Software Integration of Life Cycle Assessment and Economic Analysis for Process Evaluation

Transcription

1 Proceedings of the 6th International Conference on Process Systems Engineering (PSE ASIA) June 2013, Kuala Lumpur. Software Integration of Life Cycle Assessment and Economic Analysis for Process Evaluation Sawitree Kalakul a, Pomthong Malakul a,, Kitipat Siemanond a, and Rafiqul Gani b a The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 1033, Thailand b CAPEC, Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark Abstract Chemical product-process design challenges the developers to find designs that are not only technically and economically optimal but also environmentally acceptable. Life cycle assessment (LCA) is a tool that helps to quantify the potential environmental impacts in order to select the optimal design from various feasible alternatives. This paper presents a new LCA software, LCSoft, which is exclusively designed for evaluation of chemical processes and options for integration with other process design tools, such as sustainable design (SustainPro), economic analysis (ECON) and process simulation. The framework of LCSoft contains four main parts (life cycle inventory database, estimation of environmental factors, LCA calculation, and options for integration). The application of LCSoft to the analysis of a bioethanol process is also highlighted. Keywords: Sustainable design; Life cycle assessment; Economic analysis; Process Optimization. 1. Introduction In the present world our society has become more concerned about the issues of natural resource depletion and environmental degradation. Many industries and businesses must pay more attention on their activities that affect the environment, which means that environmental impact has become a key factor for them in their search for more sustainable options. However the development of new processes and the introduction of new advanced technologies are still occurring every day. This requires identifying the more sustainable process design options by considering process needs together with economic and environmental factors. To achieve this objective, environmental assessment of the process must be done. One effective tool for environmental assessment is LCA, a tool that helps to quantify the potential environmental impacts throughout the product or process life cycle and to evaluate improvement options in order to select the best design among various alternatives [1]. The LCA method comprises of a set of different methods for the impact assessment in a particular process. The technical framework for conducting LCA, according to the International Standardization Organization (ISO) directive, ISO 14040, is a systematic process consisting of four main steps. (i) Goal and scope definition: the intention for the use of LCA and the system boundaries are defined, together with the functional unit for evaluation, for example, 1 kg of product. (ii) Life cycle inventory (LCI): all the necessary input and output data for the processes regarding the product system is

2 918 Kalakul et al. collected in terms of the defined functional unit. The emission data for the different subprocesses is combined and presented as the total emissions of a substance. (iii) Life cycle impact assessment (LCIA): the inventory data on input (material and resources) and output (waste and emissions) are translated into information related to the impacts which the process has effects on the environment, human health, and resources such as global warming or ozone depletion. The impact assessment requires the emission data from the LCI step in terms of a list of substances that are emitted from the process and the substance-specific characterization factors (CFs) that represent their potency. (iv) Interpretation: the results from the previous steps are presented for analysis with respect to the goals of the study. In order to quantify the results, the sensitivity and uncertainty of the calculated impacts may also be analyzed in this step. Although, various LCA methodologies have been developed ([2], [3]), it is still difficult to perform the LCA because of the most time-consuming step which is LCI data collection for relevant feedstock, emission, etc., and the corresponding substance CFs. Therefore, in this work, emphasis has been put on the development of a LCI database and models for the generation of the CFs. The various LCA software (BOUSTED [4], SimaPro [5], and GaBi [6]) provide different degrees of sustainability analysis [1]. However, the existing software is not directly linked to process synthesis-design tools to generate more sustainable alternatives. Therefore, the objectives of this work are to develop the new LCA software, LCSoft, which is exclusively designed for evaluation of chemical processes and integration with other necessary tools for sustainable productprocess design. Consequently, LCSoft is integrated with ECON [7], economic analysis software; SustainPro [1], sustainable process design software; and CAPEC DB [8], property database tool. In this way, LCSoft together with its integrated tools can help the product-process developer to obtain more sustainable designs efficiently and reliably. 2. Framework The framework consists of two types of tools, those that are dedicated to environmental performance analysis (LCSoft) and those that are dedicated to integration of the LCSoft with other tools. The framework of LCSoft contains four main parts (see Figure 1) Tool-1: Knowledge management and module development Through this tool, multiple processes can be linked together through an input/output interface. The knowledge representation in the database is managed through a specially developed ontology of the system information, enabling easy maintenance and future expansion of the LCI database. For example, the emission data of electricity generation is country specific and has different entries for different countries Tool-2: Calculation factor estimation To characterize the emissions that occur in the life cycle of a product or process in terms of their potential environmental impacts, for each category of impact (such as global warming or ozone depletion), the impact assessment applies to substance-specific characterization factors (CFs) that represent the substance s potency. An emission inventory for the life cycle of a product or process often contains hundreds of substances, and many of them have the potential to damage the environment. These potential damages are quantified using characterization factors for categories of environmental impact. Although a number of different models have been developed

