Process modelling and life cycle assessment coupled with experimental work to shape the future sustainable production of chemicals and fuels

Tracing fossil-based plastics, chemicals and fertilizers production in China

Phasing down fossil fuels is crucial for climate mitigation. Even though 80-90% of fossil fuels are used to provide energy, their use as feedstock to produce plastics, fertilizers, and chemicals, is associated with substantial CO2 emissions. However, our understanding of hard-to-abate chemical production remains limited. Here we developed a chemical process-based material flow model to investigate the non-energy use of fossil fuels and CO2 emissions in China. Results show in 2017, the chemical industry used 0.18 Gt of coal, 88.8 Mt of crude oil, and 12.9 Mt of natural gas as feedstock, constituting 5%, 15%, and 7% of China's respective total use. Coal-fed production of methanol, ammonia, and PVCs contributes to 0.27 Gt CO2 emissions ( ~ 3% of China's emissions). As China seeks to balance high CO2 emissions of coal-fed production with import dependence on oil and gas, improving energy efficiency and coupling green hydrogen emerges as attractive alternatives for decarbonization.

Absolute Sustainability Assessment of Flue Gas Valorization to Ammonia and Synthetic Natural Gas

Carbon capture and utilization has gained attention to potentially curb CO2 emissions while generating valuable chemicals. These technologies will coexist with fossil analogs, creating synergies to leverage circular economy principles. In this context, flue gas valorization from power plants can assist in the transition. Here, we assessed the absolute sustainability of a simulated integrated facility producing ammonia and synthetic natural gas from flue gas from a combined-cycle natural gas power plant based in Germany, using hydrogen from three water electrolysis technologies (proton exchange membrane, alkaline, and solid oxide cells), nitrogen, and CO2. For the first time, we applied the planetary boundaries (PBs) framework to a circular integrated system, evaluating its performance relative to the safe operating space. The PB-LCA assessment showed that the alternative technologies could significantly reduce, among others, the impact on climate change and biosphere integrity when compared to their fossil counterparts, which could be deemed unsustainable in climate change. Nevertheless, these alternative technologies could also lead to burden shifting and are not yet economically viable. Overall, the investigated process could smoothen the transition toward low-carbon technologies, but its potential collateral damages should be carefully considered. Furthermore, the application of the PBs provides an appealing framework to quantify the absolute sustainability level of integrated circular systems.

Lignocellulosic biorefineries: A multiscale approach for resource exploitation

Biomass can become the source for chemicals towards a sustainable production system. However, the challenges it presents such as the variety of species, their widespread and sparse availability, and the expensive transportation claims for an integrated approach to design the novel production system. Multiscale approaches have not been properly extended to biorefineryes design and deployment, due to the comprehensive experimental and modelling work they require. A systems perspective provides the systematic framework to analyze the availability and composition of raw materials across regions, how that affects process design, the portfolio of products that can be obtained by evaluating the strong link between the biomass features and the process design. The use of lignocellulosic materials requires for a multidisciplinary work, that must lead to new process engineers with technical competences in biology, biotechnology but also process engineering, mathematics, computer science and social sciences towards a sustainable process/chemical industry.

Economic and Environmental Performance of an Integrated CO2 Refinery

The consequences of global warming call for a shift to circular manufacturing practices. In this context, carbon capture and utilization (CCU) has become a promising alternative toward a low-emitting chemical sector. This study addresses for the first time the design of an integrated CO₂ refinery and compares it against the business-as-usual (BAU) counterpart. The refinery, which utilizes atmospheric CO₂, comprises three synthesis steps and coproduces liquefied petroleum gas, olefins, aromatics, and methanol using technologies that were so far studied decoupled from each other, hence omitting their potential synergies. Our integrated assessment also considers two residual gas utilization (RGU) designs to enhance the refinery's efficiency. Our analysis shows that a centralized cluster with an Allam cycle for RGU can drastically reduce the global warming impact relative to the BAU (by ≈135%) while simultaneously improving impacts on human health, ecosystems, and resources, thereby avoiding burden-shifting toward human health previously observed in some CCU routes. These benefits emerge from (i) recycling CO₂ from the cycle, amounting to 11.2% of the total feedstock, thus requiring less capture capacity, and (ii) reducing the electricity use while increasing heating as a trade-off. The performance of the integrated refinery depends on the national grid, while its high cost relative to the BAU is due to the use of expensive electrolytic H₂ and atmospheric CO₂ feedstock. Overall, our work highlights the importance of integrating CCU technologies within chemical clusters to improve their economic and environmental performance further.

Deep eutectic solvents for improved biomass pretreatment: Current status and future prospective towards sustainable processes

Pretreatment processes - recognized as critical steps for efficient biomass refining - have received much attention over the last two decades. In this context, deep eutectic solvents (DES) have emerged as a novel alternative to conventional solvents representing a step forward in achieving more sustainable processes with both environmental and economic benefits. This paper presents an updated review of the state-of-the-art of DES-based applications in biorefinery schemes. Besides describing the fundamentals of DES composition, synthesis, and recycling, this study presents a comprehensive review of existing techno-economic and life cycle assessment studies. Challenges, barriers, and perspectives for the scale-up of DES-based processes are also discussed.

