Is helium environmentally friendly? Solutions to the global shortage

Earth’s supply of helium is running low. It’s the 2nd most abundant element in the universe, but it’s mostly found in stars – not so much on planets. Since we currently use a lot of it, we need to find alternatives, saving helium for when it’s really needed. If we’re going to run out of it, is helium environmentally friendly?

Why is helium in short supply?

Helium is really light. So much so that Earth’s gravity can’t hold it – any helium released into the atmosphere floats off into space and is lost to us forever. However, that’s not the only problem. 

Helium can’t be synthesised. It’s an element – you can’t combine chemicals to produce it. The helium we have on Earth is a product of radioactive decay. An unstable uranium atom undergoes a process called alpha decay, ejecting an alpha particle – two protons, two neutrons, but no electrons, so not a full atom. If this happens in a sealed area, such as an underground pocket of space, the alpha particle is trapped, and can gather electrons over time, eventually becoming a stable helium atom.

Alpha decay of uranium, producing a helium nucleus.

The helium gas from radioactive decay collects in underground reservoirs, combining with other, more common gases. This means our main source of helium is natural gas deposits, found deep underground. These are mostly full of fossil fuel gases like methane, with a tiny amount of helium (only about 0.3% by volume).

We can’t speed up alpha radioactive decay. So, helium is under the same constraints as fossil fuels – it’s not renewable in our lifespans. It’s estimated that Earth’s helium reserves accumulated over 4.7 billion years, and will be many millions before a reasonable amount has been produced again. It’s a scarce, non-renewable resource.

The USA’s National Helium Reserve (NHR) is a critical source of helium for the world, and it is rapidly depleting. In 2012, the USA was responsible for about 78% of the world’s helium supply, 30% of which came from the NHR. Demand for helium far exceeds the supply, and this is only going to get worse with time. Estimates from 2019 suggest that the NHR has 80-100 years of helium supply remaining.

Why do we need helium?

Helium has many desirable properties. It’s completely inert – it takes absurdly high pressures and temperatures to make it react with anything. It also has the lowest boiling point of any material known, making it indispensable for superconducting materials.

It’s not a greenhouse gas, and is non-toxic. In terms of health and safety, it’s an excellent material. The only problem is the limited supply.

Cryogenic cooling

The use of helium as a cryogenic (e.g. very cold) cooling agent has enabled amazing advances in science and medicine with magnetic fields. In chemistry research, a technique called NMR (nuclear magnetic resonance) spectroscopy allows highly accurate identification of chemicals, speeding up drug discovery and other R&D processes involving new chemistry.

In medicine, MRI (magnetic resonance imaging) is a diagnostic imaging technique based on the same physical principles, but applied to bodies rather than chemicals. It lets doctors see inside a patient’s body without having to cut them open. MRI is really good for imaging tissues (the fleshy bits) and is excellent for locating tumours, among other things.

In a slightly less relatable example, particle physicists also rely on helium. The multinational research site CERN (Conseil Européen pour la Recherche Nucléaire, or European Council for Nuclear Research) houses the Large Hadron Collider (LHC) – a giant particle accelerator which is answering fundamental questions about the nature of matter.

How is helium used for cryogenics?

The above techniques all require an extremely strong magnetic field, which is produced by a superconductor – a coil of wire that’s cooled down to near absolute zero to remove all electrical resistance. The cooling is helium’s job. Liquid helium has the coldest boiling point of any known material, sitting at -269 °C or 4.2 K. 

An MRI coil is surrounded by a tank containing 1700 litres of liquid helium, and NMR is approximately the same. The LHC requires 120 tonnes – approximately 961,500 litres – of liquid helium. These also need to be topped up on occasion, since helium can escape from containers due to its small size. A single NMR machine is estimated to lose 430 litres of helium per year.

How can helium be substituted for cryogenics?

Frankly, helium can’t be entirely substituted here. As the coldest material we have, liquid helium is necessary for some superconducting coils. This doesn’t mean that nothing can be changed, though.

Cryogenic has developed an MRI cooling apparatus that uses a cycle of compression and expansion of helium gas, instead of a simple reservoir of liquid helium. Gases cool as they expand – it’s the same idea as the cooling system in most fridges, but on a whole new level. Their system uses the equivalent of ~0.5 litres of liquid helium (in gas form – it never actually becomes a liquid), reducing the amount needed by a factor of 3400.

Reducing helium use isn’t the only benefit, though. It also massively reduces the amount of gas released if a magnet quench occurs – this is basically when some resistance returns to the coil, so it heats up and causes the liquid coolants to evaporate. Quenches result in loss of all helium in the system, and pose a danger to anyone in the facility as breathable air is replaced with non-breathable gas.

