# Demonstration of the DMX™ technology for carbon capture and storage in steel production: An environmental assessment

David Yang Shu, Leidy-Tatiana Vargas-Ibáñez, Guillaume Batôt, Fabrice Devaux, Vania Santos Moreau, Ludger Leenders, André Bardow

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## To cite this version:

David Yang Shu, Leidy-Tatiana Vargas-Ibáñez, Guillaume Batôt, Fabrice Devaux, Vania Santos Moreau, et al.. Demonstration of the DMX™ technology for carbon capture and storage in steel production: An environmental assessment. International Journal of Greenhouse Gas Control, 2025, 146, pp.104396. 10.1016/j.ijggc.2025.104396. hal-05131103

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Submitted on 26 Jun 2025

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# Demonstration of the DMX™ technology for carbon capture and storage in steel production: An environmental assessment

David Yang Shu<sup>a, ID</sup>, Leidy-Tatiana Vargas-Ibáñez<sup>b, ID</sup>, Guillaume Batôt<sup>b</sup>, Fabrice Devaux<sup>c</sup>, Vania Santos Moreau<sup>b</sup>, Ludger Leenders<sup>a, ID</sup>, André Bardow<sup>a, ID, *</sup>

## ARTICLE INFO

### Keywords:

Life-cycle assessment (LCA)

Environmental impact

Carbon capture and storage (CCS)

Steel industry

Hard-to-abate emissions

Carbon management

## ABSTRACT

Post-combustion carbon capture and storage (CCS) can be retrofitted to existing industrial plants to reduce CO₂ emissions. However, implementing CCS requires the construction and operation of additional process equipment, transport infrastructure, and geological storage facilities. The environmental impacts of the additional industrial infrastructure and its operation can be quantified using the life-cycle assessment methodology. However, life-cycle assessments often rely on generic CCS supply chain models or proxies due to a lack of data. This study evaluates the environmental impact of a megatonne-scale CCS supply chain applied to the blast furnace gas of a steel plant based on detailed data generated in the DMX™ Demonstration in Dunkirk project. In particular, a CCS supply chain is investigated that uses the DMX™ technology, a second-generation amine-based post-combustion CCS technology. Our assessment indicates high life-cycle CCS efficiencies of the supply chain under a wide range of scenarios, with life-cycle emissions below 100 kg of CO₂-eq. per tonne of CO₂ captured and stored. This efficiency results from the local energy supply's low greenhouse-gas-intensity and efficient offshore transport. Compared to primary steel production, non-climate-related impacts of the CCS supply chain are small, except for ionizing radiation, water scarcity, resource use of energy carriers, and ozone depletion, where impacts could be reduced with renewable electricity. While CCS can substantially reduce greenhouse gas emissions in steel production already today, we show that CCS is insufficient to achieve net-zero emission steel. Given high costs and supply chain complexity, CCS must be integrated into broader decarbonization strategies to avoid stranded assets.

## 1. Introduction

Limiting climate change to below 1.5 °C temperature rise requires net-zero greenhouse gas (GHG) emissions across all sectors by 2050 (Intergovernmental Panel on Climate Change, 2022). However, attaining net-zero GHG emissions is challenging, particularly in industry with process emissions. For example, in primary steel production, CO₂ is formed as a byproduct of iron oxide reduction. Such process-inherent GHG emissions are either unavoidable or extremely costly to eliminate (Davis et al., 2018). To reduce such emissions, carbon capture and storage (CCS) technologies can separate CO₂ from exhaust gases for permanent storage to reduce CO₂ emissions to the atmosphere (Davis et al., 2018).

However, CCS technologies require resources and energy, thus impacting the environment. The environmental trade-offs between GHG

emission reduction and the impacts of additional resource and energy use need to be considered in the development of large-scale carbon management strategies. To do so, environmental impact categories beyond climate change must be considered to reveal potential burden shifting, where mitigating one environmental impact inadvertently exacerbates others.

Life-cycle assessment (LCA) (International Organization for Standardization, 2006a,b) is a standardized methodology that allows to assess impacts beyond climate change and identify burden shifting (Helleweg and Milà i Canals, 2014). Applied to CCS supply chains, the LCA methodology allows to quantify GHG emissions and environmental impacts over the entire life-cycle, including raw material extraction, production, use, and end-of-life (International Organization for Standardization, 2006a).

<footnote><sup>a</sup> Energy and Process Systems Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland</footnote>

<footnote><sup>b</sup> IFP Energies nouvelles, Rueil-Malmaison 92852, France</footnote>

<footnote><sup>c</sup> TotalEnergies Onetech, Courbevoie 92400, France</footnote>

<footnote>* Corresponding author.
E-mail address: abardow@ethz.ch (A. Bardow).</footnote>
<table><thead><tr><th colspan="4">Abbreviations</th></tr></thead><tbody><tr><td>3D</td><td>DMX™ Demonstration in Dunkirk project</td><td>BFG</td><td>Blast furnace gas</td></tr><tr><td>CCS</td><td>Carbon capture and storage</td><td>GHG</td><td>Greenhouse gas</td></tr><tr><td>LCA</td><td>Life-cycle assessment</td><td></td><td></td></tr></tbody></table>

LCAs have been conducted for modeled CCS supply chains applied to fossil-based power generation using post-combustion, pre-combustion, and oxyfuel configurations (Koornneef et al., 2012; Corsten et al., 2013; Cuéllar-Franca and Azapagic, 2015; Zapp et al., 2012; Li et al., 2019; Wang et al., 2022). The LCA studies find that CCS reduces *climate change* impacts of fossil power generation by 47% to 97% compared to scenarios without CCS. Thus, substantial unabated life-cycle GHG emissions can remain despite CCS, primarily caused by fuel supply and direct emissions of the power plant. Furthermore, environmental impacts increase in categories other than *climate change* in most studies, as CCS requires additional solvents, infrastructure building materials, waste treatment, and energy (Seiler et al., 2025).

LCAs have also been conducted for applications of CCS in industry where emissions cannot easily be reduced with current technologies. For example, Chisalita et al. (2019) analyze the environmental impacts of post-combustion carbon capture in steel production. Similarly, cement production with post-combustion capture has been studied (Volkart et al., 2013; García-Gusano et al., 2015; Schakel et al., 2018), as well as cement production with oxyfuel capture focusing on negative emissions (Cavalett et al., 2022). The studies indicate that while CCS reduces *climate change* impacts in industrial applications, the degree of reduction depends on the energy supply: Reliance on fossil fuels, such as coal, in these industrial applications leads to higher direct and indirect GHG emissions, thereby diminishing the benefits of CCS.

Existing LCAs typically rely on data from generic simulations, reference plants, and proxies, since primary data from operational plants or demonstrators is limited. Relying on generic data can provide insights into critical supply chain steps but limits the accuracy of existing LCA studies. The recent increase in the development of CCS projects (Global Carbon Capture and Storage Institute Ltd, 2023) presents an opportunity to gather primary data to enhance our understanding of the environmental impacts of CCS technologies.

In this study, we assess the life-cycle environmental impacts of a CCS supply chain based on detailed data generated within a demonstrator project. The CCS supply chain is based on the DMX™ technology (Raynal et al., 2011) and applied to primary steel production in Northern France. We quantify the life-cycle CCS efficiency and environmental impacts of the CCS supply chain based on material and energy demands from the engineering studies produced in the demonstrator project.

In Section 2, we outline the CCS supply chain investigated in the demonstrator project, before we introduce the life-cycle assessment methodology in Section 3. The results of the LCA are presented and discussed in Section 4. We also provide insights into the potential of CCS to contribute to *climate change* impact reduction in steel production in Section 5, before we conclude in Section 6.

## 2. A carbon capture, transport, and storage supply chain for primary steel production

Today, steel is produced via four major production routes (Remus, 2013): (1) the blast furnace and basic oxygen furnace, (2) the electric arc furnace, (3) smelting reduction, and (4) direct reduction. Here, we consider CCS for the blast-furnace and basic-oxygen-furnace route, which represented 71% of global steel production in 2021 (World Steel Association, 2022).

The implementation of the blast-furnace and basic-oxygen-furnace route varies across individual steel plants. Typically, sinter or iron oxide pellets are reduced in a blast furnace to produce liquid iron using coke as the reduction agent. The coke is produced via dry distillation in coke ovens. In the blast furnace, quicklime is added to remove impurities by forming slag. For the reduction process in the blast furnace, oxygen is provided by a hot blast of air. The air is injected at the bottom of the blast furnace in counter-flow to the iron oxides, coke, and quicklime added from the top. The air reacts with the coke in the blast furnace, forming carbon monoxide and hydrogen to reduce iron oxide. The airflow, enriched with CO₂, carbon monoxide, hydrogen, and other trace gases exits the blast furnace as blast-furnace gas. The liquid iron, tapped at the bottom of the blast furnace, is separated from slag and undergoes further processing in a basic-oxygen furnace to produce steel (Remus, 2013).

Various strategies are proposed to reduce the *climate change* impact of steel production (Fennell et al., 2022; Fan and Friedmann, 2021), such as:

* energy efficiency and modernization measures,

* direct reduction of iron using methane or hydrogen,

* using biomass as a reduction agent,

* increasing recycling rate with electric arc furnace,

* carbon capture and storage for steel mill gases.

The viability of these approaches depends on geographic, economic, and infrastructural factors (Fan and Friedmann, 2021), suggesting a need for diverse strategies to produce steel with net-zero *climate change* impact.

The blast-furnace and basic-oxygen-furnace route has multiple CO₂ sources, including the blast furnace, the sinter plant, the coke plant, the lime kiln, and the strip mill (Leeson et al., 2017). The blast furnace is the largest CO₂ point-source emitter in primary steel plants with a CO₂ concentration around 25 vol.-% (Leeson et al., 2017). The CO₂ in the blast-furnace gas is a byproduct of the iron-oxide reduction with carbon, making the CO₂ process-intrinsic and difficult to mitigate without scalable, affordable non-fossil reduction agents. Biomass faces limitations in availability, and hydrogen faces retrofit barriers in blast furnaces (Fan and Friedmann, 2021). While hydrogen-based direct reduction could eventually replace blast furnaces, the technology requires an overhaul of the existing steel production infrastructure (Fan and Friedmann, 2021). Therefore, CCS studies at steel plants typically focus on blast-furnace gas (Leeson et al., 2019). This study examines CO₂ capture from blast-furnace gas in the 3D project (Hamidian et al., 2021) using the DMX™-process, which applies a phase-separating solvent to reduce the energy demand of CO₂ capture compared to conventional processes. In the following, we outline the CCS supply chain under investigation.

### 2.1. Carbon capture process

The DMX™ process is a second-generation amine-based carbon capture process that leverages a solvent that undergoes a liquid-liquid separation upon CO₂ absorption (Raynal et al., 2011). This separation into a CO₂-rich phase and a lean phase reduces the heat demand for regeneration compared to other amine-based carbon capture processes.
<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Process flow diagram of the DMX™ carbon capture process: The DMX™ process applies a solvent with liquid-liquid separation upon CO₂ absorption. A decanter separates the CO₂-rich phase from the lean phase to reduce the mass flow to the stripper. In this study, the carbon capture process is applied to the blast-furnace gas (BFG) of a steel plant.</figcaption></figure>

The distinct phases are separated in a decanter to reduce the mass flow to the stripper (Fig. 1) (Raynal et al., 2011). The DMX™ solvent is characterized by its non-corrosive nature and low degradation rate during operation, enabling solvent regeneration and, thus, CO₂ production under high temperatures and pressure. Previous projects have validated the solvent's properties through small-scale pilot experiments for treating flue gases of coal power plants (Raynal et al., 2014) and representative steel-mill gases (Dreillard et al., 2017).

In the 3D project, the DMX™ process is scaled up for an industrial-scale demonstration plant at the steel plant in Dunkirk. Long-term experiments under realistic conditions are conducted to evaluate the process' effectiveness. Associated engineering studies explore megatonne-scale CCS supply chain for capturing and storing 1 Mt of CO₂ captured from blast furnace gas annually.

Without CCS, the blast-furnace gas is combusted in a gas turbine for power generation, releasing exhaust gases into the environment. Removing CO₂ from the blast-furnace gas before combustion reduces the CO₂ content of the exhaust gases. We assume CO₂ separation to leave the combustion process in the gas turbine unaffected as the treated blast furnace gas is mixed with a large volume of untreated blast furnace gas and natural gas, which reduces the impact of the CO₂ separation on the gas composition at the turbine inlet. In addition, blast-furnace gas is repurposed for the CCS supply chain as fuel for a makeup boiler to supplement the steam supply for solvent regeneration. This repurposing of blast furnace gas leads to a loss of power generation, requiring the steel plant to consume additional electricity from the French grid which is considered in the LCA.

The envisioned CCS supply chain extends beyond the carbon capture process, encompassing heat provision, conditioning, intermediary storage, transport, and geological storage (Fig. 2). To provide heat for solvent regeneration, waste-heat integration from the steel plant (Losnegård et al., 2021) and blast-furnace gas combustion are considered. The captured CO₂ is conditioned to meet the specifications of the geological storage site, including the removal of trace gases, such as hydrogen sulfide, carbon monoxide, and water. The conditioning also prepares the CO₂ for transport, either by ship or pipeline. Intermediary storage of cooled and liquefied CO₂ in insulated stainless steel tanks may be required depending on the transport method before the CO₂ is finally transported to the geological storage site beneath the North Sea Losnegård et al., 2021 (Fig. 2).

The subsequent subsections provide detailed descriptions of each step in the supply chain following the capture process.

## 2.2. Heat recovery and supply

Waste heat for solvent regeneration in CCS has both environmental and economic benefits. In steel production, waste heat could be used to regenerate the solvent (Losnegård et al., 2021).

For solvent regeneration, the designed DMX™ plant requires saturated steam at 180 °C and an absolute pressure of 10 bar. To meet this requirement, the demonstration project has developed technical solutions to recover heat from 4 sources in the steel plant:

* intermediate storage for the slabs in the steel mill

* sinter cooler outlet airflow at a sinter plant

* cooling system of reheat furnaces in the hot strip mill

* slag pits

A projection of the steam production from these 4 sources of waste heat based on 2018 production data indicates an average steam output of 116t⁻¹. This analysis accounts for the regular downtime of the reheat furnaces. However, the megatonne implementation of the DMX™ process is projected to require, on average, 165t⁻¹ of steam, with a plant design accommodating up to 173t⁻¹. The available waste heat thus leaves an average deficit of 30% in steam supply.

Furthermore, steam production from waste heat recovery fluctuates due to variable steel production. Steam production is estimated within the demonstration project based on historical production data to vary between 160t⁻¹ and 40t⁻¹, excluding weeks in which the reheat furnaces are offline. These projections highlight the need for a flexible design in the heat supply system to accommodate the expected supply deficit and variability. The demonstrator project proposes compensating for the waste heat deficit with a make-up boiler fueled by locally available blast-furnace gas.

The steam generated from heat recovery and the make-up boiler is dedicated solely to regenerating the DMX™ solvent. Therefore, environmental impacts arising from the construction of equipment, such as heat exchangers and piping, are fully allocated to the CCS supply chain.

## 2.3. Conditioning

The conditioning step liquefies the captured CO₂ for ship transport or pressurizes CO₂ for pipeline transport. Furthermore, the conditioning step ensures that the captured CO₂ complies with the specifications of transport and the geological storage site by removing trace gases, such as hydrogen sulfide, carbon monoxide, and water. In particular, the conditioning step aims to meet the purity requirements of the geological storage projects Northern Lights for liquid CO₂ and Porthos for compressed CO₂. Hence, the design of the conditioning plant depends on the specifications of the CO₂ stream from the DMX™ capture plant, the selected transport mode, and the geological storage site. The designs of the conditioning plant in the demonstrator project are based on process simulations of Gong et al. (2021) and Dlamini et al. (2023).

For ship transport, the purified CO₂ is compressed to a gauge pressure of 15 bar and cooled to -25.9 °C, thus achieving a liquid state. The liquid CO₂ is then temporarily stored in insulated intermediate storage units before being loaded onto ships. The CO₂ is liquefied using a 3-stage ammonia cycle in a closed-loop configuration designed for the demonstrator project (Gong et al., 2022). Hydrogen sulfide is removed using Axtrap 4142 or activated carbon. Carbon monoxide is removed in the stripper of the conditioning plant, and water is removed assuming temperature swing adsorption using molecular sieves (Siliporite NK10), which requires an additional regeneration step. The sorbent of the dehydration step is regenerated using a heated stream of return gases from the carbon monoxide stripper and storage tanks. The liquefaction plant handles both the CO₂ stream from the DMX™ process and the return gas flow during the filling of intermediate storage units and ships.

For pipeline transport, the purified CO₂ is pressurized to a supercritical state at the pipeline inlet using multi-stage compression with 6 stages. The required pressure depends on the distance to the geological storage site and on the pipeline diameter. For economic reasons, a 10 inch pipeline is selected in the demonstrator project and the required gauge pressure at the pipeline inlet is determined to be 165.5 bar for
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** System boundary of the carbon capture, transport and storage chain investigated in the life-cycle assessment. The carbon capture and storage supply chain is applied to the blast-furnace gas (BFG) of a steel plant. A reduced system boundary is used for transport and storage (system boundary transport) for ease of comparison between alternatives.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Investigated transport options for CO₂ to three geological storage locations.</figcaption></figure>

a transport distance of 300 km and 134 bar for a distance of 200 km. Similar to the liquefaction process, the CO₂ stream undergoes purification prior to pipeline transport, removing hydrogen sulfide and water. However, no additional carbon monoxide removal is necessary given that the carbon monoxide concentration already aligns with the Porthos project specifications that are considered for pipeline transport.

