The electrolysis of CO₂ converts CO₂ into value-added products and has the potential to reduce the use of fossil feedstocks by serving as a circular alternative in chemical processes. However, existing literature lacks comprehensive and quantitative analyses of economic, environmental, and governmental factors that can hinder or support its deployment. This study addresses this gap by exploring the potential of CO₂ electrolysis for the production of synthesis gas, syngas, through a supply chain design that integrates long-term decisions on location and infrastructure and medium-term decisions on capacity expansion and aggregate production planning. We identify and quantify time-dependent and uncertain parameters using the Delphi method and employ multi-period planning and robust optimization approaches to consider them, respectively. Moreover, since the environmental impact of syngas is highly dependent on electricity consumption, renewable electricity is utilized with battery support alongside grid electricity. Accordingly, we propose a mixed integer linear programming model to design a supply chain that can serve as a benchmark to make CO₂ electrolysis financially and environmentally viable for syngas production. We conduct a case study on the Benelux region, analyzing different scenarios to derive managerial and design insights. The results show that a design that takes uncertainty into account can reduce syngas production costs by up to 22%. Additionally, although renewable electricity supply variability and different grid characteristics across countries can lead to different strategic decisions with higher costs, increased battery installations and higher government financial support for renewable electricity can help eliminate differences in designs.

The rising pressure to defossilize the chemical industry has driven research toward producing chemicals that use alternative carbon sources (ACS). However, the challenges and impacts of replacing already implemented processes and symbiotic relationships remain largely underexplored. This paper systematically assesses the impacts of defossilizing existing processes, both individually and simultaneously, in a propylene cluster in the Port of Rotterdam, the Netherlands. Nine fossil-based processes and three ACS-based processes (i.e., CO₂-based polyol, biopropylene glycol (bio-PG), and biomethyl-tert-butyl-ether (bio-MTBE)) were included in the assessment. Integrating a single ACS-based process enlarges the propylene cluster and results in an excess of upstream chemicals that are no longer required by the ACS processes. Still, relatively simple technologies can reduce total energy and water use, resulting in lower direct CO₂emissions and water consumption of the cluster. Deploying multiple processes in parallel can drive the full defossilization of the cluster, but it requires a complete overhaul. The results illustrate the extent to which combining ACS-based processes could change the layout of an existing petrochemical cluster, affecting its performance. The paper stresses the importance of assessing such deployments, considering the existing conditions in industrial clusters.

Reaching climate goals requires a rapid scale-up of clean energy technologies, which, in many cases, are still under development. Low-temperature CO₂ electrolysis (LT CO2E) is a promising pre-commercial technology (TRL 3 to 6) that can produce CO₂-based fuels and chemicals using electricity. To understand the future competitiveness of such novel technologies, techno-economic assessments (TEAs) are conducted using the best available knowledge at the time, ensuring that the highest-quality TEA information supports decision-making regarding future investments. As LT CO₂E advances, its techno-economic research must evolve toward more in-depth process designs, integrating the latest knowledge regarding the technology's development and any aspects essential to commercial implementation. To do so, it is important to understand the robustness and limitations of existing LT CO2E TEAs to identify areas for further improvement; for example, electricity and CO2 cost assumptions vary significantly between TEAs for syngas, accounting for 18–81% and up to 28% of the total operational expenditure, respectively. This review assessed the origins and justifications behind common assumptions used in TEAs of LT CO2E with three main findings: 1) the methodological justifications seem stuck in the past, relying on three key studies and mature electrolysis technologies from previous decades; 2) the latest advancements in electrolyzer modeling underscore the need to update existing LT CO₂E performance benchmarks, and 3) future LT CO₂E TEAs need to include pre-treatment of CO₂ and water, product separation steps, as well as heat integration, recycling, and waste valorization, to progress beyond the preliminary conceptual design phase.

