Issue 9, 2024

Environmental process optimisation of an adsorption-based direct air carbon capture and storage system

Abstract

Adsorption-based direct air carbon capture and storage (DACCS) removes CO2 from the atmosphere, thus helping to limit anthropogenic climate change below 2 °C when employed on a large scale. However, DACCS is energy- and cost-intense. To reduce DACCS's energy demand and costs, a major focus in research is process optimisation. The optimisation task requires sound key performance indicators (KPIs) as objectives that should reflect the purpose of DACCS, i.e., to provide net negative CO2 emissions via carbon dioxide removal. Currently used KPIs for process optimisation are the specific energy demand, the specific exergy demand, or the equivalent shaft work. However, these energy-related KPIs neglect life-cycle greenhouse gas (GHG) emissions from DACCS, caused for example, by energy consumption or plant construction. Neglecting these GHG emissions can lead to suboptimal processes in the sense of not realising the full carbon removal potential of DACCS. Therefore, we extended a detailed dynamic DACCS model to cover all life-cycle GHG emissions, enabling us to employ the climate-benefit metrics carbon removal efficiency (CRE) and carbon removal rate (CRR) as KPIs for in-depth process analyses and process optimisation. We assessed how using different KPIs for process optimisation affects the carbon removal potential of DACCS. For this purpose, we used the extended DACCS model and optimised the process for different KPIs and plant productivity, which resulted in Pareto frontiers. We found that using CRE as KPI instead of specific energy demand increased CRE by up to 4% at the same plant productivity. More importantly, at the same CRE, the plant productivity can be significantly increased when using CRE as a KPI. In addition, we demonstrated that expanding a detailed DACCS process model with life-cycle GHG emissions and the associated provision of the climate-benefit metrics CRE and CRR as KPIs provides new insights that improve our knowledge about optimal DACCS process designs. Overall, we showed that choosing a climate-benefit metric as KPI for process optimisation is imperative for realising the full carbon removal potential of DACCS.

Graphical abstract: Environmental process optimisation of an adsorption-based direct air carbon capture and storage system

Supplementary files

Article information

Article type
Paper
Submitted
05 сен 2023
Accepted
07 мар 2024
First published
08 мар 2024
This article is Open Access
Creative Commons BY license

Energy Environ. Sci., 2024,17, 3004-3020

Environmental process optimisation of an adsorption-based direct air carbon capture and storage system

P. Postweiler, M. Engelpracht, D. Rezo, A. Gibelhaus and N. von der Assen, Energy Environ. Sci., 2024, 17, 3004 DOI: 10.1039/D3EE02970K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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