Gerardo J. Ruiz-Mercado

A method for decision making using sustainability indicators

Calculations aimed at representing the thought process of decision makers are common within multiobjective decision support tools. These calculations that mathematically describe preferences most often use weighting factors for each desire or objective to combine various utility scores onto a single scale to allow a ranking of alternatives. However, seldom are the tradeoffs implied in creating a single scale for multiple objectives described explicitly. This paper illustrates how choices for combining utility scores are in fact a statement of equivalence between the weighted utility scores of these objectives, even if the choice of weighting factors was intended to be value free or “equal weighting.” In addition, relationships between objectives, perhaps developed by stakeholders, can be rewritten as a series of equations (i.e., relationships) for the weighting factors, where it should be noted that seldom will stakeholders provide a set of relationships that exactly match the number of unknowns. Depending on the number of relationships specified, the weighting factors can be underdetermined, unique, or overdetermined. Calculations using the singular value decomposition method can be used as a general method to determine the weighting factors for each of these situations, allowing for explicit representations of the implied tradeoffs for decision makers. Finally, a simple but powerful method for calculating total utility using marginal rates of substitution between utility scores rather than weighting factors is presented. In addition to using marginal rates of substitution, the calculation of utility can be done with (process) attribute values or using EPA’s GREENSCOPE tool sustainability indicator scores. Utility calculations based on these more intuitive factors (marginal rates of substitution, attribute values, and/or GREENSCOPE indicator scores) can then be used to evaluate various alternatives. The decision maker can see the effects of changing the marginal rates of substitution (i.e., utility tradeoffs) and attribute (i.e., design or operating parameter) values or GREENSCOPE indicator scores for alternatives. While an example from chemical production for terephthalic acid is presented, the methods shown are generally applicable.

A framework for multi-stakeholder decision-making and conflict resolution

Abstract We propose a decision-making framework to compute compromise solutions that balance conflicting priorities of multiple stakeholders on multiple objectives. In our setting, we shape the stakeholder dissatisfaction distribution by solving a conditional-value-at-risk (CVaR) minimization problem. The CVaR problem is parameterized by a probability level that shapes the tail of the dissatisfaction distribution. The proposed approach allows us to compute a family of compromise solutions and generalizes multi-stakeholder settings previously proposed in the literature that minimize average and worst-case dissatisfactions. We use the concept of the CVaR norm to give a geometric interpretation to this problem and use the properties of this norm to prove that the CVaR minimization problem yields Pareto optimal solutions for any choice of the probability level. We discuss a broad range of potential applications of the framework that involve complex decision-making processes. We demonstrate the developments using a biowaste facility location case study in which we seek to balance stakeholder priorities on transportation, safety, water quality, and capital costs.

Expanding GREENSCOPE beyond the gate: a green chemistry and life cycle perspective

Industrial processes, particularly those within the chemical industry, contribute products and services to improve and increase society’s quality of life. However, the transformation of raw materials into their respective final goods involves the consumption of mass and energy and the possible generation of by-products and releases. To address these issues, the new approach for chemical processing is focused on sustainable production: minimize raw material consumption and energy loads, minimize/eliminate releases, and increase the economic feasibility of the process. To evaluate these advances, a sustainability assessment methodology, GREENSCOPE, has been developed into a tool to evaluate and assist in the synthesis and design of chemical processes. New process sustainability indicators have been proposed based on input/output process data, and the base-case ratio approach is implemented to predict process changes from known process performance data and design relationships. In addition, a discussion regarding the implications of using sustainability evaluations beyond the process boundaries, applying the principles of green chemistry in all steps of chemical process development, and a description of their benefits to the life cycle inventory and the subsequent life cycle assessment is included. Finally, a new methodology approach to integrate GREENSCOPE into a life cycle inventory to develop sustainable systems is introduced.

