Published:18 Jul 2013
The 21st century has seen a growing recognition of the importance of resource management including the more careful use of resources, an awareness of their lifecycles and a move towards a more closed-loop approach to manufacturing. In the context of sustainable chemistry, while the 1990s saw the emergence of the green chemistry movement, with a strong focus on clean production and waste minimization in manufacturing, the new century has seen a move towards a much more holistic view. While clean and efficient manufacturing remains key and arguably the cornerstone of chemical sustainability, we now understand that this must be accompanied by a greater use of renewable resources as well as shift to environmentally compatible products. The emphasis to date in renewable resources has been on carbon – we have all become familiar with the challenges of declining traditional fossil feedstocks and the need for a smaller carbon footprint, yet only now are concerns over other elements and elemental cycles being taken seriously.
Society uses a very large number of the elements in its everyday activities. Carbon, nitrogen, oxygen, hydrogen and phosphorus, in particular, are fundamental and commonplace in life. Others including iron, chlorine, bromine, selenium and potassium are also vital to natural processes if perhaps less widely appreciated. In addition to these we have chosen to build a society around many other elements – nickel, tungsten, chromium, copper and vanadium alongside boron, gold, silver, palladium, platinum and many others are found in a multitude of articles from buildings to electronics and from sophisticated equipment to complex drug molecules. Ironically the move to a low-carbon economy – a laudable goal in principle, if not in practice, has made the problem worse by consuming large amounts of main group and rare earth elements that are not normally used to any great extent, in batteries, wind turbines, hybrid cars and other increasingly popular alternative, low-carbon technologies. We know where these elements occur and we know a lot about their chemistries (entire book series have been written about some of them), yet we know very little about their elemental cycles which, given our almost obsessive interest in carbon cycles, seems surprising. How does our use of fluorine for example, in an increasingly high proportion of pharmaceuticals, agrochemicals and electronic chemicals affect the natural lifecycle of fluorine (which includes large quantities of static minerals and frequent emissions of hydrogen fluoride from volcanoes)? We are very aware of the dangers of halocarbons and compounds such as sulfur hexafluoride in the atmosphere but what about less volatile organofluorine molecules in the terra-sphere? The importance of achieving a better understanding of the elements in terms of their use, recovery and interaction with the environment is discussed in Chapter 1 and at various other stages in the book, in particular in Chapter 7 where the special case of platinum group metals – with applications from the decorous (jewellery) to the essential (catalysts for emission control and for the manufacture of pharmaceuticals) are discussed in terms of anthropospheric losses. The book also focuses on both tradition and novel methods of metal recovery (Chapters 2 and 3).
Fluorine, like carbon, has a number of important volatile compounds that we and nature produce, but most elements do not. Palladium, for example, is a very valuable element frequently used in catalysts for pollution control and has no significant volatile compounds. Nature provides it in the form of ores, we then transform it, for example, to a solid (but soluble) chloro compound, use it and then discard it when it is no longer “fit for purpose” typically within a solid waste or an aqueous waste stream. This traditional but totally unsustainable linear model for resource “management” (extract, process, use, dispose) disperses what was originally a concentrated ore over a very wide area in a way that makes it very difficult to recover. Actually, palladium is one of the few and precious elements that we do make an effort to recycle, for example by returning wastes to the supplier company which has the appropriate expertise to recover and reuse the element. Unfortunately, the majority of elements are not recycled at all and largely go into landfill sites where they can leach into the soil and waterways adding an environmental hazard problem to that from a loss of limited resource. Elemental recovery and waste management are discussed in Chapter 9.
What do we need to do to redress this alarming situation? In a limited ecosphere like our planet it is obvious that the linear economy model will lead to market uncertainties, decreasing availability and increasing reliability not only on declining resources but also on resources in distant regions of the planet. We worry in Europe about getting gas from the east, what about metals from South Africa? Can we assume that a country with major social issues or political instability will continue to supply materials and not use them as political levers?
If we can learn to recover elements from waste, if we can process more efficiently and if we can design articles (or processes) better so that they use less critical elements and enable recovery of those elements when the article (or process) reaches its end of life, then we are making massive steps towards elemental sustainability even in resource-deficient regions such as western Europe. The use of benign and more efficient processes and the recovery of otherwise wasted or lost valuable elements are described in Chapters 4, 5, 6, 8 and 9. These cover bio- and non bioprocesses and also look at metals and non-metals. They include a chapter on the especially important challenge and opportunity for WEEE mining, the enormous amount of waste electronics we produce each year, which is growing at a staggering rate – surely we cannot continue to treat our slightly out-of-date phone, television and other devices which such lack of respect for the elements that went into them. This balance in favour of practical technologies is deliberate: politicians can and do spend long hours debating these issues but as scientists we have a responsibility to develop practical solutions and these must include effective ways of recovering valuable elements both to reduce environmental harm and to recover and re-use the precious and limited resources our planet gives us. To put the words of Mahatma Gandhi into a modern consumer society context: “…we can satisfy all of our needs if we are resource intelligent”.