Direct air carbon capture and storage (DACCS) has some advantages over other negative emissions technologies (NETs). NETs interacting with biomass, such as afforestation, soil carbon storage and bioenergy with carbon capture and storage (BECCS), require significant water and arable land. Other chemical NETs, such as enhanced weathering, risk changing the chemistry of oceans and rivers. DACCS avoids many of these limitations as it has a comparatively small land footprint, but does require a sustainable energy source, geological CO2 storage to operate and is relatively immature technology with as-yet unproven deployment potential. Furthermore, the varying levels of modularity of DACCS systems imply potential for easy scaling up and rapid deployment.

Current information on DACCS costs, performance, and impact of plant siting have several data gaps and significant uncertainties. Despite the climate relevance of DACCS technologies, current capture capacities are only at ktCO2/year levels. Therefore, literature on DACCS is limited to few desk-based models and high-level data shared by technology developers with commercial interests. Consequently, most integrated assessment models (IAMs) either omit DACCS or include it without granularity on specific configurations.

It is the aim of this study to collate and improve the current knowledge base on costs and performance of DACCS systems. For this, the study develops and carries out a high-level techno-economic analysis (TEA), assesses key global siting factors, derives recommendations for the IAM community on inclusion and representation of DACCS, and discusses the potentially required policy support mechanisms.

Key Messages

• Although DACCS is more expensive than many carbon mitigation and removal options, careful plant siting and rapid learnings can achieve significantly more competitive DACCS costs.
• First-of-a-kind (FOAK) DACCS projects are likely to range from ~$400-$700/net-tCO2, when global average solar photovoltaics (PV) costs are used, or ~$350-$550/net-tCO2, when lowest-cost renewables are used.
• Significant cost reduction can be achieved for nth-of-a-kind (NOAK) DACCS plants, reaching ~$194-$230/net-tCO2 for 1 MtCO2/year scale, driven by reduced electricity prices, cost of capital and upfront capital investment. Energy costs can be as much as 50% of long-term liquid DACCS costs. NOAK DACCS costs in the range of ~$150-$200/net-tCO2 may be achieved if very low-cost solar energy is used. Long-term costs were found to be significantly higher than the industry target of $100/tCO2 captured, except under ambitious cost-performance assumptions and favourable conditions.
• The lifecycle emissions associated with DACCS range from 7-17% of the CO2 captured for FOAK plants and 3-7% for NOAK plants (if low carbon energy is used).
• Since no large-scale plant is built to date, inherent uncertainties on most parameters are high. The largest uncertainties requiring major assumptions are on capital costs, plant scaling factors, future cost reductions through learning, and solid adsorbent cost-performance dynamic.
• To date DACCS representation in integrated assessment models (IAMs) has been relatively simplistic. Technical parameters compiled and developed throughout this study can be used for representation of DACCS technologies in future IAM studies. IAM practitioners should consider differentiating between DACCS technologies and considering multiple plant configurations. Practitioners should also take care to ensure consistent treatment of financing costs for all technologies across their models. Furthermore, operating and labour costs are likely to be region dependent and IAMs can use reference tables to estimate how these costs could differ between countries.
• Most current DACCS policy support consists of generic R,D&D funding, and financial support aimed at wider negative emissions technologies (NETs) or carbon capture and storage (CCS) technologies. The US, UK, EU, Canada and Australia are key regions with relatively developed CCS regulations and R&D and demonstration programmes targeting carbon removal or general CCS projects. The 45Q tax credits in the US and California's Low Carbon Fuel Standard (LCFS) are currently the only financial mechanisms in the world available for large-scale DACCS projects.