, not oxygen, keeps them fresh. Meanwhile, high concentrations of gas are used in the meat industry replace oxygen in the air, animals breathe, making them unconscious before being slaughtered.

Given our need for CO₂ in one area and its excess in another, the obvious question is: why don’t we just draw carbon dioxide outside the air? The simple answer is that despite its harmful effects, there is relatively little carbon dioxide in the air. Although we have 50% more of it in our air than before the industrial revolution, CO₂ still accounts for only 0.04% of the air content.

This makes CO₂ extremely difficult to “find” and then remove from the air. There is a lot of work ahead gas capture from the air with a view to counteracting CO₂ emissions, but this is not currently a viable source of gas for industry.

Instead, the main source of CO₂ for industrial use is from the production of nitrogen-based fertilizers, which produce CO₂ as a by-product. And with the production of fertilizers on hold in the UK due to the rapidly rising price of gas, which is widely used in fertilizer plants, the impact effect is CO₂ deficiency. So to explain the current CO₂ deficiency, we really need to look at how nitrogen-based fertilizers are produced.

Nitrogen capture

Nitrogen plays a crucial role in the biochemistry of every living thing. It is also the most common gas in our atmosphere. But nitrogen gas is largely inert, which means that plants and animals cannot extract it from the air. Therefore, the main limiting factor in agriculture has always been the presence of nitrogen.

In 1910, German chemists Fritz Haber and Carl Bosch they changed all that when they combined nitrogen and hydrogen in ammonia. This in turn can be used as fertilizer for crops, ultimately filtering the food chain to us.

Today, about 80% of the nitrogen in our body comes from Haber-Bosch process, which makes this single chemical reaction probably the most important factor in the population explosion in the last 100 years.

About 78% of our atmosphere is nitrogen, so finding this ingredient for the Haber-Bosch process is easy. But the other component, hydrogen gas, is not so readily available. There is a lot of hydrogen, most obviously like H in H₂O and CH₄ (methane), but breaking the bonds between hydrogen and oxygen in water or carbon in methane requires a huge amount of energy.

The main way it is currently produced is through a process known as methane vapor reform. This works by starting with natural gas – which becomes much more expensive in the UK – and then heating it to around 1000 ℃ in the presence of water. The end products are hydrogen gas (H₂) and CO₂.

They are divided for their respective use. Unfortunately, the amount of CO₂ produced by the fertilizer industry far exceeds that needed by other industries. So most fertilizer plants do not bother to catch it.

The fossil fuels used in the production of fertilizers and the CO₂ it creates as a by-product make it especially unfriendly to the environment. Therefore, much of the decarbonisation program is pure hydrogen production for use in fertilizers and fuels. One of the easiest ways to achieve this is through electrolysis of waterusing clean sources of electricity.

Meanwhile, with the development of carbon capture technologies, we can see carbon dioxide extracted directly from the air for use in industrial processes. But this is a long-term solution and therefore will not help soon.

But there are CO₂ alternatives that could help you. The most obvious is nitrogen gas, which can be used in the same way as CO₂ to preserve food or stun animals. Similarly, since nothing burns in nitrogen, it can be used to put out fires – just like CO₂ fire extinguishers.

The UK government holds crisis talks with the US owner of two of the largest nitrogen fertilizer plants in the UK, both of which are currently inactive. Maybe persuasion will make them come back to life. However, CO₂ shortages have revealed the complex chemical supply chains we rely on for our carbonated beverages and packaged salads.

Mark Lorch, Professor of Communication and Chemistry, University of Hull

This article has been republished by The conversation under a Creative Commons license. Read on original article.





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