In the spring of 2003, a very heterogeneous mix of chemists and engineers from industry, government and academia met in San Destin, Florida to discuss principles of green engineering. This group was intending to appeal to a slightly larger engineering audience beyond that generally associated with the chemical industry, in addition to potentially broadening the scope of previous work to incorporate principles of sustainability. The output is shown in the accompanying box.
THE SAN DESTIN DECLARATION: PRINCIPLES OF GREEN ENGINEERING 1. Engineer processes and products holistically, use systems analysis, and integrate
environmental impact assessment tools.
2. Conserve and improve natural ecosystems while protecting human health and well-being.
3. Use life cycle thinking in all engineering activities.
4. Ensure that all material and energy inputs and outputs are as inherently safe and benign as possible.
5. Minimize depletion of natural resources.
6. Strive to prevent waste.
7. Develop and apply engineering solutions while being cognizant of local geography, aspirations, and cultures.
8. Create engineering solutions beyond current or dominant technologies; improve, innovate and invent (technologies) to achieve sustainability.
9. Actively engage communities and stakeholders in development of engineering solutions.
Source:Adapted from ref. 17.
As with the previous green chemistry and green engineering principles, several of the San Destin principles are similar to previous approaches; for example, principles 6 and 8, which fits nicely with the theme of chemical and chemical technology innovation. There was also an element of pragmatism, or perhaps pessimism, as in principle 5, which asserts that natural resource depletion should be minimized, the implicit assumption being that we will never attain a situation where society will not deplete natural resources and achieve a cradle-to-cradle sustainable society.
Apart from these three principles, which were discussed previously, there are several concepts that are brought out in this declaration that are worth a moment’s consideration.
2.4.1 Systems and Life Cycle Thinking See, for example, principles 1 and 3.
In general, most human beings are reductionist thinkers; that is, we cut things down into small bits that are easily grasped or understood so that we are not overwhelmed by the considerable complexity that attends most things in our world. However, in our attempts to reduce complexity, we are sometimes guilty of not seeing the bigger picture, or optimizing one small corner of our universe to the detriment of a broader part or another aspect of the system. This is where systems and life cycle thinking come into play. Certainly, biologists and environmentalists are more attuned than most chemists and engineers to systems thinking, given their attempts to understand entire ecosystems: for example, the interplay of microorganisms, plants, invertebrates, vertebrates (animals), and humans across space and time. It is this ability to look at the big picture and discern the key interactions, responses, and impacts that is so important in green chemistry and green engineering.
impacts from chemicals and the processes used to make them is life cycle inventory and assessment (LCI/A). Although LCI/A is covered in more detail in Chapter 16, it is worth just a moment’s explanation. LCI/A is a rigorous analytical methodology developed to evaluate the environmental impacts of a product or activity, starting with the product or functional unit (e.g., a car, a single dose of a drug, a can of paint, a service) and works back through all the unit operations and materials that are used to make the product, all the way back to raw material extraction. A person does this by performing an input/output inventory or an accounting of all the mass and energy used for each unit operation or production process. It also includes a look at the product in use and its ultimate disposition (i.e., what happens to it when it no longer performs the function originally intended.) Such an exercise generally forces one to look across entire systems because most products are not simple extractions of raw materials followed by immediate use with no emissions.
LCI/A broadens our perspective as we try to understand the material and energy flows and their impacts.
The tie-in of these principles to green chemistry and green engineering is hopefully apparent. If one considers or optimizes only one reaction or one part of a process, it is easy to miss the rest of the process, or perhaps the use of a very nasty chemical in another part of the supply chain. By looking across the entire supply chain, one can optimize material use so that only the best materials, the appropriate chemistries, and the best processes are selected.
2.4.2 Community or Societal Engagement See, for example, principles 7 and 9.
As mentioned in Chapter 1, a key component of sustainability is the inclusion of societal issues or concerns, in addition to environmental and economic issues, in any decision- making process. Principles 7 and 9 are important contributions to green engineering and the San Destin declaration because they bring to any discussion an explicit consideration, from an engineering (and/or chemistry) perspective, of societal, community, or cultural issues regarding what it means to be green. Scientists are, in general, very good at pursuing science for the sake of science, at challenging the scientific status quo, or at pushing the limits of current scientific knowledge. However, scientists are generally not as well equipped to grapple with the implications of their science in terms of impacts to communities, societies, or to the broader environment. However, the capability of assessing the implications of science and technology must increasingly be embedded into scientific education as a matter of routine.
These principles are therefore key principles, insofar as they do highlight those issues and challenge scientists and engineers to practice their disciplines not only in the context of the communities they live and work in, but in the broader context of regional, national, and global communities. For example, the platinum group catalyst that may enable an interesting and potentially novel asymmetric hydrogenation probably comes at the cost of enormous impacts in others part of the world, where people, their culture, and the environment are in some instances affected significantly by the mining of that metal. At some point we need to ask if that is justifiable and if the local benefit of greening a particular process is balanced by the impact of mining. Local societies affected by mining may in fact agree that the benefits of mining outweigh the impact, but they should be a part of that decision. Similarly,
chemists and engineers should be aware of the broader impacts of their science and engineering and ask themselves if those impacts could in some way be avoided, mitigated, and/or minimized.
Example 2.4 According to the San Destin declaration of green engineering, which option is better as a fuel for the operation of vehicles: conventional gasoline or corn-derived bioethanol?
Solution It depends on which impacts one is considering. On the one hand, bioethanol represents a good renewable alternative to fossil fuel use, shows a considerable better profile for global warming and ozone depletion, but in general fares worse regarding smog formation, acidification and eutrophication, and ecotoxicity.18,19The key here is to analyze the effects of using corn-derived ethanol from a life cycle viewpoint, accounting for the general impacts.
Additional Points to Ponder Consider using corn as a crop to produce fuel, vs. other crops, such as sugarcane, from which the substrate can be extracted significantly more efficiently.
The other point to consider is the societal trade-offs of using corn or sugarcane for fuel vs.
using them for food.