Sustainable Chemical Production Metrics

The assessment of a complex phenomenon such as that of the sustainability of the chemical production requires integration of several indicators into a useful metric. The usefulness of a metric depends strongly on the number of indicators too few may not provide an adequate description of a phenomenon, whereas too many would make the cost of completing the metric prohibitively high. 

CWRT metrics have been developed on the basis of the eco-efficiency concept, defined as a ratio of product (or service) value to its environmental influence, where value is understood to be capital creation, and the main environmental influences are due to consumed energy, materials and water, and released green house and ozone depleting gases. Important aspects of the CWRT metrics are (i) normalization to dollar sales or value added, (ii) consideration for relative environmental impacts of different pollutants and (hi) use of national databases. 

The main categories included in CWRT metrics are energy, mass, water usage, pollutant, human health and eco-toxicity. Indicators of human health and eco-toxicity are based on the parameters already widely used in the assessment of chemical hazards, that is, permissible exposure limits and 50% of lethal concentration. The indicators also take into account the life-time of chemical pollutants in various media of the environment. 

IChemE metrics of sustainability consist of 49 indicators classified into three main categories economic, environmental and social. The environmental indicators within the IChemE metrics are similar to those in the CWRT metrics. However, there are some differences. The IChemE metrics include the area of land as an environmental indicator. The actual indicators are (i) the sum of directly occupied and affected land per value added and (ii) the rate of land restoration. Other differences relate to the assessment of the relative impacts of pollutants on the environment and human health. The IChemE indicators do not take into account the life-time of chemicals in various media of the environment. The human health indicator is limited to carcinogenic effects and is normalized to benzene. 

Constable et al. have compared the use of various proposed green chemistry metrics in the evaluation of four commercial pharmaceutical processes [39]. 

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These represent a simplification over a true LCA methodology, and include also aspects related to safety and risk, and economics. They thus could be a basis, which can be adapted for specific cases, for a sustainable chemical production metric, which should be integrated with other assessment tools such as LCA, Sustainable Process Index, and Risk Analysis and evaluation. 

Efforts to develop sustainability indicators and metrics have been made at various scales, ranging from global down to local community, business unit, and technology levels. In general, indicators and metrics are designed to capture the ideas inherent in sustainability and transform them into a manageable set of quantitative measures and indices that are useful for communication and decision-making. In this section, we provide an overview of sustainability indicators and metrics, especially as they relate to the chemical industry. This section will be followed by two specific case studies on the uses of sustainability metrics and indicators in product/process development in chemical companies. 

J. Schwarz, E. Beaver and B. Beloff, Sustainability Metrics Making Decisions for Major Chemical Products and Facilities, final report to the U.S. Department of Energy Office of Industrial Technologies, BRIDGES to Sustainability, Houston, 2000. 

To proceed in this direction it is necessary to use indicators, metrics and tools of analysis/assessment that allow us to compare the different alternative and options, and quantify the benefits of adoption new solutions. Several of these indicators, metrics and tools have been developed, and applicability and limits have been discussed in this book. New aggregated indicators to assess sustainability of chemical production have also been proposed. 

Mass Productivity appears to be a useful metric for focusing attention away from waste towards the use of materials. As such, it is more likely to drive chemical and technology innovations that will lead to more sustainable business practices. 

In the today s economic and social environment, Chemical Process Industries are asked to discover innovative solutions that are not only economically efficient, but also sustainable. Production-integrated environmental protection implies that ecological issues are included in the conceptual design methodology. Besides economic efficiency, metrics for ecological and sustainability performance must be included in assessing the quality of a design solution. 

Oxidation reactions play a crucial role in the chemical industry, where >90% of the feedstocks derive from hydrocarbons - the most reduced organic chemicals on the planet. Sustainability concerns are demanding a greater shift toward biomass-derived feedstocks however, oxidation methods will continue to play a major role. For example, even as this book goes to press (March 2016), BASF and Avantium have just announced plans to pursue a joint venture for the production of 2,5-furandicarboxylic acid (FDCA), an important polymer-building block derived from biomass. The proposed 50000 metric tons per year plant will undoubtedly incorporate liquid phase aerobic oxidation chemistry similar to that described in Chapter 19 of this volume. 

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