Direct Air Capture of CO2: A Climate Solution with Limitations

Carbon Engineering’s direct air capture facility sucks CO2 directly from the atmospheric air. – Carbon Engineering

To maintain climate, we need to cut greenhouse gas – especially carbon – emissions down to zero. The more greenhouse gases that are released, the hotter our planet will be. If we are seeking to keep the global temperature below 1.5-2 degree Celsius, we need to find a way to reduce CO2 emissions. Direct Air Capture (DAC) is a technology which sucks CO2 out of the atmosphere by using large fans that move air through a filter to generate a pure CO2 stream. Depending on the application of the captured CO2, DAC can be either a “carbon recycling” or “carbon removal” technology. Carbon recycling refers to the process of using CO2 produced by DAC as fuel, or in other ways which will release CO2 back into the atmosphere, such as to carbonated beverages. Carbon removal requires CO2 to be stored underground or used in materials that do not allow CO2 to be released into the atmosphere, such as in cement or plastics.

DAC Carbon Recycling Case Study: Carbon Engineering

Recently, “Carbon Engineering,” a Canadian-based company leading the commercialization of direct air capture technology, have been working on Air to Fuels project, which uses renewable electricity to generate hydrogen from water, and then combines it with CO₂ captured from the atmosphere to use it as an input to produce synthetic fuels that can substitute for diesel, gasoline, or jet fuel. DAC’s cost at a commercial scale is not exactly determined yet. However, the latest estimate cost announced by Carbon Engineering is a range cost from $94 to $232 per ton for capturing CO2 and they hope to produce fuels from the Air2fuel project for less than $1.00 per litter, once it scaled up.

DAC Carbon Removal Case Study: Climeworks

Direct air capture unit along with the cooling towers of the geothermal power plant in Hellisheidi, Iceland. (Climeworks/Zev Starr-Tambor)

Swiss firm Climeworks recently launched the world’s first “commercial” direct CO2 capture plant at Hinwil, Zurich. Climeworks has been working on CO2 for carbonated drinks and renewable fuels project through the partnership with CarbFix which working on the project of dissolving CO2 into drinking water. Also, the Gebrüder Maier fruit and vegetable company uses the captured CO2 to boost the growth of cucumbers, tomatoes, and aubergines in its large greenhouses. However, the most interesting project which is designed to be a carbon removal project is happening right now! Climeworks recently launched a pilot project in Iceland which is a geothermal power plant with direct air capture technology. The facility is capturing 50 metric tons CO2 from the air each year, which is equivalent to a single U.S household or 10 Indian households. The CO2 captured in order to convert the emissions into stone. Thus, they’re making sure that CO2 doesn’t escape back into the atmosphere for the next millions of years.

Climeworks / Julia Dunlop Carbon capture from ambient air goes commercial

Pros of DAC:

  • Full-scale operations are able to absorb significant amounts of carbon, is equivalent to the annual emissions of 250,000 average cars
  • DAC system can be sited anywhere which reduce the cost of transporting CO2 to the sequestration sites
  • DAC can be scaled easily and has a relatively small land footprint in comparison to other carbon removal technologies such as Bioenergy Carbon Capture Storage (BECCS)
  • DAC system produces fuels with 100x less land use footprint and less water use than biofuels.

Cons of DAC:

  • Energy Intensive: Direct air capture is a fairly energy intensive process because the concentration of CO2 in ambient air is relatively low. Separating CO2 from the air is challenging since it takes a significant amount of energy and air to separate and concentrate CO2 in the atmosphere. Thus, large volumes of air must be processed in order to collect meaningful amounts of CO2
  • Very Expensive: Currently, it is not a financially viable option because it is very expensive. The cost of CO2 captured from the atmosphere ranges between $94 and $232 per ton according to Carbon Engineering estimate
  • Water consumption concern: One study estimates for removing 3.3 gigatons of carbon per year, DAC could expect to use around 7.925e+13 gallons of water per year (assuming current amine technology, which is what Climeworks uses). This is equivalent to 4% of the water used for crop cultivation each year. Carbon Engineering using sodium hydroxide that would use far less, but this, in turn, is a highly caustic and dangerous substance
  • Revenue Opportunities: Revenue opportunities for DAC carbon removal systems depend on carbon markets and regulations. Without high enough carbon prices, DAC systems are likely to find the largest revenue opportunities by providing CO2 for manufacturing fuels, enhanced oil recovery, greenhouses and carbonated beverages, as DAC systems can be sited anywhere.

