Greening chemistry is a series of opinion columns, written by a rotating group of contributors.
Since time immemorial, or at least since the advent of the scientific method, researchers and innovators have developed and introduced new chemical entities to the environment before fully understanding them. Only later do the originators or others study and recognize any harm caused by their products.
That’s why a concept known as Safe and Sustainable by Design (SSbD) has recently begun spreading through the chemical sciences. This approach has roots firmly planted in green chemistry, and although it has emerged from regulatory frameworks in the European Union, SSbD is gaining traction far beyond a single continent’s borders.
Don’t panic! There’s no new raft of legislation coming your way. Applying the SSbD principles is entirely voluntary.
So, what is SSbD? It’s a way to marshal the ever-growing knowledge and understanding of what leads to health, environmental, and societal harm to prevent regrettable introductions of new chemical entities. Not surprisingly, most of the discussion about SSbD has focused on businesses and what they might do, particularly as technologies approach commercialization. There is a whole discipline dedicated to how to measure the sustainability of chemicals and processes, with ever more sophisticated tools being introduced to enable this. Most of these tools require both the consideration of a great deal of information and for people to spend a substantial amount of time doing the analysis. The level of resources required to implement these processes makes it important to be sure people know the costs before implementing them.
For those who want to bring SSbD to academic and other laboratories focusing on discovery research, the challenge is quite different. The Content team at CAS, a division of the American Chemical Society, very kindly looked for me and told me that almost 40% of the roughly 220 million chemical substances found in the chemical literature appear just once. I’m not going to ask my students to do a full-scale life cycle analysis for a one-off small-scale synthesis of one of these; they’d never get any reactions done. So, what would be appropriate for a typical academic lab?
The key thing is to get researchers to think before they jump into the experiment. First, consider whether you need to make the compound at all. Marisa Kozlowski, the editor of Organic Letters, recently showed in an editorial in the journal how a small, diverse library of examples can provide better reaction screening than a larger, ill-thought-out one. Similarly, an approach focusing on a statistical design of experiments can greatly reduce the number of experiments needed to elucidate structure-property relationships, or to optimize a process. Using these approaches will not only minimize the environmental burden of your research, but they will also save you time and money.
It’s also important to think about the properties of the compound that you are proposing to make. If the product is toxic to humans or the environment, persistent, or bioaccumulative, can you get the same information by substitution with one that is nontoxic and biodegradable?
Once you have determined that the compound is required, then consider the synthetic route. There is nearly always a choice. Which one minimizes the use of hazardous starting materials, solvents, and reagents, and can use renewable materials? Also, how much do you really need? Can you reduce waste by simply operating at a smaller scale? These questions overlap with the principles of green chemistry, which is not surprising since the originators of the SSbD concept leaned heavily on these for their inspiration.
Of course, chemicals are not the only input to a reaction. How can energy input, usually most heavily associated with heating, be minimized? Do you really have to heat under reflux overnight, or will an hour or two of moderate heating be enough? How about minimizing process water use by using an air condenser or a recirculating cooler?
Worker safety is a key part of the SSbD concept, which can include omitting and avoiding hazardous materials and processes. However, this approach is not intended to be a substitute for a full and thorough risk assessment. That process is directed at informing the researcher of the controls they need to put in place to conduct the experiment safely. In fact, the two assessments should be made alongside each other.
Finally, societal impact is an important part of the SSbD concept. This is the part that I am struggling with. While I know where to direct my students to find out about chemicals and processes, how might they identify and assess societal impacts? It has been suggested that you might just ignore this aspect at certain stages of research, but I would like to think that we could come up with something. Can you exclude the use of elements derived from conflict minerals? But what else might we use?
A man looking at the camera, with a bookshelf behind him. He’s wearing a striped shirt and has short hair that stands up.
Tom Welton
Credit:
Courtesy of Tom Welton
Applying these principles should not burden researchers and could, in fact, save them time and money. In my group, we are developing a form to enable us to consider the SSbD principles in our research, which we would like to share with the community. If you are interested in receiving updates or providing feedback about the form, please sign up at cenm.ag/ssbd. We’re looking forward to developing this resource together.
Professor Tom Welton, OBE, is an emeritus professor of sustainable chemistry at Imperial College London and past president of the Royal Society of Chemistry.
Views expressed are those of the author and not necessarily those of C&EN or the American Chemical Society.
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