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TAKE a breath. You have just inhaled about 0.6 grams of air, including 0.4 milligrams of carbon dioxide. Had you lived in the 1600s, you would have taken in less than 0.3 milligrams of CO₂ with each breath. Although it might not seem like a big difference, the additional greenhouse gas now in the atmosphere is altering the climate at a pace that threatens global havoc.

What if we could take CO₂ right back out of the air and put it to use? What if, instead of being the most dangerous waste product in human history, it could become the basis for new industries that clean up the planet instead of harming it 鈥� and turn a profit too?

That is the promise of carbon capture and use (CCU), a burgeoning industry that has attracted billions of dollars in investment, some of it from major oil and gas companies. There are notable success stories. Already, companies are turning carbon dioxide into plastics, fuel and concrete 鈥� meaning that you could build your house or power your car with products that keep carbon dioxide out of the atmosphere.

The real question is whether these start-ups can grow fast enough and to be big enough to make a difference. For that, they need to use enough CO₂ to make a significant dent in the billions of tonnes that we emit each year.

Governments have agreed to reduce annual emissions and limit global warming to 1.5 or 2掳C, the international target enshrined in the 2016 Paris Agreement. But they have left it so late that even if we all made huge cuts to our greenhouse gas emissions tomorrow, the target is nigh-on impossible.

A decade ago, policy-makers began advocating the idea of grabbing CO₂ and storing it underground, a technology called carbon capture and storage (CCS). Oil and gas companies had been doing this on a small scale since the 1970s, because it helped their bottom line. By pushing the gases emitted by their industrial plants back down into nearly spent oil seams, they were able to squeeze out the last remaining drops of crude.

On a technical level, CCS works. The Boundary Dam coal-fired power plant in Canada has been burying much of its CO₂ emissions since 2014, for example. But despite a number of governments appearing to back the technology in the early 2000s, CCS is stuck on the starting line. The sector has come up against a significant challenge: capturing carbon is expensive, and there are no financial rewards for storing it.

That is where the 鈥渦se鈥� bit of CCU comes in. Could CO₂ make money? Aside from enhancing oil extraction, it forms the bubbles in fizzy drinks and fuels plant growth in greenhouses. All this adds up to a global demand of about 80 million tonnes each year, according to a 2011 report by the Global CCS Institute. This is a mere 0.2 per cent of the 37 gigatonnes emitted globally in 2017. To increase that, researchers are now proposing that instead of trying to use pure CO₂ directly, we should make other things with it. The gas is already used to produce urea, for instance, sold as fertiliser. And in the 19th and early 20th centuries, chemists developed reactions involving carbon dioxide to make something that most of us have in our medicine cabinets: acetylsalicylic acid. 鈥淎spirin was probably the first [product] to be done commercially,鈥� says Peter Styring at the University of Sheffield, UK. The drug was initially extracted from willow bark. Then, in 1859, Hermann Kolbe at the University of Marburg in Germany found that he could produce aspirin鈥檚 precursor, salicylic acid, by reacting sodium phenolate with CO₂.

But since these early experiments, few reactions have been devised that use the chemical, says Charlotte Williams at the University of Oxford. As a result, many of the fundamentals of CO₂ chemistry are still unknown, including how to break the bonds between the oxygen atoms and the carbon at the centre of the molecule. Carbon dioxide is fairly unreactive but certainly not inert, says Styring. 鈥淚t needs a little bit of help to react.鈥� That help comes in the form of catalysts, which lower the amount of energy that has to be put in, and so much of the research around CCU involves finding the right catalysts for the job.

Williams has had her own trials and tribulations attempting to break carbon dioxide鈥檚 bonds. Her expertise is in polymers, the long, chain-like molecules that plastics are made of. At the start of her academic career, in the early 2000s, she became fascinated by the idea of taking the carbon out of carbon dioxide and using it to build a polymer backbone. The idea was simple but impossible to implement without the right catalyst to start the reactions. 鈥淲e went through four years of complete failure,鈥� she says, before finally identifying several that worked.

Her team immediately filed patents and formed Econic Technologies, based in Macclesfield, UK. Today, the firm sells its catalysts to major chemical companies making polyurethane, a plastic widely used in insulating foams, kitchen sponges, the wheels on shopping carts and skateboards, and even latex-free condoms.

Williams brought samples of plastics that had been made using Econic鈥檚 catalysts to a meeting on CCU just outside London in October 2017, where dozens of researchers, investors and industry representatives gathered to discuss the prospects of the growing industry. The meeting was convened by the Sackler Forum, a collaboration of the UK Royal Society and the US National Academies of Sciences, to assess the potential of CCU technologies and look at the range of existing ventures, from synthetic fuels to building materials (see 鈥�Out of thin air鈥�).

Some of these may seem odd at first glance. Why change carbon dioxide into artificial petrol? The reason is that by doing so we can keep using familiar, liquid fuels in our existing infrastructure without digging up additional fossil reserves. In theory, fuel made from CO₂ should also be carbon neutral, generating no net greenhouse gas emissions: carbon dioxide equivalent to that released as the fuel is burned is captured and recycled to make the next batch of fuel.