## 2.4. Intermediate storage and transport

Three potential locations are considered for geological storage: the Northern Lights project, a depleted natural gas field east of the United Kingdom (UK storage), and a potential CO₂ storage hub in the Netherlands (Dutch storage). The Northern Lights project stores CO₂ in saline aquifers and is chosen as the base case, since the project is advanced with construction completed (Northern Lights JV, 2024).

Multiple transport options are considered to deliver the CO₂ to the geological storage locations (Fig. 3): Ship transport delivering liquefied CO₂ is an option for all three locations. For the UK storage and the Dutch storage, pipeline transport is also considered. Pipeline transport is neglected for Northern Lights due to the excessive transport distance (>1000 km).

In the scenarios using ship transport, the CO₂ undergoes liquefaction and is stored in insulated stainless steel tanks before ship transport. Hence, an intermediate storage tank farm and port facilities are required at the steel plant.

For geological storage at Northern Lights, we consider transport to a receiving terminal via 2 slow-steaming ships of 10.8 kt capacity and a 13 kt intermediate storage tank farm as a base case. As alternatives, we consider 2 faster but smaller (7.5 kt) or a single larger vessel (20.5 kt). For the UK storage, we consider ship transport directly to the injection site with a single 10.8 kt capacity ship unloading CO₂ to an intermediate storage for floating storage injection, or two 10.8 kt capacity ships that directly inject CO₂ to the geological storage. For the Dutch storage, a smaller ship (5.4 kt) is considered to deliver CO₂ to a receiving terminal in the Netherlands. The intermediate storage tank farm size is adjusted with the ship sizes (Table 21).

In scenarios using pipeline transport, the CO₂ is directly transported to its destination after compression to a supercritical state in the conditioning step, as detailed in Section 2.3. Consequently, no intermediate storage or port facilities are required. Instead, pipeline-specific onshore and offshore infrastructure is considered.
## 2.5. Geological storage

The considered permanent geological storage of the CO₂ occurs in saline aquifers or depleted gas fields in the North Sea (Losnegård et al., 2021). The geological storage is included in the environmental assessment for the sake of completeness of the CCS supply chain. As geological storage is not part of the demonstrator project, the geological storage is modeled based on publicly available data from the Northern Lights project in saline aquifers (Equinor ASA, 2019). The model of the geological storage includes the construction of the receiving port, pipeline construction for transport to the offshore geological storage site, drilling of the offshore well, and the construction of the subsea facility. Furthermore, the electricity demand associated with the operation of the geological storage is considered. We assume a low likelihood of leakage (Benson et al., 2005) and, therefore, permanent geological storage.

# 3. Life-cycle assessment methodology

The LCA methodology is applied to assess the environmental impacts over the entire life-cycle of a megatonne-scale CCS supply chain applying the DMX™ carbon capture process to blast-furnace gas.

## 3.1. Goal and scope

The LCA evaluates the effectiveness of the CCS supply chain in reducing GHG emissions by quantifying the life-cycle GHG emissions of the supply chain. Further, the LCA identifies potential undesired side effects by comparing the environmental impacts of the CCS supply chain beyond climate change to those of primary steel production. The functional unit selected for the LCA is the permanent storage of 1 t of CO₂ separated from the blast furnace gas.

For these analyses, the LCA's system boundary encompasses the full CCS supply chain, including the DMX™ carbon capture process, heat generation, intermediate storage and transport, and geological storage (Fig. 2). The investigated system from capture to intermediary storage is located in Dunkirk, France. Transport is required for geological storage in the North Sea (see Fig. 3). The system boundary excludes the steel production process, which is unaffected by the end-of-pipe carbon capture and the heat-integration systems installed for this project.

## 3.2. Scenarios

To explore the impact of key parameters on the results, optimistic and pessimistic scenarios are defined, based on assumptions from project-internal discussions (Table 1). The optimistic and pessimistic scenarios vary in terms of energy supply, construction materials, and other parameters including solvent consumption, transport distance, equipment lifetime, and methane slip. We compare the results of the optimistic and pessimistic scenarios to the base case, where we assume transport of CO₂ via ship to the Northern Lights storage project (Section 2.4).

Due to uncertainties in the final geological storage location and transport mode, we compare various transport and storage alternatives to quantify their impact on the performance of the CCS supply chain. To simplify this analysis, the system boundary is reduced to include only the CCS supply chain downstream of the capture process, as the capture process and heat supply are identical across transport and storage alternatives (Fig. 2, system boundary transport).

## 3.3. Life-cycle inventory: Data acquisition

In this subsection, we outline the data sources for the life-cycle inventories of the CCS supply chain. Detailed inventories are provided in Appendix A.

The 3D demonstration project investigates a megatonne-scale implementation of the DMX™ carbon capture process, its heat integration with the steel plant, CO₂ conditioning, intermediate storage and transport. For all steps of the CCS supply chain except geological storage, the demonstration project provides engineering studies, forming the basis for the LCA.

The engineering studies provide designs of the megatonne-scale carbon capture process and heat integration options, considering siting and integration into the existing steel plant, detailed equipment and utility lists, flow diagrams, and datasheets. The studies result in demands for construction materials for equipment, operational utility and materials, land use, direct emissions to the environment, and waste streams.

Several tonnes of DMX™ solvent are synthesized for the demonstrator, yielding manufacturer data on the main inputs and consumables. This data is used in the LCA.

The conditioning units are designed using Aspen HYSYS V11 simulations and are tailored to alternative CO₂ transport options. These simulation models provide the inventories necessary for the LCA.

The investigation includes the design of onshore and offshore equipment for CO₂ transport. For ship transport, the onshore equipment designs include intermediate storage tanks for storing liquefied CO₂ prior to transport, an export terminal at the port, and a jetty. The designs provide master equipment lists and utility flow diagrams.

Offshore equipment designs include dedicated ships for CO₂ transport, floating injection facilities, and direct injection facilities. For the ships, the design considers a direct drive, two-stroke, high-pressure dual-fuel engine powered by liquefied natural gas (MAN B&W S35ME-C9.7). In our assessment of these ships, we consider exhaust emissions and methane slip of the engine based on recommendations by the International Maritime Organization (Faber et al., 2021; Pavlenko et al., 2020; Smith et al., 2015). However, recent measurements show that methane emissions can exceed the recommended values of the International Maritime Organization under real-world conditions. While insufficient measurements have been collected for conclusive results on the methane slip for high-pressure dual-fuel engines (Comer et al., 2024), a potential higher methane slip under real-world conditions would increase the *climate change* impact of the ship solutions studied. We consider this possibility by doubling the methane slip in our pessimistic scenario (Table 1).

In addition to ship transport, a pipeline transport alternative is designed, providing detailed inventories for the LCA. The design considers the sizing of the pipelines, the metering station, venting, valve and pigging stations, and pipeline end manifolds. Unlike ship transport of liquefied CO₂, pipeline transport requires no intermediate storage tanks, export terminal, or jetty.

The geological storage of CO₂ is outside the scope of the 3D project. Therefore, we develop an inventory for the geological storage in saline aquifers based on the Northern Lights CO₂ storage project (Equinor ASA, 2019). The inventory considers the depth of the offshore wells, construction of subsea and onshore facilities, length of the offshore pipeline, and electricity demand drawing on an impact assessment report of the Northern Lights project (Equinor ASA, 2019). For the construction of infrastructure, we use proxies from the offshore oil and gas industry provided in the ecoinvent database. We assume the same storage model for all three storage locations, except for the UK storage which lacks the receiving port and pipeline. Further, we adapt the electricity mix to the location of each geological storage.

The foreground system of the LCA is complemented by the life-cycle inventory database ecoinvent 3.10.1 (cut-off) (Wernet et al., 2016). The LCA is modeled using Brightway25 (Mutel, 2017).
<caption>**Table 1**</caption>

Assumptions in optimistic and pessimistic scenarios: Change of input parameters relative to the base case. Inventories of the base case are listed in Appendix A.

<table><caption>**Table 2**</caption><thead><tr><th></th><th>Parameters</th><th>Pessimistic</th><th>Optimistic</th></tr></thead><tbody><tr><td rowspan="4">Energy</td><td>Heat for capture</td><td>+10%</td><td>-</td></tr><tr><td>Waste heat availability</td><td>-10%</td><td>+10%</td></tr><tr><td>Electricity for capture, conditioning, Intermediate storage & transport</td><td>+10%</td><td>-</td></tr><tr><td>Impacts of French electricity mix</td><td>+10%</td><td>Onshore wind</td></tr><tr><td rowspan="3">Construction Material</td><td>Capture facility</td><td>+10%</td><td>-</td></tr><tr><td>Conditioning facility</td><td>+10%</td><td>-</td></tr><tr><td>Transport & storage facilities</td><td>+40%</td><td>-</td></tr><tr><td rowspan="4">Other</td><td>Solvent consumption</td><td>+20%</td><td>-20%</td></tr><tr><td>Transport distance</td><td>+10%</td><td>-</td></tr><tr><td>Equipment lifetime</td><td>-5 years</td><td>+5 years</td></tr><tr><td>Methane slip LNG ships</td><td>+100%</td><td>-</td></tr></tbody></table>

Impact categories defined in the Environmental Footprint 3.1 method including the level of recommendation for the impact assessment method (Andreasi Bassi et al., 2023; Fazio et al., 2018).

<table><thead><tr><th>Impact</th><th>Level of recommendation<sup>a</sup></th></tr></thead><tbody><tr><td>Climate change</td><td>I</td></tr><tr><td>Ozone depletion</td><td>I</td></tr><tr><td>Particulate matter</td><td>I</td></tr><tr><td>Ionizing radiation</td><td>II</td></tr><tr><td>Photochemical ozone formation</td><td>II</td></tr><tr><td>Acidification</td><td>II</td></tr><tr><td>Terrestrial eutrophication</td><td>II</td></tr><tr><td>Aquatic freshwater eutrophication</td><td>II</td></tr><tr><td>Aquatic marine eutrophication</td><td>II</td></tr><tr><td>Human toxicity (cancer effects)</td><td>III</td></tr><tr><td>Human toxicity (non-cancer effects)</td><td>III</td></tr><tr><td>Freshwater ecotoxicity</td><td>III</td></tr><tr><td>Land use</td><td>III</td></tr><tr><td>Water scarcity</td><td>III</td></tr><tr><td>Resource use (minerals and metals)</td><td>III</td></tr><tr><td>Resource use (energy carriers)</td><td>III</td></tr></tbody></table>

### 3.4. Life-cycle impact assessment method

The Environmental Footprint 3.1 method recommended by the European Commission is used to quantify the environmental impacts of the CCS supply chain (Andreasi Bassi et al., 2023; Fazio et al., 2018). We evaluate the default midpoint impact categories defined in Environmental Footprint 3.1 (Table 2).

In the discussion of the environmental assessment, we first focus on *climate change* impact as the primary motivation for implementing CCS. We calculate the life-cycle CCS efficiency ($\eta^{ccs}$) as the ratio of the net reduced GHG emissions and the permanently stored CO$_2$ ($m^s$). The net reduced GHG emissions are calculated as the difference between the permanently stored CO$_2$ $m^s$ and the life-cycle GHG emissions of the CCS supply chain $m^{ghg}$ (Eq. (1)).

$$ \eta^{ccs} = \frac{m^s - m^{ghg}}{m^s} \qquad (1) $$

In additional analyses, we compare the environmental impacts of the CCS supply chain to the impacts of a generic primary steel production process from the ecoinvent database based on the blast-furnace route.

### 3.5. Assumptions

We assume a 20-year lifetime for all equipment, with 8000 full-load hours per year, except for geological storage. For geological storage, a 25-year lifetime is assumed in alignment with the Northern Lights project (Equinor ASA, 2019).

As an end-of-pipe solution, we assume no impacts of the CCS supply chain on the steel production process. The study considers infrastructure for emergency relief of CO$_2$, but assumes steady-state operation of the CCS supply chain, excluding interruptions and CO$_2$ emissions through emergency relief valves.

The capture, conditioning, intermediary storage, and transport steps of the CCS supply chain are assumed to be located in France. Thus, we assume French inputs and waste treatment processes whenever possible. The geological storage processes are assumed to occur at their respective storage locations (Fig. 3). In cases of unavailable country-specific background data, we first apply European processes as proxies, followed by global processes where necessary.

The CCS supply chain requires decarbonized and deionized water for cooling, steam generation, and heat exchangers. We adjust the water and electricity supply in the inventories of decarbonized and deionized water from ecoinvent to better reflect the location of the CCS supply chain.

Waste treatment of the equipment materials is considered based on market activities from ecoinvent. Resource consumption for the dismantling of equipment is neglected.

In a perspective on net-zero steel production using CCS (Section 5), we estimate the life-cycle CCS efficiency for alternative heat sources, since waste heat is a limited resource at the steel plant. As alternative heat sources, we model high-temperature heat pumps based on Khan et al. (2020), assuming a French electricity supply and that an adequate heat source is available. Further, we consider heat generation from combined heat and power and gas boilers using ecoinvent processes (heat production, natural gas, at boiler modulating >100 kW and heat and power co-generation, natural gas, conventional power plant,

<footnote><sup>a</sup> Level of recommendation of the impact assessment method I: recommended and satisfactory; II: recommended but in need of some improvements; III: recommended, but to be applied with caution.</footnote>
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Life-cycle carbon capture, transport and storage efficiency (Eq. (1)) for the base case assuming geological storage at Northern Lights. The red bars indicate the range for the optimistic and pessimistic scenarios, varying demands for energy, construction material, and other parameters (Table 1).</figcaption></figure>

100 MW elect, respectively). In addition, we model direct air capture for comparison to the CCS supply chain at the steel production site based on temperature-vacuum-swing adsorption, assuming an engineered unit and amine on silica as sorbent material (Deutz and Bardow, 2021). For the sorbent material, we assume a ratio of silica gel and polyethyleneimine based on Madhu et al. (2021).

# 4. Life-cycle impact assessment results

In this section, the life-cycle CCS efficiency of the CCS supply chain is presented (Section 4.1), and additional environmental impact categories beyond *climate change* are discussed (Section 4.2) for the base case with geological storage of CO₂ at Northern Lights. In Section 4.3, we compare the *climate change* impact of the alternative transport and geological storage options.

## 4.1. *Life-cycle carbon capture, transport, and storage efficiency*

The base case achieves a life-cycle CCS efficiency of η<sub>CCS</sub> = 93%, meaning storing 1 t of CO₂ reduces CO₂-equivalent GHG emissions by about 930 kg (Fig. 4). More than half of the life-cycle GHG emissions or 41 kg per 1 t of CO₂ stored arise from transporting CO₂ by liquefied-natural-gas-powered ships. Other meaningful emissions result from conditioning and heat supply, contributing another 15 kg and 9 kg, respectively.

The high life-cycle CCS efficiency is due to low-impact energy supply at the specific steel production site: In the base case, we consider electricity from the French electricity grid (0.08 kg CO₂-eq/kWh over the full life-cycle). Further, we assume waste heat integration to supply two-thirds of heat demand. The remaining heat demand is met by a makeup boiler fueled by locally available blast-furnace gas. The blast furnace gas combusted in the makeup boiler is unavailable for the power plant, thus resulting in a loss of electricity generation. This loss is assumed to be compensated by the French electricity grid. To determine the loss of power generation, we assume average efficiencies of the makeup boiler and the power plant of 82% and 35%, respectively, based on the engineering studies conducted in the project.

The pessimistic and optimistic scenarios vary substantially in the energy supply (Table 1): In our pessimistic scenario, we assume substantially lower waste-heat availability and higher energy demands. Further, substantially higher consumption of construction materials and solvents, an increase in transport distances and methane slip from ships, as well as lower equipment lifetimes are assumed (Table 1), all of which increase the GHG emissions of the CCS supply chain. In contrast, in

the optimistic scenario, emissions decrease due to higher waste heat availability, wind power supply, lower solvent consumption, and higher equipment lifetime. Despite large parameter variations, the life-cycle CCS efficiency remains within a narrow range of 91% to 94% (Fig. 4). The efficiency thus remains high across a wide range of scenarios.

## 4.2. *Impact categories beyond climate change*

This section compares the environmental impacts of the CCS supply chain to the impacts of primary steel production in *climate change* and other impact categories. Our analysis is based on a modified version of the European primary steel production model from ecoinvent 3.10.1 (cut-off): To better reflect the local conditions of the French steel plant, we adopt the primary steel production process by replacing all inventory processes with their French equivalents when available. In particular, we replace the European electricity and gas supply with their French equivalents.

The annual steel production at the considered steel production site is approximately 6.8 Mt, corresponding to 15 Mt of CO₂-equivalent emissions over the life-cycle. In comparison, the CCS supply chain investigated here stores 1 Mt of CO₂ annually. Considering its life-cycle CCS efficiency (Section 4.1), the CCS supply chain reduces the *climate change* impact of steel production by about 6% in the base case. Hence, net-zero steel production requires additional strategies (Section 1), including a potential increase of the capture capacity beyond 1 Mt a⁻¹ assumed in this study (see Section 2).

