Five ways to turn CO₂ from pollution to a valuable product
News•Business• 21.01.2020 • Ella Adlen/University of Oxford/Cameron Hepburn/University of Oxford
What if, instead of wasting all that CO₂, it could be turned into something useful?
Here is a selection of the ways that one person’s pollution could become another’s product.
It’s far easier to avoid burning fossil fuels than it is to clean up CO₂ emissions once they’re in the Earth’s atmosphere. But the world no longer has the luxury of choice – drastic emission reductions and rapid CO₂ removal and storage will both be necessary to avoid the worst impacts of global heating.
What if, instead of wasting all that CO₂, it could be turned into something useful? There’s currently little economic incentive for industries that emit CO₂ to capture it, let alone to draw it directly down from the atmosphere. Identifying valuable products and how to make them might kickstart CO₂ removal on an industrial scale, and help bring down emissions in the process. In our recent paper, we set out to clarify what these processes and products might be.
We considered processes that use CO₂ captured from industrial emissions, and also biological processes that can directly draw down CO₂ from the air. We projected that between one and ten gigatonnes of CO₂ could be utilised per year by 2050, at costs of under USD$100 (£77) per tonne of CO₂. Humans currently emit 37 gigatonnes of CO₂ a year, and we need to reduce our impact to net zero by around 2050. Some estimates suggest this might mean removing around ten gigatonnes of CO₂ a year from 2050 onward. Some of these ideas for using CO₂, if implemented properly, could play a role in making that more economically viable.
Some ideas for using CO₂ might not get off the drawing board. But with the right investment and incentives, others may move from niche research projects into credible plans, and from the work of small businesses to the goal of entire industries. Here is a selection of the ways that one person’s pollution could become another’s product.
There are several ways in which buildings can be constructed with materials made from CO₂. The first is obvious: use wood. Growing and sustainably harvesting trees for building means that CO₂ is taken from the atmosphere, converted into a valuable commercial product, and stored as carbon in long-lived buildings.
CO₂ can be used as a feedstock for many chemical processes, with hundreds of potential end products, including hydrocarbon fuels and urea fertilisers.
Fuels made from CO₂ can exist in the form of methanol as well as more complex products like so-called synfuels. These fuels can often be blended or moved around using existing infrastructure like pipes and tankers. And although CO₂ fuels are currently very costly to manufacture, in the future they might be valuable in niches like aviation or long-distance shipping, which are more difficult to decarbonise than trains and cars because they need fuels with higher energy densities.
While it will be comparatively easy for cars and trains to undergo electrification, aeroplanes will still need liquid fuels with high energy densities for a while.Milosz Maslanka/Shutterstock
If the CO₂ product is a fuel or a fertiliser, the CO₂ ends up back in the atmosphere once used. While two uses of the carbon is better than one, if the carbon atom originally came from a fossil fuel, it’s not a long-term solution. To be climate neutral, the CO₂ feedstock will have to be sourced from the air – so the CO₂ is taken from the atmosphere, made into fuel, and then emitted back to the atmosphere. This is currently expensive and technically challenging. Crucially, the energy required for this process also needs to be renewable.
4. Increase crop yields
There’s emerging evidence that increasing the amount of carbon in soils can also increase crop yields. This is a natural form of CO₂ utilisation that already happens – scientists and farmers can just give it a helping hand. One particularly promising way is by using biochar – plant material that has been converted into a stable form of organic carbon via a process known as pyrolysis. Biochar buried in soils could store carbon for the long term and increase crop yields.
Counter-intuitively, it’s possible to both produce oil and store CO₂. That’s because injecting CO₂ into an oil well increases the amount of oil that can be recovered – so-called “CO₂ enhanced oil recovery”.
It is actually possible to operate the well so that more CO₂ is put into it than is emitted in the process of producing the oil and burning it. But policy changes would be needed to incentivise this – oil companies would not do it otherwise. And it’s a temporary fix. In a world that has fully decarbonised, demand for fossil oil should be close to zero.
All these options for using CO₂ have potential, but making them a reality will need a clear understanding of the possible unintended consequences. Many could be failures, so it’d be unwise to rely solely on any one of them, but instead, spread bets widely.