3 Software Integration of Life Cycle Assessment and Economic Analysis for Process Evaluation 919 ([9], [10]) for this purpose, they cover, however, a limited number of substances. Thus, for many substances, the characterization factor needed for LCI calculation may not be available. Therefore, within this tool-2, the CFs are calculated. The LCSoft database contains data from the USEtox TM database and the US Environmental Protection Agency (EPA) and especially developed predictive property models [8], enabling therefore, the calculation of environmental impacts such as human toxicity potential (HTP) for a very wide range of organic substances Tool-3: Calculation of LCA There are three main steps in this tool, (i) inventory calculation; (ii) classification characterization; (iii) analysis and improvement of process design. The first step performs an inventory of retrieved data from the LCI database preparing for the calculation in the next step. The second step classifies and characterizes the types of the environmental impacts and calculates them with respect to substances emitted from the life cycle of product or process and their characterization factors for each impact category. The third step analyzes the calculation results from the second step in order to decide on the environmental improvement options Tool-4: Integration of LCSoft, ECON and SustainPro In tool-4, the LCSoft is integrated with ECON and SustainPro to obtain all the necessary performance measures to analyze a design alternative. Simultaneously, it helps to obtain design targets for new and more sustainable designs. Figure 1: The framework of LCSoft and tools integration

4 920 Kalakul et al. 3. Case study This study is a cradle-to-gate LCI of bioethanol production from cassava rhizome. Production of cassava phase, transportation and manufacturing are analyzed. In the manufacturing, the mass and energy flows are taken from the simulation results which have been developed separately [11]. The input wet biomass is 377 tons/day and bioethanol production is 119 tons/day with the addition of cellulase enzyme. From this information, the emissions and environmental impacts for the process are estimated Tool-1: Knowledge management and module development Searching for the LCI related data for the upstream process (production of raw material) within the LCSoft database, it is found that data for the following substances are available: sulphuric acid, ammonia, water, ethanol, ammonia, acetic acid, con steep liquor, cellulose, calcium sulphate. On the other hand, process data for the production of cassava is not available. Therefore, it has to be created. With this tool, the data from literature is entered into the software and managed with the ontology model, making it easy to maintain, revise and retrieve the data Tool-2: Calculation factor estimation According to the base-case design, since a small amount of ethanol is emitted from the process, the environmental impacts, such as human toxicity-carcinogenics (HC), are calculated from the mass of emitted ethanol, compartment and characterization factor of ethanol for HTP. They are found to be negligible Tool-3: Calculation of LCA The results from LCSoft are carbon footprint and environmental impact. The carbon footprint of this process is calculated from raw material and utility consumption in each unit operation in the bioethanol process for 1 kg of product is presented in Figure 2. The results show that emissions of green house gases mainly come from the utility consumption. The environmental impact results are presented in different impact categories for 1 kg of ethanol product. They are found to be small as given in Table 1. These results indicate that the process is environmentally friendly. Figure 2: The results of carbon footprint