To reduce *climate change* impacts by 6%, the 1 Mt a⁻¹ CCS supply chain increases impacts in all other impact categories. However, these environmental impacts increase by less than 2% compared to the primary steel production across all impact categories, with the notable exception of *ionizing radiation* (Fig. 5).

*Ionizing radiation* impact increases by 22% relative to the generic primary steel production. The substantial increase is due to the electricity demand of the capture and conditioning processes satisfied by the French electricity grid. An additional contributing factor is the repurposing of blast-furnace gas to supply heat for regeneration. This repurposing of blast-furnace gas results in a loss of electricity generation compensated by additional electricity supply from the French grid. The French electricity mix is dominated by nuclear power plants, which constitute about 70% of the mix in 2021. The French electricity supply is thus the largest contributor to *ionizing radiation*, accounting for 21.9 percentage points of the 22% increase in impact compared to steel production. Consequently, the large impact in *ionizing radiation* results from the assumed share of nuclear power in the electricity mix.
<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Life-cycle environmental impacts of the CCS supply chain compared to French primary steel production for the base case assuming geological storage at Northern Lights. The red bars indicate the range for the optimistic and pessimistic scenarios, varying demands for energy, construction material, and other parameters (Table 1). Impact categories from EF 3.1 (European Commission, 2021): climate change (CC), ozone depletion (OD), particulate matter (PM), photochemical ozone formation (PCOF), acidification (A), terrestrial eutrophication (E<sub>t</sub>), aquatic freshwater eutrophication (E<sub>fw</sub>), aquatic marine eutrophication (E<sub>m</sub>), human toxicity (cancer effects) (HT<sub>c</sub>), human toxicity (non-cancer effects) (HT<sub>nc</sub>), freshwater ecotoxicity (ET<sub>fw</sub>), land use (LU), water scarcity (W), resource use (minerals and metals) (RU<sub>mm</sub>), resource use (energy carriers) (RU<sub>e</sub>), ionizing radiation (IR).</figcaption></figure>

Assuming wind power in the optimistic scenario reduces the ionizing radiation impact of the CCS supply chain: Compared to primary steel production, the increase due to the CCS supply chain falls to only 0.2% in the optimistic case.

In the base case, excluding ionizing radiation, environmental impacts increase most in water scarcity (+1.9%), resource use (energy carriers) (+1.9%), and ozone depletion (+1.5%), when compared to primary steel production. For all other impact categories, the increase is below 0.7%. The electricity consumption of the heat supply, conditioning step, and carbon capture process contribute 87% of the supply chain's impact in resource use (energy carriers) and more than half of the impact in ozone depletion. Electricity consumption also contributes 95% of the supply chain's impact in water scarcity, due to evaporation in cooling towers for the French electricity supply or at hydro dams for the Norwegian electricity supply. Thus, the electricity supply is the largest lever to address impacts in the resource use (energy carriers), ozone depletion, and water scarcity.

We vary key parameters in our scenario analysis to assess the sensitivity of the results to our assumptions (Table 1). While parameter variations in the pessimistic and optimistic scenarios (Table 1) have limited impact on the life-cycle CCS efficiency (Section 4.1), environmental impacts in categories other than *climate change* vary substantially across scenarios. In particular, impact compared to steel production varies the most in the four impact categories ionizing radiation, resource use (energy carriers), ozone depletion, and water scarcity. These categories are primarily dominated by the electricity supply and strongly affected by the assumed electricity supply, i.e., the increase in energy demand in the pessimistic scenario and the assumed electricity supply from wind power in the optimistic scenario. In the optimistic scenario using wind power, the impacts in the 4 impact categories are reduced to about 1% or below compared to primary steel production (Fig. 5).

The scenario analysis shows that locally available low-GHG electricity and heat supply results in a high life-cycle efficiency of the CCS supply chain, even in the pessimistic scenario. The CCS supply chain mildly increases the environmental impacts of steel production in most impact categories. Larger increases in environmental impacts can be attributed to the electricity mix today and could be addressed through renewable electricity. Our results thus support earlier findings in the literature (Seiler et al., 2025) on the importance of energy supply for the environmental performance across various impact categories.

### 4.3. Transport options to geological storage alternatives

The base case of our assessment assumes geological storage of CO<sub>2</sub> in a saline aquifer at the Northern Lights storage facility (Northern Lights) and transport of CO<sub>2</sub> in liquid state by two 10.8 kt ships. The 3D project investigates two alternative offshore geological storage locations: the United Kingdom (UK storage) and the Netherlands (Dutch storage), along with corresponding transport options and conditioning (Fig. 3, Sections 2.3–2.5).

Here, we compare the penalty of these transport and storage alternatives on the life-cycle CCS efficiency discussed in Section 4.1. We consider only the steps of conditioning, intermediate storage, transport, and geological storage in this analysis, as the transport and storage alternatives affect the CCS supply chain downstream of the capture process but not the heat recovery or the capture process itself (Fig. 2).

Among the considered alternatives, the base case has the highest data quality, being the primary focus of the 3D project. We use the inventories from the base case to estimate the inventories of ships and injection facilities in the alternative transport and storage options, thus introducing higher uncertainty. Therefore, the results of the storage and transport alternatives should be interpreted with caution. The assumptions and inventories for the alternative transport and storage options are documented in Appendix A.5.

In the base case considering Northern Lights as storage location, the conditioning, intermediate storage & transport, and geological storage steps collectively reduce the life-cycle CCS efficiency by only 6.0%. For the alternative storage concepts and corresponding transport options, the efficiency reduction varies between 4.8% and 7.1%.

The *climate change* impact and therefore penalty of transport decreases for shorter transport distances to the UK and Dutch storage (Fig. 6). However, for the floating storage and direct injection at the UK storage, the reduction of the life-cycle CCS efficiency penalties from transport is partially offset by higher penalties from geological storage. The higher penalties are due to fossil fuel combustion during direct offshore injection. However, our current estimates of the fuel demand for hotel functions, pre-treatment, and other functions are conservative and should be investigated in more detail.

The Dutch storage is closed to the capture site. However, the reduction of the penalty from transport is overcompensated by higher
<figure><img src="image_9.png" /><figcaption>**Fig. 6.** Reduction of life-cycle carbon capture, transport and storage efficiency (Eq. (1)) by storage and transport options (Fig. 3). FSI: floating storage injection; DI: direct injection.</figcaption></figure>

penalties in the geological storage step compared to the base case. The large penalties in geological storage result from electricity consumption from the Dutch electricity grid during injection. While we assume the same electricity demand during injection for the Dutch storage and Northern Lights, the Dutch electricity mix is higher in GHG intensity compared to the Norwegian electricity mix. Thus, shorter transport distances are beneficial only if low-emissions geological storage is ensured.

Pipeline transport reduces GHG emissions compared to ship-based transport. Both for the UK storage and the Dutch storage, efficiency penalties decrease due to lower GHG emissions in transport and conditioning. This reduction stems from lower electricity demands of compression for pipeline transport as opposed to liquefaction for ship transport. Furthermore, pipeline transport avoids GHG emissions from the combustion of fossil fuels in ship transport.

The ship transport scenarios for Northern Lights shows that CCS supply chains with slow-steaming ships (Northern Lights, 10.8 kt and 20.5 kt ships) outperform those with fast-steaming ships (Northern Lights, 7.5 kt). Fast-steaming ships increase efficiency penalties by about one-fifth compared to the base case, primarily due to increased fuel demand for propulsion.

Conversely, using larger ships (Northern Lights, 20.5 kt) could further reduces GHG emissions from fuel consumption, although the decrease is less pronounced and partly offset by increased life-cycle GHG emissions from larger intermediate storage tanks.

Our analysis underscores the environmental benefits of shorter transport distances and pipeline transport in terms of *climate change* impact. The environmental benefits of shorter transport distances and pipeline transport extend beyond *climate change*, where ships are outperformed in 15 out of 16 impact categories. Detailed information on the impact categories beyond *climate change* is provided in Appendix C.

**5. Perspective on carbon capture and storage for full decarbonization of steel production**

Our environmental assessment demonstrates a high life-cycle CCS efficiency of the megatonne-scale CCS supply chain in the 3D project. This finding holds even under a pessimistic scenario with increased impacts from energy supply, construction material, and other sources (Table 1) and for alternative geological storage and transport options (Section 4).

The high efficiency results from a careful design and favorable local conditions at the steel plant: The key factor is the low-GHG energy supply. Waste heat supplies 70% of the heat demand for the capture process and the electricity supply is dominated by nuclear power low in GHG-intensity. Furthermore, direct access to the sea enables low-emissions transport of the captured CO₂ through ships or offshore pipelines (Burger et al., 2024). However, replicating these conditions might be challenging in different applications or local conditions.

Expanding the capture capacity at the steel plant beyond 1 Mta⁻¹ could further reduce GHG emissions of steel production. However, expanding capture would decrease life-cycle CCS efficiency due to the limited availability of waste heat that can already only supply 70% of the heat demand for the 1 Mta⁻¹ plant.

Here, we evaluate the life-cycle CCS efficiency of the CCS supply chain for increasing capture capacities (Fig. 7). In the assessment, we assume primary steel production based on ecoinvent 3.10.1 (cut-off) where the region of the inventory data is adjusted to the French dataset whenever available. The 1 Mta⁻¹ plant corresponds to a *climate change* impact reduction of 6% for steel production (cf. Section 4.1). Without additional waste heat, expanding the capture capacity requires additional heat sources. Here, we include high-temperature heat pumps, combined heat and power, and natural gas boilers as additional heat sources (Section 3.5).

We calculate life-cycle CCS efficiencies of 90% for high-temperature heat pumps, 83% for combined heat and power, and 74% for natural gas boilers. Thus, heat pumps could retain the high CCS efficiency if low-carbon electricity supply is available, while fossil heat leads to substantial reductions. An electricity supply with high carbon footprint reduces CCS efficiencies and could eliminate the advantage of high-temperature heat pumps (e.g., reducing CCS efficiency to 73% for an additional case study for Germany, details in Appendix A.8, Fig. 8).

Furthermore, the capture process is designed for blast-furnace gas which only yields about 12% of the direct GHG emissions from steel production: At a capture rate of 90%, treating all blast-furnace gas reduces the steel plant's *climate change* impact by 10.2%, 9.9%, or 9.5% for heat supplied by the high-temperature heat pump, the combined heat and power unit, or the gas boiler, respectively. We base these projections on the blast-furnace gas production for primary steel production assumed in ecoinvent.

Once blast-furnace gas is exhausted, the capture process could be adapted to less abundant steel mill gases with lower CO₂-concentration
<figure><img src="image_10.png" /><figcaption>**Fig. 7.** Life-cycle carbon capture and storage efficiency of the carbon capture and storage supply chain depending on the share of *climate change* impact reduced at the steel plant. Considered regeneration heat sources include waste heat, locally available blast-furnace gas (BFG), high-temperature heat pumps (HTHP), gas-powered combined heat and power units (CHP), or gas boilers (gas).</figcaption></figure>

The contribution of the investigated DMX™ process to reducing *climate change* impact is limited by the availability of BFG. Residual emissions remaining after all strategies are exhausted must be offset by carbon dioxide removal, e.g., by direct air capture and storage (DACCS).

or alternative decarbonization strategies need to be applied to further reduce *climate change* impact (see Section 1). Additional decarbonization strategies might impact the deployment of CCS supply chains. For example, switching to hydrogen-based direct reduction avoids steel mill gases to which carbon capture can be applied. Finally, residual emissions, remaining after exhausting all decarbonization strategies, need to be offset by carbon dioxide removal, e.g., by DACCS. Operating direct air capture units at the steel production site can achieve a life-cycle CCS efficiency of 70%, assuming temperature-vacuum-swing adsorption (Section 3.5).

Careful design of CCS supply chains can lead to high life-cycle CCS efficiencies and contribute to GHG emission mitigation. However, the efficiency of CCS supply chains in steel production varies based on the GHG intensity of the energy supply and the availability of steel mill gases to which CCS can be applied. Hence, CCS can reduce *climate change* impact in steel production but must be carefully designed as part of a broader mix of strategies.

## 6. Conclusions

This work assesses the environmental impact of applying a megatonne-scale CCS supply chain based on the DMX™ technology to the steel plant in Dunkirk. This assessment is based on detailed engineering studies from the 3D demonstration project and offers high data quality for the full CCS supply chain, including capture, conditioning, transport, and geological storage of CO₂.

Our findings demonstrate the potential of CCS in reducing the *climate change* impact of steel already today: The CCS supply chain achieves a high life-cycle CCS efficiency of 93% in the base case. The high efficiency can be attributed to the availability of waste heat at the steel plant for solvent regeneration and the low GHG intensity of the French electricity mix. The plant's coastal location also allows for ship and offshore pipeline transport with low GHG intensities.

We further analyze two parametric scenarios with pessimistic and optimistic assumptions on energy supply, construction material, and other input parameters. Across scenarios, the life-cycle CCS efficiencies remain at high values above 91%. The megatonne-scale CCS plant could reduce steel's life-cycle GHG emissions by 6% while increasing other impacts of primary steel production by less than 1% in 11 of

15 categories. Categories with higher increases can be addressed by switching to electricity supply with lower impact, such as wind power. Thus, the investigated CCS supply chain effectively reduces *climate change* impact while environmental side-effects are small or can be addressed by a transition to renewable electricity.

Analyzing alternative transport and storage options, we find that shorter transport distances and pipeline transport can further reduce *climate change* and most other impacts, primarily by reducing the fuel combustion associated with ship transport.

While our assessment provides insights into the potential of CCS in reducing the *climate change* impact of steel production, we neglect fluctuations and interruptions in operation that are common under real-world conditions and may impact the performance of the supply chain. Further, we discuss that CCS alone is insufficient to achieve net-zero steel. However, CCS could be part of a mix of climate change mitigation strategies, including efficiency measures, direct reduction with methane or hydrogen, or an increased recycling rate with electric arc furnaces (Section 2). These other strategies impact the availability of steel mill gases and would interact with the deployment and applicability of CCS supply chains. Such interactions need to be investigated further.

In conclusion, CCS supply chains can reduce *climate change* impact of steel production with high efficiency. The high efficiency is contingent upon careful design, and the availability of low-GHG energy supply and transport options. Although CCS can contribute to reducing GHG emissions in steel production already today, CCS is insufficient to achieve steel with net-zero GHG emissions independently. Given the high investment costs and complexity of CCS supply chains, it is crucial to carefully consider their role within a broader strategy to avoid the risk of these investments becoming stranded assets.

## Funding sources

DS, LVI, GB, FD, VSM, and AB have received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 838031. LL acknowledges funding by the Swiss Federal Office of Energy's SWEET programme as part of the project PATHFNDR. The authors bear sole responsibility for the conclusions and the results presented in this publication.
### CRediT authorship contribution statement

**David Yang Shu:** Writing – original draft, Visualization, Validation, Project administration, Methodology, Investigation, Data curation, Conceptualization. **Leidy-Tatiana Vargas-Ibáñez:** Writing – review & editing, Validation, Methodology, Data curation. **Guillaume Batôt:** Writing – review & editing, Validation, Methodology. **Fabrice Devaux:** Writing – review & editing. **Vania Santos Moreau:** Writing – review & editing, Project administration. **Ludger Leenders:** Writing – review & editing, Funding acquisition, Conceptualization. **André Bardow:** Writing – review & editing, Supervision, Resources, Methodology, Funding acquisition.

### Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: DS, LVI, GB, FD, VSM, and AB report financial support provided by the European Union. LL reports financial support provided by the Swiss Federal Office of Energy. LVI, GB, and VSM are employed by IFP Energies nouvelles, a research institute that holds the patent for DMX™ technology. FD is employed by TotalEnergies Onetech, a company that is also active in carbon capture, utilization and storage projects. AB has ownership interests in firms that render services to industry, some of which may be involved in carbon capture and storage. AB served on review committees for research and development at ExxonMobil and TotalEnergies, companies that are also active in carbon capture, utilization, and storage projects.

## Appendix A. Life-cycle inventories

In the following, we summarize modeling details and the life-cycle inventories collected for the environmental assessment of the CCS supply chain based on DMX™ technology.

### A.1. Carbon capture process

The life-cycle inventories of the DMX™ carbon capture process are based on engineering studies conducted by Axens SA and ArcelorMittal Atlantique et Lorraine SAS within the 3D projects.

#### Carbon capture plant construction

See Table 3.

#### Capture plant operation

See Tables 4 and 5.

### A.2. Heat supply

The life-cycle inventories for heat supply are based on engineering studies of systems tailored to the steel plant. The studies are prepared in the 3D project by John Cockerill S.A. and GreenFlex SAS.

#### Waste heat recovery construction

We consider waste heat recovery from four sources from the steel plant: from the slab stacks in the steel mill, from the sinter plant cooler air, from the reheat furnace cooler air at the hot strip, and from the slag pits. The construction materials are listed in Tables 6–9.

#### Waste heat recovery operation

See Table 10.

#### Backup boiler construction

The waste heat availability is insufficient to supply the carbon capture unit fully. Furthermore, fluctuations in waste heat availability need to be compensated. Therefore, a backup boiler powered by blast furnace gas is used to avoid under-supply of heat (see Table 11).

