Aid for aggregating the impacts in Life Cycle assessment

Background and Objectives  Multiple Criteria Decision Aid (MCDA) methods may be employed in a great number of fields. Life Cycle Assessment (LCA) is a specific method among the MCDA Methods. A stage of MCDA methods to be respected in LCA is the comparative evaluation of the environmental impacts. This stage is the most difficult to implement because it is a question of estimating the global environmental impact of the life cycles studied. To achieve this purpose, it is necessary to model the environmental impacts and to apply a Multicriteria Analysis (MCA) method. The problem is to choose the most suitable among the available MCA methods. The objective of this paper is to help the LCA practitioner to make this choice. Methodology  The MCA methods are compared according to their non-compensatory degree, their sensitivity to thresholds, their practicability and their workability. Results and Conclusion  The protocol presented in this paper allows to choose the most appropriate MCA method for a given LCA according to the four previous criteria. This choice will depend on the priorities of the decision maker with concern to the comparison criteria.     

Hotspot Scenario Analysis

Increasingly, organizations are working to reduce the environmental footprint of their supply chains. The use of environmentally preferable purchasing criteria is one strategy organizations use to address this goal. However, evaluating the environmental performance of these criteria (e.g., recycled content, biodegradable, renewable, and so on) has remained elusive. Life cycle assessment (LCA) can measure the impact reduction potential of sourcing strategies. However, full process‐based LCAs are time‐consuming and costly across multiple criteria of thousands of products and inputs purchased in an organizational setting. A streamlined “hotspot” methodology is presented using a combination of environmentally extended economic input‐output (EEIO) approaches and extant literature to identify hotspots in which to constrain a parameterized process‐based LCA. A case study of breakfast cereal manufacturing is developed to (1) assess the efficiencies associated with the hotspotting approach and (2) demonstrate its applicability in generating comparable decision signals of environmentally preferable sourcing criteria for procurement and supply‐chain managers along the dimensions of global warming potential and water use.     

Proposal for an integrated approach for the assessment of cross-media aspects relevant for the determination of “best available techniques” bat in the european union

The EC Directive concerning integrated pollution prevention and control (IPPC Directive 96/61/EC) obliges all Member States to make an integrated assessment of the impacts on the environment “as a whole”, as regards granting permission for and the operation of environmentally relevant industrial installations. The determination of “Best Available Techniques” BAT plays an essential role in the material transformation of the IPPC-Directive. An integrated approach for the assessment of cross-media aspects of techniques for the determination of BAT is outlined in this paper, which is grounded on the basic concept of Life Cycle Assessment (LCA), emphasising the need for decision support. The proposed assessment approach is applied to a case study sinter production in an integrated iron and steel works, which forms the base for several recommendations concerning further research.     

Ranking municipal solid waste treatment alternatives based on ecological footprint and multi-criteria analysis

The selection of a municipal solid waste (MSW) treatment alternative is a complex task in which a widespread set of criteria must be taken into account. Additionally to economic or social aspects, the decision process should consider the environmental perspective. With the purpose of quantifying the environmental burdens, a wide variety of environmental and sustainability indicators have been developed in the last years. Furthermore, integrative frameworks have been highlighted as the best option to achieve more comprehensive assessments.In this work, four different options of MSW treatment were ranked from an environmental point of view applying two methods: (1) the ecological footprint (EF) as single composite indicator and (2) multi-criteria analysis (MCA) integrating the EF together with other material flow indicators related to water consumption, emissions to air and water and occupied landfill volume. The MCA methods selected were a combination of Analytic Hierarchy Process (AHP) and Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) aided by Geometrical Analysis for Interactive Aid (GAIA). The objective was twofold: on the one side, the identification of the most beneficial waste treatment alternative (including thermal plasma gasification which as yet has not been assessed systematically) from an environmental perspective and, on the other side, the comparison of the results yielded by the two ranking methods proposed.The ranking obtained in both cases was (from best to worst): thermal plasma gasification, biological treatment of organic fraction with energy recovery from refuse derived fuel, incineration with energy recovery and landfilling. Hence, the EF proved to be a good screening indicator although it did not provide a comprehensive measure of environmental impacts associated to the waste treatment options considered. Besides, the combined application of AHP and PROMETHEE/GAIA as MCA methodology was found to be a suitable way, not very complex at user level, to integrate the information provided by a set of environmental criteria and to aid decision making.     