To achieve climate change mitigation targets, defossilising the production of bulk chemicals like ethylene will be critical. These high-volume petrochemicals are typically produced from fossil-based feedstocks in industrial clusters, which are highly integrated in terms of mass and energy. Replacing fossil-based processes in interconnected industrial clusters can, therefore, impact such interactions and decrease performance or cause lock-in situations at the cluster level. This has, however, been overlooked in the literature. This paper addresses this knowledge gap by evaluating the impacts of replacing fossil-based ethylene production in an existing industrial cluster with processes that use Alternative Carbon Sources (ACS) such as biomass, CO2 and plastic waste. This study explicitly evaluates the performance of the ACS-based production routes at process and cluster levels by assessing changes in mass, energy, prices, CO2 emissions and water demand. The results show that due to the notable difference in product distribution, energy needs and waste generation, a complete re-wiring of the petrochemical cluster in terms of mass, energy and revenue will be required. The results also indicate that defossilising ethylene production in existing industrial clusters can result in a shifting of burden outside the cluster for byproduct production, which can lead to increasing fossil-fuel use outside the cluster. At process level, the main challenges to defossilise ethylene are access to large quantities of clean energy and the large investment costs. Under current market conditions, among the different options examined, plastic pyrolysis is the most competitive ACS-based technology with the lowest impact at the cluster level. However, this requires a large availability of plastic waste, which will be challenging given current recycling rates. Further improvements in waste valorisation and integration of renewable energy-based heating will also be required to make this technology environmentally appealing.

Alternative carbon sources (ACS) are increasingly considered necessary for the defossilisation of fossil-based chemicals. However, the potential and impacts of integrating ACS-based processes in existing petrochemical clusters are often overlooked. This paper aims to systematically analyse key techno-economic and environmental indicators associated with producing bio-based isobutene as an option to defossilise the production of methyl-tert-butyl-ether (MTBE) in the Port of Rotterdam, the Netherlands. The assessment is conducted at process and cluster levels. For this, the bio-isobutene (bio-IBN) process (358 kt/y of product), along with the existing fossil-based processes involved in MTBE production (i.e. the MTBE cluster), were modelled in Aspen Plus v12. The results show that under current conditions, although bio-IBN production could defossilise the MTBE cluster by c.a. 80 %, it is not cost-competitive compared to the current fossil-based process. Furthermore, deploying the bio-IBN process would significantly change the structure of the existing MTBE cluster, increasing by a factor of two or larger electricity, cooling water and bare land requirements. These requirements would affect the economic and environmental performance of the full cluster. The results emphasise the critical role of strategic change of new processes within existing petrochemical clusters.

Despite the huge efforts devoted to the development of the electrochemical reduction of CO2 (ECO2R) in the past decade, still many challenges are present, hindering further approaches to industrial applications. This paper gives a perspective on these challenges from a Process Systems Engineering (PSE) standpoint, while at the same time highlighting the opportunities for advancements in the field in the European context. The challenges are connected with: the coupling of these processes with renewable electricity generation; the feedstock (in particular CO2); the processes itself; and the different products that can be obtained. PSE can determine the optimal interactions among the components of such systems, allowing educated decision making in designing the best process configurations under uncertainty and constrains. The opportunities, on the other hand, stem from a stronger collaboration between the PSE and the experimental communities, from the possibility of integrating ECO2R into existing industrial productions and from process-wide optimisation studies, encompassing the whole production cycle of the chemicals to exploit possible synergies.

Combining intermittent renewable electricity (IRE) with carbon capture and utilisation is urgently needed in the chemical sector. In this context, microbial electrosynthesis (MES) has gained attention. It can electrochemically produce hexanoic acid, a value-added chemical, from CO₂. However, there is a lack of understanding regarding how the intermittency of renewable electricity could impact the design of a MES plant. We studied this using Aspen Plus models. A MES plant that was powered by constant grid electricity could operate from 100% down to 70% of its nominal capacity, at which point the heat exchangers and the internal geometrical design of the distillation towers became bottlenecks. The levelised production cost of hexanoic acid (LPC_C6A) was estimated at 4.0 €/kg. Switching to IRE supply increased LPC_C6A to 5.3 €/kg (for wind electricity) and 4.7 €/kg (for hybrid renewable electricity). A battery energy storage system (BESS) was deployed. The lowest LPC_C6A was found at a BESS installation of 29 GJ/h for wind electricity (5.1 €/kg) and at 12 GJ/h for hybrid renewable electricity (4.7 €/kg). In both situations, the volume flexibility of the MES plant was not improved. At the investigated market and operating conditions, coupling IRE to the MES plant was economically infeasible.