### A.2.1. Backup boiler operation

The backup boiler is operated using blast furnace gas. Prior to the installation of the carbon capture facilities, the blast furnace gas is assumed to be burnt in a gas turbine at the power station DK6 for electricity generation. For simplicity, we assume the same emissions to the environment for burning the blast furnace gas at the backup boiler or the gas turbine. Therefore, we consider only the loss of electricity generation when using the blast furnace gas in the backup boiler in the comparative LCA. The efficiencies of the backup boiler system and the gas turbine efficiency for power generation are assumed to be 82% and 35%, respectively, based on the engineering studies conducted in the project. The impacts of the loss of electricity generation are considered by assuming compensation from the French electricity mix.

### A.3. CO₂ conditioning: Liquefaction for ship transport

The conditioning plant removes trace gases and water from the captured CO₂ before compressing or liquefying the CO₂ for further transport. The design and associated construction material and operational demands depend on the final state of the CO₂. In the following, the life-cycle inventories of the conditioning plant are presented for the liquefaction of CO₂. The inventories are based on engineering studies in which process simulations were conducted in ASPEN HYSYS V11 by Danmarks Tekniske Universitet and Air Products Sp. z o.o. The inventories for plant construction are based on the engineering studies, with the exception of the compressor. For the construction of compressors, we apply the model of Bouman et al. (2016). For this study, the compressor is scaled linearly based on the capacity.

#### Conditioning plant construction: Liquefaction

See Table 12.

#### Conditioning plant operation: Liquefaction

See Table 13.

### A.4. CO₂ conditioning: Compression for pipeline transport

The inventories of the conditioning process for pipeline transport are based on process simulations in ASPEN HYSYS V11, prepared by Danmarks Tekniske Universitet and Air Products Sp. z o.o.

#### Conditioning plant construction: Compression

See Tables 14 and 15.

#### Conditioning plant operation: Compression

See Tables 16 and 17.

### A.5. Intermediate storage and transport

After conditioning, the captured CO₂ is transported to the storage location. As transport options, ship and pipeline transport are available.

The assumed transport distances to the Northern Lights storage facility (Northern Lights), the United Kingdom (UK storage), and the storage facility off the coast of the Netherlands (Dutch storage) are 1100 km, 300 km, and 200 km, respectively.

The life-cycle inventories for intermediate storage and transport are based on engineering studies that explored transport options and created designs tailored to the steel plant within the 3D project. The studies were prepared by Gassco AS and Brevik Engineering AS.

#### Intermediate storage and port facilities construction

Scenarios assuming ship transport of CO₂ require intermediate storage tanks and port facilities. In the engineering studies of the project, port facilities and storage tanks are designed for the scenario assuming 10.8 kt ships delivering CO₂ to Northern Lights (see Table 18). In the LCA, we assume the same port facilities for all ship transport scenarios. As the tank farm has a modular design, we model the construction of the tank farms by scaling the inventories of the 13 kt tank farm (Table 19) linearly with the capacity.
<table><caption>**Table 3**
Life-cycle inventory for the construction of 1 unit of the capture plant for the capture of 1 Mt a⁻¹ of CO₂ with a lifetime of 20 a.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land-use</td><td>Occupation, industrial area</td><td></td><td>225 000</td><td>m² a</td><td>150 m × 75 m</td></tr><tr><td>Building structure</td><td>Market for reinforcing steel</td><td>GLO</td><td>974</td><td>t</td><td></td></tr><tr><td>Building structure</td><td>Market for alkyd paint, white, without water, in 60% solution state</td><td>RER</td><td>2870</td><td>kg</td><td></td></tr><tr><td>Building wall</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>674</td><td>m³</td><td></td></tr><tr><td>Building wall</td><td>Market for reinforcing steel</td><td>GLO</td><td>50.6</td><td>t</td><td></td></tr><tr><td>Building insulation</td><td>Market for stone wool, packed</td><td>GLO</td><td>19.8</td><td>t</td><td></td></tr><tr><td>Concrete piping</td><td>Market for concrete block</td><td>DE</td><td>180</td><td>t</td><td></td></tr><tr><td>Building excavation work</td><td>Processing excavation, hydraulic digger</td><td>RER</td><td>42 800</td><td>m³</td><td></td></tr><tr><td>Road Construction</td><td>Market for road, company, internal</td><td>GLO</td><td>30 000</td><td>m² a</td><td></td></tr><tr><td>Piping of process unit</td><td>Market for carbon steel pipe</td><td>GLO</td><td>2280</td><td>t</td><td>Based on ecoinvent process: Chromium steel pipe (GLO) assuming the use of carbon steel instead of chromium steel</td></tr><tr><td>Piping of process unit</td><td>Market for chromium steel pipe</td><td>GLO</td><td>552</td><td>t</td><td></td></tr><tr><td>Process unit structure</td><td>Market for reinforcing steel</td><td>GLO</td><td>150</td><td>t</td><td></td></tr><tr><td>Concrete piles of process unit foundation</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>404</td><td>m³</td><td></td></tr><tr><td>Excavation work for process unit foundation</td><td>Processing excavation, hydraulic digger</td><td>RER</td><td>404</td><td>m³</td><td></td></tr><tr><td>Piping for utilities (glass reinforced fiber)</td><td>Production glass fiber reinforced plastic, polyamide, injection molded</td><td>RER</td><td>181</td><td>t</td><td></td></tr><tr><td>Compressed air piping</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 &amp; EFTA</td><td>1.91</td><td>t</td><td></td></tr><tr><td>Compressed air piping</td><td>Section bar extrusion, aluminum</td><td>RER</td><td>1.91</td><td>t</td><td></td></tr><tr><td>Process equipment</td><td>Market for reinforcing steel</td><td>GLO</td><td>1805</td><td>t</td><td></td></tr><tr><td>Cabling</td><td>Market for cable, unspecified</td><td>GLO</td><td>234</td><td>t</td><td></td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Concrete piping and piles of process unit foundation</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>571</td><td>t</td><td>Assume half of the concrete is treated at the end of life, assume a density of 2380 kg m⁻³ (ecoinvent)</td></tr><tr><td>Building insulation</td><td>Market for waste mineral wool</td><td>Europe without Switzerland</td><td>19.8</td><td>t</td><td></td></tr><tr><td>Building wall, concrete</td><td>Market for waste reinforced concrete</td><td>RoW</td><td>1690</td><td>t</td><td></td></tr><tr><td>Compressed air piping, aluminum</td><td>Market for waste aluminum</td><td>GLO</td><td>1.91</td><td>t</td><td></td></tr><tr><td>Steel in building structure, piping of process unit, process equipment</td><td>Market for waste reinforcement steel</td><td>RoW</td><td>5060</td><td>t</td><td></td></tr><tr><td>Chromium steel piping of process unit</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>522</td><td>t</td><td></td></tr><tr><td>Drilling waste from excavation work for process unit foundation</td><td>Treatment of drilling waste, residual material landfill</td><td>CH</td><td>1230</td><td>t</td><td></td></tr></tbody></table>
<table><caption>**Table 4**

Life-cycle inventory for the operation of the capture plant for the capture of 1 t of CO₂, assuming 20 a lifetime at a capture rate of 1 057 000 t a⁻¹.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Construction of capture plant</td><td>Capture plant construction</td><td>–</td><td>4.730E-08</td><td>p</td><td></td></tr><tr><td>Solvent, initial charge</td><td>DMX™ production</td><td>–</td><td>–</td><td>kg</td><td>Value can be provided on request</td></tr><tr><td>Solvent, make up</td><td>DMX™ production</td><td>–</td><td>–</td><td>kg</td><td>Value can be provided on request; solvent losses are due to losses to the treated blast furnace gas that is sent to be burnt at the gas power plant DK6 (37% of losses) and due to losses via the concentrated CO₂ and trace amounts in water draw-off (63%). There is negligible degradation due to the absence or low concentration of O₂, NOx, SOx in the treated gas. We assume that no solvent is released to the environment.</td></tr><tr><td>Cooling water</td><td>Cooling water production, France</td><td>–</td><td>–</td><td>MWh</td><td>Value can be provided on request</td></tr><tr><td>Caustic soda</td><td>Market for sodium hydroxide, without water, in 50% solution state</td><td>GLO</td><td>0.09249</td><td>kg</td><td></td></tr><tr><td>Antifoam</td><td>Market for ethylene glycol</td><td>GLO</td><td>0.07058</td><td>kg</td><td>Proxy for antifoam</td></tr><tr><td>Electricity</td><td>Market for electricity, medium voltage</td><td>FR</td><td>–</td><td>kWh</td><td>Value can be provided on request</td></tr><tr><td>Heat</td><td>Heat for capture plant</td><td>–</td><td>–</td><td>kWh</td><td>Value can be provided on request</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste water</td><td>Treatment of wastewater, average, wastewater treatment</td><td>Europe without Switzerland</td><td>0.1041</td><td>m³</td><td></td></tr><tr><td>Waste solvent</td><td>Market for hazardous waste, for incineration</td><td>Europe without Switzerland</td><td>–</td><td>kg</td><td></td></tr></tbody></table>

<table><caption>**Table 5**

Life-cycle inventory for the local cooling water production in France of 1 MWh.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Pump Construction</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>0.001267</td><td>kg</td><td>Based on horizontal single-stage double-suction centrifugal pump Shinko GHD 600, assuming half of the weight to be cast iron and half to be stainless steel, assume lifetime of 20 a. 3 pumps are needed and 1 additional pump as a backup for seawater pumping; same number of pumps for the cooling circuit, total of 8 pumps</td></tr><tr><td>Pump Construction</td><td>Market for cast iron</td><td>GLO</td><td>0.001267</td><td>kg</td><td></td></tr><tr><td>Pump Construction</td><td>Cast iron milling, average</td><td>RER</td><td>0.0002914</td><td>kg</td><td></td></tr><tr><td>Pump Construction</td><td>Electric motor production, vehicle (electric powertrain)</td><td>GLO</td><td>0.0001845</td><td>kg</td><td></td></tr><tr><td>Electricity</td><td>Market for electricity, medium voltage</td><td>FR</td><td>55.70</td><td>kWh</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Pump construction steel</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>1420</td><td>kg</td><td></td></tr></tbody></table>
<caption>**Table 6**</caption>

Life-cycle inventory for the construction of the infrastructure for waste heat recovery from the intermediary storage of slab stacks at the steel mill with a lifetime of 20 a.

<table><caption>**Table 7**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>183</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for low-alloyed steel</td><td>GLO</td><td>95</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>37</td><td>t</td><td></td></tr><tr><td>Insulation layer</td><td>Market for stone wool packed</td><td>GLO</td><td>26</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 & EFTA</td><td>1</td><td>t</td><td></td></tr><tr><td>Foundation</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>2.52</td><td>m<sup>3</sup></td><td>The density of ordinary concrete is assumed to be 2380 kg m<sup>-3</sup> (ecoinvent)</td></tr><tr><td>Auxiliary devices</td><td>Market for reinforcing steel</td><td>GLO</td><td>103</td><td>t</td><td>Valves, pumps, measuring equipment</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>418</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste mineral wool</td><td>Europe without Switzerland</td><td>26</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for scrap aluminum</td><td>Europe without Switzerland</td><td>1</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>6</td><td>t</td><td></td></tr></tbody></table>

Life-cycle inventory for the construction of 1 p the infrastructure for waste heat recovery from the sinter cooler outlet air at the sinter plant with a lifetime of 20 a.

<table><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>658</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>1</td><td>t</td><td></td></tr><tr><td>Insulation layer</td><td>Market for stone wool packed</td><td>GLO</td><td>14</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 & EFTA</td><td>1</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Metal working, average for aluminum product manufacturing</td><td>RER</td><td>1</td><td>t</td><td></td></tr><tr><td>Foundation</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>4.2</td><td>m<sup>3</sup></td><td>The density of ordinary concrete is assumed to be 2380 kg m<sup>-3</sup></td></tr><tr><td>Auxiliary devices</td><td>Market for reinforcing steel</td><td>GLO</td><td>103</td><td>t</td><td>Valves, pumps, measuring equipment</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>762</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste mineral wool</td><td>Europe without Switzerland</td><td>14</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for scrap aluminum</td><td>Europe without Switzerland</td><td>1</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>10</td><td>t</td><td></td></tr></tbody></table>

## Ship construction

The ship construction materials are estimated based on the detailed ship design and the material take-off and master equipment list. For the ship hull material, we have assumed a 12% wastage of steel during construction based on Notten et al. (2018). Here, we present the life-cycle inventory for the construction of the slow steaming ship with a capacity of 10.8 kt of liquefied CO₂ assumed in the base case (see Table 20).

The ship design of the base case is the most detailed one created within the 3D project. Hence, the environmental impacts of construction for different ship sizes are estimated based on the life-cycle inventory of ship construction with a capacity of 10.8 kt. To extrapolate from the ship in the base case, we scale the life-cycle inventory for construction with the capacity of the ship, assuming a linear relationship between capacity and construction activities.

## Ship operation

Ship operation contributes to emissions to the air due to fuel combustion and CO₂ leakage, and to emissions to water from the protective antifoul painting.

The fuel demands of the ships are estimated based on the engine types assumed for different ship sizes and cruising speeds. Furthermore, we account for the changing requirements on the tank farm capacity for intermediate storage depending on the storage and transport options. The floating storage injection and direct injection have additional fuel demands for hotel functions, pre-treatment, and other functions that are conservatively approximated by assuming continuous operation of a generator throughout the year (Table 21). The emissions from the ship paint to water are modeled following the method of Notten et al. (2018).

For CO₂-storage at Northern Lights and the Dutch storage, we assume half the onshore electricity consumption of ships to be consumed in France and half the electricity to be consumed at the respective destinations, as the ships are assumed to deliver the CO₂ to a port at the destination. For the UK storage, we assume the onshore electricity
<table><caption>**Table 8**
Life-cycle inventory for the construction of the infrastructure for waste heat recovery from the reheat furnace cooling system at the hot strip mill with a lifetime of 20 a.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>264</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for steel, low-alloyed</td><td>GLO</td><td>651</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>5</td><td>t</td><td></td></tr><tr><td>Insulation layer</td><td>Market for stone wool packed</td><td>GLO</td><td>20</td><td>t</td><td></td></tr><tr><td>Refractory</td><td>Market for refractory, fireclay, packed</td><td>GLO</td><td>782</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 & EFTA</td><td>2</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Metal working, average for aluminum product manufacturing</td><td>RER</td><td>2</td><td>t</td><td></td></tr><tr><td>Foundation</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>4.2</td><td>m<sup>3</sup></td><td>The density of ordinary concrete is assumed to be 2380 kg m<sup>-3</sup> (ecoinvent)</td></tr><tr><td>Auxiliary devices</td><td>Market for reinforcing steel</td><td>GLO</td><td>590</td><td>t</td><td>Valves, pumps, measuring equipment</td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>1510</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste mineral wool</td><td>Europe without Switzerland</td><td>20</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for scrap aluminum</td><td>Europe without Switzerland</td><td>2</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>50</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 9**
Life-cycle inventory for the construction of the infrastructure for the waste heat recovery from the slag pits at the co-product treatment site with a lifetime of 20 a.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>1150</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>207</td><td>t</td><td></td></tr><tr><td>Insulation layer</td><td>Market for stone wool packed</td><td>GLO</td><td>34</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 & EFTA</td><td>1</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Metal working, average for aluminum product manufacturing</td><td>RER</td><td>1</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>174</td><td>m<sup>3</sup></td><td>The density of ordinary concrete is assumed to be 2380 kg m<sup>-3</sup> (ecoinvent)</td></tr><tr><td>Auxiliary devices</td><td>Market for reinforcing steel</td><td>GLO</td><td>770</td><td>t</td><td>Valves, pumps, measuring equipment</td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>2127</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste mineral wool</td><td>Europe without Switzerland</td><td>34</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for scrap aluminum</td><td>Europe without Switzerland</td><td>2</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>415 000</td><td>t</td><td></td></tr></tbody></table>
<caption>**Table 10**</caption>

Life-cycle inventory for the operation of the waste heat generation facility for providing of 1 MJ of heat for regeneration, assuming 20 a lifetime at a heat recovery of 1 936 300 000 MJ a⁻¹.

<table><caption>**Table 11**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Electricity</td><td>Market for electricity, medium voltage</td><td>FR</td><td>2.405E-03</td><td>kWh</td><td></td></tr><tr><td>Make-up water</td><td>water production, deionized</td><td>FR</td><td>7.146E-03</td><td>kg</td><td></td></tr><tr><td>Construction</td><td>Construction of heat recovery solution 1</td><td>–</td><td>2.582E-11</td><td>p</td><td></td></tr><tr><td>Construction</td><td>Construction of heat recovery solution 2</td><td>–</td><td>2.582E-11</td><td>p</td><td></td></tr><tr><td>Construction</td><td>Construction of heat recovery solution 3</td><td>–</td><td>2.582E-11</td><td>p</td><td></td></tr><tr><td>Construction</td><td>Construction of heat recovery solution 4</td><td>–</td><td>2.582E-11</td><td>p</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste-water treatment</td><td>Treatment of wastewater, average, wastewater treatment</td><td>Europe without Switzerland</td><td>7.146E-03</td><td>kg</td><td></td></tr></tbody></table>

Life-cycle inventory for the construction of a backup boiler for providing heat to the capture unit with a lifetime of 20 a.

