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.

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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.

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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.

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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.@en

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.

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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.

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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.@en

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.@en

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.

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Electrochemical reduction of CO2 (CO2ER) is an emerging technology with the potential to limit the use of fossil-based feedstocks in the petrochemical industry by converting CO2 and renewable electricity into useful products such as syngas. Its successful deployment will depend not only on the technology's performance but also on its integration into the supply chain. In this work, a facility location model is used to gain insights regarding the capacity of CO2ER plants that produce syngas and the implications for the central/decentral placement of these CO2-based syngas plants. Different optimal configurations are examined in the model by changing the syngas transport costs. In this exploratory case, the results indicate that centralization is only an option when the syngas and CO2 transport costs are similar. When syngas transport is more expensive, decentralizing CO2-based syngas plants in the supply chain appears more feasible.@en

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.

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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%).@en

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.@en

The storage of renewable electricity in chemical bonds is a compelling technological option that combines flexibility with the synthesis of high energy-dense fuels and chemicals and may use CO2 as raw material. The electrochemical conversion of CO2 is not yet a mature technology. Both fields, electrochemical conversion and carbon dioxide utilisation (CDU), have their own trade-offs; CO2 electrochemical reduction (CO2ER) environmental and economic performance is highly context-dependent. The successful deployment of CO2 electrochemical conversion will depend not only on the further development and scaling of the technology but also on finding appropriate combinations of technologies, business models, and socioeconomic strategies. The current project aims to create critical knowledge on the sustainable implementation of CO2 electrochemical devices for a variety of contexts. The research approach presented in the current work will develop a multidisciplinary framework to assess the contributions and trade-offs of CO2 electrochemical systems, including centralised and decentralised configurations, which are evaluated under realistic conditions. This is a crucial step in understanding the role and contribution of CO2ER within the different CO2 mitigation options in place in the upcoming years. To achieve the project’s goal, we propose a multidisciplinary methodology that includes process systems engineering (PSE) and operations research (OR) tools, and humanistic and social sciences methodologies. Modelling and optimisation techniques, value-sensitive design, and identification of government and market-based governance interventions will help identifying potential areas of improvement and bottlenecks to successfully bring CO2ER to the market. The assessment will be performed at several levels: unit (reaction pathways), process (scheduling and operation, plant layout optimisation), supply chain (optimisation under deterministic and stochastic conditions), and system (social, governance and markets perspectives) of CO2ER. The project results will (i) propose optimal CO2ER-based plants and (ii) supply chains under different contexts; (iii) translate stakeholders’ sustainability value into design requirements for CO2ER; (iv) propose a list of government interventions and market mechanisms that will allow CO2ER market penetration, and (v) identify, quantify and mitigate the influence of the most relevant sources of uncertainty. @en

Reversible solid oxide cells (rSOC) can convert excess electricity to valuable fuels in electrolysis cell mode (SOEC) and reverse the reaction in fuel cell mode (SOFC). In this work, a five – cell rSOC short stack, integrating fuel electrode (Ni-YSZ) supported solid oxide cells (Ni-YSZ || YSZ | CGO || LSC-CGO) with an active area of 100 cm2, is tested for cyclic durability. The fuel electrode gases of H2/N2:50/50 and H2/H2O:20/80 in SOFC and SOEC mode, respectively, are used during the 35 reversible operations. The voltage degradation of the rSOC is 1.64% kh−1 and 0.65% kh−1 in SOFC and SOEC mode, respectively, with fuel and steam utilisation of 52%. The post-cycle steady-state SOEC degradation of 0.74% kh−1 suggests improved lifetime during rSOC conditions. The distribution of relaxation times (DRT) analysis suggests charge transfer through the fuel electrode is responsible for the observed degradation.@en

Electricity production and consumption must be balanced for the electrical grid. However, the rapidly growing intermittent power sources are now challenging the supply-demand balance, leading to large flexibility needs for grid management. The plant integrating biomass gasification and reversible solid-oxide cell stacks can be potential means of flexibility, which could flexibly switch among power generation, power storage, and power neutral modes. This paper investigates the economic feasibility of such grid-balancing plants, i.e., plant capital expenditure (CAPEX) target, via a systematic overall decomposition-based methodology for real geographical zones and flexibility-need scenarios. The plant CAPEX target (€/ref-stack) is defined as the maximum affordable investment cost for each reference stack (active cell area 5,120 cm2). The results show that, for a 5-year payback time, 5-year stack lifetime, and 40 €/MWh grid balancing price, the plant concept with 10–100 MWth gasifier has high economic potential with target reaching 17,000 €/ref-stack; however, the plant concept with 100–1,000 MWth gasifier has a limited commercialization potential with the target reaching below 1,000 €/ref-stack due to high biomass supply costs. Considering the sale of chemical product, plant CAPEX target can reach up to 22,000 and 3,000–12,000 €/ref-stack for the plants with 10–100 and 100–1,000 MWth, respectively. The plant CAPEX target is decreased by increasing the total capacities of all plants deployed since more and more capacities will be put into power neutral mode (isolated from the electrical grid) via the coordination of multiple plants. The plant CAPEX target can be further increased by higher grid up/down-regulating price and longer payback years.@en

The large market penetration of non-dispatchable renewable power sources (vRES), i.e., wind and photovoltaic, may be hampered by an increasing need for large scale energy storage capacity and the challenges of balancing the power grid. Novel technologies integrating waste gasification with reversible Solid-Oxide Cell systems have been proposed to provide flexible grid balancing services. The rSOC system operated in electrolysis mode uses excess power from vRES to generate hydrogen (H2), which is combined with syngas derived from waste gasification to produce methane (CH4). The rSOC system can also be operated in fuel cell mode by oxidising syngas to produce electricity. This paper presents a well-defined case study which aimed to estimate the potential deployment of a novel rSOC technology in a future power system dominated by intermittent renewables. The hourly power grid residual loads (i.e., the difference between load and vRES power generation) and the availability of low-grade organic waste and residues are quantified and matched for the southern Italian peninsula in 2030. The results show that the theoretical grid flexibility needs approximately 10 TW h of overproduction and 5 TW h of underproduction in 2030 to ensure the complete disposal of the municipal organic waste generated in 2030 (6.7 Mt) and that production of renewable CH4 will need to be 1.4–2.4 Mt, pointing to an intriguing perspective for the deployment of rSOC systems at a large scale. The multifunctionality of the system proposed is an added value that can make it a convenient and efficient piece of the puzzle of technologies required in a climate-neutral and circular economy. The results and methods here presented are intended to form the basis for estimations of future potential deployment and economic and environmental assessments of competing technologies.@en

BLAZE aims at developing Low cost, Advanced and Zero Emission first-of-a-kind small-to-medium Biomass CHP. This aim is reached by developing dual bubbling fluidised bed technology integrated with high temperature gas cleaning & conditioning systems and Solid Oxide Fuel Cells. The technology is characterised by the widest solid fuel spectrum applicable, high efficiencies (50% electrical versus the actual 20%), low investment (<4 k€/kWe) and operational (≈ 0.05 €/kWh) costs, as well as almost zero noxious gaseous and PM emissions, projecting electricity production costs below 0.10 €/kWh. This paper shows the midterm project achievements, i.e. the biomass waste gasification and SOFC tests, the overall simulation and the progress on the realisation of 25 kWe SOFC pilot plant.@en