Mining Available Data from the United States Environmental Protection Agency to Support Rapid Life Cycle Inventory Modeling of Chemical Manufacturing

Demands for quick and accurate life cycle assessments create a need for methods to rapidly generate reliable life cycle inventories (LCI). Data mining is a suitable tool for this purpose, especially given the large amount of available governmental data. These data are typically applied to LCIs on a case-by-case basis. As linked open data becomes more prevalent, it may be possible to automate LCI using data mining by establishing a reproducible approach for identifying, extracting, and processing the data. This work proposes a method for standardizing and eventually automating the discovery and use of publicly available data at the United States Environmental Protection Agency for chemical-manufacturing LCI. The method is developed using a case study of acetic acid. The data quality and gap analyses for the generated inventory found that the selected data sources can provide information with equal or better reliability and representativeness on air, water, hazardous waste, on-site energy usage, and production volumes but with key data gaps including material inputs, water usage, purchased electricity, and transportation requirements. A comparison of the generated LCI with existing data revealed that the data mining inventory is in reasonable agreement with existing data and may provide a more-comprehensive inventory of air emissions and water discharges. The case study highlighted challenges for current data management practices that must be overcome to successfully automate the method using semantic technology. Benefits of the method are that the openly available data can be compiled in a standardized and transparent approach that supports potential automation with flexibility to incorporate new data sources as needed.

Using GREENSCOPE indicators for sustainable computer-aided process evaluation and design

Abstract Manufacturing sustainability can be increased by educating those who design, construct, and operate facilities, and by using appropriate tools for process evaluation and design. The U.S. Environmental Protection Agencys GREENSCOPE methodology and tool, for evaluation and design of chemical processes, suits these purposes. This work describes example calculations of GREENSCOPE indicators for the oxidation of toluene and puts them into context with best- and worst-case limits. Data available from the process is transformed by GREENSCOPE into understandable information which describes sustainability. An optimization is performed for various process conversions, with results indicating a maximum utility at intermediate conversions. Lower conversions release too much toluene through a purge stream; higher conversions lead to the formation of too many byproducts. Detailed results are elucidated through the context of best- and worst-case limits and graphs of total utility and GREENSCOPE indicator values, which are calculated within an optimization framework for the first time.

Coupling Computer-Aided Process Simulation and Estimations of Emissions and Land Use for Rapid Life Cycle Inventory Modeling

A methodology is described for developing a gate-to-gate life cycle inventory (LCI) of a chemical manufacturing process to support the application of life cycle assessment in the design and regulation of sustainable chemicals. The inventories were derived by first applying process design and simulation to develop a process flow diagram describing the energy and basic material flows of the system. Additional techniques developed by the United States Environmental Protection Agency for estimating uncontrolled emissions from chemical processing equipment were then applied to obtain a detailed emission profile for the process. Finally, land use for the process was estimated using a simple sizing model. The methodology was applied to a case study of acetic acid production based on the Cativa process. The results reveal improvements in the qualitative LCI for acetic acid production compared to commonly used databases and top-down methodologies. The modeling techniques improve the quantitative LCI results for inputs and uncontrolled emissions. With provisions for applying appropriate emission controls, the proposed method can provide an estimate of the LCI that can be used for subsequent life cycle assessments.

Modeling and Advanced Control for Sustainable Process Systems

This chapter introduces a novel process systems engineering framework that integrates process control with sustainability assessment tools for the simultaneous evaluation and optimization of process operations. The implemented control strategy consists of a biologically inspired, multiagent-based method derived for chemical processes. The sustainability and performance assessment of process operating points is carried out using the US Environmental Protection Agencys GREENSCOPE assessment tool that provides scores for the selected economic, efficiency, environmental, and energy indicators. The indicator results supply information on whether the implementation of the controller is moving the process toward a more sustainable operation. The effectiveness of the proposed framework is illustrated through a case study of a continuous bioethanol fermentation process whose dynamics are characterized by steady-state multiplicity and oscillatory behavior.

Using GREENSCOPE for Sustainable Process Design: An Educational Opportunity

Abstract Increasing sustainability can be approached through the education of those who design, construct, and operate facilities. As chemical engineers learn elements of process systems engineering, they can be introduced to sustainability concepts. The EPA’s GREENSCOPE methodology and tool, valuable in the evaluation and design of chemical processes, can be used to teach these concepts. This work describes example calculations of GREENSCOPE indicators for the oxidation of toluene and puts the indicators into context with best- and worst-case limits. The data available from the process is developed into understandable information which describes sustainability. Targets for more sustainable process designs are understood, and enhancements can be considered to improve designs, either for real-world processes or in an educational environment.