<table><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>280</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for low-alloyed steel</td><td>GLO</td><td>35</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>1</td><td>t</td><td></td></tr><tr><td>Insulation layer</td><td>Market for stone wool packed</td><td>GLO</td><td>30</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market for aluminum, primary, cast alloy slab from continuous casting</td><td>GLO</td><td>5</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Metal working, average for aluminum product manufacturing</td><td>RER</td><td>5</td><td>t</td><td></td></tr><tr><td>Equipment material</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>12.6</td><td>m³</td><td>The density of ordinary concrete is assumed to be 2380 kg m⁻³ (ecoinvent)</td></tr><tr><td>Auxiliary devices</td><td>Market for reinforcing steel</td><td>GLO</td><td>146</td><td>t</td><td>Valves, pumps, measuring equipment, fans, burners</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>462</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste mineral wool</td><td>Europe without Switzerland</td><td>30</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for scrap aluminum</td><td>Europe without Switzerland</td><td>5</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>30</td><td>t</td><td></td></tr></tbody></table>

demand of the ships to be fully satisfied by the French grid mix, as the CO₂ is directly unloaded offshore.

The life-cycle inventory for transporting CO₂ in the base case using two 10.8 kt ships over 1100 km is presented in Table 22. The life-cycle inventory for other ship sizes and distances is assumed the same, except scaled by the travel distance to the geological storage and the number of ships. Further, fuel demands are adjusted as given in Table 21, and ship construction activities are scaled linearly by capacity.

### Ship maintenance

Ship maintenance considers the renewal of ship painting. According to the ship design experts of the 3D consortium, the equipment of the ships can be assumed to last for the full lifetime of the ship resulting in no need for replacement materials. Maintenance includes removal and reapplication of paint for a 10.8 kt ship throughout its lifetime with associated environmental emissions of diesel consumption based on Notten et al. (2018). The life-cycle inventory presented by Notten et al. (2018) is scaled linearly by the ship's lightweight mass and lifetime. The construction of maintenance facilities is neglected (see Table 23).

### Pipeline construction

The pipeline construction materials are estimated based on engineering studies and discussions conducted within the consortium

(see Tables 24 and 25). We assume half of the pipeline material to be recovered for waste treatment after the end-of-life. For pipeline transport, compression in the conditioning step is assumed sufficient to deliver the CO₂ to the geological storage location. Recompression is unnecessary due to the short transport distance to the UK storage (300 km) and Dutch storage (200 km). The pipeline construction for the UK storage and Dutch storage differ only by the length of the pipeline.

### A.6. Geological storage: Northern lights

The design, operation, and monitoring of the geological storage wells are not part of the 3D project. However, 3 geological storage locations are selected within the project and considered as the storage destination for the CO₂ captured at the steel plant in Dunkirk.

In the LCA, we aim to capture the environmental impacts of geological storage based on literature data. We apply construction and emission data is available for the Northern Lights geological storage project (Equinor ASA, 2019).

The same environmental impacts of the Northern Lights geological storage project are assumed for the Dutch storage as a first approximation. This is because the geological storage off the coast of the Netherlands is selected due to its proximity to the steel plant in Dunkirk without targeting any specific project. Hence, data on construction,
<table><caption>**Table 12**
Life-cycle inventory for the construction of the conditioning plant for liquefaction of CO₂ for ship transport with a lifetime of 20 a.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Occupation, industrial area</td><td></td><td>270000</td><td>m² a</td><td></td></tr><tr><td>Land</td><td>Transformation, to industrial area</td><td></td><td>13500</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, from unspecified</td><td></td><td>13500</td><td>m²</td><td></td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>235.6</td><td>t</td><td>Coolers/heat exchangers, stripper, flash drums/ separators</td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>239.7</td><td>t</td><td>Coolers/heat exchangers, flash drums/ separators</td></tr><tr><td>Construction</td><td>Building, hall, steel Construction</td><td>CH</td><td>13500</td><td>m²</td><td>Estimated due to lack of data (ecoinvent)</td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td>–</td><td>0.178</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td>–</td><td>0.180</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td>–</td><td>0.281</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td>–</td><td>0.149</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td>–</td><td>0.150</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td>–</td><td>0.0109</td><td>p</td><td></td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>475.3</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 13**
Life-cycle inventory for the operation of the conditioning plant for liquefaction of CO₂ for ship transport, per 1 t of CO₂, assuming 20 a lifetime and conditioning of 1.057 Mt of captured CO₂ per year.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Captured CO₂<br>Electricity</td><td>Operation of the capture plant<br>Market for electricity, medium voltage</td><td>FR</td><td>1.006<br>80.92</td><td>t<br>kWh</td><td></td></tr><tr><td>Cooling</td><td>Cooling water production, France</td><td>–</td><td>188.9</td><td>kWh</td><td></td></tr><tr><td>Activated carbon</td><td>Market for activated carbon, granular</td><td>GLO</td><td>0.6350</td><td>kg</td><td>For desulfurization</td></tr><tr><td>Construction</td><td>Construction of conditioning plant for liquefaction</td><td>–</td><td>4.760E-08</td><td>p</td><td></td></tr><tr><td colspan="6">Emission</td></tr><tr><td>Carbon dioxide leakage<br>Ammonia</td><td>Carbon dioxide, fossil<br>Ammonia</td><td>To air<br>To air</td><td>0.005528<br>6.664E-07</td><td>t</td><td></td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Waste-water treatment</td><td>Treatment of wastewater, average, wastewater treatment</td><td>Europe without Switzerland</td><td>0.007482</td><td>m³</td><td></td></tr><tr><td>Waste sorbent for desulfurization</td><td>Market for inert waste, for final disposal</td><td>CH</td><td>0.7645</td><td>kg</td><td></td></tr></tbody></table>

operation, and emissions are unavailable. Similarly, we assume the same life-cycle inventory for the well drilling at the geological storage site off the coast of the United Kingdom (UK storage). However, the direct injection and floating storage injection facilities are based on designs created in the 3D project.

The facilities for permanent geological storage of CO₂ are modeled for saline aquifers based on the Northern Lights project's phase 1 (Equinor ASA, 2019). The model of the geological storage facilities consists of the onshore facilities for receiving liquefied CO₂ via ship, pipelines for transport to the injection site, offshore facilities, and offshore wells.

The pipeline is modeled following the assumptions of ecoinvent (Wernet et al., 2016) for the construction of a long-distance offshore natural gas pipeline with high capacity. The life-cycle inventory is adapted assuming construction materials for a pipeline diameter of 323.9 mm (Equinor ASA, 2019), including steel, aluminum, polyethylene, rock for protection of the pipelines, and diesel consumption for construction. Furthermore, direct emissions to air of CO₂, nitrogen

oxides, sulfur oxides, and non-methane volatile organic compounds are adapted based on Equinor ASA (2019) assuming half of the emissions to be attributed equally to pipeline construction and well construction.

To model the drilling of the injection borehole, we adapt a model for drilling activities from the oil and gas industry from ecoinvent as a proxy (offshore well, oil/gas (GLO)) (Wernet et al., 2016). In addition, the emissions for drilling and well operation are added, and the diesel demand for construction is adapted to align with the reporting of Northern Lights (Equinor ASA, 2019).

### Port facilities and injection infrastructure construction

See Tables 26–30.

### Geological storage facilities operation

See Table 31.
<table><caption>**Table 14**
Life-cycle inventory for the construction of the conditioning plant for compression of CO₂ for pipeline transport to the UK storage with 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Occupation, industrial area</td><td></td><td>270000</td><td>m<sup>2</sup> a</td><td></td></tr><tr><td>Land</td><td>Transformation, to industrial area</td><td></td><td>13500</td><td>m<sup>2</sup></td><td></td></tr><tr><td>Land</td><td>Transformation, from unspecified</td><td></td><td>13500</td><td>m<sup>2</sup></td><td></td></tr><tr><td>Construction equipment</td><td>Market for reinforcing steel</td><td>GLO</td><td>44.59</td><td>t</td><td></td></tr><tr><td>Construction equipment</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>44.7371</td><td>t</td><td></td></tr><tr><td>Construction</td><td>Building, hall, steel</td><td>CH</td><td>13500</td><td>m<sup>2</sup></td><td>Estimated due to lack of data</td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1582</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1541</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1474</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1410</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1143</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.06414</td><td>p</td><td></td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>89.33</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 15**
Life-cycle inventory for the construction of the conditioning plant for compression of CO₂ for pipeline transport to the Dutch storage with 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Occupation, industrial area</td><td></td><td>270000</td><td>m<sup>2</sup> a</td><td></td></tr><tr><td>Land</td><td>Transformation, to industrial area</td><td></td><td>13500</td><td>m<sup>2</sup></td><td></td></tr><tr><td>Land</td><td>Transformation, from unspecified</td><td></td><td>13500</td><td>m<sup>2</sup></td><td></td></tr><tr><td>Construction equipment</td><td>Market for reinforcing steel</td><td>GLO</td><td>43.29</td><td>t</td><td></td></tr><tr><td>Construction equipment</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>42.21</td><td>t</td><td></td></tr><tr><td>Construction</td><td>Building, hall, steel</td><td>CH</td><td>13500</td><td>m<sup>2</sup></td><td>Estimated due to lack of data (ecoinvent)</td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1498</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1461</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1404</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1358</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.1139</td><td>p</td><td></td></tr><tr><td>Compressor</td><td>Centrifugal compressor</td><td></td><td>0.08310</td><td>p</td><td></td></tr><tr><td colspan="6">Waste streams</td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>85.50</td><td>t</td><td></td></tr></tbody></table>

### Geological storage off the coast of the United Kingdom

For the geological storage option off the coast of the United Kingdom (UK storage), we assume direct injection and floating storage injection.

Detailed information is unavailable on construction, wet-tow from the shipyard, installation, and decommissioning of the floating storage injection. Hence, we neglect the wet tow from the shipyard and assume the same impacts from installation and decommissioning as for the ship construction. As there is no information available on the wells of the UK storage, we assume the same requirements for well construction as for Northern Lights.

### Permanent storage facility construction

See Tables 32–35.

### Storage facilities operation

Marine gas oil and liquefied natural gas are combusted for the floating storage injection and direct injection of the operation for the geological storage off the coast of the United Kingdom. The emissions

to the environment for the combustion of marine gas oil and liquefied natural gas are modeled based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021) and assumes low methane slip of dual-use liquefied natural gas and diesel-powered ships (see Tables 36 and 37).

## A.7. Other inventory assumptions

In the material demand for equipment and construction, we distinguish between carbon steel, low-alloyed steel, and stainless steel. In addition to the production of steel, we consider basic metal working by default (Table 38). Similarly, we consider basic metal working for aluminum, as a default (Table 38). The metal working processes are omitted in the life-cycle inventories tabulated in this appendix for brevity. Any further processing of steel or aluminum is explicitly noted in the tabulated inventories.
<caption>**Table 16**</caption>

Life-cycle inventory for the operation of the conditioning plant for compression of CO₂ for pipeline transport to the UK storage, per 1 t of CO₂, assuming 20 a lifetime and conditioning of 1.057 Mt of captured CO₂ per year.

<table><caption>**Table 17**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Captured CO<sub>2</sub></td><td>Operation of the capture plant</td><td></td><td>1.006</td><td>t</td><td></td></tr><tr><td>Electricity</td><td>Market for electricity, medium voltage</td><td>FR</td><td>65.50</td><td>kWh</td><td></td></tr><tr><td>Cooling</td><td>Cooling water production, France</td><td>–</td><td>135.8</td><td>kWh</td><td></td></tr><tr><td>Heating</td><td>Backup boiler operation</td><td>–</td><td>1.629</td><td>kWh</td><td></td></tr><tr><td>Activated carbon</td><td>Market for activated carbon, granular</td><td>GLO</td><td>0.6350</td><td>kg</td><td>For desulfurization</td></tr><tr><td>Construction</td><td>Construction of conditioning plant for compression for the UK storage</td><td>–</td><td>4.760E-08</td><td>p</td><td></td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Carbon dioxide leakage</td><td>Carbon dioxide, fossil</td><td>To air</td><td>0.005529</td><td>t</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste-water treatment</td><td>Treatment of wastewater, average, wastewater treatment</td><td>Europe without Switzerland</td><td>0.007309</td><td>m<sup>3</sup></td><td></td></tr><tr><td>Waste sorbent for desulfurization</td><td>Market for inert waste, for disposal</td><td>CH</td><td>0.0007887</td><td>t</td><td></td></tr></tbody></table>

Life-cycle inventory for the operation of the conditioning plant for compression of CO₂ for pipeline transport to the Dutch storage, per 1 t of CO₂, assuming 20 a lifetime and conditioning of 1.057 Mt of captured CO₂ per year.

<table><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Captured CO<sub>2</sub></td><td>Operation of the capture plant</td><td></td><td>1.006</td><td>t</td><td></td></tr><tr><td>Electricity</td><td>Market for electricity, medium voltage</td><td>FR</td><td>64.60</td><td>kWh</td><td></td></tr><tr><td>Cooling</td><td>Cooling water production, France</td><td>–</td><td>131.5</td><td>kWh</td><td></td></tr><tr><td>Heating</td><td>Backup boiler operation</td><td>–</td><td>1.587</td><td>kWh</td><td></td></tr><tr><td>Activated carbon</td><td>Market for activated carbon, granular</td><td>GLO</td><td>0.6350</td><td>kg</td><td>For desulfurization</td></tr><tr><td>Construction</td><td>Construction of conditioning plant for compression for the Dutch storage</td><td>–</td><td>4.760E-08</td><td>p</td><td></td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Carbon dioxide leakage</td><td>Carbon dioxide, fossil</td><td>To air</td><td>0.005529</td><td>t</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste-water treatment</td><td>Treatment of wastewater, average, wastewater treatment</td><td>Europe without Switzerland</td><td>0.007309</td><td>m<sup>3</sup></td><td></td></tr><tr><td>Waste sorbent for desulfurization</td><td>Market for inert waste, for disposal</td><td>CH</td><td>0.0007887</td><td>t</td><td></td></tr></tbody></table>

## A.8. Perspective on carbon capture and storage for full decarbonization of steel production

For the calculation of life-cycle CCS efficiencies in Section 5, high-temperature heat pumps are modeled based on Khan et al. (2020), assuming a French electricity supply and an adequate heat source. We select an ecoinvent activity to represent heat generation from a combined heat and power plant (heat and power co-generation, natural gas, conventional power plant, 100 MW elect) and gas boilers (heat production, natural gas, at boiler modulating >100 kW). We use the model by Deutz and Bardow (2021) for direct air capture, assuming the engineered unit and amine on silica as sorbent material with the same ratio of silica gel and polyethyleneimine as Madhu et al. (2021).

To provide additional context, we calculate the life-cycle CCS efficiencies assuming that electricity at the capture site is supplied by the German mix, which is characterized by substantial shares of fossil power plants (Fig. 8). The CCS efficiency drops substantially for all considered cases to below 80% for all regeneration heat supplies apart from waste heat. The efficiency drops most for waste heat supplied

by high-temperature heat pumps and the combustion of BFG, due to resulting electricity consumption and loss of electricity generation, respectively. However, heat supplied by gas boilers remains the least efficient option, with a CCS efficiency of below 70%.

## Appendix B. DMX™ solvent production

We include the environmental impact of DMX™ solvent production in the capture step of the CCS supply chain within our LCA. In this section, we analyze the environmental impacts of solvent production separately to identify any critical impacts in comparison to monoethanolamine, a common solvent for CO₂ separation.

The life-cycle environmental impacts of the DMX™ solvent production are determined based on production data provided by the solvent manufacturer for the demonstrator plant built in the 3D project. We compare the environmental impacts of the production of 1 kg of DMX™ solvent in aqueous solution to the impacts of 1 kg of MEA in a 30% to 40% aqueous solution.
<table><caption>**Table 18**
Life-cycle inventory for the construction of the port facilities for ship transport of CO₂ with a 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Port facilities</td><td>Market for reinforcing steel</td><td>GLO</td><td>36.40</td><td>t</td><td>Loading arm</td></tr><tr><td>Port facilities</td><td>Synthetic rubber production</td><td>RER</td><td>1.5</td><td>t</td><td>Vapor return line</td></tr><tr><td>Port facilities</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>1.5</td><td>t</td><td>Vapor return line</td></tr><tr><td>Port facilities</td><td>Market for low-alloyed steel</td><td>GLO</td><td>44</td><td>t</td><td>Vapor return line</td></tr><tr><td>Port facilities</td><td>Synthetic rubber production</td><td>RER</td><td>0.1485</td><td>t</td><td>Hose drinking water</td></tr><tr><td>Port facilities</td><td>Market for reinforcing steel</td><td>GLO</td><td>4.585</td><td>t</td><td>Forklift</td></tr><tr><td>Port facilities</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>1.215</td><td>t</td><td>AMP dispenser</td></tr><tr><td>Port facilities</td><td>Market for copper, cathode</td><td>GLO</td><td>1.215</td><td>t</td><td>AMP dispenser</td></tr><tr><td>Port facilities</td><td>Wire drawing copper</td><td>RER</td><td>1.215</td><td>t</td><td>AMP dispenser</td></tr><tr><td>Port facilities</td><td>Polyvinylchloride production, bulk polymerization</td><td>GLO</td><td>0.27</td><td>t</td><td>AMP dispenser</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>87.70</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market scrap copper</td><td>Europe without Switzerland</td><td>1215</td><td>kg</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste polyvinylchloride</td><td>FR</td><td>270</td><td>kg</td><td></td></tr></tbody></table>

<table><caption>**Table 19**
Life-cycle inventory for the construction of the intermediate storage tank farm with a capacity of 13 kt for ship transport of CO₂ with a 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Occupation, industrial area</td><td></td><td>51 300</td><td>m<sup>2</sup> a</td><td></td></tr><tr><td>Land</td><td>Transformation, to industrial area</td><td></td><td>2563</td><td>m<sup>2</sup></td><td></td></tr><tr><td>Land</td><td>Transformation, from unspecified</td><td></td><td>2563</td><td>m<sup>2</sup></td><td></td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>264</td><td>t</td><td>Tank farm</td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>47</td><td>t</td><td>Cladding of storage tanks</td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>3296</td><td>t</td><td>Storage tank material</td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>5336</td><td>t</td><td>Storage tank skirts</td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>5.2</td><td>t</td><td>Nozzles, manholes</td></tr><tr><td>Equipment material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>12</td><td>t</td><td>Piping</td></tr><tr><td>Equipment material</td><td>Market for cast iron</td><td>GLO</td><td>13.10</td><td>t</td><td>Loading pumps, (pressure safety) valves</td></tr><tr><td>Insulation layer</td><td>Market for polyurethane, rigid foam</td><td>RER</td><td>673</td><td>m<sup>2</sup></td><td>Insulation of storage tanks</td></tr><tr><td>Equipment material</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>1292</td><td>m<sup>3</sup></td><td>Tank farm foundation</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste construction material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>8960</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste polyurethane</td><td>Europe without Switzerland</td><td>673</td><td>t</td><td></td></tr><tr><td>Waste construction material</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>3076</td><td>t</td><td></td></tr></tbody></table>

The production of DMX™ solvent exceeds the environmental impact of MEA solvent production in 7 out of 16 impact categories in comparison on a mass basis, i.e., per 1 kg of solvent (Fig. 9). On a mass basis, environmental impacts of DMX™ solvent exceed the environmental impact of MEA production by up to 229% and on average by 10% across impact categories.