Climeworks direct air capture plant founders Christoph Gebald and Jan Wurzbacher onsite. Climeworks / Julia Dunlop

Policy Approach:

There have been some policies that provided a shift toward greater development and deployment of carbon dioxide removal and recycling. In February 2018, the U.S budget bill passed by Congress which extends and reforms the federal Section 45Q tax credit. 45Q provides credits for businesses that use CO2 for enhanced oil recovery (EOR) and for CO2 injection into underground geologic formations. Mostly, the 45Q tax credits benefits fossil fuels industry. Based on the bill, any new fossil-fuel power plant or carbon-dioxide producing industry that commences construction before 2024 is eligible for tax credits for up to 12 years. The tax credits offered up to $35 per metric ton of carbon dioxide captured if the CO2 is put to use (pushing out oil from depleting fields is the most popular use) or up to $50 if it is simply buried in underground storage. Hence, the bill benefits fossil fuels companies at a lower cost of carbon capture and help fossil fuels companies expand oil production, and continue to build coal plants. Thus, the carbon removal companies are not willing to sequestrate carbon when there is a market for selling it. The only way to make money off sequestration is if the government is directly subsidizing it or if there is an extremely high carbon price. Currently, there is no carbon price anywhere in the world great enough to make sequestration profitable. At present, carbon is trading at a low price in the global market compared to the cost of storing it underground.

However, tax credits could make negative emission projects more financially attractive and more economically viable. Based on the incentives provided by 45Q bill, direct air capture could be a critical tool for CO2 removal since it has a countless potential for removing carbon and reuse it. Since the high cost of the technology in pilot projects has been an obstacle to a large-scale implementation, hopefully, new regulations and tax credits such as 45Q bill ease the process and lower the costs. Although the tax credit will not cover the full cost of these technologies, it will make a noticeable reduction in the operating cost.

Tax credits and regulations mean greater opportunities for developers and suggest positive movement in wider efforts to stem climate change, as carbon capture and storage is widely considered to be a significant element of addressing climate change. Recently, several private investors and fossil fuels companies have started investments in DAC technology. Especially, the oil and coal industry since the captured CO2 can be used for Enhanced Oil Recovery (EOR). However, utilizing DAC technology to develop EOR would neutralize any efforts regarding climate mitigation actions.

Direct air capture could hold the promise of capturing CO2 from the atmosphere. However, since there is an economic benefit of using CO2 to make fuels or for enhanced oil recovery, fossil fuels industry are making money off the technology. In a time that there is relatively little carbon budget left to keep the world temperature below 1.5C or 2C, nations need to focus on cutting CO2 emissions rapidly by shifting their reliance away from fossil fuels to the renewable energy, in particular.

Leading DAC Projects in the World:

  1. Carbon Engineering is pursuing a liquid potassium hydroxide based system, which they will use to enable the production of ultra-low carbon fuels. They have a pilot plant in Squamish, British Columbia and the company has started capturing CO2 since 2015. The company is funded by several government agencies and private investors including Bill Gates founder of Microsoft and Murray Edwards oil sands financier. Bill Gates has given about $4.6 million of his money to the Carbon Engineering for geoengineering research.
  2. Climeworks, based in Zurich, Switzerland, is employing a novel sorbent coupled with a temperature swing to release the captured CO2. Climeworks has secured a commercial partnership for CO2 recycling with Audi and Sunfire.
  3. Global Thermostat is pursuing a DAC technology based on proprietary amine sorbents with a temperature swing for regeneration. Global Thermostat has partnered with NRG Energy and Linde, and has a pilot plant up and running in Menlo Park, CA.
  4. Infinitree is using a humidity swing process for concentrating CO2. They are targeting the greenhouse market for initial customers. This technology is based on the DAC system developed by now-bankrupt Kilimanjaro Energy.
  5. Skytree is a direct air capture company that focuses on the CO2 capture for the consumer market, producing small-scale prototypes that source CO2 for aquariums, greenhouses, local air purification, and water treatment.
  6. Center for Negative Carbon Emissions: is based in Arizona and is an academic group headed by Professor Klaus Lackner and is developing a DAC technology based on a humidity swing process.