Co-electrolysis of CO2 (CO2E) and water enables the production of syngas for sustainable aviation fuels (SAF) that are compliant with European RFNBO (renewable fuels of non-biological origin) regulations. However, a mismatch exists between the intermittent renewable electricity supply and the continuous operation of the downstream Fischer-Tropsch plants. To address this, we developed a two-stage linear optimization model to optimize the operation of a 540 MW electrolysis plant, alongside the sizing and operation of the connected renewable generation, battery storage, and syngas storage. Applying this model to a Dutch case study, we explored grid integration with an electrolyzer across future scenarios with global warming potentials (GWPs) ranging between 35 and 370 g CO2-eq per kWh. For generation, the preferred renewable mix is onshore wind combined with PV. When grid mix electricity consumption is restricted, the electrolyzer has an optimal capacity factor of 78% but requires a battery of comparable capacity to the electrolyzer and multi-kilotonne syngas storage to ensure continuous output. Crucially, we found that producing RFNBO-compliant syngas for SAF is impossible with the 2025 Dutch grid mix. Even at a reduced grid intensity of 205 g CO2-eq per kWh, RFNBO compliance limits grid consumption to just 1% of grid mix electricity per hour. This results in a levelized cost of 2350 EUR2019 per tonne syngas. Unrestricted grid electricity consumption becomes feasible when emissions drop below 36 g CO2-eq per kWh, reducing production costs by 43% (1344 EUR2019 per tonne syngas). Consequently, we demonstrate that grid composition intensity is a bottleneck for the short-term economic viability and regulatory compliance of CO2E-based SAF in the Netherlands.

Over 50% of the feedstock carbon in petrochemical clusters stems from the production of high-volume chemicals like benzene and p-xylene. These are typically produced from fossil-based carbon sources within highly integrated systems, where mass and energy flows are tightly interconnected. Transitioning to alternative carbon sources (ACS) can significantly disrupt these interactions, an aspect that is overlooked in existing literature. This paper addresses this knowledge gap by evaluating the impact of replacing fossil-based benzene production with ACS-based routes using CO2, biomass, and plastic waste. It explicitly evaluates performance at both the process and cluster levels by assessing changes in mass, energy, prices, CO2 emissions, and water demand. The results show that due to differences in product distribution, energy requirements, and waste generation, ACS-based processes can trigger unintended ripple effects across downstream units, utility providers, and waste treatment plants. Among the evaluated options, plastic waste-based benzene emerges as the most competitive technology under current market conditions, with the lowest impact at the cluster level. However, its viability depends on the availability of plastic waste, which is a constraint given current recycling rates. Further improvements in waste valorisation and integrating renewable heat are essential to improve the environmental performance of this technology.

Alternative carbon sources (ACSs) such as CO2, biomass, and plastic waste can be used to defossilize chemical building blocks (CBBs) such as methanol, olefins, and aromatics. While the existing literature estimates the quantities of ACSs to replace fossil fuel in specific processes, hubs, or areas, this work adds to the current state of the art by evaluating the impact of ACS feedstock availability on the portfolio of technologies that can be deployed to defossilize an existing petrochemical cluster. A superstructure-based multiobjective optimization model of the Port of Rotterdam was run with eight novel ACS-based processes to evaluate the impact of defossilizing CBB production. The paper explicitly evaluates the performance of the cluster using the following performance indicators: amount of feedstock use, byproduct production, CAPEX, electricity demand, water demand, and change in the minimum selling price of the products. Three cases are analyzed: the fossil-based cluster and two cases, one with unlimited and one with limited feedstock availability. The results show that if feedstocks are considered unlimited, plastic waste-based pyrolysis, methanol-to-olefin, and methanol-to-aromatics routes appear to be the most promising technologies. However, when feedstock constraints are included in the model, a combination of ACS and fossil-based technologies is required to meet product demand, and the level of defossilization significantly decreases. This research underscores the critical need to balance technological choices and realistic assessments of ACS feedstock availability to ensure a sustainable and economically viable transition of the chemical industry.