However, the environmental impact of DMX™ solvent production is expected to be significantly lower compared to the production of MEA when compared based on CO₂ captured due to the high stability of the DMX™ solvent: Lab-scale experiments and simulations indicate a solvent make-up of approximately 0.04 kg of undiluted DMX™ per ton of CO₂ captured, which is orders of magnitude lower than the make-up required for MEA-based carbon capture: The LCA literature typically assumes a make-up of 1.5 kg to 2.3 kg of pure MEA per ton of CO₂ captured Koornneef et al., 2008; Fadeyi et al., 2013; Giordano et al., 2018; Moser et al., 2020). Moser et al. (2020) measured a MEA consumption of 0.21 kg to 3.65 kg per ton of CO₂ captured during an 18-month test of a carbon capture facility applied to a lignite power plant. Hence, the suggested decrease in DMX™ solvent makeup

could overcompensate for the higher environmental impact of solvent production in some categories. Based on consumption of 0.04 kg of undiluted DMX™ solvent and an optimistic consumption of 0.21 kg MEA per ton of CO₂ captured, the impacts of DMX™-solvent makeup production are at least 37% lower than MEA in all impact categories. However, the makeup demand for DMX™ solvent in full-scale carbon capture processes remains to be confirmed in practice.

Additionally, the DMX™ solvent is currently produced on a small scale: Within the 3D project, 5 t of a mixture of DMX™-A and DMX™-B in aqueous solution are produced for use in the demonstrator. The manufacturing of DMX™ solvent is already scaled-up substantially within the 3D project compared to previous laboratory-scale synthesis. However, the production volume remains far below the volumes of established solvents such as MEA. In particular, the DMX™-B solvent is produced in a batch hydrogenation process. Thus, we expect substantial improvements in resource and energy efficiency for a scaled-up production of DMX™ solvent.
<table><caption>**Table 20**
Life-cycle inventory for the construction of a ship with the capacity to transport 10.8 kt of liquefied CO₂ with a 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Ship hull material</td><td>Market for reinforcing steel</td><td>GLO</td><td>7583</td><td>t</td><td>Losses of metal in metal working included based on Notten et al. (2018)</td></tr><tr><td>Other material</td><td>Market for copper, cathode</td><td>GLO</td><td>40</td><td>t</td><td></td></tr><tr><td>Other material</td><td>Market for cast iron</td><td>GLO</td><td>100</td><td>t</td><td></td></tr><tr><td>Other material</td><td>Market for bronze</td><td>GLO</td><td>100</td><td>t</td><td></td></tr><tr><td>Insulation material</td><td>Market for polyurethane, rigid foam</td><td>RER</td><td>50</td><td>t</td><td></td></tr><tr><td>Painting</td><td>Market for alkyd paint, white without water, in 60% solution state</td><td>RER</td><td>50.49</td><td>t</td><td>Estimated based on Notten et al. (2018)</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Emissions during painting</td><td>NMVOC, non-methane volatile organic compounds</td><td>To air</td><td>41.31</td><td>t</td><td>Paint solvent emission to air (45% of paint weight)</td></tr><tr><td>Emissions during painting</td><td>Hydrocarbons, unspecified</td><td>To water</td><td>1.652</td><td>t</td><td>Paint emission to water</td></tr><tr><td>Emissions during painting</td><td>Hydrocarbons, unspecified</td><td>to soil</td><td>1.6524</td><td>t</td><td>Paint emission to water</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste ship hull material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>7584</td><td>t</td><td></td></tr><tr><td>waste other materials</td><td>Market for scrap copper</td><td>Europe without Switzerland</td><td>40</td><td>t</td><td></td></tr><tr><td>Waste other materials</td><td>Market for waste bulk iron, excluding reinforcement</td><td>RoW</td><td>100</td><td>t</td><td></td></tr><tr><td>Waste other materials</td><td>Market for bronze scrap, post-consumer</td><td>GLO</td><td>100</td><td>t</td><td></td></tr><tr><td>Waste insulation</td><td>Market for waste polyurethane</td><td>FR</td><td>50</td><td>t</td><td></td></tr><tr><td>Waste painting</td><td>Market for waste paint</td><td>Europe without Switzerland</td><td>47.18</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 21**
Fuel demands and tank farm capacity for ship transport alternatives at 15 bar gauge pressure for the storage locations. liquefied natural gas (LNG), marine diesel oil (MDO), pilot fuel (PF).</caption><thead><tr><th rowspan="2">Storage</th><th rowspan="2">Ship</th><th colspan="3">Fuel demand in ta<sup>-1</sup></th><th rowspan="2">Tank farm capacity</th></tr><tr><th>LNG</th><th>MDO</th><th>PF</th></tr></thead><tbody><tr><td rowspan="3">Northern Lights</td><td>2 ships, 10.8 kt, 10 kt</td><td>2052</td><td>1026</td><td>46</td><td>13 kt</td></tr><tr><td>2 ships, 7.5 kt, 15 kt</td><td>5786</td><td>930</td><td>130</td><td>9 kt</td></tr><tr><td>1 ship, 20.5 kt, 12 kt</td><td>2360</td><td>410</td><td>53</td><td>25 kt</td></tr><tr><td rowspan="4">UK storage</td><td>Floating storage injection:</td><td></td><td></td><td></td><td rowspan="4">13 kt</td></tr><tr><td>1 ship, 10.8 kt, shuttle</td><td>660</td><td>330</td><td>15</td></tr><tr><td>Hotel functions, other functions</td><td>0</td><td>1702</td><td>0</td></tr><tr><td>Direct injection:</td><td></td><td></td><td></td></tr><tr><td></td><td>2 ships, 10.8 kt, shuttle</td><td>660</td><td>740</td><td>15</td><td rowspan="2">13 kt</td></tr><tr><td></td><td>CO₂ pretreatment</td><td>0</td><td>564</td><td>0</td></tr><tr><td>Dutch storage</td><td>1 ship, 5.4 kt, 10 kt</td><td>641</td><td>380</td><td>14</td><td>9 kt</td></tr></tbody></table>

## Appendix C. Environmental impacts of transport and storage alternatives

In the following, the environmental impact of the transport alternatives for the geological storage options (Fig. 3) are presented relative to the environmental impacts of the base case (Northern Lights, 10.8 kt ships). The results are presented for the steps of the CCS supply chain that are impacted by the transport alternatives downstream of the capture unit. The life-cycle inventories for the alternative ship transport options and geological storage are approximated based on the base case (see Appendix A). The approximations result in a high uncertainty of the results. Hence, the results are indicative only and should be interpreted with caution (see Fig. 10).

Environmental impacts of conditioning are lower in scenarios assuming pipeline transport compared to scenarios assuming ship transport. This is because the impacts of conditioning are dominated by electricity consumption, which is lower for pipeline transport where CO₂ is compressed instead of liquefied.

Furthermore, in the intermediary storage and transport step, pipeline transport avoids the environmental impacts of fuel combustion

in ship transport. Fuel consumption is particularly high in the scenario assuming ship transport to Northern Lights with fast-steaming ships (Northern Lights, 7.5 kt ships) due to the long transport distance and higher speed that lowers efficiency. The scenarios considering floating storage injection and direct injection at the UK storage consider additional marine gas oil consumption for hotel functions, pre-treatment plants for injection, and other functions.

The environmental impacts of the ship transport alternative are dominated by fuel combustion. Hence, more fuel-efficient transport alternatives reduce environmental impacts in climate change and other environmental impact categories. Further, the impacts of marine gas oil combustion are higher compared to liquefied natural gas combustion, especially in climate change, photochemical ozone formation, acidification, terrestrial eutrophication, and aquatic marine eutrophication. Thus, reducing marine gas oil consumption is particularly beneficial. The combustion of marine gas oil and liquefied natural gas is modeled based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021) and assumes low methane slip of dual-use liquefied natural gas and diesel-powered ships.
<table><caption>**Table 22**
Life-cycle inventory for transporting 1 t km of liquefied CO₂ using a 10.8 kt ship assuming a 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Ship Construction</td><td>Ship with the capacity to transport 10.8 kt of liquefied CO₂</td><td></td><td>8.642E-11</td><td>p</td><td></td></tr><tr><td>Fuel</td><td>Market for natural gas, liquefied</td><td>GLO</td><td>0.003461</td><td>m³</td><td></td></tr><tr><td>Fuel</td><td>Market group for heavy fuel oil</td><td>RER</td><td>9.264E-4</td><td>kg</td><td>Production of MDO and HFO is modeled using heavy fuel oil as a proxy</td></tr><tr><td>Maintenance</td><td>Maintenance, 10.8 kt ship, for liquefied carbon dioxide</td><td>-</td><td>4.321E-11</td><td>p</td><td>Sanding and renewal of painting</td></tr><tr><td>Cooling water</td><td>Market for water, deionized</td><td>Europe without Switzerland</td><td>6.308E-08</td><td>t</td><td>Make-up for the cooling system</td></tr><tr><td>Tap water</td><td>Market for tap water</td><td>Europe without Switzerland</td><td>8.642E-07</td><td>t</td><td></td></tr><tr><td>Electricity</td><td>Electricity, medium voltage</td><td>NO</td><td>1.728E-05</td><td>kWh</td><td>Onshore electricity supply, assuming half the electricity is supplied in France and half in Norway</td></tr><tr><td>Electricity</td><td>Electricity, medium voltage</td><td>FR</td><td>1.728E-05</td><td>kWh</td><td>Onshore electricity supply, assuming half the electricity is supplied in France and half in Norway</td></tr><tr><td>Fuel</td><td>Combustion of LNG</td><td>-</td><td>0.001773</td><td>kg</td><td>Based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021)</td></tr><tr><td>Fuel</td><td>Combustion of MDO</td><td>-</td><td>8.866E-4</td><td>kg</td><td>Based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021)</td></tr><tr><td>Fuel</td><td>Combustion of HFO</td><td>-</td><td>3.975E-5</td><td>kg</td><td>Based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021)</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Paint emissions</td><td>Copper ion</td><td>To water</td><td>3.264E-08</td><td>t</td><td></td></tr><tr><td>Paint emissions</td><td>Fungicides, unspecified</td><td>To water</td><td>3.129E-09</td><td>t</td><td></td></tr><tr><td>Paint emissions</td><td>Hydrocarbons, unspecified</td><td>To water</td><td>4.352E-06</td><td>t</td><td></td></tr><tr><td>Paint emissions</td><td>Thiocyanate</td><td>To water</td><td>5.215E-10</td><td>t</td><td></td></tr><tr><td>Paint emissions</td><td>Tributyltin compounds</td><td>To water</td><td>4.772E-09</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 23**
Life-cycle inventory for the maintenance of a 10.8 kt ship for liquefied CO₂ transport throughout its 20 a lifetime.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Paint renewal</td><td>Market for alkyd paint, white, without solvent, in 60% solution state</td><td>RER</td><td>158.3</td><td>t</td><td></td></tr><tr><td>Sand blasting</td><td>Market for sand</td><td>RoW</td><td>157.0</td><td>t</td><td></td></tr><tr><td>Sand blasting</td><td>Market for diesel, burned in building machine</td><td>GLO</td><td>15400</td><td>MJ</td><td>Diesel for sandblasting (compressor)</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Repainting</td><td>NMVOC, non-methane volatile organic compounds</td><td>To air</td><td>129.5</td><td>t</td><td></td></tr><tr><td>Sand blasting</td><td>Particulate matter, &lt;2.5 µm</td><td>To air</td><td>7.224</td><td>kg</td><td></td></tr><tr><td>Sand blasting</td><td>Particulate matter, &gt;10 µm</td><td>To air</td><td>86.68</td><td>kg</td><td></td></tr><tr><td>Sand blasting</td><td>Particulate matter, &gt;2.5 µm and &lt;10 µm</td><td>To air</td><td>267.3</td><td>kg</td><td></td></tr><tr><td>repainting and Sand blasting</td><td>hydrocarbons, unspecified</td><td>To water</td><td>9603</td><td>kg</td><td></td></tr><tr><td>Sand blasting</td><td>Solids, inorganic</td><td>To water</td><td>15700</td><td>kg</td><td></td></tr><tr><td>repainting and Sand blasting</td><td>Hydrocarbons, unspecified</td><td>to soil</td><td>9603</td><td>kg</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Sand blasting</td><td>Market for waste foundry sand</td><td>GLO</td><td>137700</td><td>kg</td><td></td></tr><tr><td>Sand blasting</td><td>Market for waste paint</td><td>Europe without Switzerland</td><td>167800</td><td>kg</td><td></td></tr></tbody></table>
<caption>**Table 24**</caption>

Life-cycle inventory for the construction of the onshore and offshore pipeline facilities for connection to the pipeline including CO₂ tower, pig launcher, metering, piping, structural steel, onshore pipeline, and wires for transporting 1 Mta⁻¹ of pressurized CO₂ with a 20 a lifetime.

<table><caption>**Table 25**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Transformation, from unspecified</td><td></td><td>5329</td><td>m²</td><td>Own assumption of 0.4 m width trench</td></tr><tr><td>Land</td><td>Transformation, to industrial area</td><td></td><td>5329</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Occupation, industrial area</td><td></td><td>106 600</td><td>m² a</td><td></td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>400.4</td><td>t</td><td>CO₂ tower, pig launcher, metering, piping, structural steel, onshore pipeline</td></tr><tr><td>Equipment material</td><td>Market for reinforcing steel</td><td>GLO</td><td>100</td><td>t</td><td>offshore PLEM including pig launcher</td></tr><tr><td>wiring</td><td>Market for copper, cathode</td><td>GLO</td><td>20</td><td>t</td><td></td></tr><tr><td>Construction</td><td>Market group for concrete, normal strength</td><td>GLO</td><td>2672</td><td>m³</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>waste Equipment material</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>500.4</td><td>t</td><td></td></tr><tr><td>waste concrete</td><td>Market for waste concrete</td><td>Europe without Switzerland</td><td>3076</td><td>t</td><td></td></tr><tr><td>waste copper</td><td>Market for copper, cathode scrap, sorted, pressed</td><td>GLO</td><td>20</td><td>t</td><td></td></tr></tbody></table>

Life-cycle inventory for constructing 1 km of a 10 in pipeline for transporting 1 Mta⁻¹ of pressurized CO₂ with a 20 a lifetime.

<table><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Transformation, from seabed, unspecified</td><td></td><td>400</td><td>m²</td><td>Own assumption of 0.4 m width trench</td></tr><tr><td>Land</td><td>Transformation, to seabed, infrastructure</td><td></td><td>400</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, from seabed, infrastructure</td><td></td><td>200</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, to seabed, unspecified</td><td></td><td>200</td><td>m²</td><td></td></tr><tr><td>Pipeline material</td><td>Market for reinforcing steel</td><td>GLO</td><td>70.43</td><td>t</td><td></td></tr><tr><td>Pipeline material</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 & EFTA</td><td>0.5</td><td>t</td><td></td></tr><tr><td>Pipeline material</td><td>Bitumen seal production</td><td>RER</td><td>0.6850</td><td>t</td><td></td></tr><tr><td>Construction</td><td>Market for gravel, crushed</td><td>RoW</td><td>1485</td><td>T</td><td></td></tr><tr><td>Construction</td><td>Market for diesel, burned in building machine</td><td>GLO</td><td>2 242 000</td><td>MJ</td><td>Based on the Leviathan Field gas field project (Genesis Oil and Gas Consultants Ltd. and Noble Energy Mediterranean Ltd, 2016) which reports a fuel consumption for pipe laying of 130 t/day and a pipe laying speed of 9.6 km d⁻¹ - We assume a constant ratio of fuel consumption for pipelaying and of total fuel consumption of pipeline construction projects of 2340 t/9065.6 t. We assume a heating value of 42.735 MJ kg⁻¹ for diesel.</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Sacrificial anode</td><td>Aluminum III</td><td>ocean</td><td>0.425</td><td>t</td><td>Assume 85% utilization of sacrificial anode</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Waste pipeline</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>35.22</td><td>t</td><td>assume half the pipeline is recovered for waste treatment</td></tr><tr><td>Waste pipeline</td><td>Market for hazardous waste, for incineration</td><td>Europe without Switzerland</td><td>2.843</td><td>t</td><td>bitumen</td></tr></tbody></table>
<caption>**Table 26**</caption>

Life-cycle inventory for the construction of the port facilities for receiving liquefied CO₂, intermediate storage, and further pumping to the injection site with a capacity of 1.5 Mta⁻¹ and a 25-year lifetime based on (Equinor ASA, 2019).