Life Cycle Assessments for Waste, Part III: The Case of Paint Packaging Separation and General Conclusions

This is the final paper of a series of three on the use of LCA in a strategic EIA made for the second Dutch National Hazardous Waste Management Plan (NHWMP). A comparison of two options for paint packaging waste separation is given: cryogenic versus shredder-flush separation. The high liquid nitrogen use in the cryogenic process, and particularly the energy needed to produce it, tends to make the cryogenic process environmentally less favourable. As for the other technology comparisons in the EIA, no particular problems arose. The EIA passed its peer review successfully and survived a very extensive public review procedure, in spite of the fact that it supported decisions involving very high financial stakes. Several lessons can be learned from this experience. First, LCA is a suitable tool in strategic EIAs on waste. Second, time-consuming, interactive public participation in LCA is no precondition for public acceptance — a process ofstakeholder deliberation that ensures that the practitioner knows the relevant perspective is enough. Third, high decision stakes do not automatically demand very extensive LCA work. Our experience shows that LCAs just above screening level can provide robust support to decisions involving dozens of million Euros. More extensive work would not have lead to more specified preferences. Rather, in our view, being well aware of the key discussion points in advance which are seen as relevant for the comparison by stakeholders, and having good insight in the related inherent limits of LCA, is the key to optimal decision support with LCA.     

Combining Material Flow Analysis,Life Cycle Assessment,and Multiattribute Utility Theory

Three assessment methods, material flow analysis (MFA), life cycle analysis (LCA), and multiattribute utility theory (MAUT) are systematically combined for supporting the choice of best end‐of‐life scenarios for polyethylene terephthalate (PET) waste in a municipality of a developing country. MFA analyzes the material and energy balance of a firm, a region, or a nation, identifying the most relevant processes; LCA evaluates multiple environmental impacts of a product or a service from cradle to grave; and MAUT allows for inclusion of other aspects along with the ecological ones in the assessment. We first systematically coupled MFA and LCA by defining “the service offered by the total PET used during one year in the region” as the functional unit. Inventory and impacts were calculated by multiplying MFA flows with LCA impacts per kilogram. We used MAUT to include social and economic aspects in the assessment. To integrate the subjective point of view of stakeholders in the MAUT, we normalized the environmental, social, and economic variables with respect to the magnitude of overall impacts or benefits in the country. The results show large benefits for recycling scenarios from all points of view and also provide information about waste treatment optimization. The combination of the three assessment methods offers a powerful integrative assessment of impacts and benefits. Further research should focus on data collection methods to easily determine relevant material flows. LCA impact factors specific to Colombia should be developed, as well as more reliable social indicators.     

A Transparent, Interactive Software Environment for Communicating Life-Cycle Assessment Results: An Application to Residential Windows

Life-cycle assessments (LCAs) can be used to support the selection of environmentally preferable building materials. But the dominance of the usage phase in the life cycle of building materials represents a special challenge for two reasons. First, many aspects of a building material's usage phase can be context specific. Second, the LCA outcome may rest on a building material's service life, a parameter for which there is typically insufficient information for proper determination. For example, in the selection of a window, important usagephase, context-specific factors that could be determinant include lo-cation/climate, heating-system characteristics (efficiency and fuel), and product durability. A prototype software tool, the Life Cycle Explorer, has been developed that enables decision makers to assess the relative importance of literally dozens of such influential parameters in determining the outcomes of LCA evaluations for building components. The software employed by the Life Cycle Explorer permits extensive layering while maintaining ease of browsing, with the intent of accessibility to both the layperson and the expert. An initial application of the tool addressed residential window selection; the design principles of the software are relevant to the communication phase of a wide variety of LCA and industrial-ecologyrelated modeling projects.     

Energy simulation and LCA for macro-scale analysis of eco-innovations in the housing stock

Purpose

Energy consumption of buildings is one of the major drivers of environmental impacts. Life cycle assessment (LCA) may support the assessment of burdens and benefits associated to eco-innovations aiming at reducing these environmental impacts. Energy efficiency policies however typically focus on the meso- or macro-scale, while interventions are typically taken at the micro-scale. This paper presents an approach that bridges this gap by using the results of energy simulations and LCA studies at the building level to estimate the effect of micro-scale eco-innovations on the macro-scale, i.e. the housing stock in Europe.

