Proceedings of International Symposium on EcoTopia Science 2007, ISETS07 (2007)

Transcription

1 Evaluation of Site Remediation Technologies by Applying Risk Assessment and Life Cycle Assessment: Modification of Comprehensive Index, the Rescue Number for Soil (RN SOIL ) Yasushi Inoue 1 and Arata Katayama 1 1. EcoTopia Science Institute, Nagoya University, Nagoya, Japan Abstract: On the decision-making among stakeholders for a site remediation, it is difficult to select a technology applied due to the conflict of their interests, such as health damage, economic or environmental impacts. An index indicating comprehensive performance of technologies will help them determine their selection. We had developed and proposed a comprehensive evaluation index for remediation technologies, the rescue number for soil (RN SOIL ). The RN SOIL had been composed of two evaluating terms, a residual human health risk and total cost for the implementation of remediation. Applying to virtual scenarios of site remediation, the RN SOIL had been found available for a performance ranking among the alternative remediation technologies. However, environmental impacts occurring from the implementation of remediation had not yet been considered. Moreover, it had been difficult to evaluate the effect of technological improvements for upgrading. In this study, to overcome these problems, the RN SOIL was modified by introducing the life cycle assessment (LCA) to estimate an amount of CO 2 emission as an indicator of environmental risk during the remediation. Process schemes of remediation technologies were established to carry out an inventory analysis in LCA. Integration of an inventory of each process made an evaluation of technological improvements using the RN SOIL possible. In typical scenarios of the remediation technologies for the site contaminated with Persistent Organic Pollutants (POPs), including the Excavation-disposal, High Temperature Thermal Desorption (HTTD), and improved technologies. A residual human health risk as a risk index and an amount of CO 2 emission as an environmental risk index were estimated, and then the RN SOIL was calculated. The successful estimation of these risk indices demonstrated the usefulness of the RN SOIL not only in the ranking of remediation technologies but also in the evaluation of effectiveness of technological improvement. According to the comparison between the Excavation-disposal and normal scenario, had much less competitiveness than the Excavation-disposal. Furthermore, improved scenario was evaluated, and then an effectiveness of technological improvement was reflected on the indices adequately. Keywords: comprehensive evaluation index, remediation technology, risk, LCA, CO 2 emission 1. INTRODUCTION To facilitate selecting a remediation technology of contaminated site in the risk communication, a comprehensive evaluating method will be needed to indicate a ranking among candidate technologies by considering various factors such as a risk reduction, cost necessary or environmental impact. We have proposed a comprehensive evaluation index for remediation technologies, the rescue number for soil (RN SOIL ) [1], applying the rescue number that had been developed to evaluate a treatment technology of the Waste Difficult to Treat [2]. It was composed of two evaluating index, a cost index and a risk index, reflecting the properties of a cost and risk reduction of remediation technology to the specific site. Applying this index to many applicable alternatives, a comparative evaluation of technologies is possible by a comprehensive manner. Reflecting the difference in the period necessary correctly, a time dependent human health risk and total cost from a performance data were used as a risk index and cost index, respectively. In a typical scenario of remediation in an urban contaminated site, a possibility of technological evaluation was indicated by a comparison of the RN SOIL value not using a cost or risk solely. In general, a site remediation needs large quantity of energy to remove or degrade a contaminant. It just substitutes a human health risk caused by the contaminant with an environmental risk such as a global warming due to CO 2 emission. In the technology evaluation, however, it is not considered an environmental burden caused by the implementation of remediation. However, a cost index was estimated from the database of average performance, such as a cost per unit volume soil or area, released by the US governmental organization, for example, the Federal Remediation Technologies Roundtable (FRTR) [3] or the technical information from US Navy [4]. It means that a detail evaluation was quite difficult, because a technical improvement can not be reflected in the cost index. In this study, to consider the risk by an environmental burden due to the implementation of remediation, Life Cycle Assessment (LCA) was introduced to estimate an amount of CO 2 emission as an index of environmental burden. There were few examples of application of LCA to the remediation processes. Meanwhile, for public works projects, LCA was carried out as a part of environmental impact assessment. Therefore, to modify the RN SOIL index which enables a detailed evaluation not only for a current assessment but also for a technology devel- Corresponding author: Y. Inoue, inoue@esi.nagoya-u.ac.jp 1371

