Why green chemistry and sustainability of resources are essential to our future

Roger A. Sheldon

Roger Sheldon is a recognised authority on Green Chemistry and Catalysis and Professor Emeritus of Biocatalysis and Organic Chemistry at the Delft University of Technology. He is the author of several books on the subject of catalysis as well as ca. 400 professional papers and >40 granted patents. Recently, he co-authored, with his coworkers Isabel Arends and Ulf Hanefeld, a book on “Green Chemistry & Catalysis”. He is widely known for developing the concept of E factors for assessing the environmental footprint of chemical processes. Prior to joining Delft University in 1991, he had more than 20 years industrial experience, as Vice President for Research and Development at DSM/Andeno from 1980 to 1990 and with Shell Research Amsterdam from 1969 to 1980. He is also CEO of CLEA Technologies, a start-up biotech company.

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The roots of the current preoccupation with Green Chemistry and Sustainability can be traced back to the environmental movement of the 1960s and 1970s. The publication of Rachel Carson's Silent Spring and Barry Commoner's The Closing Circle focused public attention on the negative side effects of a multitude of chemical products on our natural environment. These problems were in turn a direct consequence of economic growth which can be traced back to the industrial revolution which created a need for new chemicals and materials to meet the growing demands of an industry largely fueled by coal. With the advent of the petrochemicals industry, in the 1920s, the basic feedstock changed to crude oil and natural gas. This industry had its heyday in the 1950s and 1960s when predictions of future growth rates tended to be exponential curves. This simplistic and optimistic view of the future was disturbed in the early 1970s by the publication of the report for the Club of Rome on the ‘Limits to Growth’ which emphasized the finite nature of non-renewable fossil fuel resources. The Oil Crisis of 1973 subsequently highlighted the vulnerability of an energy and chemicals industry that is based largely on a single fossil fuel.

The environmental movement did not have a broad industrial or societal impact, however, probably because emphasis was placed largely on the environmental problems rather than devising technological solutions. The prevailing opinion was that chemistry is the problem rather than the solution. This is underlined by the turn of phrase which I once heard: “engineering a better world without chemistry”. But the solution is clearly not no chemistry but new and better chemistry, that is cleaner, greener chemistry.

A turning point can, in hindsight, be traced back to the publication, in 1987, of the report Our Common Future by the World Commission on Environment and Development which recognised that industrial and societal development must be sustainable over time. Sustainable development was defined as: ‘development that meets the needs of the present generation without compromising the ability of future generations to meet their own needs’. A decade later the concept was endorsed and further elaborated in the report, Our Common Journey by the Board on Sustainable Development of the US National Research Council. It is not a new concept, however. The Great Law of the Iroquois Confederacy, which formed a basis for the US Constitution (see http://www.iroquoisdemocracy.pdx.edu), stated that: ‘In our every deliberation, we must consider the impact of our decisions on the next seven generations’. This inspired one company to adopt the name “Seventh Generation” (http://www.seventhgeneration.com).

One could say that the environmental movement defined the problem and the sustainability movement has defined our common goal. The latter has been further delineated by Thomas Graedel as (i) using natural resources at rates that do not unacceptably deplete supplies over the long term, and (ii) generating and dissipating residues at rates no higher than can be assimilated by the natural environment. So, now that we know the problems and we have defined our goals all we need are the technical solutions, the underlying science and engineering of sustainable development. That's where green chemistry enters the scene.

Green chemistry can be succinctly defined as follows: ‘Green chemistry efficiently utilises (preferably renewable) raw materials, eliminates waste and avoids the use of toxic and/or hazardous reagents and solvents in the manufacture and application of chemical products. The term ‘Green Chemistry’ was coined by Anastas and colleagues of the US Environmental Protection Agency (EPA). In 1993 the EPA officially adopted the name ‘US Green Chemistry Program’ which has served as a focal point for activities within the United States. This does not mean that research on green chemistry did not exist before the early 1990s, merely that it did not have the name.

It is important to stress that green chemistry addresses both chemical products and the processes by which they are manufactured. The emphasis is clearly on design of greener products and processes. I purposely say greener rather than green as there are many shades of green. Green chemistry embodies two components: (i) efficient utilisation of raw materials and the elimination of waste, and (ii) health, safety and environmental aspects of chemicals and their manufacturing processes. Green chemistry eliminates waste at source. It is primary pollution prevention not end-of-pipe solutions. Waste remediation may be useful and necessary in the short term but it does not constitute green chemistry.

As I have emphasized many times, the waste problem in the chemical industry can largely be eliminated by the widespread application of catalysis—homogeneous, heterogeneous and enzymatic—and alternative reaction media. The fine chemical and pharmaceutical industries have taken up this challenge and devoted substantial resources to developing cleaner processes. More recently, the petrochemical and oil refining industry has focused its attention on another aspect of green chemistry: the use of renewable resources. The utilisation of biomass for sustainable fuels and chemicals has become a top priority on the political agenda. Here again the development of efficient chemo- and biocatalytic processes is the key to success. A first generation of biofuels and bio-based commodity chemicals is currently being produced from starch, sucrose and vegetable oils as feedstocks. However, their availability is limited and they compete, directly or indirectly, with food, which is already effecting the price of food. Consequently, it is abundantly clear that this is not the long term solution. The next generation of biorefineries will utilise lignocellulosic biomass and inedible oilseed crops as feedstocks for the production of a broad spectrum of products ranging from biofuels to biodegradable plastics and platform and specialty chemicals. This will radically change the structure of supply chains in the chemical industry, creating a need for innovative, sustainable chemistry based on green catalytic methodologies. In my opinion it will also lead, inevitably, to the design of greener products, e.g. polymers that are not only derived from renewable raw materials but are recyclable and/or readily biodegraded. Not only will the processes be different but we will be making a different palette of products. Chemical companies that ignore this trend may fall by the wayside in the future. In short, the challenges for the current and future generations of chemists and chemical engineers are daunting but I have no doubt that they will rise to the occasion and invent green, sustainable solutions. Clearly, green chemistry and sustainability of resources are essential to our future.

Another prerequisite for progress is reliable measurement. As Lord Kelvin said “to measure is to know”. Meaningful metrics for sustainability and green chemistry, for comparing the different shades of green, and reliable methods for monitoring the environmental footprint of chemical products are both necessary and complementary. Hence, cooperation between the two communities of environmental chemistry and green chemistry should be stimulated. And the scientific results of such collaborations can be published in the Journal of Environmental Monitoring. It is my great pleasure to congratulate the Journal on its 10^th anniversary and wish it many more decades of publishing outstanding work.

Delft,

January 2008

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