By Elisa Carrera, Trivia Coordinator for the GCI
As chemists, we are used to thinking about relatively small-scale reactions, and when faced with synthetic challenges we are often most concerned with improving yields of reactions. We can do this by changing reagents, solvents, temperature, and time of reaction. As green chemists, we can incorporate greener pathways into our syntheses by choosing less hazardous reagents and solvents, and designing reactions to be atom economical with low energy inputs.
If we want to translate our lab-scale syntheses to an industrial scale, however, things become more complicated. Cost and economics become the driving force in this case, so not only are yields important, but the entire process itself, including product purification (column chromatography on an industrial scale is not the purification method of choice because it is expensive and wasteful!). Of course, the environmental impacts are much higher, since huge amounts of solvents and waste could be involved in a single process. Thus, incorporating greener processes into industry is where we can see the biggest relief in environmental impact.
This is where Green Engineering comes into play. A lot of engineering goes into developing an industrial-scale process, so it’s no surprise that if we want to make commercialization greener we need a new set of principles to follow. This led to the development of the 12 Principles of Green Engineering by Paul Anastas and Julie Zimmerman in 2003:
- Inherent Rather Than Circumstantial
Designers need to strive to ensure that all materials and energy inputs and outputs are as inherently nonhazardous as possible.
- Prevention Instead of Treatment
It is better to prevent waste than to treat or clean up waste after it is formed.
- Design for Separation
Separation and purification operations should be designed to minimize energy consumption and materials use.
- Maximize Efficiency
Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
- Output-Pulled Versus Input-Pushed
Products, processes, and systems should be “output-pulled” rather than “input-pushed” through the use of energy and materials.
- Conserve Complexity
Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.
- Durability Rather Than Immortality
Targeted durability, not immortality, should be a design goal.
- Meet Need, Minimize Excess
Design for unnecessary capacity or capability (e.g., “one size fits all”) solutions should be considered a design flaw.
- Minimize Material Diversity
Material diversity in multicomponent products should be minimized to promote disassembly and value retention.
- Integrate Material and Energy Flows
Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
- Design for Commercial “Afterlife”
Products, processes, and systems should be designed for performance in a commercial “afterlife.”
- Renewable Rather Than Depleting
Material and energy inputs should be renewable rather than depleting.
While some of the principles parallel some of the 12 Principles of Green Chemistry quite closely, these were created with engineering in mind rather than chemistry, so most of the principles are quite different from the way us chemists usually think. While Green Chemistry looks to reduce the use and generation of hazardous substances, Green Engineering is focused on developing processes that are economically feasible and reduce risk to the environment and human health. This is not just limited to chemical engineering either! All areas of engineering can incorporate these Green Engineering Principles to develop less harmful materials and processes.
Although this is a bit outside of our area, Green Chemistry and Green Engineering are directly linked to each other, and I think it is important for chemists to think about Green Engineering. In fact, a lot of our Green Chemistry decisions will ultimately affect Green Engineering (see this article, “Promoting Green Engineering through Green Chemistry“), and both areas ultimately have the common vision of reducing risks to human health and the environment!
What do you think about the 12 Principles of Green Engineering? Which do you think are most important? Were you surprised by any of these principles? Share your thoughts in the comments section!
For more details on each of the 12 Principles of Green Engineering please see the original article by Anastas and Zimmerman:
Anastas, P.T., and Zimmerman, J.B., “Design through the Twelve Principles of Green Engineering”, Env. Sci. Tech. 2003, 37(5), 94A-101A. http://pubs.acs.org/doi/abs/10.1021/es032373g