Methods

LCA and dynamic energy simulations are integrated to accurately assess the life cycle environmental burdens and benefits of eco-innovation measures at the building level. This allows quantitatively assessing the effectiveness of these measures to lower the energy use and environmental impact of buildings. The analysis at this micro-scale focuses on 24 representative residential buildings within the EU. For the upscaling to the EU housing stock, a hybrid approach is used. The results of the micro-scale analysis are upscaled to the EU housing stock scale by adopting the eco-innovation measures to (part of) the EU building stock (bottom–up approach) and extrapolating the relative impact reduction obtained for the reference buildings to the baseline stock model. The reference buildings in the baseline stock model have been developed by European Commission-Joint Research Centre based on a statistical analysis (top–down approach) of the European housing stock. The method is used to evaluate five scenarios covering various aspects: building components (building envelope insulation), technical installations (renewable energy), user behaviour (night setback of the setpoint temperature), and a combined scenario.

Results and discussion

Results show that the proposed combination of bottom–up and top–down approaches allow accurately assessing the impact of eco-innovation measures at the macro-scale. The results indicate that a combination of policy measures is necessary to lower the environmental impacts of the building stock to a significative extent.

Conclusions

Interventions addressing energy efficiency at building level may lead to the need of a trade-off between resource efficiency and environmental impacts. LCA integrated with dynamic energy simulation may help unveiling the potential improvements and burdens associated to eco-innovations.

     

Time Horizon and Dominance in Dynamic Life Cycle Assessment

Temporal aspects have traditionally not been recognized adequately in life cycle assessment (LCA). The dynamic LCA model recently proposed offers a significant step forward in the dynamic assessment of global warming impacts. The results obtained with dynamic LCA are highly sensitive to the choice of a time horizon. Therefore, decision making between alternative systems can be critical because conclusions are dependent on the specific time horizon. In this article, we develop a decision‐making methodology based on the concept of time dominance. We introduce instantaneous and cumulative time dominance criteria to the dynamic LCA context and argue why the dominance of an alternative should also imply preference. Our approach allows for the rejection of certain alternatives without the determination of a specific time horizon. The number of decision‐relevant alternatives can thereby be reduced and the decision problem facilitated. We demonstrate our methodology by means of a case study of end‐of‐life alternatives for a wooden chair derived from the original authors of dynamic LCA and discuss the implications and limitations of the approach. The methodology based on time dominance criteria is supplementary to the dynamic LCA model, but does not substitute it. The overall value of this article stretches beyond LCA onto more general assessments of global warming, for example, in policy where the choice of a time horizon is equally significant.     

Interpreting life cycle assessment results for integrated sustainability decision support: can an ecological economic perspective help us to connect the dots?

Life cycle assessment (LCA) is often described as a sustainability decision support tool. In practice, however, the interpretation and application of most LCA studies are restricted to eco-efficiency considerations, which provide an important but incomplete basis for sustainability decision-making. Recent methodological advances in the field enable assessing LCA results against sustainability boundaries or thresholds at planetary or more finely resolved scales. Weighting, although controversial, facilitates consistent, stakeholder-appropriate decision-making that reflects prioritization among multiple and potentially competing sustainability outcomes. Here, we discuss how the three minimum necessary criteria for sustainability (i.e., sustainable scale relative to biocapacity, distributive justice, and efficient allocation), as proposed by ecological economist Herman Daly, may provide an internally consistent basis for integrating these methodological developments, and for subsequently better positioning LCA as a sustainability decision support framework.

     

Using Attributional Life Cycle Assessment to Estimate Climate‐Change Mitigation Benefits Misleads Policy Makers

Life cycle assessment (LCA) is generally described as a tool for environmental decision making. Results from attributional LCA (ALCA), the most commonly used LCA method, often are presented in a way that suggests that policy decisions based on these results will yield the quantitative benefits estimated by ALCA. For example, ALCAs of biofuels are routinely used to suggest that the implementation of one alternative (say, a biofuel) will cause an X% change in greenhouse gas emissions, compared with a baseline (typically gasoline). However, because of several simplifications inherent in ALCA, the method, in fact, is not predictive of real‐world impacts on climate change, and hence the usual quantitative interpretation of ALCA results is not valid. A conceptually superior approach, consequential LCA (CLCA), avoids many of the limitations of ALCA, but because it is meant to model actual changes in the real world, CLCA results are scenario dependent and uncertain. These limitations mean that even the best practical CLCAs cannot produce definitive quantitative estimates of actual environmental outcomes. Both forms of LCA, however, can yield valuable insights about potential environmental effects, and CLCA can support robust decision making. By openly recognizing the limitations and understanding the appropriate uses of LCA as discussed here, practitioners and researchers can help policy makers implement policies that are less likely to have perverse effects and more likely to lead to effective environmental policies, including climate mitigation strategies.     