Different alternative carbon sources like CO₂, biomass and plastic waste, can be used to replace fossil carbon as feedstock in the production of methanol. Based on current literature, the plastic-based methanol route is the most competitive one among the three based on price indicator, but there is still a lack of comprehensive understanding of the techno-economic differences between alternative feedstock technologies. In this study, three technologies from each alternative feedstock were assessed to evaluate the techno-economic trade-offs between them. The research shows that even though currently the plastic-based route is comparatively cost competitive with the conventional route of producing methanol, the CO₂-based methanol route can also be competitive with green hydrogen prices in the range of 1400-1100 EUR/t. While the biomass-based route showed superior energy performance compared to the other two.

The present study utilizes a value sensitive design (VSD) inspired approach to contribute to the design and implementation of CO₂ electrolysis (CO₂E) within the framework of carbon capture and utilization (CCU) technologies, which convert CO₂ into valuable products. The focus of this study is on a low technology readiness level (TRL) technology, yet likely relevant to reach climate neutrality by 2050. We examine the perspectives of stakeholders along the supply chain and proactively identify relevant sustainability-related values and potential conflicts among them. Thus the current work highlights the importance of considering a broad range of stakeholders and their values in the early stages of technological design. The research approach is consisting of various steps inspired by value sensitive design (VSD): identifying relevant values and norms associated with CO2 electrolysis through literature analysis, conducting qualitative interviews with relevant stakeholders to triangulate the results. Subsequently, a value-based alignment network analysis was employed to examine shared values that are central for the design of the technology. The findings indicate that sustainability-related values such as concern for nature, climate change mitigation, the use of renewable energy, critical raw materials, cost, and return on investment, albeit with potential differences in interpretation, are increasingly becoming central considerations in the decision-making processes of individuals, businesses, and governments alike. Based on these findings, specific aspects of technology design, namely scale, location, integration, and synthesized product, that can impact a wide range of identified values, are discussed.

Microbial electrosynthesis (MES) is a novel carbon utilisation technology aiming to contribute to a circular economy by converting CO₂ and renewable electricity into value-added chemicals. This study presents a cradle-to-gate life cycle assessment (LCA) of hexanoic acid (C6A) production using MES, comparing this production with alternative technologies. It also includes a cradle-to-grave LCA for potentially converting C6A into a neat sustainable aviation fuel (SAF). On a cradle-to-gate basis, MES-based C6A exhibits a carbon footprint at 5.5 t CO₂eq/tC6A, similar to fermentation- and plant-based C6A. However, its direct land use is more than one order of magnitude lower than plant-based C6A. On a cradle-to-grave basis, MES-based neat SAF emits 325 g CO₂eq/MJ neat SAF, which is significantly higher than the counterparts from currently certified routes and conventional petroleum-derived jet fuel. However, its negligible indirect land use change emissions might potentially make it competitive against neat SAFs originating from first-generation biomass.

Electrochemical ammonia synthesis via the nitrogen reduction reaction (NRR) has been poised as one of the promising technologies for the sustainable production of green ammonia. In this work, we developed extensive process models of fully integrated electrochemical NH ₃ production plants at small scale (91 tonnes per day), including their techno-economic assessments, for (Li-)mediated, direct and indirect NRR pathways at ambient and elevated temperatures, which were compared with electrified and steam-methane reforming (SMR) Haber-Bosch processes. The levelized cost of ammonia (LCOA) of aqueous NRR at ambient conditions only becomes comparable with SMR Haber-Bosch at very optimistic electrolyzer performance parameters (FE > 80% at j ≥ 0.3 A cm ⁻²) and electricity prices (<$0.024 per kW h). Both high temperature NRR and Li-mediated NRR are not economically comparable within the tested variable ranges. High temperature NRR is very capital intensive due the requirement of a heat exchanger network, more auxiliary equipment and an additional water electrolyzer (considering the indirect route). For Li-mediated NRR, the high lithium plating potentials, ohmic losses and the requirement for H ₂, limits its commercial competitiveness with SMR Haber-Bosch. This incentivises the search for materials beyond lithium.