Emergy analysis for the sustainable utilization of biosolids generated in a municipal wastewater treatment plant

This contribution describes the application of an emergy-based methodology for comparing two management alternatives of biosolids produced in a wastewater treatment plant. The current management practice of using biosolids as soil fertilizers was evaluated and compared to another alternative, the recovery of energy from the biosolid gasification process. This emergy assessment and comparison approach identifies more sustainable processes which achieve economic and social benefits with a minimal environmental impact. In addition, emergy-based sustainability indicators and the GREENSCOPE methodology were used to compare the two biosolid management alternatives. According to the sustainability assessment results, the energy production from biosolid gasification is energetically profitable, economically viable, and environmentally suitable. Furthermore, it was found that the current use of biosolids as soil fertilizer does not generate any considerable environmental stress, has the potential to achieve more economic benefits, and a post-processing of biosolids prior to its use as soil fertilizer improves its sustainability performance. In conclusion, this emergy analysis provides a sustainability assessment of both alternatives of biosolid management and helps decision-makers to identify opportunities for improvement during the current process of biosolid management.

Transformation towards sustainable bioenergy systems

Societal progress, economic growth, and protection of the environment all constitute into a systems-based development framework for addressing current challenges. An example of such challenge is developing alternative routes for energy generation using non-conventional renewable energy sources (e.g. bio-based, forest biomass, agricultural, etc.), coupled with nutrient recovery, water conservation, emissions mitigation, and revenue generation. In addition, as described in the Brundtland Report, the sustainable development of these energy systems should “meet the needs of the present without compromising the ability of future generations to meet their own needs”. Moreover, preventing and reducing emissions of pollutants, across all media, for energy production can be approached through other means, including the design, evaluation, and improvements of these processes, products, and their supply chains. More recently, there has been a shift towards transforming and applying these pollution prevention/reduction and cost-effective solutions into bioenergy systems. Sustainable bioenergy systems will play a decisive role on the path forward to meeting the energy demands of a growing global population and their economic desires. Indeed, given contemporary climate change challenges, sustainable bioenergy systems have a role to play in mitigation, adaptation, and transformation efforts. Therefore, the search for sustainable energy will continue to influence the twenty-first-century research, business and policy needs. For example, in the manufacturing sector, these solutions can improve efficiencies as well as public perceptions by decreasing the use of materials and reducing the negative environmental impacts, ultimately increasing shareholder value over the long term. This special issue of Clean Technologies and Environmental Policy is promoted by the Mexican Network of Bioenergy.1 This network belongs to the National Council for Science and Technology (CONACYT) of Mexico whose main aim is to promote scientific, technological, and innovative development for stimulating the sustainable use of bioenergy. The special issue is a combination of contributed articles by a diverse set of experts in the Americas and Europe, addressing a multitude of sustainability concepts such as pollution reduction and prevention, social responsibility, materials management, life cycle assessment, and industrial ecology all for the development of more sustainable and cost-effective uses of bio-based/renewable resources for energy systems. These energy systems include products (e.g. biomass, biogas, nutrients, biofuels, etc.), processes (e.g. biorefinery, gasification, bio-digesters, etc.), and supply chains of feedstocks and products. Such topics are of great interest in the local, regional, national, and international communities. This includes government, industry, academia, and decision-makers due to the multiple sustainable applications that can be carried out in bioenergy systems with the intention of achieving a substantial transition in synergistic combination with non-renewable sources, to energy based on biomass and other renewable sources. Finally, we would like to extend our sincere appreciation to all the authors for their contributions. Also, we greatly appreciate the time and efforts taken by the reviewers to provide input and thoughts on each manuscript to improve the quality and contribution of the submission. We are thankful to the editorial team at Clean Technologies and Environmental Policy and to Editor-in-Chief Dr. Subhas K. Sikdar for their great support. We hope this special issue serves as a valuable source of information and concepts to assist as our society continues to implement the framework and concepts associated with arriving at the most sustainable and costeffective uses of bio-resources, energy options, and materials management for energy production. * Gerardo J. Ruiz-Mercado Ruiz-Mercado.Gerardo@epa.gov