A smart, faster path to Zero Lifecycle Emission: advances from the EU in direct carbon capture from air

0
160
Above: a visualization of what a commercial-scale DAC plant might look like, from the Center for Carbon Removal

The Tesla Model 3 is on the way and the world is celebrating a shift towards Zero Tailpipe Emissions — but of course, with the Tesla, you’re driving the grid and the grid is still dirty.

A more powerful goal is a shift towards Zero Lifecycle Emission — that is, no net carbon at all. Using waste is the first and best path (and even can result in negative lifecycle emissions — cleaning the atmosphere as you drive) — but there are limits on residues and already we are hearing squawking from competing users of waste fats, oils and greases. As waste acquires value, others will cry boo-hoo, too.

The most scalable solution is liquid fuels that use water, captured CO2 and renewable electricity.

The New Thinking

Thinkers have been coming around to the realization that this might be the most sustainable path, notwithstanding the joys of electric vehicles. This article by B. Zhao from Energy Policy typifies that New Thinking.

Why will the dominant alternative transportation fuels be liquid fuels, not electricity or hydrogen” Energy Policy Vol108, September 2017, Pages 712-714.

And Bill Gates stated recently that a “process that uses sunlight to produce hydrogen, oxygen, and carbon” has a potential he calls “Magical. With liquids you don’t have the intermittency problem batteries. You can put the liquid into a big tank and burn it whenever you want. If we can improve the efficiency of this process, we may produce ample clean fuel for the vehicles of tomorrow.”

Solar fuels? They’ve been much thought about, and occasionally big chunks of work have been funded privately or publicly. If we can convert solar energy directly via a photovoltaic route we can make use of about ± 20% solar energy capture as the basis for liquid solar ”fuels instead of first producing biomass with ± 1-2% solar energy capture using plants. We wrote about this technological tip of the spear recently, here.

Where are we in development?

ANTECY has been working on this route since 2010, and reports now that “We have now come to the conclusion that it is technically and economically feasible, making use of electrolysis to produce hydrogen from solar (or wind, hydroelectric or geothermal) energy and converting the hydrogen produced with clean and concentrated carbon dioxide to methanol or any other (preferably) liquid hydrocarbon.

Paul O’Connor and his ANTECY team report that “economically, this route becomes feasible when the cost of renewable electricity drops to about US$ 3 cents/KwH.”

The EU is paying close attention. The European Fund for Regional development Oost Nederland (EFRO) recently awarded a €2M grant to a team led by ANTECY and including Wageningen University & Research and Bronswerk Heat Transfer. Shell Global Solutions is also supporting the project for improvement, development and demonstration of the carbon dioxide capture technology.

Let’s look at ANTECY’s work in more detail.

O’Connor reports: “The technology to do so is already available and in fact state-of-the art except for the step to economically harvest carbon dioxide (and water) directly from the air. Direct Air Capture (DAC) of carbon dioxide will be necessary as in many cases no secure carbon dioxide point sources are present or will be present in the future at the locations where the lowest cost electricity (to produce Hydrogen) is available. Furthermore it may be prudent not to rely too much on carbon dioxide point sources of fossil origin to produce zero carbon emissions fuels.”

Direct Air Capture is no small thing. The problem with CO2 concentration is that it is too high to support a cool climate, but too low to be easily Hoovered from the sky. The concentration we are worried over is 400ppm, that’s 400 parts per million. That means you have to capture 2500 tons of air for every ton of carbon dioxide — and right there, that’s the reason we have left the job of capturing carbon to plants — not industrial plants, just the garden kind.

Direct Air Capture Technology

And where are we with Direct Air Capture?

You may have read recently that Climeworks has opened its first small commercial plant near Zurich, and will capture around 900 tons of CO2 per year. A great step but a tiny one — it would take 25 million of these to capture the world’s annual CO2 emissions, the inventors say.

Limitations on the current approaches?

The existing technologies to capture carbon dioxide from gaseous streams are based on liquid or solid amines, which are sensitive to degradation particularly in the presence of oxygen. Degradation will result in a lower stability, meaning a higher consumption and therefore costs. The degradation products are toxic or even carcinogenic, leading to health and safety issues.

Antecy’s DAC technology called CAIR: ”Carbon from Air” is based on a robust non-amine inorganic solid sorbent, which has several advantages in terms of higher stability, and no environmental risks such as from potentially toxic amine degradation and emissions.

Some highlights:

• Captures and adsorbs Carbon (CO2) from air and/or CO2 rich flue gas
• Energy efficient (low ΔH)
• Desorbs CO2 at temperatures < 80oC, enabling use of low value heat ( e.g. electrolysis)
• Smart heat integration with water splitting/electrolysis (H2) and methanol/fuel synthesis
• Sorbent is stable and can be reused
• Sorbent (K2CO3, KHCO3) is environmentally friendly

The Lifecycle Edge

Let’s look at a lifecycle analysis that Antecy developed:


Note: The above table does not give the full story yet. We are still missing a full life cycle analysis for various options, including for instance the impact of battery disposal and/or recycling.

The pros and cons

With every technological advance, we have to visit the Department of the Painful Tradeoffs and Uncertain Unwanted Consequences. After all, someone thought DDTs were a good idea, and chloroflourocarbons were a solution to a refrigeration problem before they landed us in ozone hell.

On the negative side, the conversion efficiency of power (electricity) to fuel energy content is low — there is still a lot of energy lost in the conversion to fuels.

But there are some avoided negatives, too. For example, the difficulties and costs of changing to mass-scale battery electrical vehicles, the infrastructure cost. Plus, batteries have inefficiency problems too. It has been claimed elsewhere — and Michael Tamor, a Henry Ford Technical Fellow at Ford, ruminated on this topic at the recent DOE Bioeconomy event in Washington — that at least double the electrical power capacity will be required to be able to charge all battery electrical vehicles. Also the recycling of batteries and its LCA effects remains an issue.

In the end, here’s the great advantage, and it’s infrastructure. With batteries, you have to rebuild the fleet, rebuild the energy delivery system, and rebuild the grid. Fail in any of those and you’ve failed to change the carbon picture. Each of them is massive — together, it’s the biggest industrial transformation ever attempted.

With liquid fuels, you have just the one transition, and that’s the replacement of the energy supply, so long as drop-ins are used. And there’s gradualism — there’s a transition to better energy supply today — and possibly to fuel cells down the line where you get electric motor efficiencies added to the mix.

The Bottom Line

Though ANTECY is “cooperating with specific potential customers with as goal a first semi-commercial industrial demonstration of ANTECY’s CAIR technology,” it remains early days.

But let’s be encouraged by this. Any system that is going to make direct air capture economically viable, first, is going to be producing a valuable product — and liquid fuels and chemicals are excellent candidates. Nature puts a premium on liquid storage — try living without water for a while, in case you wonder how valuable it is — and those dense liquid fuels are a worthy goal.