CO2 electroreduction driven by renewable energy is a promising technology for defossilizing the chemical industry, but intermittency challenges its operation. This work aims to understand the impacts of intermittency on the design, volume flexibility, and scheduling of a microbial electrosynthesis (MES) plant that converts CO2 to hexanoic acid. A battery and a storage tank were considered to buffer the intermittency. Explorative case studies showed that batteries were economically unfavorable. Restricted by the downstream processing (DSP) flexibility, a storage tank with optimized size combined with optimal scheduling, under the assumed conditions in this work, improved the plant’s volume flexibility only by 10%. The carbon footprint became 3 times lower when switching from grid to renewable electricity, but the levelized production cost of hexanoic acid increased. Hence, coupling with renewable electricity was not economically but environmentally favorable. Developing more flexible DSP technologies or synthesizing higher-purity chemicals are needed to enhance MES’s attractiveness.

Reaching our climate goals will require urgent advancements in the development of fossil-free technologies. Solid-oxide electrolysis (SOE) at high-temperature is a promising candidate for combining CO₂ utilization and renewable electricity use. Explorative techno-economic analyses are being performed to understand the full plant design requirements for integrated SOE systems. However, there is still a lack of understanding of the potential impact that the pre-treatment of CO₂ will have on the overall design and economics of a SOE-based system. To address this knowledge gap, as a first step, the process model of the pre-treatment units needed to purify CO₂ from a bioethanol plant is developed in Aspen Plus in the current work. Based on the preliminary results of this paper, the equipment costs mainly stem from the units related to the removal of sulfur (~65%) and alcohols (~32%). The energy costs are almost entirely related to the cryogenic distillation step required for the removal of non-condensable gases (~96%).

Due to the heavy dependence on fossil-fuels as raw materials, the defossilization of feedstocks in the petrochemical industry represents a challenge. A large number of possible process routes that use alternative carbon sources (ACS) like CO2, biomass, and waste are being developed for the feedstock replacement. For instance, to produce ethylene, more than 40 ACS process routes were identified. These multiple options make the selection of the promising process route a complex task. By replacing feedstocks, a process can change significantly and the impacts related to these changes in a highly interconnected industrial cluster can create cascading effects due to system interdependencies. This work aims to understand the cascading impacts in carbon flows and prices of implementing an ACS production process in an ethylene cluster. The results show that PVC will be the highest impacted and defossilizing one value-chain can have cascading effect on other value-chains as observed for PET.

The production of base chemicals by electrochemical conversion of captured CO₂ has the potential to close the carbon cycle, thereby contributing to a future energy transition. With the feasibility of low-temperature electrochemical CO₂ conversion demonstrated at lab scale, research is shifting toward optimizing electrolyser design and operation for industrial applications, with target values based on techno-economic analysis. However, current techno-economic analyses often neglect experimentally reported interdependencies of key performance variables such as the current density, the faradaic efficiency, and the conversion. Aiming to understand the impact of these interdependencies on the economic outlook, we develop a model capturing mass transfer effects over the channel length for an alkaline, membrane electrolyser. Coupling the channel scale with the higher level process scale and embedding this multiscale model in an economic framework allows us to analyze the economic trade-off between the performance variables. Our analysis shows that the derived target values for the performance variables strongly depend on the interdependencies described in the channel scale model. Our analysis also suggests that economically optimal current densities can be as low as half of the previously reported benchmarks. More generally, our work highlights the need to move toward multiscale models, especially in the field of CO₂ electrolysis, to effectively elucidate current bottlenecks in the quest toward economically compelling system designs.

An educational workshop for developing Process Systems Engineering (PSE) courses will be held during ESCAPE-33, following the model workshop that was run during the CAPE Forum 2022 held at the University of Twente, in the Netherlands. This 3-hour workshop distributes the participants into four teams working together to develop the outline of a course on a novel application area in PSE motivated by a selected plenary or keynote talk at the conference, with each team led by authors of this contribution. This paper provides an overview of the approach used in the workshop for the effective development of a PSE course.

Using alternative carbon sources (ACS) to produce downstream derivatives (DDs) is a promising option for defossilising the chemical industry. However, the potential consequences of using ACS in interconnected petrochemical clusters are generally overlooked. This paper aims to develop a methodological approach for systematically analysing defossilisation impacts at the value chain level. For this, a single value chain for producing methyl-tert-butyl-ether (MTBE) was used as a case study. The individual components of the value chain were modelled in Aspen Plus v12. Both ACS- and fossil-based value chains were compared in terms of (i) changes in the structure of the value chain and (ii) the magnitude of the impacts. The results show that the defossilisation of a single value chain causes additional impacts at the cluster level.