The basic idea of carbon capture is fairly simple – in order to counteract industries that release CO2 into the atmosphere, we develop technologies that remove CO2 from the atmosphere. If these industries exist in near balance, then there will be no net increase in CO2.

When you think about it, we do have to eventually get there – to the point that human activity does not result in a net increase in CO2 in the atmosphere. Any significant amount will build up over time and have an effect. We need to get down to negligible amounts, compatible with homeostasis and indefinite sustainability.

Clearly we are not there now. Currently the world emits about 9.8 gigatonnes (billion tonnes) of carbon per year. That carbon winds up in the air (44%), ocean (26%) and land (30%). Ninety-one percent of these emissions come from fossil fuels: “coal (42%), oil (33%), gas (19%), cement (6%) and gas flaring (1%).”

One obvious way to reduce global carbon emissions, therefore, is to use carbon neutral sources of energy to replace fossil fuels. But no energy source is completely carbon neutral – you still have to build the wind turbines and solar panels, or farm the biofuels. Also, until we find a replacement for cement, that industry will still release massive amounts of carbon. So there is certainly a lot of room to reduce our carbon emissions, but it does not seem that we will reduce them to globally negligible anytime soon.

Carbon capture, therefore, is an attractive idea. However much carbon we remove from the environment (air, water, and soil) gives us a budget of carbon we can afford to release into the environment with other industries. The consensus, however, is that carbon capture technology is no where near being a magic solution to climate change and carbon. At best it will be one of many technologies that inch us toward a carbon-neutral future.

There are a few things to consider with carbon capture technology: what is the carbon efficiency of the process, what is the cost efficiency, and what do we do with the carbon? The carbon efficiency simply means, what is the net effect on environmental carbon. If we burn coal to power the process of removing carbon, that probably won’t accomplish anything except wasting a lot of energy.

That is why most research is looking into processes that can be powered by solar or wind. We have processes that are carbon effective, so this is not really an obstacle.

Cost effectiveness is the real issue. If we want to create an industry of carbon capture, there has to be money in it. This means we need a process that can scale up to industrial scale, that will produce carbon cheaper than the value of the carbon itself. If a company can make money removing carbon from the air, then it will happen.

There are essentially two ways to value carbon – as a material resource, and as a service (the service of removing it from the atmosphere). The latter is all about counting the externalized cost of emitting carbon. Releasing carbon into the atmosphere will carry a cost to society, and it is therefore reasonable to expect the emitters to pay that cost, rather than transfer it to society in general while they make all the profit.

This is the whole idea behind carbon trading. Countries, for example, could charge companies a tax for releasing carbon, and can also give them credits for reducing carbon emissions, or (theoretically) for removing carbon. Companies that remove carbon could sell those credits to companies that emit carbon.

This is a fiat method of pricing carbon – countries, states, or cities pass laws that assign a cost to environmental carbon. Right now, for example, the current price of carbon is about $6 per tonne. Some experts argue, however, that this price will need to increase steeply if this system is going to significantly help reduce carbon emissions – up to $100 per tonne. (That price of $100 per tonne is interesting, as we will see below.)

If you are capturing carbon, however (not just not releasing it), then there is potentially also the value of the carbon itself. What the market value of such carbon is depends on what form you capture it into. One company simply sells the CO2 directly to a nearby greenhouse to grow crops.

One option is to combine the CO2 with hydrogen to make liquid fuel. The hydrogen can be split from water using either solar or wind-derived energy. This process is similar to what plants do, and in essence this would be making artificial biofuel. Why not, then, just use plants to make biofuel? Well, we are already at the point that artificial biofuel using carbon capture uses less land and water than growing biofuel crops. You can also do it in the desert, and don’t have to use arable land.

Making biofuel from captured carbon will likely be necessary as part of a carbon-neutral energy infrastructure. Some applications, like jets, will likely still need liquid fuel (rather than all-electric engines). Capturing and then releasing the same CO2 is better than releasing carbon that has been sequestered for millions of years.

The cost of this process has been around $600 per tonne, which is too expensive to be competitive in the market, even with carbon credits. But now a Canadian company, Carbon Engineering, has published a study claiming that they have gotten the process down to $100 per tonne. That is the same price some have argued carbon needs to get to in order to have a significant impact on reducing carbon emissions. And of course, the company hopes that by scaling up the process they will be able to drive down the cost per tonne.

But also – at the end of the process they have biofuel. Their plant currently makes 2000 barrels a day (a drop in the bucket – the US alone consumes about 20 million barrels of petroleum products per day). But this is just their prototype plant. They hope to build a plant with 10 times that production – build a thousand of those, and now we’re talking.

Keep in mind, these plants do not result in net carbon removal, because they would be making fuel that will be burned and the carbon released again. But it would be a low net carbon process – much better than just burning fossil fuels.

Perhaps the real future is in carbon removal to create solid carbon that will remain solid, therefore sequestering that carbon long term from the environment. This is the “artificial tree” approach. We could do this, and then just bury the solid carbon, which may be cost effective if the service of removing carbon is valued enough and the process is cheap enough. But why waste all that carbon?

Ironically, at the same time that we are ringing our hands about all the carbon we are releasing, material scientists are telling us that we are at the dawn of the age of carbon as a building material. Carbon fiber is already a common and extremely useful building material. The global price of graphite, used for batteries, lubricants, and other things (not carbon fibers, though), is about $1000 per metric ton. So if we could turn captured carbon into basic graphite, that would already be cost effective.

Meanwhile, graphene, carbon nanotubes, bucky balls, and perhaps other forms of carbon have incredible physical properties that could transform many industries. We are still sorting out how to mass produce these materials in sufficient quantities, sizes, and qualities, but there are many companies working on it and making steady progress.

What if (I am just speculating here) we could connect these two industries – carbon capture and graphene production?  We could literally make stuff out of the air.

There are many potential paths forward, but it seems obvious that we need to be thinking of global industries in terms of their net environmental effects and long-term sustainability. I don’t know what role carbon capture will play in the future, but it seems as if it will have to play some role.