5 Software Integration of Life Cycle Assessment and Economic Analysis for Process Evaluation 921 Table 1: Results of environmental impact calculation from LCSoft Impact category Impact value Unit human toxicity by ingestion (HTPI) 1.77E-04 human toxicity by exposure (HTPE) 1.36E-05 aquatic toxicity (ATP) 8.16E-05 terrestrial toxicity (TTP) 1.77E-04 global warming (GWP) 1.23E+00 kg of CO 2 eq. ozone depletion (ODP) 6.75E-06 Kg of CFC-11 eq. photochemical oxidation (PCOP) 3.94E-05 Kg of C 2 H 2 eq. acidification (AP) 2.04E-03 Kg of H + eq. human toxicity-carcinogenics (HTC) 9.05E-04 Kg of benzene eq. human toxicity-non carcinogenics (HTNC) 2.65E-01 Kg of toluene eq. fresh water ecotoxicity (ET) 2.65E-05 Kg 2,4-D eq a LD 50 is one kilogram body weight of rat administered in milligrams of toxic chemical by mouth (mg emission /kg rat ).; b TWA is time weighted average concentration (mg emission /m 3 ).; c LC 50 is lethal concentration (mg emission /kg fathead minnows ) Tool-4: Integration of LCSoft, ECON and SustainPro After application of ECON for economic evaluation, a major part of the operating costs are found to involve the raw materials and utilities (see Table 2). SustainPro proved to be a valuable tool for its ability to identify potential targets for improvement. The sustainable indicators (material value added (MVA), energy and waste cost (EWC), and total value added (TVA)) for each open path (OP) and close path (CP) have been investigated. They indicate that the corn steep liquor (CSL) and cellulase (enzyme) loose their value as they exit the process, and therefore, they should be improved (see Table 3). The excess flow of CSL should be reduced and cellulase should be recovered and recycled, if possible. However, cellulase is difficult to be recovered and recycled and therefore, other options, such as, use of the lignin waste and recycle of water needs to be investigated. The future work will analyze these data to generate new feasible and more sustainable designs through SustainPro. Table 2: the cost of Bioethanol base case in ECON Name Annual price ($/year) Raw material $ 7,600, Product $ 448,255, Total capital cost $ 53,692, Operating cost $ 20,792, Utility cost $ 3,459, Equipment cost $ 9,646,570.00

6 922 Kalakul et al. Table 3: Bioethanol base case results in SustainPro after ordering indicators Path MVA TVA Probability Path EWC Probability OP 322 (CSL) OP 326 (Cellulase) High OP Medium High OP Medium 4. Conclusion and Future Work A LCA tool, LCSoft, that can help to evaluate environmental performance of a process has been presented together with a case study highlighting its application. The LCA tool is based on a framework that allows a systematic calculation and analysis of inventories and emissions, and, the integration with other important tools for economic and sustainability analysis. A new database has been created and new predictive models for estimation of the environmental impacts have been developed. The LCA of bioethanol production from cassava rhizome has been analyzed Current and future work is improving and extending the framework with respect to integration with external tools and for performance of sensitivity and uncertainty analysis related to the predicted environmental impacts. References 1. Carvalho, A., Gani, R., Matos, H. (2008), Process Safety and Environmental Protection, 86, Pant, R., Van Hoof, G., Schowanek, D., Feijtel, T. C. J., De Koning,A., Hauschild, M., Olsen, S. I., Pennington, D. W., Rosenbaum, R. (2004). Int. J. LCA Hauschild, M. Environ. Sci. Technol. 2005, 39(4), 81A 88A. 4. Boustead, I. & Hancock, G. F. (1979). Handbook of Industrial Energy Analysis. EllisHorwood, Chichester/John Wiley, New York, USA. 5. Consultants BV, SimaPro user manual. 6. GaBi Software Saengwirun, P., (2012). Cost calculations and Economic ananlysis (ECON). MSc-thesis,The Petroleum and Petrochemical College (PPC), Chulalongkorn University, Bangkok, Thailand. 8. Hukkerikar, A. S., Kalakul, S., Sarup, B., Young, D. M., Sin, G., Gani, R. (2012). Chemical Information and Modeling, 56, McKone, T.E., Hertwich, E.G. (2001). The human toxicity potential and a strategy for evaluating model performance in life cycle assessment. Int J Life Cycle Assess 6(2), National Research Council (NRC). (2008). Models in Environmental Regulatory Decision Making; Committee on Models in the Regulatory Decision Process, Board on Environmental Studies and Toxicology, Washington, DC. 11. Mangnimit, S., (2012). Sustainable Process Design of Biofuels :Bioethanol Production from Cassava rhizome. MSc-thesis. The Petroleum and Petrochemical College (PPC), Chulalongkorn University, Bangkok, Thailand.