A Decision Support Framework for Sustainable Waste Management

This article describes a decision support framework for the evaluation of scenarios for the integrated management of municipal solid waste within a local government area (LGA).
The work is initially focused on local government (i.e., municipal councils) in the state of Queensland, Australia; however, it is broadly applicable to LGAs anywhere. The goal is to achieve sustainable waste management practices by balancing global and regional environmental impacts, social impacts at the local community level, and economic impacts. The framework integrates life-cycle assessment (LCA) with other environmental, social, and economic tools. For this study, social and economic impacts are assumed to be similar across developed countries of the world. LCA was streamlined at both the life-cycle inventory and life-cycle impact assessment stages.
For this process, spatial resolution is introduced into the LCA process to account for impacts occurring at the local and regional levels. This has been done by considering social impacts on the local community and by use of a regional procedure for LCA data for emissions to the environment that may have impacts at the regional level.
The integration follows the structured approach of the pressure-state-response (PSR) model suggested by the Organisation for Economic Cooperation and Development (OECD). This PSR model has been extended to encompass nonenvironmental issues and to guide the process of applying multiple tools.
The framework primarily focuses on decision analysis and interpretation processes. Multiattribute utility theory (MAUT) is used to assist with the integration of qualitative and quantitative information. MAUT provides a well-structured approach to information assessment and facilitates objective, transparent decisions. A commercially available decision analysis software package based on MAUT has been used as the platform for the framework developed in this study.     

Model-based Conservation Decision Aiding in the Presence of Goal Conflicts and Uncertainty

Goal conflicts and uncertainty are two major problems in decision-making for conservation and species protection. Conflicts can often be found between ecological goals on the one hand and socio-economic goals on the other, but also among different ecological goals. They can be formally analysed by methods of multi-criteria analysis. As the solution of a multi-criteria decision problem usually depends on the weights put on the individual criteria (objectives), sensitivity and robustness analyses are necessary to understand the decision problem, concentrate on the essential aspects, and support actual decision processes fully. Uncertainty in the decision problem is often caused by scarcity of information needed to predict the consequences of management actions. The so-called outranking concept proved very useful in the consideration of such uncertainty. Based on a simple fictitious case study the paper demonstrates how multi-criteria decision analysis (in particular the PROMETHEE outranking method) in combination with population model analysis can assist in conservation biological decision-making.     

Applying Life Cycle Tools and Process Engineering to Determine the Most Adequate Treatment Process Conditions. A Tool in Environmental Policy (12 pp)

Background The analysis of a wastewater treatment technology, under a expanded boundaries system which includes both the technology and the inputs required for its operation, quantifies the overall environmental impact that may result from the treatment of a wastewater stream. This is particularly useful for environmental policy makers being that a expanded boundaries system tends to provide a holistic view. The former view can be highly enriched with the use of process engineering tools, such as mathematical process modelling, process design, performance assessment and cost optimised models. Main Features The traditional approach used to assess waste treatment technologies is contrasted with a life cycle analysis (LCA) approach. The optimal design of a granular activated carbon adsorption (GAC) process is used as a model system to demonstrate the advantages of LCA approaches over traditional approaches. Further sections of the paper describe a mathematical framework for the assessment of technologies, design considerations applied in the cost optimised carbon adsorption model, the use of LCA techniques to perform an inventory of all emissions associated to the process system and, some of its environmental impacts. Results Economic and environmental considerations regarding the optimum process design are introduced as a basis for decision towards the selection and operating conditions of wastewater treatment technologies. Moreover, the use of LCA has revealed that the environmental burden associated with the wastewater treatment may produce a higher environmental impact than one that can be caused by untreated discharges. Conclusion The paper highlights the string advantages that environmental policy makers may have by combining LCA and process engineering tools. Furthermore, this approach can be incorporated into other existing treatment processes or for process designers.     