Converting biogenic CO2 into synthetic sustainable aviation fuel (e-SAF) requires significant amounts of renewable energy, and alignment between system elements and sizes. However, the optimal scale and configuration of CO2 electrolysis remains unresolved. This study examines the economics of RFNBO-compliant e-SAF production from CO2 electrolysis via Fischer-Tropsch synthesis in centralized and decentralized configurations in the Netherlands. A two-stage optimization framework sized the renewable generation, storage, and use of grid electricity for electrolysis plants (9-900 MW). The model projects scenarios from 2025 to 2050, including expected cost and efficiency improvements. The lowest near-term (2025) levelized cost of e-SAF (around 5230 EUR2019/tonne) is achieved for a centralized 90 MW electrolysis plant powered by onshore wind and photovoltaics. A 23 MW decentralized system yields comparable costs. While conversion investment costs are higher at smaller scales, they are counterbalanced by avoided grid fees, higher allowed grid mix electricity consumption, and lower CO2 supply cost. By 2050, decentral e-SAF production costs are projected at 2750 EUR2019/tonne (a 35-70% premium over current SAF prices). These systems provide a near-term route for demonstration projects by co-locating renewable energy, e-SAF production, and regional airports. However, two fundamental caveats remain. First, the cost of CO2 electrolysis-based fuels is incompatible with bulk fuel margins. Second, the limited production volumes from a decentralized configuration are misaligned with the high demand of the aviation sector. Therefore, CO2 electrolysis appears best deployed in a high-value niche product or where high-quality renewable resources geographically overlap with distributed biogenic CO2 streams.

Syngas production via high-temperature co-electrolysis of CO2 (CO2E) shows great potential to reduce the reliance on fossil fuels within the chemical industry. This paper presents an optimization model (MILP) to investigate syngas production from CO2 in the European chemical sector. The model assesses the economic performance of CO2E in prospective supply chains and explores alternative supply chain configurations under different syngas market sizes. The results reveal that the optimal placement of the CO2 electrolysis plant in the supply chain is co-located or decentralized at the product location. This configuration reduces the need for syngas transportation by delivering CO2 to the demand site, which is typically more cost-effective. At a syngas market fulfillment of 2 %, the lowest levelized cost of syngas is achieved at 673 EUR2018/tonne, with electrolysis plants averaging a production capacity of 100 ktonne syngas/year. This levelized cost is between 1.5 and 4 times higher than the fossil-based reference.

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 methyltert-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.

By-product fuel gases from refinery operations are a major heat source in fossil refineries and their availability poses a challenge to the deployment of low-carbon heat sources. This study evaluates the valorization of refinery fuel gases (RFG) into low-carbon methanol via co-processing with residual biogenic gas streams from biomass thermochemical conversion. Results from techno-economic analysis indicate that up to 44 wt.% of biogenic blend is possible without the need for external hydrogen supply, while electricity and heat requirements per tonne of methanol change by -4 % and + 80% respectively. Nevertheless, at the 44 wt.% blend, the estimated methanol cost increases only by 2.4 % (0.43 EUR/kg), while the reduction in methanol carbon intensity is approximately 40 %. This highlights promising benefits that can contribute to the integration of bio-oils producing technologies within fossil refineries.

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.

Steam generating heat pumps show great potential for reducing carbon emissions in the industrial sector.However, predicting their performance is challenging as the exergy destruction of e.g., compressors and expansion valves increases with the temperature lift and condenser temperature.With over seventy design improvements mentioned in the literature, selecting the most effective design improvements is crucial.In this study, energy and exergy-based methods were compared in their ability to identify design improvements for a single stage subcritical heat pump to produce steam from hot condensate.The energy-based method suggested the addition of a sequential compressor with an intermediate cooler; however, this design did not improve the heat pump's techno-economic performance.The suggestion of adding either an internal heat exchanger or a flash vessel by exergy-based methods did lead in both cases to improved techno-economic performance.The internal heat exchanger performed best and increased the coefficient of performance from 2.3 to 2.8 and reduced operational costs by 0.8 M€ after 5 years of operation.Additionally, the initial investment decreased by 135 k€, and the total costs of operation decreased from 10.3 M€ to 8.7 M€.These findings show that exergy-based methods are the way forward in identifying effective design improvements for steam generating heat pumps.

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.

