Overview of Leading Direct Air Capture technologies
This week we’re taking a closer look at Direct Air Capture technology — what is it, who are the global leaders in this space and the future outlook for DAC tech
What is Direct Air Capture of CO2?
As it says on the tin, direct air capture of CO2 is a technological process of capturing and separating CO2 from ambient air.
One very attractive proposition offered by DAC technologies is that they are geographically agnostic — theoretically their application is not geo-constrained to a particular location. The capture and separation technology has a relatively small footprint when compared to nature-based carbon removal solutions such as reforestation, and ongoing projects have demonstrated that DAC’s modular nature can be scaled up to meet the desired capital outlay.
Theoretically, because as of today the technology is still quite an expensive proposition requiring either subsidies or policy incentives to ensure its continued development towards lowering unit costs and long-term economic viability.
And practically speaking — its cost is today by far its largest limitation.
Direct Air Capture of CO2 can be thought of as a 2 stage process:
- Capture
- CO2 Separation
And with a third necessary step to close the circular loop — Utilisation / Storage / Sequestration of the captured CO2.
1. Capture
Capturing air for CO2 separation can be considered the “simple” part of the process.
After all, compressing ambient air using mechanical fans / compressors is a very well-established technique with various types of compressors readily available for pretty much any sensible target application pressure and operating environment.
Air for CO2 separation can also be captured from industrial flue gases (more conventional Carbon Capture technologies), and even entirely passively via natural movement of air aka wind.
But how do we go about separating CO2 from the captured air?
2. CO2 Separation
This is where things get more tricky.
Actual separation of CO2 can be done by either chemical or physical means, and the 3 basic methods which are known to be effective are:
- Chemical — using solvents / sorbents
- Physical — membrane separation
- Physical — cryogenic separation
We’ll leave the intricacies of each CO2 separation method for a separate Insight as they each have their own advantages and disadvantages with lots of ongoing research for further improvements. For the purposes of DAC, most current leading technologies use sorbents.
3. Utilisation / Storage / Sequestration
And finally, to close the loop and in order for DAC to be an effective net zero or even negative emissions tool for removing CO2 from the atmosphere, the captured gas needs to be either utilised, stored or sequestered.
This can be achieved either by purifying to an acceptable standard for industrial use (see graphic from Royal Society below), or permanent storage / sequestration in e.g. underground geological formations.
Today, by far the most dominant use of CO2 is for enhanced oil recovery which at best is helping achieve net zero CO2 emissions — though with the touted growth of the “carbon economy” [LINK] this is speculated to change over the coming years.
Leading DAC Companies
Currently there are a handful of companies involved in commercially developing DAC technologies.
Let’s take a look at each of these to see the variety of CO2 separation technologies employed, their ongoing projects, and key aspects of their business models.
A list of companies is also provided at the end.
Carbon Engineering
Overview
Carbon Engineering is one of the largest companies in the DAC space. Founded in 2009 and headquartered in British Columbia, Canada, it has been removing CO2 from the atmosphere since deploying its pilot project in 2015. It also pioneered the “Air to fuels” concept — utilising the captured CO2 to produce low-carbon synthetic fuels.
Technology
Utilises “air contractors” — fans designed to pull air into the process, which uses liquid alkali metal oxide sorbents regenerated by heat at around 800°C.
Carbon Engineering currently uses natural gas to power its machines, co-capturing CO2 from the flue gas stream of the burnt natural gas in addition to atmospheric capture (Keith et al., 2018).
Projects
DAC Pilot Plant demonstration in Squamish, BC, Canada
Operational as of 2015
Capacity = 1tCO2/day
DAC Plant in Permian Basin, USA
Planned Construction Start — 2022
Planned Operational — 2024
Capacity = upto 1M tCO2/annum
DAC Plant in UK
Announced engineering and design works start in June 2021
Funding
Estimated total funding amount = $110.4M
Cost of Capturing CO2
Carbon Engineering claims that capture costs of $94 to $232 per tonne were achievable depending on financial assumptions, energy costs and specific plant configuration.
How does the business model work?
- Carbon removal as a service allows customers to buy removal of CO2 from the atmosphere. Signed Shopify as its first customer for 10,000t.
- Using captured CO2 for Enhanced Oil Recovery — per barrel cost of DAC-EOR fuel is about 20% higher than the cost of conventional oil and it has a carbon intensity that is lower than most biofuels. Low carbon intensity fuels command a premium in carbon-constrained transportation markets such as California’s Low Carbon Fuel Standard.
Climeworks
Overview
Climeworks is another global leader in the DAC space. Founded in 2009 in Switzerland, their pilot project in Hinwil, Switzerland is in operation since 2017 and is touted as the world’s first commercial project, actively selling the captured CO2 to a greenhouse operator. Similar to Carbon Engineering, Climeworks is also involved in developing CO2 to synthetic fuel technologies.
