Can we use atmospheric carbon for food?

Climate scientist Ella Gilbert and geoengineer Gernot Wagner weigh in...

Chris - This week you've probably been watching the headlines here in the UK, food production is apparently under pressure due to a lack of CO2. Listen to this...

NEWS READER - The threat comes after two huge fertilisation plants in Teesside shut down due to gas price rises. CO2 is a byproduct of fertilisation and the supply constraints could be felt across the food and drink industry.

Chris - On that subject, Cornelia is wondering why the shortage of CO2 should be causing problems in the food supply chain? At the same time, we're continuously being told there's too much CO2 in the atmosphere. We've got too much of the stuff. What's going on?

Ella - I know it's a bit of a head-scratcher isn't it, that you can simultaneously have too much CO2 and too little. First off, CO2 emissions or carbon dioxide emissions are the primary cause of climate change. CO2 is a greenhouse gas. It forms in the atmosphere which makes it a problem, which is why we're constantly being told that we need to reduce our CO2 emissions so that we can have less of an impact on the environment. When we're thinking about the food industry, it has a variety of different uses. That's for things like carbonated drinks and, as I only learned this week, for killing pigs. These sorts of uses require a lot of CO2 and you have to manufacture it. Lots of those plants manufacture it as a by-product of other processes, things like fertiliser. In the atmosphere CO2 is in relatively low concentration. At the moment we've got 420 parts of CO2 for every million parts of air. To actually concentrate that CO2 would actually be very challenging because we don't have the sorts of geoengineering techniques that I'm sure Gernot will be talking about later, like carbon capture, to actually distill them into a really concentrated form.

Chris - One big source is methane, natural gas, isn't it? We rip away the hydrogen off of it and turn the carbon that's in it into carbon dioxide. Gernot, that seems something of a contradiction. When we're thinking we're trying to get rid of CO2, why can't we use the stuff we've got in the atmosphere? We're told that we've increased the amount of CO2 in the atmosphere by enormous amounts since the industrial revolution. If there's so much there, why is it so difficult to just grab it back?

Gernot - As we speak the very first demonstration plant like this is operating. It's a Swiss startup, a Swiss company, operating in Iceland, taking CO2 out of thin air and concentrating it. It costs them about a thousand euros per ton of CO2, which is incredibly costly if you look at it from lots of different perspectives, and frankly it doesn't pay to do that for food, it is too costly. But costs are only going to come down - you need to start at a thousand to get a hundred eventually, and so on. The technology does exist, it's just very pricey.

Chris - How does it work?

Gernot - In some sense, in a chemical sense, it's literally reversing the process that we use when we burn fossil fuels and release the CO2. That alone sounds energetically very costly. There is a reason why this Swiss startup is operating in Iceland. Why? Because there's a lot of cheap geothermal energy, cheap and low carbon, zero carbon. Those are the key ingredients here in this process.

Chris - Is that the way it's going to go then? Do you think that what we'll end up doing is we'll put CO2 scavenging plants where we're currently seeing a waste of energy things, like hot rocks and volcanoes, there'll be certain countries where their growth industry in the future could actually be pulling CO2 out of the atmosphere and then turning it into stuff?

Gernot - Here's hoping. Way too many people who make too much money taking fossil fuels out of the ground are burning them, and of course, to be clear, this process itself is useful, it provides energy. But by now we have better ways of doing that, cheaper ways of doing that; solar photovoltaic, solar PV, is the cheapest form of electricity in history. There are better ways of doing that and we should stop burning fossil fuels and there is already too much CO2 in the atmosphere. We should, and frankly will be, taking that CO2 out at some point, at a cost.