Heat pumps are a promising option to decarbonize the industrial sector. However, their performance at a plant-level can be affected by other process changes. In this work, process changes that improve the heat pump's performance have been identified using Process Change Analysis (PCA), where the background pinch point is used as a reference point for appropriate placement. The effects of the process changes on the heat pump's work requirements are studies by introducing exergy to PCA to form the split exergy grand composite curve. This graph shows the work potential of the streams connected to the heat pump and therefore its work targets. The framework is demonstrated in two case studies. In a biodiesel production plant, it allowed to identify technologies that enhance heat pump performance while reducing overall heating requirements. Here, a heat pump transfers 1.9 MW with a COP of 4.2 but incurs a 40 kW penalty for transferring heat above the background process's pinch temperature. Replacing the wet water washer with a membrane separation unit avoided this penalty, while drastically reducing energy requirements from 0.9 MW to 0.3 MW. in a vinyl chloride monomer-purification process, PCA showed how the extraction of heat by the heat pump impacted the formation of the background pinch, from which an implementation strategy was derived that increased the heat pump's plant-level performance by 6.5% with respect to standard implementation.

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 325g 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.

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 (LPCC6A) was estimated at 4.0 €/kg. Switching to IRE supply increased LPCC6A 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 LPCC6A 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.

Abstract Carbon dioxide capture, transport, and storage (CCS) is essential in achieving the net-zero target. Despite this increasing recognition, current CCS deployments are far behind targeted ambitions. A key reason is that CCS is often perceived as too expensive. While assessments of the costs of CCS have traditionally looked at impact at the plant level, the present study seeks to understand the costs and environmental benefits that will be passed to consumers via end-products and services. In particular, nine end-products/services (bridge construction, electricity from onshore wind power, electricity from offshore wind power, transport of a container via ship, a magazine, the production and transport of an avocado, a beer can, waste treatment via waste-to-energy, and long-distance air travel) connected to ten potential areas of application for CCS (cement production, iron and steel production, oil and gas production, natural gas processing, refining, ship propulsion engines, pulp and paper production, urea production, waste-to-energy, and direct air capture). The evaluations highlight that significant emission reductions (beyond 50%) could be achieved at marginal costs for end-users in six end-products/services: bridge construction, electricity from onshore wind power, electricity from offshore wind power, transport by ship, magazine, and waste treatment. Moderate emission reductions (between 11 and 37%) could be achieved in two cases at virtually no cost (increase below 1%): beer can and avocado production. Finally, only the case of using direct air capture to compensate for emissions from air travel was found to raise the cost for end-users significantly. Although more research is still needed in this area, this work broadens our understanding of the real cost and benefits of CCS and provides useful insights for decision-makers and society.

Carbon capture and storage (CCS) is an essential technology to mitigate global CO2 emissions from power and industry sectors. Despite the increasing recognition of its importance to achieve the net-zero target, current CCS deployment is far behind targeted ambitions. A key reason is that CCS is often perceived as too expensive. The costs of CCS have however traditionally been looked at from the industrial plant perspective, which does not necessarily reflect the end user's one. This paper addresses the incomplete view by investigating the impact of implementing CCS in industrial facilities on the overall costs and CO2 emissions of end-user products and services. As an example, we examine the extent to which an increase in costs of raw materials (cement and steel) due to CCS impacts the costs of building a bridge. Results show that although CCS significantly increases cement and steel costs, the subsequent increment in the overall bridge construction cost remains marginal (∼1%). This 1% cost increase, however, enables a deep reduction in CO2 emissions (∼51%) associated with the bridge construction. Although more research is needed in this area, this work is the first step to a better understanding of the real cost and benefits of CCS.

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%).

Carbon capture and storage (CCS) is an essential technology to mitigate global CO2 emissions from power and industry sectors. Despite the increasing recognition of its importance to achieve the net-zero target, current CCS deployment is far behind targeted ambitions. A key reason is that CCS is often perceived as too expensive.

• The combined CO 2 reduction potential is dependent on the deployment sequence. • Deployment of CO 2 mitigation measures opens and closes deployment paths. • Conservative estimates do not represent the potential of heat integration measures. • Approaches (e.g. MACC) are not fit for the assessment of heat integration measures. • Heat pumps have a high reduction potential with a high sensitivity to changes.