Technology
Climeworks’ DAC design is based on an adsorption/desorption process on alkaline-functionalized adsorbents. CO2 adsorption is performed at ambient conditions and CO2 desorption is performed through a temperature-vacuum-swing (TVS) process (Wurzbacher et al., 2016). During this process, the pressure in the system is reduced and the temperature is increased to 80 to 120°C, thereby releasing the CO2. After a cooling phase, the whole process begins anew. The process results in the production of gaseous CO2 at 1 bar with a purity level of >99.8%.
Projects
DAC Pilot and Commercial plant in Hinwil, Switzerland
Operational as of 2017
Capacity = 900tCO2/annum
DAC Demo Project at Hellisheiði Power Station, Iceland
Commissioned in 2017 — status unknown
Capacity = unknown
DAC Plant “Orca” in Iceland
Announced in August 2020
Capacity = 4,000tCO2/annum
Funding
Estimated total funding amount = $138.7M
Cost of Capturing CO2
Climeworks’ Swiss pilot plant extracts CO2 at a cost between $500-$600 per tonne. Climeworks also hopes to bring down the cost to below $100 within 5–10 years.
How does the business model work?
- Selling high-purity CO2 to niche industries such as greenhouses
- Carbon removal as a service allows customers to buy removal of CO2 from the atmosphere. Known customers include Stripe, Shopify and Audi.
Global Thermostat
Overview
Global Thermostat was founded in 2006 and is headquartered in New York, USA. It has constructed 2 pilot plants since 2010 and recently extended their joint development agreement with ExxonMobil to advance their DAC technology.
It is also a company which Bloomberg reported to be rife with conflict and mismanagement. Read the article here
Technology
Global Thermostat’s DAC process uses a solid amine-based sorbent material, regenerated at around 80–100°C (Ping et al., 2018).
Projects
DAC Pilot in Menlo Park, California
Constructed in 2010 — assumed to be operational
Capacity is unknown
DAC Pilot in Huntsville, Alabama
Abandoned in 2019
Capacity is unknown
Funding
Estimated total funding amount = $unknown.
Cost of Capturing CO2
Global Thermostat estimate that their current costs are around $100 per tonne and they can get down to $50 per tonne or less at scale.
How does the business model work?
- Not sure whether it works at all. Read this.
Carbon Collect
Overview
A relatively new entrant into commercialising DAC tech, Carbon Collect takes a radically different approach than the aforementioned companies with their passive MechanicalTree concept. The company still looks to be at the conceptual stage and little specifics could be readily found in the public domain though they did recently obtain funding from the US Department of Energy to further develop their concept.
Technology
From their website: Unlike other developing Direct Air Capture technologies, MechanicalTrees require no energy for CO2 capture. Instead, just like real trees, they let the wind deliver ambient air resulting in low capture costs. This allows CO2 to be profitably sequestered in underground geological formations or recycled as an industrial gas for synthetic fuels, food, beverage, cement, agriculture and other industries.
A very interesting concept indeed.
Projects
Planned to develop three ‘carbon farms’ — announced in June 2021.
Funding
Estimated funding amount = $2.5M (award by US DoE)
Cost of Capturing CO2
Estimated to be less than $100 per tonne for pure CO2.
Concluding remarks
DAC is increasingly gaining traction as a promising technology for atmospheric carbon removal to address excessive anthropological CO2 emissions with all leading companies continuing their growth and commercialization of their tech (even Global Thermostat, despite their controversies, is claiming to be on the growth path backed by Exxon).
Economic viability of this technology is proving to be a significant challenge though all leading companies in this space are confident they can get their unit costs to below $100 per tonne of captured CO2.
The National Academies of Sciences report from 2018 estimated that direct air capture could cost as little as $18 per tonne all the way through to $1,000+ per tonne, noting that costs of $88–228/t CO2 for a generic solid sorbent direct air capture system are plausible to be reached within a decade.
As for an outlook on the role DAC can play in our future energy mix — the International Energy Agency’s Net Zero by 2050 Roadmap for the Energy Sector noted that the biggest innovation opportunities concern advanced batteries, hydrogen electrolyzers and Direct Air Capture and storage technologies. The stated projection was that CO2 from Carbon Capture and Direct Air Capture technologies will account for $15‐70/barrel of the cost of synthetic hydrocarbon fuels in 2050.
And with the US Department of Energy recently announcing the award of approx $72m to advance carbon capture technologies, with $21m going towards 18 projects for advancing Direct Air Capture technologies, specifically for the development of new materials as well as field testing, this technology is most certainly one to keep an eye on — especially when we can see from the award list new entrants coming into the market.
References
Carbon Engineering — DAC as an enabler of low-carbon fuels
Carbon Engineering — DAC Report
Institute of Physics — scaling up DAC
Bloomberg — article re: Global Thermostat
Carbon Collect funding announcement
