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      This short section consists of a chapter on green chemistry and engineering. It introduces the 12 principles of green chemistry and various drivers for making a given process or product greener. Further, ways to improve sustainability are discussed mainly in terms of the cost of the waste produced. A brief introduction is provided on how to evaluate the sustainability or green credentials of a given process or product leading to a discussion on ways to improve sustainability. These concepts will be used in other chapters in the book in order to explore potential (un)sustainable aspects of a given method for nanomaterials synthesis. This section aims to set the scene for the book and the principles explained will be revisited in later sections of the book, in order to put them in the context of nanomaterials synthesis and manufacturing.

      IOP Publishing

      Green Nanomaterials

      From bioinspired synthesis to sustainable manufacturing of inorganic nanomaterials

       Siddharth V Patwardhan and Sarah S Staniland

      Chapter 1

      Green chemistry and engineering

      1.1 Principles of green chemistry and engineering

      1.1.1 Overview

      At present, we are highly reliant on chemical processes because of the benefits they bring to us. Examples of sectors where chemical industry has impacted our lives include healthcare, transportation, communications and food, constituting total sales of around €1.5 trillion globally [1]. In recent times, society has become more aware and concerned about the negative environmental impact associated with chemical industry. As such, there have been wider legislative interventions in order to ensure greater control and monitoring of chemical processes. These changes have led to increasing pressure on the chemical industry to continue to deliver high value products in an economical fashion, while minimising or eliminating the adverse environmental burden. This new challenge has driven the development of green chemistry for sustainable chemical processing.

      Sustainable development has been defined by the United Nations as ‘…meeting the needs of the present without compromising the ability of future generations to meet their own needs’ [2]. Further, the United States Environmental Protection Agency (EPA) has extended this definition to give birth to green chemistry where the main goal is to ‘promote innovative chemical technologies that reduce or eliminate the use or generation of hazardous substances in the design, manufacture and use of chemical products’ [3]. Related to this is green engineering, which pertains to the design, commercialisation and the use of processes and products in an economical fashion to minimise pollution and risks to health and the environment. Utilising these concepts, 12 principles of green chemistry have been formulated [4], which are shown in figure 1.1.

      Figure 1.1. 12 principles of green chemistry, after [4]. Copyright of OUP 1998.

      Applying these green and sustainable principles has the potential to address the challenges facing chemical industry, in balancing the high value of products against the environmental burden. A common perception is that green chemistry is costly and/or can lead to costly products, thus reducing the profit for industry. However, this is not always true. While there may be initial investment needed for the development of green technologies, which can replace existing processes, such changes can also lead to reduced costs of production and products. Besides, considering the long-term benefits of adopting green chemistry, initial costs can be offset. Some of these points and the 12 principles will be discussed further in chapters 4 and 5 with specific relevance to nanomaterials.

1.1.2 Drivers for green approaches

      One of the main issues leading to adverse environmental impact is the generation of waste in a chemical process. Depending on the technological, economical and legislative frameworks, the quantities of waste produced, in particular, in relation to the amount of product produced, vary from sector to sector. For example, some industrial sectors are technologically very advanced, such that they have developed ways to minimise waste, e.g. petroleum refining. On the other hand, in some other sectors, the cost of the product is significantly higher than the loss of value from waste or cost of treating waste, and hence waste minimisation is not given due importance (e.g. pharmaceuticals). There are also examples where pro-active legislation has driven the chemical industry to find innovative ways to minimise waste. Waste relates to inefficiencies in a given process, which leads to loss of valuable resources (e.g. substances and energy) and it can cause risks to the environment and health, which ultimately increases the process costs. Figure 1.2 illustrates the financial, environmental and societal origins of the costs associated with waste.

      Figure 1.2. Costs associated with waste. Reproduced with permission of the Royal Society of Chemistry from [1].

      If one considers the total costs for waste originating from all areas as shown in figure 1.2,

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