Issue Date: July 4, 2016
Green chemistry celebrates 25 years of progress
For chemists and chemical engineers, it’s not easy being green. It’s a creative challenge to choose safer reagents and solvents, design more efficient catalysts, develop cleaner chemical manufacturing processes, use biobased materials when possible, and find better ways to dispose of or recycle waste. Being green is also a challenge for educators, who are working to modernize curriculum materials for training the next generation of chemists.
For a quarter-century, since the concept of green chemistry was formally introduced, the chemistry community has been chipping away at these challenges. Hundreds of scientists and engineers gathered to celebrate their progress last month in Portland, Ore., one of the world’s most environmentally conscious cities, at the annual Green Chemistry & Engineering Conference (GC&E). It was a milestone event, marking 25 years since the U.S. Environmental Protection Agency established its Green Chemistry Program and the 20th year of the conference, which is organized by the American Chemical Society and its Green Chemistry Institute (GCI).
“Green chemistry above all else is a tool to do chemistry,” Yale University’s Paul T. Anastas said in a keynote address. “It’s not a method or a new discipline, but it is a framework. And over the years, we have made it a point to let every chemist know they have a role to play in green chemistry.”
Anastas was an early champion of green chemistry while he was a staff member at EPA in the 1990s, and he was one of the organizers of the first GC&E. In Portland, he reflected on the work by EPA, ACS, the National Science Foundation, and others to develop green chemistry and engineering.
Green chemistry came into being, Anastas noted, as a result of protective health and environmental laws such as the Pollution Prevention Act and the recently overhauled Toxic Substances Control Act. Awareness of the environmental impacts of unfettered use of industrial and agricultural chemicals was growing, he said. Yet environmental solutions were still about lawsuits and bulldozers cleaning up hazardous waste sites. The solution to pollution was to treat waste, not prevent it. Chemists had little role, other than analysis and quantification of pollution.
“We started asking ourselves, ‘Can we do better?’ ” Anastas recalled. “We wanted to begin a shift away from regulation and mandated reduction of industrial emissions, toward the active prevention of pollution through the innovative design of production technologies themselves. And we placed an emphasis on both environmental and economic value, because we knew the concept would not be viable otherwise.”
To start, the chemists needed a definition, Anastas said. So they created one: Green chemistry is the design of chemical products and processes to reduce or eliminate the use or generation of hazardous substances. “There is a reason why ‘design’ is the most important word in the definition of green chemistry,” Anastas explained. “Design requires a thoughtful planning of products, processes, and systems. It’s one thing to look at your chemistry to make it less polluting, or less wasteful, or a little bit more efficient. But it is another thing to drive a genuine innovation.”
Next, Anastas and his colleagues needed to establish a global community to embrace that definition and act upon it. To get the chemical industry engaged, EPA created the Presidential Green Chemistry Challenge Awards. The awards are not just a pat on the back, Anastas said, but are also a way to highlight cutting-edge work for everyone to see. “We made it a competition to see who could do better. Then we created a database of winners to quantify the progress being made.” This year’s awards were presented in Portland in conjunction with the conference (C&EN, June 20, page 20).
Green chemistry also needed a set of goals so chemists and engineers were on the same page. In 1998, Anastas and John C. Warner, then at Polaroid and now head of the Warner Babcock Institute for Green Chemistry, published a molecular-level how-to book that included the 12 principles of green chemistry, which helped codify the framework.
Creating GCI was yet another brick in green chemistry’s foundation, Anastas related. The institute was needed, he said, as an independent community center capable of facilitating industry-government partnerships with universities and national laboratories.
Hosting GC&E has become one of GCI’s primary means of maintaining the green chemistry community. Another of GCI’s flagship efforts has been creating a set of industrial roundtables to catalyze green chemistry and engineering for various sectors, including pharmaceuticals, commodity chemicals, consumer products, and industrial biotechnology.
For example, at the Portland meeting, the ACS GCI Pharmaceutical Roundtable, made up of representatives from more than a dozen drugmakers and contract manufacturers, unveiled a set of reagent guides. These guides are an online information resource for common types of chemical reactions, such as alcohol oxidations, amide reductions, fluorinations, and Suzuki coupling, to give researchers sustainable options for reaching their target destination.
