Raymond L. Smith

Environmental Indicators of Biofuel Sustainability: What About Context?

Indicators of the environmental sustainability of biofuel production, distribution, and use should be selected, measured, and interpreted with respect to the context in which they are used. The context of a sustainability assessment includes the purpose, the particular biofuel production and distribution system, policy conditions, stakeholder values, location, temporal influences, spatial scale, baselines, and reference scenarios. We recommend that biofuel sustainability questions be formulated with respect to the context, that appropriate indicators of environmental sustainability be developed or selected from more generic suites, and that decision makers consider context in ascribing meaning to indicators. In addition, considerations such as technical objectives, varying values and perspectives of stakeholder groups, indicator cost, and availability and reliability of data need to be understood and considered. Sustainability indicators for biofuels are most useful if adequate historical data are available, information can be collected at appropriate spatial and temporal scales, organizations are committed to use indicator information in the decision-making process, and indicators can effectively guide behavior toward more sustainable practices.

Assessing resource intensity and renewability of cellulosic ethanol technologies using eco-LCA.

Recognizing the contributions of ecosystem services and the lack of their comprehensive accounting in life cycle assessment (LCA), an in-depth analysis of their contribution in the life cycle of cellulosic ethanol derived from five different feedstocks was conducted, with gasoline and corn ethanol as reference fuels. The relative use intensity of natural resources encompassing land and ecosystem goods and services by cellulosic ethanol was estimated using the Eco-LCA framework. Despite being resource intensive compared to gasoline, cellulosic ethanol offers the possibility of a reduction in crude oil consumption by as much as 96%. Soil erosion and land area requirements can be sources of concern for cellulosic ethanol derived directly from managed agriculture. The analysis of two broad types of thermodynamic metrics, namely: various types of physical return on investment and a renewability index, which indicate competitiveness and sustainability of cellulosic ethanol, respectively, show that only ethanol from waste resources combines a favorable thermodynamic return on investment with a higher renewability index. However, the production potential of ethanol from waste resources is limited. This finding conveys a possible dilemma of biofuels: combining high renewability, high thermodynamic return on investment, and large production capacity may remain elusive. A plot of renewability versus energy return on investment is suggested as one of the options for providing guidance on future biofuel selection.

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.

Designing environmentally friendly chemical processes with fugitive and open emissions

Fugitive or open emissions can dominate the potential environmental impacts of a chemical process. In this work the design and simulation calculations of a process provide an opportunity to visualize relationships between economic potentials and potential environmental impacts. The analysis of the economic and environmental effects of process alternatives are completed quickly and easily using order-of-magnitude costing techniques and the Waste Reduction algorithm for environmental evaluation. In the example studied, the hydrodealkylation of toluene, both the economic and environmental results point towards the alternative of recycling diphenyl to extinction, which is a form of pollution prevention by source reduction. As open emissions are eliminated, the importance of fugitive emissions is shown to increase. Finally, results show where economic optimum and minimal environmental impact designs occur, and therefore one can see tradeoffs between these designs. Published by Elsevier Ltd.

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.

Predicting Evaporation Rates and Times for Spills of Chemical Mixtures

Spreadsheet and short-cut methods have been developed for predicting evaporation rates and evaporation times for spills and constrained baths of chemical mixtures. Steady-state and time-varying predictions of evaporation rates can be made for six-component mixtures, including liquid-phase non-idealities as expressed through the UNIFAC method for activity coefficients. A group-contribution method is also used to estimate vapor-phase diffusion coefficients, which makes the method completely predictive. The predictions are estimates that require professional judgement in their application. One application that the evaporation time calculations suggest is a method for labeling chemical containers that allows one to quickly assess the time for complete evaporation of spills of both pure components and mixtures. The labeling would take the form of an evaporation time that depends on the local environment. For instance, evaporation time depends on indoor or outdoor conditions and the amount of each chemical among other parameters. This labeling would provide rapid information and an opportunity to premeditate a response before a spill occurs.

Using national inventories for estimating environmental impacts of products from industrial sectors: a case study of ethanol and gasoline

PurposeIn order to understand the environmental outcomes associated with the life cycle of a product, to compare these outcomes across products, or to design more sustainable supply chains, it is often desirable to estimate results for a reference supply chain representative of the conditions for a sector in a specific region. This paper, by examining ethanol and gasoline production processes, explains how choices made in the calculation of sector-representative emission factors can have a significant effect on the emission estimates used in life cycle assessments.MethodsThis study estimates reference emission factors for United States dry-grind corn ethanol production and gasoline production processes suitable for use in baseline life cycle assessment unit processes. Based on facility-specific emissions and activity rates from the United States National Emissions Inventory, the Energy Information Administration, and an ethanol industry trade publication, the average emissions per unit energy content of fuel are computed using three different approaches. The Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) characterization factors are used to estimate impact potentials for six environmental and three human health categories. Sector-specific direct emissions and impact potentials are compared across the three approaches and between the two sectors. The system boundary for this analysis is limited to the fuel production stage of these transportation fuel lifecycles.Results and discussionFindings from this work suggest that average emission factors based on total emissions and total production may significantly under estimate actual process emissions due to reporting thresholds and otherwise unreported emissions.ConclusionsBecause of the potential for unreported emissions in regional inventories, it is more appropriate to estimate sector reference emission factors based on matched sets of facility or process level emissions and activity rates than to use aggregated totals. This study demonstrates a method which can be used for inventory development in cases where multiple facilities producing the same product are involved.

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.

Methods for evaluating the sustainability of green processes

Abstract A methodology, called GREENSCOPE (Gauging Reaction Effectiveness for the ENvironmental Sustainability of Chemistries with a multi-Objective Process Evaluator), is under development at the U.S. EPAs Office of Research and Development to directly compare the sustainability of processes that employ various chemistries or technologies. Evaluations using the method answer two questions: is an alternative green (i.e., does it have a lower environmental burden) and is it sustainable? For evaluating sustainability, methods are being developed in four areas, called the four Es: Efficiency, Environment, Energy and Economics. This paper represents the first descriptions of the evaluation methods for GREENSCOPE, including an example for the oxidation of toluene.