Two viable technologies to extract carbon dioxide from the atmosphere have been evaluated as part of an international research effort led by the National Renewable Energy Laboratory (NREL).
Direct air carbon capture and sequestration (DAC), which is still in its early phases of development, is seen as essential to attaining a net-zero economy for greenhouse gas emissions by 2050 and keeping global warming to less than 1.5 degrees Celsius by 2100.
Despite playing such a significant role, DAC technologies have not yet been evaluated in the context of a dynamic, forward-looking system. For this reason, researchers from NREL, the Netherlands, Germany, and Switzerland as well as from Pennsylvania and California offered a dynamic life-cycle evaluation of two promising DAC technologies to remove carbon dioxide from the atmosphere and store it in geological storage locations.
The paper, which is published in the journal Nature Communications, offers a preliminary assessment of the environmental trade-offs associated with the technologies over a long-term planning horizon.
“If we don’t push hard for additional removal of carbon dioxide from the atmosphere,” said Patrick Lamers, a senior researcher in NREL‘s Strategic Energy Analysis Center and corresponding author of the new paper, “Environmental trade-offs of direct air capture technologies in climate change mitigation toward 2100. We will not hit our carbon-neutral targets by midcentury or our climate targets by the end of the century.”
During his internship at NREL the previous year, he had started this work and oversaw Yang Qiu, a Ph.D. student at the University of California, Santa Barbara, who was another important contributor.
A novel computer model that places the DAC technologies in the context of climate change mitigation scenarios created by Integrated Assessment Models was used to evaluate them. The Intergovernmental Panel on Climate Change of the United Nations makes extensive use of these in its projections.
In this instance, the scenarios are in line with the climate goals of the Paris Agreement and were developed by academics at Utrecht University in the Netherlands, where Lamers received his doctorate.
The environmental performance of DAC was evaluated by the researchers in the context of three situations. The strictest demanded that efforts be made to mitigate climate change in accordance with the Biden administration’s present targets of decarbonizing the domestic electricity sector by 2035, reaching a decarbonized economy by 2050, and adhering to the Paris Agreement through 2100. These scenarios predict that DAC deployment in the US will begin around 2050.
The Two DAC’sUnder Investigation Are:
Solvent-based: Calcium hydroxide and a chemical solution react to produce potassium carbonate, which subsequently reacts with carbon dioxide to produce calcium carbonate. To release the carbon dioxide for further storage, the calcium carbonate is collected, dried, and heated to temperatures of roughly 900 degrees Celsius.
Carbon dioxide bonds to a silica component of an air contactor using a sorbent-based process. The silica component is heated with steam at a temperature of about 100 degrees Celsius to release the carbon dioxide, which is subsequently cooled and has extra moisture removed.
In both systems, the carbon dioxide will undergo more compression before being transported by pipeline to a storage location, where it will undergo additional compression before being injected into a geological reservoir through wells 1.8 miles below the surface. Facilities in Canada (using the solvent approach) and Iceland are currently running pilot plants testing both technologies (using the sorbent method).
The analysis is not intended to endorse any particular technology; rather, it is intended to help direct policy discussions and help establish priorities for R&D on emerging technologies that support long-term decarbonization goals. The framework can assist in determining which technological and system elements tend to drive the results rather than identifying winners or losers.
The scientists pointed out that the use of DAC can aid in long-term climate goals but advised against lowering decarbonization ambitions. They came to the conclusion that quick decarbonization is necessary to boost DAC’s ability to remove carbon dioxide and lessen the effects of climate change. In fact, the scientists stressed that simultaneous progress in DAC technology and the decarbonization of the energy sector “are crucial to avoid environmental problem-shifting.”
Reduced human toxicity or eutrophication effects of the technologies are supported by a clean energy system. Yet, to keep the levels of ecotoxicity and metal depletion per tonne of carbon dioxide sequestered via DAC from rising over time, additional technological and material efficiency advancements for zero-emissions energy technologies, including solar and wind, are required.
According to Lamers, this life-cycle evaluation approach offers a better understanding of the effects of certain decisions.
In a complicated and interconnected system, it enables you to analyze prospectively the effects of particular acts and inactions, according to Lamers. “In order to prevent potential future, unexpected repercussions, we need to examine the feedback effects that the large-scale deployment of new technology is likely to have on the system. Our research demonstrates environmental performance enhancements for measures like human toxicity in a changing energy system and highlights the benefits of various direct air capture methods for net carbon dioxide removal.”
According to Lamers, he saw several measures like ecotoxicity and metal depletion rise over time.
But this is not the technology’s fault, he continued. “This is a result of considering decarbonization of our energy system to be a universal problem. So, if you pay close attention, our work really emphasizes the significance of the circular economy of energy materials and how it serves as a foundation for an energy system that is truly sustainable in the future and heavily reliant on clean, renewable energy sources.”
The internal Laboratory Directed Research and Development program financed the NREL scientists’ efforts.
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