“These guides put a spotlight on which existing reagents are best and encourage their use,” said Barry Dillon of AstraZeneca, who along with Stefan Koenig of Genentech cochairs the Pharmaceutical Roundtable. And because there are still only a few “better” reagents, Dillon said, “the guides implicitly challenge chemists to continue to discover new reagents and chemistries that make synthetic chemistry more sustainable.”
When it comes to creating the complex molecules that drug companies need, a key element of going green is to develop a range of reaction choices for flexibility in improving synthetic economy, said conference keynote speaker Jin-Quan Yu of Scripps Research Institute California. One of the more successful approaches for doing that is precious-metal-catalyzed C–H activation chemistry.
Although catalysis is a primary aspect of green chemistry, Yu told the Portland crowd that using precious-metal catalysts and running reactions in organic solvents are sustainability trade-offs. To compensate, the goal becomes how many steps can be cut out of a synthesis to reduce the burden of solvent, water, and energy use.
To start, reducing the amount of catalyst needed becomes a goal, Yu said. Then when it comes to catalyst ligands, which can be just as expensive as a precious metal such as palladium, it’s important to select ones that help reduce thermodynamic energy costs and help speed up reactions.
Some of the Yu group’s go-to ligands are readily available and environmentally friendly amino acids. In a recent example, the researchers developed an amino acid reagent that serves as a transient directing group in palladium-catalyzed C–H activation of aldehydes and ketones for the addition of aryl groups. The approach is fast and reduces reaction steps by avoiding the need to install and remove directing groups (Science 2016, DOI: 10.1126/science.aad7893).
Another focal point for greening up C–H activations is that they typically require an oxidant in the catalytic cycle, Yu explained. Oxidants can be expensive and often are used in large amounts. Developing new redox chemistry, such as reactions that use the oxygen in air, can dispense with typical oxidants. Yu’s group also shops around looking for different solvents that will work with a reaction to provide more synthesis options.
“Not every reaction we do is green, but as we develop them, we can later make them greener,” Yu said. “My students are learning how to do this chemistry very well—they are beating me in developing more efficient reactions.”
But the advantages of green chemistry permeate the chemical industry beyond organic synthesis. At GC&E, Leo Kenny of of the consultancy Planet Singular reviewed environmental and natural resource management challenges and opportunities in the semiconductor industry. The industry needs to establish a strategic, long-term vision and framework, Kenny said, starting in the design phase, for the ongoing evaluation of existing materials and the selection of more benign replacements.
Also at the Portland meeting, General Electric Healthcare’s William Flanagan shared results of an analysis of using single-use fermentation plastic bags versus traditional stainless steel reactors for producing monoclonal antibodies for vaccines. It turns out the throwaway bag system is greener, Flanagan said, primarily because it reduces the amount of water and energy needed during sterilization steps.
And Robert J. Giraud of Chemours and Amit Sehgal of Solvay, members of the ACS GCI Chemical Manufacturer’s Roundtable, outlined a new program, called AltSep, to create low-energy-intensity separations technologies as alternatives to distillations and solvent extractions.
These examples emphasize the need for chemists and chemical engineers to design chemicals and processes that not only serve their intended uses, but are of minimal hazard and reduce waste, said EPA’s Stephen C. DeVito. DeVito analyzes Toxics Release Inventory data and helps make them publicly available to verify corporate green claims. “Companies spend $1.00 per lb to manage waste,” DeVito told C&EN. “That computes to a tremendous number and in itself is a needless waste.”
One crucial component of helping the chemistry community improve on synthetic processes and prevent pollution has been education, said nanomaterials researcher and conference cochair James E. Hutchison of the University of Oregon. “When the green chemistry community was forming 20 years ago, we asked ourselves, ‘What if we could use green chemistry as an excuse to modernize chemistry, to step away from the way core chemistry courses and labs have been taught?’ ”
Some courses hadn’t changed much for 50 years or more, Hutchison said. And some senior professors tend to rely on the same curriculum materials for decades, using outdated chemicals and procedures. “We are not out to create a separate type of degree or discipline,” Hutchison emphasized. “It’s really about accelerating the infusion of green chemistry skills throughout the chemistry curriculum to better reflect what’s happening in today’s chemical industry.”