<table><caption>**Table 27**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Transformation, from grassland, natural (non-use)</td><td>–</td><td>35 000</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, to industrial area</td><td>–</td><td>35 000</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, from seabed, unspecified</td><td>–</td><td>60 000</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, to dump site, residual material landfill</td><td>–</td><td>60 000</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Occupation, industrial area</td><td>–</td><td>875 000</td><td>m² a</td><td></td></tr><tr><td>construction material</td><td>Market for chromium steel 18/8</td><td>GLO</td><td>2400</td><td>t</td><td>Intermediate storage tanks</td></tr><tr><td>Construction activities</td><td>Market for explosive, tovex</td><td>GLO</td><td>260</td><td>t</td><td></td></tr><tr><td>Construction activities</td><td>Diesel, burned in building machine</td><td>GLO</td><td>2.29E7</td><td>MJ</td><td>Assuming a lower heating value of diesel of 42.8 MJ kg⁻¹</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Construction work</td><td>Carbon dioxide, fossil</td><td>To air</td><td>1806</td><td>t</td><td></td></tr><tr><td>Construction work</td><td>Nitrogen oxides</td><td>To air</td><td>5.5</td><td>t</td><td></td></tr><tr><td>Construction work</td><td>Sulfur oxides</td><td>To air</td><td>0.1</td><td>t</td><td></td></tr><tr><td>Construction work</td><td>Ammonia</td><td>To air</td><td>74</td><td>t</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Decommissioning intermediate storage tanks</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>2400</td><td>t</td><td></td></tr></tbody></table>

Life-cycle inventory for the construction of a pipeline to transport CO₂ from the receiving terminal to the injection site with a length of 110.4 km, a capacity of 1.5 Mta⁻¹, and a 25 a lifetime.

<table><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Occupation, seabed, infrastructure</td><td>–</td><td>8.13E4</td><td>m² a</td><td>Assuming 90% of the pipeline to be covered</td></tr><tr><td>Land</td><td>Transformation, from seabed, unspecified</td><td>–</td><td>3.25E3</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, to seabed, infrastructure</td><td>–</td><td>3.25E3</td><td>m²</td><td></td></tr><tr><td>Construction material</td><td>Market for aluminum, primary, ingot</td><td>IAI Area, EU27 &amp; EFTA</td><td>30 000</td><td>kg</td><td></td></tr><tr><td>Construction material</td><td>Market for reinforcing steel</td><td>GLO</td><td>1.22E4</td><td>t</td><td>Assuming a density of steel of 7850 kg m⁻³</td></tr><tr><td>Construction material</td><td>Market for drawing of pipe, steel</td><td>GLO</td><td>1.22E4</td><td>t</td><td></td></tr><tr><td>Construction material</td><td>Market for polyethylene, low density, granulate</td><td>GLO</td><td>275</td><td>t</td><td></td></tr><tr><td>Construction activities</td><td>Diesel, burned in building machine</td><td>GLO</td><td>3.04E8</td><td>MJ</td><td>Assuming a lower heating value of diesel of 42.8 MJ kg⁻¹</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Construction work</td><td>Carbon dioxide, fossil</td><td>To air</td><td>22 720</td><td>t</td><td>Emissions from construction work, we assume half of the emissions from marine operations for well construction, and half for pipeline construction</td></tr><tr><td>Construction work</td><td>Nitrogen oxides</td><td>To air</td><td>497</td><td>t</td><td>Emissions from construction work, we assume half of the emissions from marine operations for well construction, and half for pipeline construction</td></tr></tbody></table>

(continued on next page)
<table><caption>**Table 27 (continued).**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Construction work</td><td>Sulfur oxides</td><td>To air</td><td>7.1</td><td>t</td><td>Emissions from construction work, we assume half of the emissions from marine operations for well construction, and half for pipeline construction</td></tr><tr><td>Construction work</td><td>NMVOC, non-methane volatile organic compounds</td><td>To air</td><td>35.5</td><td>t</td><td>Emissions from construction work, we assume half of the emissions from marine operations for well construction, and half for pipeline construction</td></tr><tr><td>Sacrificial anode</td><td>Aluminum III</td><td>To water</td><td>2.55E4</td><td>kg</td><td>Assuming 85% utilization of anode</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Pipeline decommissioning</td><td>Market for decommissioned pipeline, natural gas</td><td>CH</td><td>1.22E4</td><td>t</td><td></td></tr><tr><td>Pipeline decommissioning</td><td>Market for waste polyethylene</td><td>NO</td><td>275</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 28**
Life-cycle inventory for a subsea facility for CO₂ injection with a capacity of 1.5 Mt a⁻¹ and an assumed lifetime of 25 a based on (Equinor ASA, 2019).</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Land</td><td>Occupation, seabed, drilling and mining</td><td>–</td><td>6324</td><td>m² a</td><td></td></tr><tr><td>Land</td><td>Transformation, from seabed, unspecified</td><td>–</td><td>253</td><td>m²</td><td></td></tr><tr><td>Land</td><td>Transformation, to seabed, drilling and mining</td><td>–</td><td>253</td><td>m²</td><td></td></tr><tr><td>Construction material</td><td>Market for steel, chromium steel 18/8</td><td>GLO</td><td>146</td><td>t</td><td></td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>End of life of construction material</td><td>Market for scrap steel</td><td>GLO</td><td>146</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 29**
Adjustment of the ecoinvent process for the construction of the offshore well, oil/gas (GLO) based on (Equinor ASA, 2019).</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Construction activities</td><td>Diesel, burned in building machine</td><td>GLO</td><td>3.72E4</td><td>MJ</td><td>Assuming a lower heating value of diesel of 42.8 MJ kg<sup>-1</sup></td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Construction work</td><td>Carbon dioxide, fossil</td><td>To air</td><td>2.75</td><td>t</td><td></td></tr><tr><td>Construction work</td><td>Nitrogen oxides</td><td>To air</td><td>0.045</td><td>t</td><td></td></tr><tr><td>Construction work</td><td>Sulfur oxides</td><td>To air</td><td>0.000865</td><td>t</td><td></td></tr><tr><td>Construction work</td><td>Ammonia, NO</td><td>To air</td><td>0.00447</td><td>t</td><td></td></tr></tbody></table>

<table><caption>**Table 30**
Construction of a permanent storage facility (Northern Lights) based on (Equinor ASA, 2019).</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Port facilities</td><td>Port facilities for receiving liquefied CO₂</td><td></td><td>1</td><td>p</td><td></td></tr><tr><td>Pipeline</td><td>Pipeline for the transport of CO₂ from the receiving terminal to the injection site</td><td></td><td>1</td><td>p</td><td>100.4 km</td></tr><tr><td>Subsea facility</td><td>Subsea facility for CO₂ injection</td><td></td><td>2</td><td>p</td><td>Accounts for backup injection site</td></tr><tr><td>Offshore well</td><td>Offshore well production, oil/gas</td><td>GLO</td><td>5320</td><td>m</td><td>Adjusted diesel demand and emissions as in Table A 25, accounts for backup injection site</td></tr></tbody></table>
<caption>**Table 31**</caption>

Life-cycle inventory for the permanent geological storage of 1 t of CO₂ in an offshore saline aquifer in Norway, assuming a 25-year lifetime of all equipment and a capacity of 1.5 Mta⁻¹ based on (Equinor ASA, 2019).

<table><caption>**Table 32**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>CO<sub>2</sub></td><td>Liquefied CO<sub>2</sub> delivered via ship</td><td>-</td><td>1</td><td>t</td><td></td></tr><tr><td>Storage facility</td><td>Permanent storage facility</td><td>-</td><td>2.667E-8</td><td>p</td><td></td></tr><tr><td>Electricity</td><td>Market for electricity, medium voltage</td><td>NO</td><td>33.83</td><td>kWh</td><td>Conservatively includes electricity demand for heating of liquefied CO<sub>2</sub> which may not be necessary if heating by seawater is sufficient</td></tr><tr><td colspan="6"><strong>Emission</strong></td></tr><tr><td>Fugitive emissions and gas turbine emissions</td><td>Carbon dioxide, fossil</td><td>To air</td><td>3.53E-5</td><td>t</td><td></td></tr></tbody></table>

Life-cycle inventory for the construction of the permanent storage facility (floating storage injection).

<table><caption>**Table 33**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Floating ship</td><td>Floating storage injection ship</td><td></td><td>1</td><td>p</td><td></td></tr><tr><td>Subsea facility</td><td>Subsea facility for CO<sub>2</sub> injection</td><td></td><td>1.067</td><td>p</td><td>Based on Northern Lights, accounts for the backup injection site, scaled considering 1.5 Mta<sup>-1</sup> capacity and 25 a lifetime of Northern Lights</td></tr><tr><td>Offshore well</td><td>Offshore well production, oil/gas</td><td>GLO</td><td>2837</td><td>m</td><td>Following assumptions from Northern Lights, adjusted diesel demand and emissions as in Table A 25, accounts for backup injection site; scaled considering 1.5 Mta<sup>-1</sup> capacity and 25 a lifetime of Northern Lights</td></tr><tr><td>Mooring system</td><td>Construction of mooring system</td><td></td><td>1</td><td>p</td><td></td></tr></tbody></table>

Construction of the floating storage injection ship approximated by scaling the construction of the base case ship.

<table><caption>**Table 34**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Floating storage injection ship</td><td>Ship with the capacity to transport 10.8kt of liquefied CO<sub>2</sub></td><td></td><td>2.215</td><td>p</td><td>Rough approximation based on steel weight of the floating storage</td></tr></tbody></table>

Life-cycle inventory for the construction of the permanent storage facility (direct injection).

<table><caption>**Table 35**</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Subsea facility</td><td>Subsea facility for CO<sub>2</sub> injection</td><td></td><td>1.06667</td><td>p</td><td>Based on Northern Lights, accounts for the backup injection site, scaled considering 1.5 Mta<sup>-1</sup> capacity and 25 a lifetime of Northern Lights</td></tr><tr><td>Offshore well</td><td>Offshore well production, oil/gas</td><td>GLO</td><td>2837.33333</td><td>m</td><td>Following assumptions from Northern Lights, adjusted diesel demand and emissions as in Table A 25, accounts for backup injection site; scaled considering 1.5 Mta<sup>-1</sup> capacity and 25 a lifetime of Northern Lights</td></tr><tr><td>Mooring system</td><td>Construction of mooring system</td><td></td><td>2</td><td>p</td><td></td></tr></tbody></table>

Life-cycle inventory for the construction of the mooring system for the floating storage injection and direct injection.

<table><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>Mooring system</td><td>Market for chromium steel 18/8</td><td>GLO</td><td>1000</td><td>t</td><td>Buoy, mooring line, riser, pipeline end manifold, and anchor</td></tr><tr><td colspan="6"><strong>Waste streams</strong></td></tr><tr><td>Steel</td><td>Market for scrap steel</td><td>Europe without Switzerland</td><td>1000</td><td>t</td><td></td></tr></tbody></table>
<table><caption>**Table 36**
Life-cycle inventory for the permanent geological storage of 1 t of CO₂ via floating storage injection off the coast of the United Kingdom.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>CO<sub>2</sub></td><td>Liquefied CO<sub>2</sub> delivered by ship</td><td>-</td><td>1</td><td>t</td><td></td></tr><tr><td>Storage facility</td><td>Permanent storage facility (floating storage injection)</td><td>-</td><td>5E-8</td><td>p</td><td>Assuming a lifetime of 20 a</td></tr><tr><td>Fuel</td><td>Market for heavy fuel oil</td><td>Europe without Switzerland</td><td>1.702E-3</td><td>kg</td><td></td></tr><tr><td>Fuel</td><td>Combustion of MDO</td><td>-</td><td>1.702E-3</td><td>kg</td><td>Based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021)</td></tr></tbody></table>

<table><caption>**Table 37**
Life-cycle inventory for the permanent geological storage of 1 t of CO₂ via direct injection off the coast of the United Kingdom.</caption><thead><tr><th>Input</th><th>Process</th><th>Location</th><th>Value</th><th>Unit</th><th>Comment</th></tr></thead><tbody><tr><td>CO<sub>2</sub></td><td>Liquefied CO<sub>2</sub> delivered by ship</td><td>-</td><td>1</td><td>t</td><td></td></tr><tr><td>Storage facility</td><td>Permanent storage facility (direct injection)</td><td>-</td><td>5E-8</td><td>p</td><td>Assuming a lifetime of 20 a</td></tr><tr><td>Fuel</td><td>Market for heavy fuel oil</td><td>Europe without Switzerland</td><td>5.64E-4</td><td>kg</td><td></td></tr><tr><td>Fuel</td><td>Combustion of MDO</td><td>-</td><td>5.64E-4</td><td>kg</td><td>Based on reports of the International Maritime Organization (Smith et al., 2015; Faber et al., 2021)</td></tr></tbody></table>

<table><caption>**Table 38**
Considered steel types and aluminum with corresponding ecoinvent processes.</caption><thead><tr><th>Metal type</th><th>Ecoinvent processes</th></tr></thead><tbody><tr><td>Carbon steel</td><td>Market for reinforcing steel, GLO<br>Metal working, average for steel product manufacturing, RER</td></tr><tr><td>Low-alloyed steel</td><td>Market for low-alloyed steel, GLO<br>Metal working, average for steel product manufacturing, RER</td></tr><tr><td>Stainless steel</td><td>Market for steel, chromium 18/8, GLO<br>Metal working, average for chromium steel product manufacturing, RER</td></tr><tr><td>Aluminum</td><td>Market for aluminium, primary, ingot, IAI Area, EU27 &amp; EFTA<br>Metal working, average for aluminium product manufacturing, RER</td></tr></tbody></table>

<figure><img src="image_11.png" /><figcaption>**Fig. 8.** Life-cycle carbon capture and storage efficiency of the carbon capture and storage supply chain depending on the share of *climate change* impact reduced assuming the German electricity grid mix. Considered regeneration heat sources include waste heat, locally available blast-furnace gas (BFG), high-temperature heat pumps (HTHP), gas-powered combined heat and power plant (CHP), or gas boilers (gas).</figcaption></figure>

The contribution of the investigated DMX™ process to reducing *climate change* impact is limited by the availability of BFG. Residual emissions remaining after all strategies are exhausted must be offset by carbon dioxide removal, e.g., by direct air capture and storage (DACCS).
<figure><img src="image_12.png" /><figcaption>**Fig. 9.** Environmental impact of the production of DMX™ in aqueous solution relative to the production of monoethanolamine (MEA) in aqueous solution on a mass basis. The range indicates values for MEA with a concentration of 40% (low end) to 30% (high end). MEA in an aqueous solution is modeled using a mix of the market activities for MEA (GLO) and deionized water (Europe without Switzerland) corresponding to the concentration of the aqueous solution.</figcaption></figure>

Impact categories shown are part of the life-cycle impact assessment method *Environmental Footprint 3.1* (European Commission 2018); resource use (energy carriers) ($RU_e$), human toxicity (non-cancer effects) ($HT_{nc}$), climate change (CC), photochemical ozone formation (PCOF), human toxicity (cancer effects) ($HT_c$), freshwater ecotoxicity ($ET_{fw}$), terrestrial eutrophication ($E_t$), aquatic freshwater eutrophication ($E_{fw}$), particulate matter (PM), land use (LU), acidification (A), ionizing radiation (IR), ozone depletion (OD), aquatic marine eutrophication ($E_m$), water scarcity (W), resource use (minerals and metals) ($RU_{mm}$).

<figure><img src="image_13.png" /><figcaption>**Fig. 10.** Environmental impacts of transport and geological storage options for the conditioning, intermediary storage and transport, and geological storage of CO₂ relative to the base case. The bars represent the options in the following order from left to right: Northern Lights, 10.8 kt ships (base case); Northern Lights, 20.5 kt ship; Northern Lights, 7.5 kt ships; UK storage, floating storage injection (FSI); UK storage, direct injection (DI); UK storage, pipeline; Dutch storage, 5.4 kt ship; Dutch storage, pipeline (Fig. 3).</figcaption></figure>

Impact categories shown are part of the life-cycle impact assessment method *Environmental Footprint 3.1* (European Commission 2018): climate change (CC), ozone depletion (OD), particulate matter (PM), photochemical ozone formation (PCOF), acidification (A), terrestrial eutrophication ($E_t$), aquatic freshwater eutrophication ($E_{fw}$), aquatic marine eutrophication ($E_m$), human toxicity (cancer effects) ($HT_c$), human toxicity (non-cancer effects) ($HT_{nc}$), freshwater ecotoxicity ($ET_{fw}$), land use (LU), water scarcity (W), resource use (minerals and metals) ($RU_{mm}$), resource use (energy carriers) ($RU_e$), ionizing radiation (IR).
# Data availability

Data used for the study is included in the SI of the manuscript.