Trade-offs between Sustainable Development Goals in carbon capture and utilisation

Carbon capture and utilisation (CCU) provides an appealing framework to turn carbon emissions into valuable fuels and chemicals. However, given the vast energy required to activate the CO₂ molecule, CCU may have implications on sustainable development that are still poorly understood due to the narrow scope of current carbon footprint-oriented assessments lacking absolute sustainability thresholds. To bridge this gap, we developed a power-chemicals nexus model to look into the future and understand how we could produce 22 net-zero bulk chemicals of crucial importance in a sustainable manner by integrating fossil, CCU routes and power technologies, often assessed separately. We evaluated the environmental performance of these technologies in terms of their contribution to 5 Sustainable Development Goals (SDGs), using 16 life cycle assessment metrics and 9 planetary boundaries (PB) to quantify and interpret the impact values. We found that fossil chemicals could hamper the attainment of SDG 3 on good health and well-being and SDG 13 on climate change. CCU could help meet SDG 13 but would damage other SDGs due to burden-shifting to human health, water scarcity, and minerals and metals depletion impacts. The collateral damage could be mitigated by judiciously combining fossil and CCU routes with carbon-negative power sources guided by optimisation models incorporating SDGs-based performance criteria explicitly. Our work highlights the importance of embracing the SDGs in technology development to sensibly support the low-carbon energy and chemicals transition.

Optimization and Determination of Kinetic Parameters of the Synthesis of 5-Lauryl-hydroxymethylfurfural Catalyzed by Lipases

Hydroxymethylfurfural esters (HMF-esters) have great potential for additive development; for this reason, the goal of this work was to study the optimization of the esterification conversion of HFM and lauric acid using two lipases: the Novozym 435® biocatalyst and immobilized lipase from Thermomyces lanuginosus (TL). For the optimization of conversion, a three-level three-factorial Box–Behnken experimental design was used. The models achieved a good fit (R2 over 90%) for reactions catalyzed with Novozym 435® and immobilized TL lipase. The best conversion, 78.4%, was achieved with immobilized TL lipase using 30 mM HMF, 16 U of biocatalytic activity, and 50 °C. The kinetic parameters without inhibition by the substrate were determined using the Michaelis–Menten mechanism, whereby VMax  for both biocatalysts reached the highest values at 50 °C, and the highest enzyme–substrate affinities (low Km) were reached at temperatures of 30 °C and 40 °C. It can be concluded that immobilized TL lipase has the potential to catalyze this reaction since, under optimal reaction conditions, an 80.6% conversion (value predicted) could be achieved.

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides

The inevitable emission of carbon dioxide (CO₂ ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO₂ transformations into commodity chemicals are a favorable approach in the CO₂ mitigation strategy. Among these transformations, selective hydrogenation of CO₂ to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO₂ adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO₂ adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO₂ binding modes, mechanistic studies, effects of dopant on CO₂ adsorption, and carbon/metal ratio in the CO₂ hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO₂ hydrogenation reactions.

Development of an online assessment system to evaluate knowledge on chemical safety and security

Education and information dissemination are fundamental to safety and security risk management and mitigation. A web-based examination system called OPCW eQChemSS was developed to assess individuals on their knowledge in chemical safety and security. This can be used as an evaluation tool for chemical safety and security courses, workshops, and seminars. A database of questions was included in this web-based software, which was divided into three categories. Category A is general chemistry level safety, Category B is chemical safety related to organic and inorganic compounds, and Category C is on chemical safety and security and the Chemical Weapons Convention (CWC). The system was designed to automatically check the examination and instantly provide the result of the test in terms of percentage correct answers. A feedback mechanism from the examinees was also included to assess the effectiveness of this e-learning educational material. The importance of e-learning materials in this time of COVID-19 pandemic cannot be more emphasized. The need for readily accessible e-sources that will aid in virtual learning for various topics will be significant even in the coming new normal of hybrid or flexible learning where both online and face-to-face learning may be implemented.

Planetary metrics for the absolute environmental sustainability assessment of chemicals

Environmental assessments in green chemistry often rely on simplified metrics that enable comparisons between alternative routes but fail to shed light on whether they are truly sustainable in absolute terms, viz. relative to the Earth's ecological capacity. To expand our currently limited knowledge of the extent to which chemicals are environmentally sustainable, here we analyse 492 chemical products through the lens of seven planetary boundaries representing critical biophysical limits that should never be exceeded. We found that most of them transgress these environmental guardrails, mainly the ones strongly connected to greenhouse gas emissions (i.e., climate change, ocean acidification and biosphere integrity). However, their levels of transgression fail to correlate with their carbon footprints, currently the focus of most studies, implying that chemicals entailing higher greenhouse gas emissions are not necessarily less environmentally sustainable in absolute terms. Our work points towards the need to embrace absolute sustainability criteria in current environmental assessments, which will require agreeing on how to allocate shares of the planet's ecological capacity among anthropogenic activities, including chemicals' production. This work's absolute environmental sustainability assessment (AESA) method, which could complement standard life cycle assessment approaches, might help experimental researchers working in green chemistry develop truly 'green' products. The AESA method should be taken as a starting point to devise holistic approaches for quantifying the absolute environmental impact of chemicals to guide research and policymaking more sensibly.