People might have once considered oxygen a human right. But the pandemic has revealed that access to oxygen – in pure form for medical use – is a luxury in most low-income and middle-income countries.
Accessing pure oxygen for medical treatments is a complicated, expensive and often very dangerous business. The current situation in India is a stark reminder of this issue. The second wave of Covid-19 has hit the country hard, the total number of deaths has just passed 2.00,000 marks. Oxygen is missing.
Due to the current emergency, Indian citizens have turned to the black market to buy oxygen well above the normal price.
This has happened in part because of the way oxygen is produced, stored and transported around the world. That is why researchers like me are working to find a cheaper alternative.
Oxygen is obtained mostly from liquid air. Engineers transform the air we breathe into a liquid using a combination of processes that cool gases until they condense. Once they have succeeded in liquefying the mixture, they use distillation ̵
This process requires enormous amounts of energy and enormous industrial facilities, so it is limited to just a few areas of the world, most of them in the global north. Liquid oxygen must be stored and transported under great pressure, which creates serious logistical and safety problems – oxygen is really explosive.
This means that the most important bottleneck in oxygen production is precisely bottles. The United States relies on heavy pipes to transport oxygen under pressure. In Europe, transport takes place mainly through liquid oxygen transported in large tanks. For countries with lower incomes are distributed in bottles.
But the oxygen bottle market is the corner of only a handful of chemical companies. The use of bottles also adds another layer of safety considerations, as handling them properly requires more precautions and proper training. Developing countries therefore lack both the necessary infrastructure to produce liquid oxygen and the one to easily and cheaply transport it to a hospital.
Outside the air
Another way to “produce” oxygen is by using concentrators, devices that selectively remove nitrogen – the gas that makes up 78% of our atmosphere – using a variety of membranes, porous materials and filters. These began to be produced in the mid 70’s and the technology is very well established.
These units convert air into a stream of oxygen-enriched gas, typically above 95% (the remainder is mainly formed of argon). This is usually good enough for respirators and fans. The advantage of a concentrator is that it can be produced as a small unit to be used in hospitals or nursing homes. Commercially available concentrators are now available, but they are expensive and difficult to produce in developing countries.
This is why researchers like me are looking for solutions. My team is studying new types of materials that store and separate gases, some of which provide potentially affordable solutions for devices such as oxygen concentrators. We develop two main types of materials – zeolites (crystals of silicon, aluminum and oxygen) and organometallic frames. Both are very porous materials. You can imagine them as mushrooms in miniature size.
Like mushrooms, these porous materials adsorb more liquids than you could intuitively imagine. Although the millions of pores inside zeolites and organometallic frames may seem small, their total surface area is monumental. In fact, a gram of certain record-breaking organometallic frames have a surface area of over 7,000 square meters.
Small amounts of zeolites and organometallic frames can store huge amounts of liquid, often gases, and they have been used for gas storage, purification, carbon capture and water harvesting.
Some of my team, working with the engineering firm Cambridge Precision and the Center for Global Equality, have begun investigating whether they can be used to store oxygen. We have developed an initial prototype that works. We hope to have a final prototype in place in two months, after which we will have to seek medical approval.
How it’s done
The principle is quite simple. We have an aluminum cylinder full of porous materials and we circulate an air stream through it. This purifies the oxygen up to 95% – with the remaining most argon. Nitrogen is trapped in the zeolite due to the way in which the electric charge is distributed in nitrogen atoms, which means that it interacts more strongly with the electric field of the zeolite. Oxygen and argon are not.
The nitrogen therefore remains trapped inside the millions of small pores and we empty them later after storing our oxygen.
Usually, we commercialize our porous materials through Immaterial, a spin-out from the University of Cambridge. Yet it seemed immoral to make big profits by selling oxygen in a pandemic. In Africa, for example, oxygen Five times more expensive than in Europe and the United States. Our team and Immaterial therefore collaborated with other researchers in Cambridge to create the Oxygen and Ventilator System Initiative with the aim of promoting and manufacturing oxygen treatments at an affordable price.
We hope the benefits of a cheap oxygen concentrator will survive the pandemic. Oxygen supply is the key to treating pneumonia in children and chronic lung disease – both conditions that globally kill more people than AIDS or malaria. Everyone must have access to oxygen, and technology like ours may one day help provide this access.
David Fairen-Jimenez is a lecturer in molecular engineering at the University of Cambridge.
This article first appeared on The Conversation.