# References

Andreasi Bassi, S., Biganzoli, F., Ferrara, N., Amadei, A., Valente, A., Sala, S., 2023. Updated characterisation and normalisation factors for the environmental footprint 3.1 method. http://dx.doi.org/10.2760/798894, URL https://op.europa.eu/en/publication-detail/-/publication/145f8401-a82a-11ed-b508-01aa75ed71a1.

Benson, S., Cook, P., Anderson, J., Bachu, S., Nimir, H.B., Basu, B., Bradshaw, J., Deguchi, G., Gale, J., von Goerne, G., Heidug, W., Holloway, S., Kamal, R., Keith, D., Lloyd, P., Rocha, P., Senior, B., Thomson, J., Torp, T., Wildenborg, T., Wilson, M., Zarlenga, F., Zhou, D., 2005. Underground geological storage. In: Metz, B., Davidson, O., de Coninck, H., Loos, M., Meyer, L. (Eds.), IPCC Special Report on Carbon Dioxide Capture and Storage. Cambridge Univ. Press, Cambridge, pp. 195-276.

Bouman, E.A., Öberg, M.M., Hertwich, E.G., 2016. Environmental impacts of balancing offshore wind power with compressed air energy storage (CAES). Energy 95, 91-98. http://dx.doi.org/10.1016/j.energy.2015.11.041.

Burger, J., Nöhl, J., Seiler, J., Gabrielli, P., Oeuvray, P., Becattini, V., Reyes-Lúa, A., Riboldi, L., Sansavini, G., Bardow, A., 2024. Environmental impacts of carbon capture, transport, and storage supply chains: Status and the way forward. Int. J. Greenh. Gas Control. 132, 104039. http://dx.doi.org/10.1016/j.ijggc.2023.104039.

Cavalett, O., Watanabe, M.D.B., Fleiger, K., Hoenig, V., Cherubini, F., 2022. LCA and negative emission potential of retrofitted cement plants under oxyfuel conditions at high biogenic fuel shares. Sci. Rep. 12 (1), 8924. http://dx.doi.org/10.1038/s41598-022-13064-w.

Chisalita, D.-A., Petrescu, L., Cobden, P., van Dijk, H., Cormos, A.-M., Cormos, C.-C., 2019. Assessing the environmental impact of an integrated steel mill with post-combustion CO₂ capture and storage using the LCA methodology. J. Clean. Prod. 211, 1015-1025. http://dx.doi.org/10.1016/j.jclepro.2018.11.256.

Comer, B., Beecken, J., Vermeulen, R., Sturrup, E., Paschinger, P., Osipova, L., Gore, K., Delahaye, A., Verhagen, V., Knudsen, Bettina, Knudsen, Jon, Verbeek, R., 2024. Fugitive and unburned methane emissions from ships (FUMES): Characterizing methane emissions from LNG-fueled ships using drones, helicopters, and onboard measurements. URL https://theicct.org/wp-content/uploads/2023/10/Marine-real-world-NOx-Working-paper-20-A4-v6.pdf.

Corsten, M., Ramírez, A., Shen, L., Koornneef, J., Faaij, A., 2013. Environmental impact assessment of CCS chains - lessons learned and limitations from LCA literature. Int. J. Greenh. Gas Control. 13, 59-71. http://dx.doi.org/10.1016/j.ijggc.2012.12.003.

Cuéllar-Franca, R.M., Azapagic, A., 2015. Carbon capture, storage and utilisation technologies: A critical analysis and comparison of their life cycle environmental impacts. J. CO₂ Util. 9, 82-102. http://dx.doi.org/10.1016/j.jcou.2014.12.001.

Davis, S.J., Lewis, N.S., Shaner, M., Aggarwal, S., Arent, D., Azevedo, I.L., Benson, S.M., Bradley, T., Brouwer, J., Chiang, Y.-M., Clack, C.T.M., Cohen, A., Doig, S., Edmonds, J., Fennell, P., Field, C.B., Hannegan, B., Hodge, B.-M., Hoffert, M.I., Ingersoll, E., Jaramillo, P., Lackner, K.S., Mach, K.J., Mastrandrea, M., Ogden, J., Peterson, P.F., Sanchez, D.L., Sperling, D., Stagner, J., Trancik, J.E., Yang, C.-J., Caldeira, K., 2018. Net-zero emissions energy systems. Sci. (N. Y. N. Y.) 360 (6396), http://dx.doi.org/10.1126/science.aas9793.

Deutz, S., Bardow, A., 2021. Life-cycle assessment of an industrial direct air capture process based on temperature-vacuum swing adsorption. Nat. Energy 6 (2), 203-213. http://dx.doi.org/10.1038/s41560-020-00771-9.

Dlamini, G.M., Fosbol, P.L., Ness, K., Remiezowicz, E., Losnegård, S.-E., von Solms, N., 2023. Optimisation of carbon dioxide pressurisation pathways for pipeline offshore delivery. Int. J. Greenh. Gas Control. 128, 103943. http://dx.doi.org/10.1016/j.ijggc.2023.103943.

Dreillard, M., Broutin, P., Briot, P., Huard, T., Lettat, A., 2017. Application of the DMXTM CO₂ capture process in steel industry. Energy Procedia 114, 2573-2589. http://dx.doi.org/10.1016/j.egypro.2017.03.1415.

Equinor ASA, 2019. EL001 northern lights - receiving and permanent storage of CO₂: Plan for development, installation and operation part II - impact assessment.

European Commission, 2021. Commission recommendation (EU) 2021/2279 of 15 december 2021 on the use of the environmental footprint methods to measure and communicate the life cycle environmental performance of products and organisations.

Faber, J., Hanayama, S., Zhang, S., Pereda, P., Comer, B., Hauerhof, E., Schim van der Loeff, W., Smith, T., Zhang, Y., Kosaka, H., Adachi, M., Bonello, J.-M., Galbraith, C., Gong, Z., Hirata, K., Hummels, D., Kleijn, A., Lee, D.S., Liu, Y., Lucchesi, A., Mao, X., Muraoka, E., Osipova, L., Qian, H., Rutherford, D., Suárez de la Fuente, S., Yuan, H., Perico, C.V., Wu, L., Sun, D., Yoo, D.-H., Xing, H., 2021. Fourth IMO greenhouse gas study 2020.

Fadeyi, S., Arafat, H.A., Abu-Zahra, M.R., 2013. Life cycle assessment of natural gas combined cycle integrated with CO₂ post combustion capture using chemical solvent. Int. J. Greenh. Gas Control. 19, 441-452. http://dx.doi.org/10.1016/j.ijggc.2013.10.008.

Fan, Z., Friedmann, S.J., 2021. Low-carbon production of iron and steel: Technology options, economic assessment, and policy. Joule 5 (4), 829-862. http://dx.doi.org/10.1016/j.joule.2021.02.018.

Fazio, S., Biganzioli, F., de Laurentiis, V., Zampori, L., Sala, S., Diaconu, E., 2018. Supporting information to the characterisation factors of recommended EF life cycle impact assessment methods: Version 2 from ILCD to EF 3.0. http://dx.doi.org/10.2760/002447, URL https://publications.jrc.ec.europa.eu/repository/handle/JRC114822.

Fennell, P., Driver, J., Bataille, C., Davis, S.J., 2022. Cement and steel - nine steps to net zero. Nature 603 (7902), 574-577. http://dx.doi.org/10.1038/d41586-022-00758-4.

García-Gusano, D., Garraín, D., Herrera, I., Cabal, H., Lechón, Y., 2015. Life cycle assessment of applying CO₂ post-combustion capture to the spanish cement production. J. Clean. Prod. 104, 328-338. http://dx.doi.org/10.1016/j.jclepro.2013.11.056.

Genesis Oil and Gas Consultants Ltd., Noble Energy Mediterranean Ltd, 2016. Environmental impact assessment for installation, operation and maintenance of pipelines and submarine systems for leviathan field development: Chapter C - description of actions stemming from performance of the application.

Giordano, L., Roizard, D., Favre, E., 2018. Life cycle assessment of post-combustion CO₂ capture: A comparison between membrane separation and chemical absorption processes. Int. J. Greenh. Gas Control. 68, 146-163. http://dx.doi.org/10.1016/j.ijggc.2017.11.008.

Global Carbon Capture and Storage Institute Ltd, 2023. Global status of ccs 2023.

Gong, W., Remiezowicz, E., Fosbol, P.L., von Solms, N., 2022. Design and analysis of novel CO₂ conditioning process in ship-based CCS. Energies 15 (16), 5928. http://dx.doi.org/10.3390/en15165928.

Gong, W., Timmermans, R., Remiezowicz, E., Fosbol, P.L., von Solms, N., 2021. Design and analysis of novel CO₂ conditioning processes in the 3D project. SSRN Electron. J. http://dx.doi.org/10.2139/ssrn.3819391.

Hamidian, A., Bonnart, R., Lacroix, M., Moreau, v., 2021. A pilot plant in dunkirk for DMX process demonstration. SSRN Electron. J. http://dx.doi.org/10.2139/ssrn.3821422.

Hellweg, S., Milà i Canals, L., 2014. Emerging approaches, challenges and opportunities in life cycle assessment. Sci. (N. Y. N. Y.) 344 (6188), 1109-1113. http://dx.doi.org/10.1126/science.1248361.

Intergovernmental Panel on Climate Change (Ed.), 2022. Global Warming of 1.5° C: An IPCC Special Report on the Impacts of Global Warming of 1.5° C Above Pre-Industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty. Cambridge University Press, Cambridge, UK and New York, NY, USA, http://dx.doi.org/10.1017/9781009157940.

International Organization for Standardization, 2006a. Environmental management - Life cycle assessment - Principles and framework.

International Organization for Standardization, 2006b. Environmental management - Life cycle assessment - Requirements and guidelines.

Khan, U., Zevenhoven, R., Tveit, T.-M., 2020. Evaluation of the environmental sustainability of a stirling cycle-based heat pump using LCA. Energies 13 (17), 4469. http://dx.doi.org/10.3390/en13174469.

Koornneef, J., Ramírez, A., Turkenburg, W., Faaij, A., 2012. The environmental impact and risk assessment of CO₂ capture, transport and storage - an evaluation of the knowledge base. Prog. Energy Combust. Sci. 38 (1), 62-86. http://dx.doi.org/10.1016/j.pecs.2011.05.002.

Koornneef, J., van Keulen, T., Faaij, A., Turkenburg, W., 2008. Life cycle assessment of a pulverized coal power plant with post-combustion capture, transport and storage of CO₂. Int. J. Greenh. Gas Control. 2 (4), 448-467. http://dx.doi.org/10.1016/j.ijggc.2008.06.008.

Leeson, D., Mac Dowell, N., Shah, N., Petit, C., Fennell, P.S., 2017. A techno-economic analysis and systematic review of carbon capture and storage (CCS) applied to the iron and steel, cement, oil refining and pulp and paper industries, as well as other high purity sources. Int. J. Greenh. Gas Control. 61, 71-84. http://dx.doi.org/10.1016/j.ijggc.2017.03.020.

Leeson, D., Ramirez, A., Mac Dowell, N., 2019. Chapter 9. Carbon capture and storage from industrial sources. In: Reiner, D., Bui, M., Mac Dowell, N. (Eds.), Carbon Capture and Storage: In: Energy and Environment Series, The Royal Society of Chemistry, Cambridge, pp. 296-314. http://dx.doi.org/10.1039/9781788012744-00296.

Li, H., Jiang, H.-D., Yang, B., Liao, H., 2019. An analysis of research hotspots and modeling techniques on carbon capture and storage. Sci. Total. Environ. 687, 687-701. http://dx.doi.org/10.1016/j.scitotenv.2019.06.013.

Losnegård, S.-E., Solvang, S., Strømme, P.-A., Knudsen, K., Larsen, A., Belgaroui, J., Forin, P., Merat, C., Capillou, C., 2021. Evaluation of CO₂ storage locations and transport solutions from capture plant in dunkirk. SSRN Electron. J. http://dx.doi.org/10.2139/ssrn.3821437.

Madhu, K., Pauliuk, S., Dhathri, S., Creutzig, F., 2021. Understanding environmental trade-offs and resource demand of direct air capture technologies through comparative life-cycle assessment. Nat. Energy http://dx.doi.org/10.1038/s41560-021-00922-6.
Moser, P., Wiechers, G., Schmidt, S., Garcia Moretz-Sohn Monteiro, J., Charalambous, C., Garcia, S., Sanchez Fernandez, E., 2020. Results of the 18-month test with MEA at the post-combustion capture pilot plant at Niederaussem – new impetus to solvent management, emissions and dynamic behaviour. Int. J. Greenh. Gas Control. 95, 102945. http://dx.doi.org/10.1016/j.ijggc.2019.102945.

Mutel, C., 2017. Brightway: An open source framework for life cycle assessment. J. Open Source Softw. 2 (12), 236. http://dx.doi.org/10.21105/joss.00236.

Northern Lights JV, 2024. Northern lights celebrates completion of world's first commercial CO₂ transport and storage service. URL https://norlights.com/news/northern-lights-celebrates-completion-of-worlds-first-commercial-co2-transport-and-storage-service/.

Notten, P., Althaus, H.-J., Burke, M., Läderach, A., 2018. Life cycle inventories of global shipping - global: for the SRI project.

Pavlenko, N., Comer, B., Zhou, Y., Clark, N., Rutherford, D., 2020. The climate implications of using LNG as a marine fuel.

Raynal, L., Alix, P., Bouillon, P.-A., Gomez, A., de Le Nailly, M.F., Jacquin, M., Kittel, J., Di Lella, A., Mougin, P., Trapy, J., 2011. The DMX™ process: An original solution for lowering the cost of post-combustion carbon capture. Energy Procedia 4, 779–786. http://dx.doi.org/10.1016/j.egypro.2011.01.119.

Raynal, L., Briot, P., Dreillard, M., Broutin, P., Mangiaracina, A., Drioli, B.S., Politi, M., La Marca, C., Mertens, J., Thielens, M.-L., Laborie, G., Normand, L., 2014. Evaluation of the DMX process for industrial pilot demonstration – methodology and results. Energy Procedia 63, 6298–6309. http://dx.doi.org/10.1016/j.egypro.2014.11.662.

Remus, R., 2013. Best Available Techniques (BAT) Reference Document for Iron and Steel Production: Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control). In: Scientific and technical research series, vol. 25521, Publications Office of the European Union, Luxembourg, http://dx.doi.org/10.2791/97469, URL http://bookshop.europa.eu/en/best-available-techniques-bat-reference-document-for-iron-and-steel-production-pbLFNA25521/.

Schakel, W., Hung, C.R., Tokheim, L.-A., Strømman, A.H., Worrell, E., Ramírez, A., 2018. Impact of fuel selection on the environmental performance of post-combustion calcium looping applied to a cement plant. Appl. Energy 210, 75–87. http://dx.doi.org/10.1016/j.apenergy.2017.10.123.

Seiler, J., Shu, D.Y., Burger, J., Langhorst, T., von der Aßen, N., Bardow, A., 2025. Environmental aspects: Life-cycle assessment of carbon capture, transport, and storage value chains. In: Roussanaly, S., Anantharaman, R. (Eds.), Handbook on Advanced Carbon Capture and Storage—a Comprehensive Guide. Woodhead Publishing, Accepted.

Smith, T.W.P., Jalkanen, J.-P., Anderson, B.A., Corbett, J.J., Faber, J., Hanayama, S., O’Keeffe, E., Parker, S., Johansson, L., Aldous, L., Raucci, C., Traut, M., Ettinger, S., Nelissen, D., Lee, D.S., Ng, S., Agrawal, A., Winebrake, J.J., ’t Hoen, M., Chesworth, S., Pandey, A., 2015. Third IMO greenhouse gas study 2014.

Volkart, K., Bauer, C., Boulet, C., 2013. Life cycle assessment of carbon capture and storage in power generation and industry in europe. Int. J. Greenh. Gas Control. 16, 91–106. http://dx.doi.org/10.1016/j.ijggc.2013.03.003.

Wang, Y., Pan, Z., Zhang, W., Borhani, T.N., Li, R., Zhang, Z., 2022. Life cycle assessment of combustion-based electricity generation technologies integrated with carbon capture and storage: A review. Environ. Res. 207, 112219. http://dx.doi.org/10.1016/j.envres.2021.112219.

Wernet, G., Bauer, C., Steubing, B., Reinhard, J., Moreno-Ruiz, E., Weidema, B., 2016. The ecoinvent database version 3 (part I): Overview and methodology. Int. J. Life Cycle Assess. 21 (9), 1218–1230. http://dx.doi.org/10.1007/s11367-016-1087-8.

World Steel Association, 2022. 2022 world steel in figures. URL https://worldsteel.org/publications/bookshop/world-steel-in-figures-2022/?do_download_id=74c6ae4c-36ed-438f-99e5-1bdfec92b3e3.

Zapp, P., Schreiber, A., Marx, J., Haines, M., Hake, J.-F., Gale, J., 2012. Overall environmental impacts of CCS technologies—A life cycle approach. Int. J. Greenh. Gas Control. 8, 12–21. http://dx.doi.org/10.1016/j.ijggc.2012.01.014.