Green Metrics, Volume 11

Paul T. Anastas

• Publisher: Wiley-VCH
• Year: 2018
• Print ISBN:
  9783527326440
• eBook ISBN:
  9783527695270
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Environmental Science

Volume 11 of the Handbook of Green Chemistry series identifies, explains and expands on green chemistry and engineering metrics, describing how the two work together, backed by numerous practical applications.
Up-to-date and authoritative, this ready reference covers the development and application of sustainable chemistry along with engineering metrics in both academia and industry, providing the latest information on fundamental aspects of metrics, practical realizations and example case studies. Additionally, it outlines how metrics have been used to facilitate developments in sustainable and green chemistry. The different concepts of and approaches to metrics are applied to fundamental problems in chemistry and the focus is firmly placed on their use to promote the development and implementation of more sustainable and green chemistry and technology in the production of chemicals and related products.
Starting with molecular design, followed by chemical route evaluation, chemical process metrics and product assessment, by the end readers will have a complete set of metrics to choose from as they move a chemical conception to final product.
Of high interest to academics and chemists working in industry.

1
Green Chemistry Metrics

David J.C. Constable

1.1 Introduction and General Considerations

Green chemistry has recently been recognized as having achieved its twenty-fifth anniversary [1,2]. Across this span of time there has been a steady growth in green chemistry-related research and a deepening understanding of what green chemistry is and what it is not, although it is fair to say that it is still consistently debated. Since the earliest discussions about green chemistry, it is also fair to say that the field of chemistry has not embraced green chemistry nor seen the pursuit of green chemistry for the good science and innovation opportunities that are inherent to it. Green chemistry is fundamentally how one thinks about chemistry and how one performs or practices chemistry. Interestingly and perhaps unfortunately, green chemistry has been seen by many chemists as something akin to a social movement similar to other environmental movements [3]. A consequence of this perception is that green chemistry is sometimes seen as not being worthy of serious scientific consideration, in spite of the fact that the major proponents of green chemistry have always pointed to the fact that it is intended to spur innovation and promote the very best science while seeking to avoid or prevent human health and environmental problems. Green chemistry is not about environmental chemistry; to do the best green chemistry, one must however, understand environmental chemistry. It is also not about end-of-pipe environmental improvement, although this is often an important area to pursue.

Part of the problem for this mistaken perception of green chemistry, especially when the term was beginning to be used, was a lack of precision or rigor in providing evidence when making claims about chemistry and labeling a new innovation as “environment-friendly” or “eco-friendly” or “green” or “greener.” The good news is that over the past 15 or so years, there has been considerable work on the part of many in the green chemistry and engineering community to develop methodologies and approaches to systematically and rigorously assess whether or not something is green or sustainable [4–23] (Curzons, A.D., Constable, D.J.C., and Cunningham, V.L. (2002) Bond Economy: An Alternative Approach to Synthetic Efficiency, Unpublished, GlaxoSmithKline.). Ironically, perhaps, despite all the work to develop metrics, there are still a large number of researchers and practitioners in chemistry publishing research in the top green chemistry and engineering journals who either ignore the use of metrics, claim that it is impossible to assess whether or not something is truly green or sustainable, or use a single metric to justify calling their chemistry innovation “green.” This is truly unfortunate because much of what is published in the green chemistry and engineering literature, if viewed from a multivariate metrics perspective, is decidedly lacking in sufficient justification for a chemistry innovation to be called “green,” “greener,” sustainable, or more sustainable.

It is worth taking a moment to discuss some general ideas about metrics before getting into the details of green chemistry and engineering metrics. Generally speaking, it is commonly accepted that metrics must be clearly defined, simple to interpret and use, measurable, rely on objective determinations rather than subjective approaches, and should ultimately drive some kind of desired behavior or practice. The best way to use metrics is in a comparative sense; it is generally not very productive to engage in assessments from an absolute or absolutist frame of mind, particularly when focusing on sustainability. Rather, one should choose a frame or point of reference against which to apply a metric or make a comparison. In this way, one is able to say with some confidence that one particular outcome or impact is better or worse, greener or more sustainable than the alternatives. Absolutes tend to get in the way of people moving forward and making progress, and the lack of knowing something absolutely is frequently the reason given as to why nothing can or should be done. For example, “there are many possible approaches to metrics and who knows which ones are the best” is frequently offered as a reason for not applying metrics of any kind. This is a spurious argument at best.

Another thing to consider is that one's approach to metrics should be from a multivariate perspective. That is to say that the assessment of “green” or “sustainable” should be from multiple discreetly different kinds of measurements and adapted for a given context. Stated slightly differently, a single metric is insufficient to characterize a chemical, a type of chemistry, a process, or a product as being green, greener, or more sustainable. For example, just because a chemical transformation is done with a catalyst does not mean that it is as green as may be presumed. If, for example, that catalytic transformation is carried out using a platinum group element, and the catalyst is a homogeneous one (as opposed to a heterogeneous one), it is not green or sustainable from multiple perspectives. First, platinum group metals currently favored by many chemists, for example, iridium or platinum, are extremely rare, with relatively low abundance in the Earth's crust. Second, the mining and subsequent extraction of these metals from ore, followed by the refining of those metals to separate the various elements that commonly occur in the ore is a highly mass and energy intensive process and results in significant environmental impacts from waste ore, spent extraction liquors, and so on. Finally, running a catalytic reaction homogeneously where the metal is not extracted from the spent mother liquors, it is likely for that metal to end up as a trace contaminant of incinerator slag, unlikely to be recycled, and most likely disposed of as hazardous waste.

The last example about platinum group metals is also a good example of thinking about chemistry from a systems perspective, and/or using life cycle thinking to make a more realistic assessment of whether or not something is “green” or sustainable. Systems thinking is something that is more common in the biological sciences, where dependencies and connections between and among living systems are seen in the context of their ecological niche, the ecosystem an organism inhabits, and the broader environment containing that ecosystem. In other words, life is seen to exist as a complex web of interactions and interdependencies where perturbations to that system are felt in multiple parts of the system, although they may not be immediately noticeable. Systems thinking is also more common in chemical engineering, where one is forced to see a particular unit operation in the context of the overall process, or one is thinking about mass and energy integration across a plant. In the latter instance, mapping the mass and energy inputs and outputs of every unit operation and thinking about how these might be better utilized to increase the overall mass and energy efficiency of the plant is now quite comm...

Table of contents

• Cover
• Related Titles
• Title Page
• Copyright
• List of Contributors
• Preface
• Chapter 1: Green Chemistry Metrics
• Chapter 2: Expanding Rational Molecular Design beyond Pharma: Metrics to Guide Safer Chemical Design
• Chapter 3: Key Metrics to Inform Chemical Synthesis Route Design
• Chapter 4: Life Cycle Assessment
• Chapter 5: Sustainable Design of Batch Processes
• Chapter 6: Green Chemistry Metrics and Life Cycle Assessment for Microflow Continuous Processing
• Chapter 7: Benchmarking the Sustainability of Biocatalytic Processes
• Chapter 8: How Chemical Hazard Assessment in Consumer Products Drives Green Chemistry
• Chapter 9: Tying it all Together to Drive Sustainability in the Chemistry Enterprise
• Index
• End User License Agreement