Green chemistry, which was established about two decades ago, has attracted much attention. It reflects the efforts of academia and industry to address the challenges related to sustainable development of the chemical industry, and continuous progress is being made, both in academia and industry. Briefly, green chemistry is the utilization of a set of principles to reduce or eliminate the use or generation of hazardous substances in the design, manufacture and applications of chemical products. Green chemistry is a multidisciplinary field and covers areas such as synthesis, solvents, catalysis, raw materials, products and efficient processes, as shown in figure.
Important examples of green chemistry include: phasing out the use of chlorofluorocarbons (CFCs) in refrigerants, which have played a role in creating the ozone hole; developing more efficient ways of making pharmaceuticals, including the well-known painkiller ibuprofen and chemotherapy drug Taxol; and developing cheaper, more efficient solar cells. Making chemical compounds, particularly organic molecules (composed predominantly of carbon and hydrogen atoms), is the basis of vast multinational industries from perfumes to plastics, farming to fabric, and dyes to drugs. In a perfect world, these would be prepared from inexpensive, renewable sources in one practical, efficient, safe and environmentally benign chemical reaction. Unfortunately, with the exception of the chemical processes found in nature, the majority of chemical processes are not completely efficient, require multiple reaction steps and generate hazardous by-products. While in the past traditional waste management strategies focused only on the disposal of toxic by-products, today efforts have shifted to eliminating waste from the outset by making chemical reactions more efficient.
This adjustment has, in part, led to the advent of more sophisticated and effective catalytic reactions, which reduce the amount of waste. The 2001 Chemistry Nobel Laureate Ryoji Noyori stressed that catalytic processes represent “the only methods that offer the rational means of producing useful compounds in an economical, energy-saving and environmentally benign way”.
Green chemistry will be one of the most important fields in the future. Although this field has developed rapidly in the last 20 years, it is still at an early stage. Promoting green chemistry is a long-term task, and many challenging scientific and technological issues need to be resolved; these are related to chemistry, material science, engineering, environmental science, physics and biology. Scientists, engineers and industrialists should work together to promote the development of this field. There is no doubt that the development and implementation of green chemistry will contribute greatly to the sustainable development of our society.
Green chemistry is spreading from academic labs into industry as a way to reduce costs, as well as environmental, health and safety risks. Applications of the 12 guiding principles are found on scales small and large, from choosing ingredients for reactions that minimize waste and risk to metrics that quantify waste and process efficiency. And principles of engineering and process design lead green chemists to track energy use during production, search for sustainable raw materials, and build biodegradable or recyclable products to prevent waste.
The elements of achieving sustainable regional production include:
However, green chemistry is still not widely implemented. Current estimates put green chemistry products at only 1% of the products from the chemical sector. Several barriers hinder implementation of green chemistry in the United States. The challenge of developing sustainability metrics keeps companies from evaluating their processes and incorporating green chemistry into business decisions. Regulations around drug production and the investment tied up in existing chemical plants hinder the development and implementation of new technologies. The interdisciplinary nature of green chemistry also challenges the specialized knowledge gained in current training and industrial work experience. In the USA., government policies that forward knowledge sharing or provide economic incentives can help spur green chemistry innovation. Thus, it appears that a new vision for chemical education is required, encompassing many new dimensions, as suggested in the figure, if it is to address the challenges inherent in engaging environmental sustainability.
It is evident that sustainable chemistry education involves different methodologies in teaching fundamental chemistry concepts, whereby new terms and new philosophies are introduced. The core topic of thermodynamics needs to be discussed in terms of energy efficiency of chemical processing and manufacture in addition to energetics and spontaneity of chemical reactions. The core topic of kinetics needs to be discussed in terms of selective catalysts, which maximise product yield by decreasing by-product formation. Such discussions interlink core chemistry knowledge with green chemistry principles and form the foundation on which sustainability of the chemical enterprise is progressed. As a consequence of such inclusions in chemistry curricula, a suite of new terms emerges such as ‘feedstock’ replacing ‘reactant’ and ‘E-factor’, which is the ratio of the mass of ‘waste’ compared to that of ‘product’. The latter is a simple empirical measure of the ‘green-ness’ of a chemical process, and hence, its sustainability.
Similarly, a discussion of ‘renewable energy resources’ must be prefaced by a discussion of present primary energy resources, namely fossil fuels, in order to address climate change; arguing that these have to be replaced progressively by clean, green, renewable energy resources, such as solar energy.
Sustainable chemistry also embraces environmental chemistry, whereby fundamental chemical concepts such as the p-block elements – C, N, O, P and S – are termed ‘nutrients’ and ‘salts’ are responsible for ‘salinity’ of soils and surface waters. Pollutants disturb the natural nutrient cycles and salinity reduces soil and freshwater quality with overall degradation of the natural environment. Similarly, increasing acidity of rivers and oceans disturbs aquatic ecosystems and is a direct consequence of increased levels of carbon dioxide in the atmosphere. Furthermore, increasing toxicity of the environment due to chemical waste in soils, air and surface waters is of greatest concern in terms of addressing environmental sustainability. Sustainable chemistry intuitively involves engagement with the generation of new smart materials, and hence, with nanotechnology and its envisaged linkages to global clean energy requirements. The rapidly advancing nano-chemistry is perhaps the most significant exemplar of leading edge sustainable chemistry with its focus on the development of new smart materials for energy storage, production and conversion, for advancing agricultural productivity, water purification and desalination food processing, building construction, health monitoring and for pest control. Of these applications, rapid advancement in the production of photo-voltaic devices and carbon nano-tube solar cells is accelerating the solar energy industry. Similarly, the development of nano-catalysts for hydrogen production, coupled with carbon nano-tube hydrogen storage systems are promoting hydrogen as a viable, alternative clean energy resource. Thus, sustainable chemistry via nano-chemistry directly engages with environmental sustainability by providing processes and products which directly benefit humanity without harming the environment.
However, all of these dimensions of sustainable chemistry present formidable challenges for chemical education, both in terms of future direction and scope. It is clear that ‘sustainable chemistry’ cannot be considered as a single academic course, but requires the concept and philosophy of sustainability to be progressively introduced into all chemistry courses, both at the secondary and post-secondary/tertiary levels. Furthermore, the complexity of sustainable chemistry and the diversity attached to its implementation demand flexible teaching methodologies, such as Problem Based Learning supported with multimedia anchors, leading to carefully designed learning outcomes (research into which is, at best, embryonic).
In conclusion, since ‘sustainability’ and ‘sustainable development’ are complex, multi-dimensional’ concepts, sustainable chemistry is also multi-dimensional in character, embracing disciplines not normally aligned with it such as economics, accounting, humanities, sociology, cultural studies, health sciences, food science and agricultural science. Hence, successful engagement of chemical education with sustainability involves developing partnerships with these disciplines to form a united educational platform for moving towards environmental sustainability. Fundamentally, sustainable chemistry education is a powerful philosophy integrating ‘chemistry’ into the ‘sustainable future’ syndrome and offers challenging educational opportunities to achieve identifiable sustainable outcomes.
“This article is authored by Sreedha Sambhudevan, Assistant Professor, School of Arts & Sciences, Amritapuri.
