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Do we need direct air capture?

Dawid Hanak's picture
Senior Lecturer in Energy and Process Engineering Cranfield University

I'm a climate warrior who believes that achieving our climate commitments requires immediate action. We can do this by deploying green energy technologies and building world-leading engineering...

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  • Sep 17, 2021 3:41 pm GMT
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A lot of interesting things happened when I was away from LinkedIn.

But the one that makes me excited is the launch of the world's largest direct air capture facility by Climeworks and Carbfix.

The Orca plant will capture 4000 tons of CO2 per year and fix it permanently in the form of stable carbonate materials.

To give you perspective, this is equivalent to planting 400000 trees that, on average, remove 10 kg of CO2 per year each.

There is still work to do to reduce the energy requirement, footprint and cost of DAC.

But we need to realise that DAC IS NOT the green light for further fossil fuel use - this needs to stop now.

I know many of you may disagree and believe that we don't need DAC at all - I was sceptical about this tech too a couple of years ago.

But now, I can see the value it can bring. In addition to environmental benefits, provided it's powered via green energy, it could be a technology that would provide net-zero carbon needed by various sectors of our economy.

Let's discuss! 👇🏼👇🏼👇🏼

#environment #sustainability #climate

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Matt Chester's picture
Matt Chester on Sep 17, 2021

I think if the tech can get there and be profitable for these companies, then there's no real downside-- the only risk becomes if we divert too many public resources (whether subsidies, R&D spending, or otherwise) to DAC at the expense of clean generation, efficiency, etc. But when the DAC companies are taking the risk and -- it looks like-- proving it works, I think we should all be paying attention for sure. 

Bob Meinetz's picture
Bob Meinetz on Sep 17, 2021

"As energy sources, we solely use renewable energy, energy-from-waste, or other waste heat. Typical energy consumption figures expected for scaled-up machines are approx. 2'000 kWh heat and approx. 650 kWh electricity per ton of carbon dioxide that is captured."

Climeworks's energy balance description creates more questions than answers:

1) What are the sources of renewable energy, and their lifetime carbon footprint?
2) What "energy-from-waste"...from landfills? From recovered plastic waste? How much energy required to recover it? The devil is in the details.
3) Does the plant shut down when renewable energy and/or waste heat isn't available?
4) So now Orca has a ton of captured carbon dioxide. How much energy is required to sequester it?

Yet another DAC technology powered by source(s) of renewable energy that relies on "expected" figures for "scaled up" machines that don't exist. I say, "Build your scaled-up machines and perform a complete lifecycle carbon analysis. Prove there isn't a net CO2 surplus, and I'll be an amazed believer. Otherwise, Climeworks has all the hallmarks of another hype factory seeking venture capital."

On the other hand - power it with nuclear energy, and we have a potential game-changer.

 

Roger Arnold's picture
Roger Arnold on Sep 18, 2021

Having steady nuclear power available would solve a lot of problems. That said, DAC is an example of a process that can probably be adapted to utilize cheap, as-available energy from intermittent renewables, without incurring an excessive penalty in capital cost.

The CO2 capture phase of the process -- the air contact and CO2 adsorption part -- is rate limited and capital intensive. It needs to operate with a high duty cycle for economic efficiency. On the other hand, it doesn't take a lot of energy. The cost of sufficient battery capacity to keep it going when VRE output is down isn't prohibitive. The energy-intensive part of the operation is sorbent regeneration and release of the captured CO2. For most CC methods, the sorbent material per se is a minor cost; it's not a big deal to provide the system with a larger reservoir of sorbent and buffer storage for holding charged sorbent until energy for regeneration becomes available.

Of course it's always better, in terms of minimizing capital cost, to have a steady and reliable supply of energy available. But for this type of operation, the somewhat higher capital cost may be economically justified by reduced operational cost from use of low-priced, as-available energy. It's a good candidate application for DR.

Jim Stack's picture
Jim Stack on Sep 20, 2021

Dawid, I agree with you. We need every clean tech we can find. Renewables are growing fast yet we need to clean the air too so we can make more progress faster. I just hope it is fast enough. 

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