Comparative Energy, Environmental, and Economic Analysis of Traditional and E-commerce DVD Rental Networks

This study is a comparative life-cycle assessment (LCA) of two competing digital video disc (DVD) rental networks: the e-commerce option, where the customer orders the movies online, and the traditional business option, where the customer goes to the rental store to rent a movie. The analytical framework proposed is for a customer living in the city of Ann Arbor, Michigan in the United States. The primary energy and environmental performance for both networks are presented using a multicriterion LCA. The package selected by the traditional network is responsible for 67% of the difference in total energy consumption of the two alternatives. Results show that the e-commerce alternative consumed 33% less energy and emitted 40% less CO2 than the traditional option. A set of sensitivity analyses test the influence of distance traveled, transportation mode, and reuse of DVD and DVD packaging on the final results. The mode of transportation used by the customer in the traditional business model also affects global emissions and energy consumption. The customer walking to the store is by far the best option in the traditional network; however, the e-commerce option performed comparatively better despite all transportation modes tested. A novel economic indicator, ESAL, is used to compare different transportation modes based on the level of stress exerted on the pavement. The two networks are compared on the basis of cost accounting; consistent with its energy and environmental advantages, the e-commerce network also exerts lesser economic impact, by $1.17, for the functional unit tested.     

LCA and decision making: when and how to use consequential LCA; 62nd LCA forum,Swiss Federal Institute of Technology,Zürich, 9 September 2016

The 62nd life cycle assessment (LCA) forum was held on 9 September 2016 to discuss the state of research and application with regard to consequential life cycle assessment. This conference report presents the highlights of the LCA forum. The state of the art of consequential LCA was presented from different viewpoints. It was pointed out that consequential LCA is more than marginal mixes and avoided burdens and involves causal modelling. It was also said that social responsibility calls for consequential LCA. Currently, different models are used to support decision making. It was suggested to make use of the variety of models to check the conclusiveness of their results and thus the reliability of the LCAs. Current and future implementations of consequential LCI models in background databases and linking algorithms were presented. Several speakers presented consequential LCA case studies covering the sectors energy, transport, housing and mining. Some of the LCA models used in the case studies are complemented with general and partial computable equilibrium models and agent-based models and use environmentally extended input-output data or process-based LCA data. Some of the presentations focused on elements such as constrained production, marginal market mixes and technologies or recycling and system expansion. In three parallel workshops, the needs, contents and methodology, and implementation of consequential LCA approaches were discussed. The participants seemed to generally agree on the basic goal that LCA should be able to reflect the consequences of decisions. The inquiry among the participants showed that the demand for consequential LCA studies is hardly existent. The appropriate implementation of consequential modelling in LCA databases and on the appropriate model to be used in consequential LCA case studies was debated. It revealed a need for further and extensive discussions to be able to reach (minimum) consensus.     

On the uncanny capabilities of consequential LCA

Purpose

Plevin et al. (2014) reviewed relevant life cycle assessment (LCA) studies for biofuels and argued that the use of attributional LCA (ALCA) for estimating the benefits of biofuel policy is misleading. While we agree with the authors on many points, we found that some of the arguments by the authors were not presented fairly and that a number of specific points warrant additional comment. The main objective of this commentary is to examine the authors’ comparative statements between consequential LCA (CLCA) and ALCA.

Methods

We examined the notion that the LCA world is divided into CLCA and ALCA. In addition, we evaluated the authors’ notion of “wrong” models.

Results

We found that the authors were comparing an idealized, hypothetical CLCA with average (or less than average), real-life ALCAs. Therefore, we found that the comparison alone cannot serve as the basis for endorsing real-life CLCAs for biofuel policy. We also showed that there are many LCA studies that do not belong to either of the two approaches distinguished by the authors. Furthermore, we found that the authors’ notion of “wrong” models misses the essence of modeling and reveals the authors’ unwarranted confidence in certain modeling approaches.

Conclusions

Dividing the LCA world into CLCAs and ALCAs overlooks the studies in between and hampers a constructive dialog about the creative use of modeling frameworks. Unreasonable confidence in certain modeling approaches based on their “conceptual” superiority does not help support “robust decision making” that should ultimately land itself on the ground.     

