Which Carbon XPrize Finalist's Idea Do You Think is the Best?

The Carbon XPrize is a $20 million prize that hopes to incentivize the development of technologies that utilize carbon dioxide, in particular concepts that convert coal or natural gas power plant emissions into valuable products. While only a handful of teams will win prizes and only two will win $7.5 million grand prizes, dozens will advance cutting edge ideas with the potential to change the world and help us avert a climate catastrophe while minimizing the economic cost of doing so.

Finalists were recently chosen and I want to know who you think has the most promising idea! I've included summaries below, but I encourage you to follow the links and check out their videos!

C2NT
C2CNT is a team from George Washington University that is using CO₂ to create carbon nanotubes. Nanotubes are definitely valuable and have numerous potential uses in nanoelectronics, energy storage, and many other fields given their many unique properties that include conductivity, flexibility, and incredible strength. I worked in a lab that used carbon nanotubes for water treatment, and I can tell you they are expensive. Luckily, C2CNT says they are "rapidly scaling-up our new chemistry which directly converts CO₂ at high rate to carbon nanotubes using low cost materials".
https://carbon.xprize.org/teams/c2cnt
http://www.c2cnt.com/

C4X
C4X is based in Suzhou, China. I'm not positive based on the description, but I assume they are working on wood-plastic composites that utilize super critcal CO₂. My understanding is that such composites may have benefits in terms of durability and resistance to the elements.
https://carbon.xprize.org/teams/c4x

Carbicrete
I've been a big fan of less-carbon intensive concrete technologies for a few years now and not to bias the voting here, but I think in general carbon neutral or carbon negative concretes will play a huge role in decreasing our society's carbon intensity. Carbicrete has devised a way to make concrete without using cement and WITH not one, but TWO waste products! They replace cement in the mix with steel slag, which is an industrial waste. Their concrete is then cured with CO₂, which is permanently sequestered within the construction product.
https://carbon.xprize.org/teams/carbicrete
http://carbicrete.com/

Carbon Upcycling Technologies
Carbon Upcycling Technologies is based out of Calgary, Canada. CUT "utilizes CO₂ emissions to cultivate nanoparticles that enhance materials like concrete, plastics, and batteries". They claim one of their products, Nano-fly Ash (NFA) can increase the strength of conventional concrete by over 30%.
https://carbon.xprize.org/teams/carbon-upcycling-technologies
http://www.carbonupcycling.com/

Carbon Upcycling UCLA
Another Carbon Upcycling team here, but based out of UCLA in California. Like Carbicrete they are also looking into less carbon intensive concrete and they also have a clever name for it: CO₂NCRETE™ . CO₂ from flue gas "is embedded in a building material, “CO₂NCRETE™.” Lego®-like building components formed of CO₂NCRETE™ offer higher structural efficiency and flexibility in construction and accelerate onsite assembly; thereby lowering project periods and labor costs. CO₂NCRETE™ has a CO₂ footprint that is approximately 50% lower than that of traditional concrete; an industry responsible for nearly 9% of CO₂ emissions globally".
https://carbon.xprize.org/teams/carbon-upcycling-ucla
http://www.co2upcycling.com/

Newlight Technologies
Newlight Technologies from Huntington Beach, California "has developed a carbon capture technology that converts greenhouse gas into a bioplastic material called AirCarbon. AirCarbon is made by pulling carbon out of greenhouse gas and using that carbon to build sustainable materials that replace oil-based plastics."
https://carbon.xprize.org/teams/newlight
http://newlight.com/

Breath
Breath from Bangalore, India has an interesting idea that doesn't sound like it is quite as far along as some of the ones discussed above. Since it is a bit over my head, I'll paste in their description. They "propose a new strategy to design promising materials for the efficient and selective conversion of CO₂ into methanol. Using combined information obtained from experiments and first-principles calculations on alloys/intermetallic/bimetallics/core-shell materials based on low cost Cu, Ni, Fe catalysts, we will identify descriptors of catalytic activity using machine-learning algorithms".
https://carbon.xprize.org/teams/breathe
http://breathesciences.com/

Cert
Cert is a multidisciplinary team of over 15 researchers based at the University of Toronto in Canada. Pretty heavy stuff here so another paste job is in order: "Our system provides the electrocatalytic conversion of CO₂ into value added fuels and feedstocks using novel, high efficiency catalysts. Advances in catalyst design and performance have been achieved both for the anodic oxygen evolution reaction (OER) and the cathodic CO₂ reduction reaction (CO2RR) using nanostructured materials. Our water splitting anode catalyst is made from cheap and common abundant earth metals in an easy scalable synthetic way. Our CO₂ conversion catalyst is based on nanostructured metals synthesized using advanced materials processing techniques".
https://carbon.xprize.org/teams/cert
https://co2cert.com/

Carbon Cure
Carbon Cure is another team from Canada and another one looking into concrete and cement, however they sound pretty far along and have the interesting benefit of being able to retrofit existing operations. "The retrofit process uses the existing concrete production equipment and Portland cement chemistry to react with CO₂ emissions to produce an in-situ nano sized mineral carbonate embedded within the concrete. The nano material enhance the material properties and economics of concrete manufacturing without impacting the normal plant operations or supply chain".
https://carbon.xprize.org/teams/carbon-cure
http://info.carboncure.com/xprize-team

Carbon Capture Machine
This team straight outta Scotland has developed "processes and products that yield high economic value, by (i) replacing other carbon intensive materials and products, and (ii) creating greater value by converting “wastes” into useful products".

They dissolve "CO₂ flue gas directly into slightly alkaline water, that is then faced with a suitable brine source containing dissolved Ca and Mg (and other) ions as found in connate formation, produced, and other abundantly available waters. A proprietary multi-stage precipitation technology is used to selectively separate and produce nearly insoluble Ca and Mg carbonate minerals that have useful properties, and hence commercial value in existing established and new markets".
https://carbon.xprize.org/teams/carbon-capture-machine

Let me know in the comments below which idea is your favorite! Which will work and which has no chance? Why?

Note: I'm very interested in this competition and have worked in related fields. Check out my older articles to learn more about my work on using algae to treat wastewater and create biofuels and my research with Project Drawdown on the top 100 climate solutions.

If you want to learn more, Project Drawdown discusses some of these concepts (and closely related ones), including:
Direct Air Capture
Alternative Cement
Bioplastic