Life Cycle Assessment for the Design of Chemical Processes, Products, and Supply Chains

Models for Decarbonization in the Chemical Industry

Various technologies and strategies have been proposed to decarbonize the chemical industry. Assessing the decarbonization, environmental, and economic implications of these technologies and strategies is critical to identifying pathways to a more sustainable industrial future. This study reviews recent advancements and integration of systems analysis models, including process analysis, material flow analysis, life cycle assessment, techno-economic analysis, and machine learning. These models are categorized based on analytical methods and application scales (i.e., micro-, meso-, and macroscale) for promising decarbonization technologies (e.g., carbon capture, storage, and utilization, biomass feedstock, and electrification) and circular economy strategies. Incorporating forward-looking, data-driven approaches into existing models allows for optimizing complex industrial systems and assessing future impacts. Although advances in industrial ecology-, economic-, and planetary boundary-based modeling support a more holistic systems-level assessment, more efforts are needed to consider impacts on ecosystems. Effective applications of these advanced, integrated models require cross-disciplinary collaborations across chemical engineering, industrial ecology, and economics.

A framework for integrating safety and environmental impact in the conceptual design of chemical processes

Multiple factors influence chemical process design and technology selection, including technical, economic, environmental, and safety considerations. Traditionally, a techno-economic analysis has been used to select a base case design, while safety and environmental impact have been subsequently assessed. This may leave out designs that exhibit better environmental and safety performance than the selected base case at a very early stage of design, where abundant opportunities for incorporating these objectives are present. Furthermore, although safety is an integral part of the overall sustainability of a chemical plant, historically it has been addressed separately from sustainability. Thus, there is a growing awareness for simultaneous consideration of these objectives during the conceptual process design phase of a project in order to select the most sustainable process route. The key to an effective sustainability assessment method for selecting the most sustainable process route involves the parsimonious selection of adequate metrics which define the sustainability profile of the process and an integrated multi-criteria decision-making (MCDM) framework. In this context, this work investigates gaps in conceptual process design and existing sustainability assessment methods through a review of existing environmental impact and safety assessment methodologies/tools. A possible workflow that incorporates both safety and environmental impact in a holistic multi-criterion decision-making framework (MCDM) has been proposed to select the most sustainable process route. The use of this framework is illustrated through a simple case study involving assessing solvent alternatives for palm oil recovery to highlight the scope and significance of the proposed framework.

Embedding systems thinking in tertiary chemistry for sustainability

In response to the IUPAC call to introduce systems thinking in tertiary chemistry education, we have developed and implemented two interventions at the first-year undergraduate level: one was designed to integrate systems thinking in first-year organic chemistry using the topic of surfactants and the other in a first-semester service course to engineering students using the stoichiometry of the synthesis of aspirin. We demonstrate how the systems thinking approach in both interventions did not lose the focus of the chemistry content that needed to be covered, exposed students to the concept of systems thinking, started to develop some systems thinking skills, and made a case for the contribution that chemistry can and should make to meet the UN sustainable development goals. Through both the design and the implementation process, it has become clear that introducing systems thinking is complex and it remains a challenge to keep the complexity manageable to avoid cognitive overload. Both interventions leveraged the power of group work to help students deal with the complexity of the topics while also developing participatory competence required for sustainability. The development of systems thinking skills and a capacity to cope with complexity requires multiple opportunities. Infusing syllabus themes that relate to real chemical systems with a systems thinking perspective can provide such an opportunity without compromising chemistry teaching. We believe that skills development should continue throughout the undergraduate chemistry degree to deliver chemistry graduates who can make a difference to global sustainability.

What Shall We Do with Steel Mill Off-Gas: Polygeneration Systems Minimizing Greenhouse Gas Emissions

Both the global steel and chemical industries contribute largely to industrial greenhouse gas (GHG) emissions. For both industries, GHG emissions are strongly related to the consumption of fossil resources. While the chemical industry often releases GHGs as direct process emissions, steel mills globally produce 1.78 Gt of off-gases each year, which are currently combusted for subsequent heat and electricity generation. However, these steel mill off-gases consist of high value compounds, which also can be utilized as feedstock for chemical production and thereby reduce fossil resource consumption and thus GHG emissions. In the present work, we determine climate-optimal utilization pathways for steel mill off-gases. We combine a nonlinear, disjunctive model of the steel mill off-gas separation system with a large-scale linear model of the chemical industry to perform environmental optimization. The results show that the climate-optimal utilization of steel mill off-gases depends on electricity's carbon footprint: For the current electricity grid mix, methane, hydrogen, and synthesis gas are recovered as feedstocks for conventional chemical production and enable a methanol-based chemical industry. For low electricity footprints in the future, the separation of steel mill off-gases supports CO₂-based production processes in the chemical industry, supplying up to 30% of the required CO₂. By coupling the global steel and chemical industry, industrial GHG emissions can be reduced by up to 79 Mt CO₂-equivalents per year. These reductions provide up to 4.5% additional GHG savings compared to a stand-alone optimization of the two industries, showing a limited potential for this industrial symbiosis.