The drawbacks of changing the cooling system are largely in the cost. MRI equipment is very expensive, so choosing something that you’re not certain will work as well as the standard is a big risk for companies. Alternative cooling on the scale required for the LHC has not yet been developed and would require a lot of costly research, as well as temporarily stopping LHC operation to implement the new system.

Gas Chromatography (GC)

GC (gas chromatography) is a common, affordable analytical chemistry technique that separates the different chemicals in a mixture. It’s used in many fields – quality control of most chemicals, analytical research, and forensics. A liquid sample is injected into the instrument, where it boils into a gas and is pulled through a long column by a carrier gas (mobile phase). The inside of the column is coated with a stationary phase that is designed to interact with the chemicals in the sample, holding some of them back and separating the sample components for analysis. At the last stage of the process, the sample is burned and the carrier gas released into the atmosphere.

How is helium used for GC?

Helium is a very common mobile phase in GC. It works well because it’s inert. Also, it only has very weak interactions with the mobile and stationary phases, meaning the samples are carried along by the flow rather than intermolecular forces.

How can helium be substituted for GC?

The best answer to this is hydrogen – H2 gas. It’s cheaper and massively abundant, since it’s produced by splitting water.

Hydrogen has proven to be a better mobile phase than helium in many cases. It can allow faster sample processing due to its higher optimal linear velocity (OLV) range (the best speed to have the gas travel through the column).

Higher velocity may cause problems with analysis, as the different components of the sample may not separate fully. This complicates regular GC, and is totally unacceptable for GC-MS (gas chromatography that feeds directly into mass spectrometry). If you opt for higher sample throughput, you may see slight broadening in signal peaks. Fortunately, hydrogen can be used at the same velocity as helium with approximately the same level of peak broadening.

Unlike helium, hydrogen is an extremely flammable gas, so using it does present some risks, particularly if you store canisters of hydrogen on site. An alternative that mitigates this risk is the use of a hydrogen generator. These machines split water into hydrogen and oxygen on demand, meaning that you’re safely storing water instead of hydrogen when the GC is not in use.

How else is helium used?

Welding

Helium is used as a shielding gas in welding due to its inertness. It stops the molten parts of the weld from being exposed to oxygen, nitrogen, hydrogen, and water vapour from the atmosphere.

In this case, helium could be replaced by argon. It’s the most common shielding gas, and even performs better than helium when working with some metals. It’s produced by fractional distillation of liquid air, since it’s 0.93% of our atmosphere. This means that it’s also environmentally friendly. It doesn’t have helium’s problem of escaping the atmosphere, so when it’s released after use it just returns to the air, effectively getting recycled. It costs approximately 1/7 as much as helium, but about 3x more than nitrogen.

Decorative balloons

Helium can be used to fill party balloons, floating them in the air to lend a festive atmosphere to any occasion. This used to be popular, but recently helium has become so expensive that this usage has declined. 

There are plenty of other festive decorative options. When flammability isn’t an issue, hydrogen can be used to float balloons. For a safer option, air and a bit of tape does the job.

Deep-sea diving gases

Helium is commonly mixed into breathing gases to prevent nitrogen narcosis in divers during resurfacing. It can be mixed with oxygen and a fixed amount of nitrogen, or with oxygen alone.

Hydrogen/oxygen mixtures are already fairly common as non-helium alternatives. However, it’s not a perfect solution: hydrogen can be a little narcotic too, and mixtures of hydrogen and oxygen can be extremely flammable. Care must be taken to avoid all sources of ignition.

Purge gas

In laboratories and manufacturing processes, a common safety measure to prevent the formation of flammable atmospheres is flushing (purging) a container with inert gas. This is most frequently done with nitrogen, which makes up 78% of our atmosphere so it’s abundant, and can be recycled into the air in the same way as argon. Helium and argon are also quite commonly used, so an easy way to reduce helium usage would be to swap to the other two, where possible.

Controlled atmospheres

Helium is one of a few inert gases used for the storage of foodstuffs under controlled conditions, as it can slow spoilage by eliminating oxygen. However, nitrogen works too, offering lower cost and long-term resource sustainability.

How can you reduce helium usage?

For the average person, it’s a simple matter of skipping helium balloons in favour of alternative party decorations. However, if your job involves helium in one of the uses listed above, you may be able to make more of a difference.

Carefully consider each of the ways you use helium, and why – is it tradition, or is there a good reason? If an alternative is available within your means, it may be worth pursuing. Weighing up the costs and benefits of changing to an environmentally friendly option now could save your company quite a lot in the long run, as helium will only get more expensive over time.

Further reading

https://www.youtube.com/watch?v=mOy8Xjaa_o8
Tom Scott interviewing a worker from the NHR.