Green and sustainable chemistry: challenges and perspectives

In the last ten years, following the appearance of the first issue of the journal Green Chemistry, the attention devoted world-wide to the concepts of green chemistry and sustainability, both in industry and academia, has undergone an explosive growth. The design of greener, more sustainable products and processes has become a top priority item in annual reports and many chemical and pharmaceutical companies have appointed global green chemistry managers. I stress the words “greener” and “more sustainable” rather than “green” and “sustainable” because there are many shades of green as well as degrees of sustainability.

Green chemistry and sustainability essentially go hand in hand. Sustainable development is meeting the needs of the present generation without compromising the ability of future generations to meet their own needs. We need greener chemistry—chemistry that efficiently utilises (preferably renewable) raw materials, eliminates waste and avoids the use of toxic and or hazardous solvents and reagents in both products and processes—in order to achieve this noble and lofty goal. Green chemistry embodies two main components. First, it addresses the problem of efficient utilisation of raw materials and the concomitant elimination of waste. Second, it deals with the health, safety and environmental issues associated with the manufacture, use and disposal or re-use of chemicals.

The waste problem in the fine and specialty chemical industries is being dramatically reduced by replacing antiquated technologies employing stoichiometric reagents by greener, catalytic alternatives—homogeneous, heterogeneous and enzymatic. It is now widely accepted that the use of organic solvents is a major source of waste in the fine and specialty chemical industries and, in the case of many traditional organic solvents, is associated with serious health hazards and/or environmental problems. Hence, the need for alternative reaction media is now widely acknowledged and has become a major focus of research in industry and academia. Research on ionic liquids, for example, has undergone exponential growth in the last decade. More recently, the petrochemical and oil refining industries have focused their attention on the third aspect of green chemistry (after catalysis and alternative reaction media): the use of renewable raw materials as alternatives to fossil resources—oil, coal and natural gas—as feedstocks for liquid fuels and commodity chemicals. It is becoming increasingly clear that in the longer term biorefineries will utilise waste and/or inedible biomass as feedstocks for the manufacture of a broad spectrum of products, from biofuels to biodegradable plastics and platform commodity chemicals. This will inevitably lead to the development of greener products such as polymers that are recyclable and/or biodegradable.

It is no mere coincidence that the industrial applications of biocatalysis, what has become known as white biotechnology (to distinguish it from red and green biotechnology for medical and agricultural applications, respectively), has also undergone explosive growth in the same period. In addition to being green catalytic processes that are performed at ambient temperature and pressure, often in water as solvent, the catalysts themselves (enzymes) are biocompatible, have low ecotoxicity and are produced from natural, renewable raw materials. What more could you want? It is appropriate, therefore, that this part-themed issue of Green Chemistry, in its tenth year, contains a review, by Junhua Tao, on recent applications of biocatalysis in the industrial scale synthesis of pharmaceuticals, fine chemicals, commodity chemicals and polymers.

In addition to this timely review, this issue contains a selection of papers based on lectures presented at the 3rd International Conference on Green and Sustainable Chemistry (GSC-3) which was held in Delft, The Netherlands in July 2007. The major themes of GSC-3 reflected the multifaceted, interdisciplinary nature of research on green and sustainable chemistry at the academic/industrial interface. They included homogeneous, heterogeneous and enzymatic catalysis, multicatalytic cascade processes, alternative reagents and reaction media, renewable raw materials and sustainable energy, and life cycle analysis. Graham Hutchings, a pioneer in catalysis by gold, presented the Green Chemistry Lecture, entitled “Selective oxidation using supported gold and gold palladium nanoparticles”. This issue contains a contribution, based on this lecture, devoted to the direct synthesis of hydrogen peroxide from hydrogen and oxygen over Au–Pd supported nanocrystals. An effective and inexpensive method for the direct synthesis of hydrogen peroxide from its elements paves the way for the broad application of this green oxidant in a multitude of processes. The growing importance of gold as a catalyst is further underscored by two more contributions, from the group of Christensen, that deal with supported gold-catalysed oxidations, of amines, and glycerol and propane diols, respectively. Two contributions concerned with renewable raw materials are the production of biodiesel by transesterification over nanocrystalline magnesia catalysts (Parvelescu et al.) and the use of palladium nanoparticles supported on polysaccharide-based mesoporous materials as catalysts in C–C coupling reactions (Clark et al.). Further contributions deal with the immobilization of homogeneous catalysts, on silica (van Koten et al.) or in a supported ionic liquid phase (Luis et al.), the biocatalytic resolution of amines and the immobilisation of the industrially important group of enzymes, the nitrile hydratases.

Finally, I note that many current developments have a familiar ring to readers of Ernest Callenbach's book, Ecotopia, published in 1975. The setting was a future, ecologically sustainable society formed by the creation, in 1999, of an independent country, Ecotopia, comprising Northern California, Oregon and Washington State, with a woman as president. The disposition of Ecotopians to modern technology was not one of rejection but rather one of careful selection on the basis of sustainability. Only fully recyclable plastics were permitted, for example, and the word “consumer” was not used in polite company. Ecotopia was clearly based on the concepts of green and sustainable chemistry avant la lettre.

The journal Green Chemistry continues, in its tenth year, to play a pivotal role in promoting green and sustainable chemistry by publishing papers that combine excellent science with practical and social relevance. I wish the journal continued success in the future and hope that the reader will enjoy the papers in this part-themed issue.

Roger A. Sheldon

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