鈥淎spirin was probably the first commercial product to be made from CO₂鈥�

This is particularly useful for aircraft, which need a lot of energy to fly long distances, but can鈥檛 carry heavy batteries powered on eco- electricity. Today, they burn energy-dense but polluting kerosene. An artificial kerosene made from CO₂ might be the best way to make planes climate-friendly, says Styring.

Similarly, it may not seem obvious that CO₂ can be used to make buildings, but it is a simple chemical step away from limestone and other carbonates. 鈥淚 can take a slurry of calcium oxide, put CO₂ into a bottle, shake it up and it鈥檒l react very quickly [to make calcium carbonate],鈥� says Styring.

All these reactions depend on new catalysts like Econic鈥檚, and much of the talk at the Sackler Forum centred on trial-and-error attempts to find the ones that work best, minimising the energy we must put in.

The other challenge the meeting highlighted was hydrogen. Many CCU products, including some of the synthetic fuels, are built around a carbon and hydrogen backbone that we can make only if lots of hydrogen is available to react with CO₂. The trouble is, hydrogen gas is hard to come by. Its molecules are so light that the newly formed Earth had already lost almost all its free hydrogen to space. Nowadays, the planet鈥檚 hydrogen is locked up in molecules like water, and breaking them apart, as with CO₂, takes energy.

The hydrogen hurdle may simply narrow the usefulness of CCU, says Styring. It might not be worthwhile to create synthetic fuels for cars if you have to first make hydrogen 鈥� we can make electric cars instead. But the trade-off might make sense for aircraft since batteries cannot carry enough power for them.

Undoubtedly, it is early days yet, but it hasn鈥檛 stopped big bucks from pouring in. 鈥淲e think that by 2030 the market opportunity would be between 800 billion and 1.1 trillion dollars a year,鈥� says Issam Dairanieh of the Global CO₂ Initiative, a private company that both funds research into CCU and invests in start-ups working in the field.

The company estimates that CCU鈥檚 future market potential is about double the size of today鈥檚 smartphone market. Coming from an organisation that has money in the game, that shouldn鈥檛 be a surprise. But it is worth noting that big oil is also dipping its toe in the CCU pond. The Oil and Gas Climate Initiative (OGCI) is a collaboration between large fossil fuel companies, including Shell, BP, Statoil and Total. Together, they have over the next 10 years. Pratima Rangarajan, CEO of the OGCI鈥檚 investment wing and formerly employed in the renewables sector, says CCU is in the same place recycling was 20 years ago.

Carbon recycling

鈥淧eople said, 鈥楲ook, there鈥檚 no way everyone鈥檚 going to collect all the rubbish and people won鈥檛 separate it鈥�,鈥� she says. Newspapers also mocked the idea that they might one day be published on 鈥渟econd-rate recycled paper鈥�. Yet in 2016, 67 per cent of paper used in the US was recycled, according to the American Forest & Paper Association.

Rangarajan says CCU needs to become normalised the way recycling has been. 鈥淚f it鈥檚 just 10 companies and only we are successful, we might make a lot of money, but we鈥檙e not going to make the impact we need,鈥� she says.

Profit is ultimately what people like Rangarajan hope will distinguish carbon capture and use from its predecessor, carbon capture and storage. 鈥淚t has to make commercial sense,鈥� says Dairanieh. The firms may need help at the start, but ultimately some will succeed and make money.

Governments could provide support in a number of ways, from accelerating patent applications to setting a high price on carbon emissions. The latter is a long-cherished dream of many climate activists. A global price on carbon is still a long way off, but regions are setting precedents, such as in the Canadian province of Ontario, where a sweeping carbon price system came into force in January 2017.

鈥淲e need to move towards a circular economy, where everything is reused鈥�

Even if all this comes to pass, CCU is not, by itself, going to mop up all of our greenhouse gas emissions. In 2015, Styring and his colleague Katy Armstrong a 鈥渞ealistic yet challenging鈥� scenario in which we would make use of 1.3 gigatonnes of CO₂ annually by 2030. That is only 3.5 per cent of our current annual emissions. A more optimistic report published in 2016 by the Global CO₂ Initiative, using data from consultants McKinsey, said we could be using 7 gigatonnes of CO₂ per year by 2030 鈥� still far short of what is needed.

There is also the matter of timing. Most CCU technologies are 鈥渟till in the difficult phase of needing to prove [themselves] at scale, engage with customers and get product to market鈥�, says Williams. So CCU is not the proverbial silver bullet. 鈥淭he way to solve [climate change] is to stop burning fossil oil, and that鈥檚 the only way,鈥� says Styring bluntly.

CCU鈥檚 promise is that it fleshes out a vital principle. Every year, environmentalists mark Earth Overshoot Day: the point when our collective demand for resources passes what the environment can generate in a year. In 2017, it fell on 2 August. To stop us living on credit, many environmentalists advocate moving towards a circular economy, one where everything we use is reused. Not just paper and glass, but every by-product of industrial processes 鈥� including gases. As one participant pointed out at the Sackler Forum: 鈥淐arbon dioxide is the only gas we can emit into the atmosphere with impunity.鈥� It is time we started recycling it.

This article appeared in print under the headline 鈥淔rom pollution to solution鈥