Integration of Design, Manufacturing, and Service Based on Digital Twin to Realize Intelligent Manufacturing

Complex product design, manufacturing, and service are the key elements of a product’s life cycle. However, the traditional manufacturing processes of design, manufacturing, and service are independent of each other, so lack deep integration. The emergence of digital twins offers an opportunity to accelerate the integration of complex product design, manufacturing, and services. For intelligent manufacturing, physical entity and virtual entity transformation can be realized through digital information. A collaborative framework for complex product design, manufacturing, and service integration based on digital twin technology was proposed. The solutions of process integration, data flow, modeling and simulation, and information fusion were analyzed. The core characteristics and key technologies of service-oriented manufacturing, design for service and manufacturing, and manufacturing monitoring based on the deep integration of the digital twin were discussed. Finally, the feasibility of the framework was verified by a self-balancing multistage pump manufacturing case. The performance of the upgraded pump under the framework was tested, and the test results proved the effectiveness of the integrated framework.

Synthesis design using mass related metrics, environmental metrics, and health metrics

The efforts to integrate environmental aspects, health aspects as well as safety aspects into chemical production has led to the development of measurable and thus objectifying metrics. The application of these metrics is considered to be most promising, especially during the earliest phases of synthesis design. However, the operability in daily work suffers from the lack of available data, or a large variety of data, and the complexity of data processing. If a life cycle assessment is not practical in the early development phase, environmental factor and process mass intensity can give a quick and reliable overview. I will show that this often says the same in advance as a subsequently prepared life cycle assessment. Readers will realise that, based on preparative descriptions, they can quickly determine these metrics for individual syntheses or extensive synthesis sequences applying the available software support. Environmental relevance in terms of persistence, bioaccumulation and toxicity (PBT) can be presented using a modification of the European ranking method ‘DART’ (Decision Analysis by Ranking Techniques). Based on corresponding PBT data, readers can determine a hazard score between 0 and 1 for any substance using the spreadsheet file provided, with which the mass of (potentially emitted) substances can be weighted. Occupational health can be represented using a modification of the recognized ‘Stoffenmanager’. Both concepts are presented and spreadsheet files are offered. This article is based on a presentation which was given at the Green Chemistry Postgraduate Summer School in Venice, 6th–10th July 2020.

Paving the Way for a Green Transition in the Design of Sensors and Biosensors for the Detection of Volatile Organic Compounds (VOCs)

The efficient and selective detection of volatile organic compounds (VOCs) provides key information for various purposes ranging from the toxicological analysis of indoor/outdoor environments to the diagnosis of diseases or to the investigation of biological processes. In the last decade, different sensors and biosensors providing reliable, rapid, and economic responses in the detection of VOCs have been successfully conceived and applied in numerous practical cases; however, the global necessity of a sustainable development, has driven the design of devices for the detection of VOCs to greener methods. In this review, the most recent and innovative VOC sensors and biosensors with sustainable features are presented. The sensors are grouped into three of the main industrial sectors of daily life, including environmental analysis, highly important for toxicity issues, food packaging tools, especially aimed at avoiding the spoilage of meat and fish, and the diagnosis of diseases, crucial for the early detection of relevant pathological conditions such as cancer and diabetes. The research outcomes presented in the review underly the necessity of preparing sensors with higher efficiency, lower detection limits, improved selectivity, and enhanced sustainable characteristics to fully address the sustainable manufacturing of VOC sensors and biosensors.

Major contaminants of emerging concern in soils: a perspective on potential health risks

Soil pollution by the contaminants of emerging concern (CECs) or emerging contaminants deserves attention worldwide because of their toxic health effects and the need for developing regulatory guidelines. Though the global soil burden by certain CECs is in several metric tons, the source-tracking of these contaminants in soil environments is difficult due to heterogeneity of the medium and complexities associated with the interactive mechanisms. Most CECs have higher affinities towards solid matrices for adsorption. The CECs alter not only soil functionalities but also those of plants and animals. Their toxicities are at nmol to μmol levels in cell cultures and test animals. These contaminants have a higher propensity in accumulating mostly in root-based food crops, threatening human health. Poor understanding on the fate of certain CECs in anaerobic environments and their transfer pathways in the food web limits the development of effective bioremediation strategies and restoration of the contaminated soils and endorsement of global regulatory efforts. Despite their proven toxicities to the biotic components, there are no environmental laws or guidelines for certain CECs. Moreover, the information available on the impact of soil pollution with CECs on human health is fragmentary. Therefore, we provide here a comprehensive account on five significantly important CECs, viz., (i) PFAS, (ii) micro/nanoplastics, (iii) additives (biphenyls, phthalates), (iv) novel flame retardants, and (v) nanoparticles. The emphasis is on (a) degree of soil burden of CECs and the consequences, (b) endocrine disruption and immunotoxicity, (c) genotoxicity and carcinogenicity, and (d) soil health guidelines.

Contaminants of emerging concern: sources, soil burden, human exposure, and toxicities.

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.

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

Meeting the sustainable development goals and carbon neutrality targets requires transitioning to cleaner products, which poses significant challenges to the future chemical industry. Identifying alternative pathways to cover the growing demand for chemicals and fuels in a more sustainable manner calls for close collaborative programs between experimental and computational groups as well as new tools to support these joint endeavours. In this broad context, we here review the role of process systems engineering tools in assessing and optimising alternative chemical production patterns based on renewable resources, including renewable carbon and energy. The focus is on the use of process modelling and optimisation combined with life cycle assessment methodologies and network analysis to underpin experiments and generate insight into how the chemical industry could optimally deliver chemicals and fuels with a lower environmental footprint. We identify the main gaps in the literature and provide directions for future work, highlighting the role of PSE concepts and tools in guiding the future transition and complementing experimental studies more effectively.