To that end, Hutchison, Julie A. Haack, and their colleagues created Greener Education Materials for Chemists, or GEMs, an interactive database of lecture course and lab materials. They run the Green Chemistry Education Network, which is a social network for educators to share opportunities to develop these materials. In addition, they host an annual NSF-supported workshop for green chemistry educators and support ACS’s annual Summer School on Green Chemistry & Sustainable Energy.
During his presentation in Portland, Hutchison reflected on the progress that has been made in green chemistry education. He worries that a widespread, systematic approach to green chemistry education doesn’t yet exist—there are too many overlapping efforts in some areas, while gaps remain in others. “We want to galvanize our efforts to move forward,” he said.
The solution, Hutchison noted, is a green chemistry education road map, being coordinated by GCI. The goal for the road map is to not be a onetime fix, but rather a long-term living approach that can evolve as it is continuously reviewed and upgraded.
One gap the road map is addressing is the lack of toxicology considerations in organic chemistry courses. Designing reagents or molecules for reduced toxicity is one of the toughest nuts to crack, Hutchison said, because it doesn’t fall squarely into the training or developed expertise of most chemists. Yet it is fundamental to how chemistry needs to progress. Simply requiring a toxicology course might not be the best approach, he said. “It is more valuable to identify the elements of toxicology that chemists need to design greener chemicals and incorporate them into the current curriculum.”
In one effort, conference cochair Adelina Voutchkova-Kostal of George Washington University is developing new course materials to help teach students how to interpret toxicological data and materials properties as they learn lab skills. “As a new professor, I wanted to introduce new ideas so students can become more engaged in the environmental impact of chemistry,” she said. “We want to teach skills that allow students to use organic chemistry to understand the connections between reactants and products and their biological activity; to think about exposure routes such as through the eyes, skin, and respiratory system; and to know the impact of chemicals in our bodies and in the environment.”
The organic chemistry curriculum is already packed, Voutchkova-Kostal added, so there is only so much wiggle room for adding new material without taking something else out. But the effort is worth it, she believes. Making the next generation of chemists more aware of green chemistry principles should benefit the types of chemicals produced in the future, she said.
Another challenge the road map is addressing is how to train students to use life-cycle analysis (LCA) and whole-systems thinking to evaluate products or processes. Chemical engineer Eric J. Beckman of the University of Pittsburgh is applying these concepts with his students.
LCA allows scientists to peel back the layers of their processes to see how subtle changes can make a difference, Beckman explained. Areas to consider are extensive: sourcing raw materials, selecting solvents and catalysts, controlling water usage, making process equipment more energy efficient, managing distribution supply chains, and designing products for end-of-life reuse or recycling.
“We don’t do a good job at teaching these skills in chemistry and chemical engineering,” Beckman said. “Part of the reason is that it’s hard. But for our graduates, as soon as they enter the workplace, this is what they will be facing. We owe it to them. We don’t necessarily need new courses; we just need to integrate these ideas into what we have.”
For example, Beckman tasked one group of his students to determine which all-purpose cleaner is greener: Windex or something similar to Windex called Simple Green. Beckman assumed the students would do an LCA focusing on the active ingredients. But the students expanded the scope of the analysis, Beckman related, and included the bottle and paper towel needed to use the product.
“The answer turned out to be, ‘Who cares if you use Windex or Simple Green?’ ” Beckman noted. “It’s, ‘Don’t use a paper towel.’ The greenest option is to use a microfiber cloth, despite the extra resources it takes to wash it once in a while.
“This exercise shows that if you push the boundaries, you get to see the problem in a new way,” Beckman continued. “We need to start addressing the systems approach with our students, to get them thinking about end users’ perspectives during the product design phase, to promote designs for multiple benefits, and to show that there is rarely one right answer to a problem.”
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