Direct Air Capture - Is it Full of Air?
Direct air capture (DAC), the process of extracting CO2 from atmospheric air, has gained increasing attention in the climate space. This includes strong support from the Inflation Reduction Act, and for good reason. DAC offers carbon offsetting as a decarbonisation lever for hard to abate industries and provides value through chemical utilisation or the sale of carbon credits.
In this article, we won’t delve too deeply into specific technologies or use cases – these are well reported elsewhere. Instead, we’ll briefly summarise the technology and then speak to the energetic cost of implementation and scale of impact by assessing a current example.
What is DAC?
DAC synthetically removes CO2 from the air around us. It benefits from a direct and easily measurable drawdown of carbon.
Other approaches to carbon removal, including enhanced weathering, soil modification, and ocean modification, all show promise in their ability to capture carbon but fall short in the verification of how much carbon is stored and how long it is stored for. Usually, this is referred to as MRV - Measurement, Reporting, Verification. Thus, other methods face challenges in accuracy and robustness, with a typically high sensitivity to local geography and climate trends. We won’t discuss these in any more detail here, but they are key considerations for the respective technologies.
Unlike the competition, DAC relies on a direct physical or chemical interaction in a controlled environment between a compound and atmospheric CO2 to achieve capture. Here, measurement is straightforward and repeatable. Once CO2 is captured, heat, pressure, moisture, or a combination of the above are applied to the compound to release pure CO2 and prepare (regenerate) the compound for its next cycle. This regeneration and the energy required to power the contactor fans to blow air over the compound describe the key energy demands of the process.
The Cost of DAC - A Case Study
DAC is expensive. Not just in terms of money to set up, build, and run a plant, but in terms of the sheer energy it takes to remove carbon out of the atmosphere.
Current DAC projects include the DAC 1 megaton plant, using Carbon Engineering’s solvent technology, which is targeting 1 MtCO2/year capacity commencing from 2024. Their reported cost of capture stands at 1824.3 kWh/tCO2. For context, this figure is 30% of an average NSW household’s annual energy consumption, per ton of captured carbon.
In comparing DAC plants, we must be careful around the lifecycle of a plant. Plants that run off non-renewables reduce their impact significantly and can even become net emitters. ~80% of the DAC 1 plant uses natural gas to heat and regenerate the solvent. We've converted that into a kWh consumption, so our number is for comparison rather than technical correctness. Should the project become fully green, this heat would be electrified or at least stem from renewable natural gas, making this electrification analogy more sensible.
At its full scale, the DAC 1 plant will draw 1.824 TWh of energy per year to take 1 megaton of CO2 out of the atmosphere. This is roughly 1.5 times the electrical energy demands of a large industrial player, BlueScope steel, who produce 3 megatons of steel annually compared to 1 megaton of carbon dioxide for DAC 1. Every tonne of steel on average produces 1.89 tonnes of CO2. So, BlueScope's emissions from its annual steel production are roughly 5.7 megatons of CO2.
So, DAC 1 would use more energy than BlueScope to capture less than one fifth of BlueScope's emissions.
It’s clear the energy demands are high, and we haven’t even discussed the transportation or sequestration costs. It is foreseeable to double these figures after gas compression and geological preparation are considered which further compounds the energy requirement problem.
Contextualising the impact of the plant in the bigger climate picture, at the megaton size, DAC 1 will offset just 0.0027% of global emissions using 2022 data. Its impact is tiny, needing ~37,500 other DAC 1 projects to capture the globe’s yearly emissions. Current DAC is no “Band-Aid” solution to the climate crisis. Relative energy costs are great, which emphasises the need for emission reduction across all industries. We need to kerb our existing outflux of CO2 so that DAC and other complementary technologies can be effective in cleaning up existing emissions.
The Future of DAC
However, the space is constantly changing. Carbon Engineering’s solvent was first proposed in 2009 and since then many new technologies come to light. Exciting advances in the sorbent space using moisture swing, metal organic frameworks, and high surface area zeolites show promise with lab tests reporting cost of capture as low as 100kWh/tCO2, a 94.5% reduction over the original DAC 1 solvent.
As with all nascent technologies, the science and industry to scale them is developing and so deployment of these technologies will take time. Ultimately, excitement (investment) in the space will bring down the cost of capture sparking the creation of new technologies, and with scale have real impact.
Key questions for the future include: how we develop infrastructure with existing DAC technology whilst remaining flexible on new, technologies, how we will utilise the captured carbon and, if it is stored, how we value the high quality credits sold in otherwise murky carbon crediting marketplace.
At Twynam, we are cautiously excited about the technology and always have an ear to the ground on the industry. After all, if the world became net-zero tomorrow, the world has already warmed by around 1ºC. Find out more about our investment focuses here.