Environmental Impacts of Products: A Detailed Review of Studies

Environmental effects of economic activities are ultimately driven by consumption, via impacts of the production, use, and waste management phases of products and services ultimately consumed. Integrated product policy (IPP) addressing the life‐cycle impacts of products forms an innovative new generation of environmental policy. Yet this policy requires insight into the final consumption expenditures and related products that have the greatest life‐cycle environmental impacts. This review article brings together the conclusions of 11 studies that analyze the life‐cycle impacts of total societal consumption and the relative importance of different final consumption categories. This review addresses in general studies that were included in the project Environmental Impacts of Products (EIPRO) of the European Union (EU), which form the basis of this special issue. Unlike most studies done in the past 25 years on similar topics, the studies reviewed here covered a broad set of environmental impacts beyond just energy use or carbon dioxide (CO₂) emissions. The studies differed greatly in basic approach (extrapolating LCA data to impacts of consumption categories versus approaches based on environmentally extended input‐output (EEIO) tables), geographical region, disaggregation of final demand, data inventory used, and method of impact assessment. Nevertheless, across all studies a limited number of priorities emerged. The three main priorities, housing, transport, and food, are responsible for 70% of the environmental impacts in most categories, although covering only 55% of the final expenditure in the 25 countries that currently make up the EU. At a more detailed level, priorities are car and most probably air travel within transport, meat and dairy within food, and building structures, heating, and (electrical) energy‐using products within housing. Expenditures on clothing, communication, health care, and education are considerably less important. Given the very different approaches followed in each of the sources reviewed, this result hence must be regarded as extremely robust. Recommendations are given to harmonize and improve the methodological approaches of such analyses, for instance, with regard to modeling of imports, inclusion of capital goods, and making an explicit distinction between household and government expenditure.     

Life cycle assessment of electrical and thermal energy systems for commercial buildings

Background, Aim and Scope The objective of this life cycle assessment (LCA) study is to develop LCA models for energy systems in order to assess the potential environmental impacts that might result from meeting energy demands in buildings. The scope of the study includes LCA models of the average electricity generation mix in the USA, a natural gas combined cycle (NGCC) power plant, a solid oxide fuel cell (SOFC) cogeneration system; a microturbine (MT) cogeneration system; an internal combustion engine (ICE) cogeneration system; and a gas boiler. Methods LCA is used to model energy systems and obtain the life cycle environmental indicators that might result when these systems are used to generate a unit energy output. The intended use of the LCA analysis is to investigate the operational characteristics of these systems while considering their potential environmental impacts to improve building design using a mixed integer linear programming (MILP) optimization model. Results The environmental impact categories chosen to assess the performance of the energy systems are global warming potential (GWP), acidification potential (AP), tropospheric ozone precursor potential (TOPP), and primary energy consumption (PE). These factors are obtained for the average electricity generation mix, the NGCC, the gas boiler, as well as for the cogeneration systems at different part load operation. The contribution of the major emissions to the emission factors is discussed. Discussion The analysis of the life cycle impact categories indicates that the electrical to thermal energy production ratio has a direct influence on the value of the life cycle PE consumption factors. Energy systems with high electrical to thermal ratios (such as the SOFC cogeneration systems and the NGCC power plant) have low PE consumption factors, whereas those with low electrical to thermal ratios (such as the MT cogeneration system) have high PE consumption factors. In the case of GWP, the values of the life cycle GWP obtained from the energy systems do not only depend on the efficiencies of the systems but also on the origins of emissions contributing to GWP. When evaluating the life cycle AP and TOPP, the types of fuel as well as the combustion characteristics of the energy systems are the main factors that influence the values of AP and TOPP. Conclusions An LCA study is performed to eraluate the life cycle emission factors of energy systems that can be used to meet the energy demand of buildings. Cogeneration systems produce utilizable thermal energy when used to meet a certain electrical demand which can make them an attractive alternative to conventional systems. The life cycle GWP, AP, TOPP and PE consumption factors are obtained for utility systems as well as cogeneration systems at different part load operation levels for the production of one kWh of energy output. Recommendations and Perspectives Although the emission factors vary for the different energy systems, they are not the only factors that influence the selection of the optimal system for building operations. The total efficiencies of the system play a significant part in the selection of the desirable technology. Other factors, such as the demand characteristics of a particular building, influence the selection of energy systems. The emission factors obtained from this LCA study are used as coefficients of decision variables in the formulation of an MILP to optimize the selection of energy systems based on environmental criteria by taking into consideration the system efficiencies, emission characteristics, part load operation, and building energy demands. Therefore, the emission factors should not be regarded as the only criteria for choosing the technology that could result in lower environmental impacts, but rather one of several factors that determine the selection of the optimum energy system. ESS-Submission Editor: Arpad Horvath (horvath@ce.berkeley.edu)