2 opment or improvement evaluation, the life cycle approach was adopted to the remediation technologies. Simultaneously, the cost index was replaced into the environmental risk index expressing by the amount of CO 2 emission for indicating the magnitude of environmental risk caused by the implementation of remediation technologies. As an example in the typical scenario, the remediation technologies of contaminated farmland were analyzed by LCA to divide a whole process into several sub-processes. Life Cycle Costing (LCC) and Life Cycle Inventory Analysis of CO 2 emission were both carried out, and the indices were estimated. Then, adequacy of the RN SOIL for a technological evaluation based on the risk assessment and LCA was examined. 2. THEORETICAL CONSIDERATION The risk index, FTP (Figure of Treatment Priority) [1], was defined as the number of persons who were exposed to the contaminants over Acceptable Daily Intake (ADI), considering daily health hazards caused by the contaminant [2]. The number of persons who were exposed to the contaminants was obtained by the product of the probability that the daily exposure exceeds the ADI and the population in the target domain. To represent the difference in a time required for remediation, the integral FTP with time (FTP(t)) indicating a residual risk was estimated from the temporal change of a risk index due to the progress of remediation. The cost index, FUW (Figure of Unprocessibility for Waste) [1], was defined as total cost of remediation [2]. A comprehensive evaluation index for a remediation technology, the RN SOIL was defined as the product of integral FTP(t) and FUW, and expressed in eq. (1). RN SOIL t L = FTP() t dt FUW (1) 0 t L is the period covered. Smaller values of a RN SOIL are judged to indicate a better technology. A RN SOIL represents an immaturity of remediation technologies and its value is just an index for comparative evaluation. In this study, an environmental risk index was introduced instead of a cost index. An environmental risk index was defined as an amount of CO 2 emission estimated from LCA of remediation. A whole remediation process was divided into sub processes. The cost of each sub process i (i =1,2,...n: n means number of sub processes) was estimated from the species and quantity of materials, equipments, machineries, fuel, electricity, water and labors, and their unit cost. Furthermore, integrating the costs for all sub processes, ct i, total cost of remediation, CT was estimated. FUW Cost was defined as shown in the eq. (2). FUW FUW = CT = Cost ct i i= 1 CO2 = EM CO2 n = n i= 1 em CO2i Applying the unit CO 2 emission of products or business, total CO 2 emission from a remediation activity can be calculated. As same as the eq. (2), FUW CO2 was defined as (2) (3) represented in the eq. (3). Integrating the CO 2 emission for all sub processes, em CO2, total CO 2 emission of remediation, EM CO2 was estimated. Applying the redefined FUW cost and FUW CO2, the RN SOIL,Cost and RN SOIL,CO2 were defined as shown in the eq. (4). RN SOIL X t L () dt FUWX, = FTP t (4) 0 The subscript X means a cost or CO 2. Table 1. Contaminated site 3. METHOD 3.1. Contaminated site and remediation technologies For examining an adequacy of the RN SOIL based on a risk assessment and LCA, typical scenarios of remediation for farmland contaminated with dieldrin was modeled. Dieldrin was used widely as a pesticide, but it was forbidden to produce and use in the 1970s because of their high toxicity and persistency in the environment. They were buried to abandon until an efficient treatment technology is developed. We have a requirement to treat dieldrin itself or dieldrin contaminated soil under the Stockholm Convention on Persistent Organic Pollutants took effect in As illustrated in Table 1, the contaminated farmland was located near an urban region with an area of 1,000m 2.The surface soil depth and concentration were 1m and 1mg/kg-soil, respectively. Three candidate technologies, Excavation-disposal, High Temperature Thermal Desorption (HTTD) and were selected. was focused on as a promising technology. A type of was assumed an on-site remediation and a stimulation of microorganisms by the aeration. To test the response of technological improvement on the indices, the time required of was as- Contaminant Dieldrin (ADI: mg/kg) Population density 4,179.6 persons/km 2 * Initial concentration 1mg/kg-soil Contaminated area 1,000m 2 Duration 30 years (after contaminated) *Calculated based on the data from the Ministry of Agriculture, Forestry and Fisheries in Japan[6] sumed 36 months for the normal remediation and 24 months for the improved remediation. A standard half-life of dieldrin in soil was 180 days. In the improved scenario, the half-life of dieldrin in a soil was set in 120 days, estimating from the degradation rate of dieldrin degradable white-rot fungus [5] Risk assessment and life cycle inventory analysis The risk index, FTP was calculated using the multimedia model, CalTOX (DTSC, California EPA, USA), combined with the Crystal Ball (Kozo Keikaku Engineering, Tokyo, Japan) for the Monte Carlo simulation. An inventory analysis was conducted from the initial process to the end process of remediation. The quantity and unit cost of materials, machineries, labor, fuel and energy used in every process were listed and estimated from the data from the US Navy and the Ministry of Land, 1372

3 Infrastructure and Transport, Japan. Unit CO 2 emission was collected from the data based on the inter-industry input-output table [7]. Estimation of total cost and total CO 2 emission were carried out by the life cycle inventory analysis for determining the FUW X index. In the scenario which reaches the target level concentration (0.001 mg/kg-soil), whole process was divided into several sub processes and materials, equipments, fuels and labor needed in each process were listed. The quantity and unit cost were obtained from the technical documents or information [8], [9], [10]. The items used, its quantity and unit cost in the sub processes of remediation technologies, were collected. Sub process cost was estimated by building-up all cost of items, and then total cost was estimated by integrating the cost of all sub processes. The unit cost of materials, fuels, water and labor used in this site were decided by the actual price [11]. The thermal desorption process in the HTTD was referred from the technical document released by the US Navy [12]. For the, the cost estimating program released by the US Navy [13] was used. For non-disposable and repeatedly-used equipments such as trucks or pump, the cost of usage was estimated by the depreciation cost through the remediation period, using the list of depreciation cost calculation for construction machinery [14]. The fuel consumption rate of heavy machineries was decided by the estimation standard [8], [10]. The numbers of worker needed also decided by the estimation standard. The cost for labor was estimated by the standard unit cost for labor service published by the Ministry of Land, Infrastructure and Transport [15]. CO 2 emission also estimated using unit CO 2 emission based on the inter-industry input-output table released by the National Institute for Environmental Studies [7]. In this study, (I-A) -1 type of embodied environmental intensity in 1995 was applied and most likely sector was selected for each items used for descriptive purposes. Representative unit emission used was listed in Table 2. For diesel oil and electricity, unit emission was obtained from the Japanese Society of Civil Engineering. For machineries, the CO 2 emission was calculated by multiplying the unit emission to the depreciation [16]. The emission from labor was estimated by applying the method proposed by Kusuda [17]. From yearly CO 2 emission from a domestic Amount of CO 2 emission (t-co 2) source [18], Japanese population [19] and daily working time, hourly CO 2 emission per person was calculated. 4. RESULTS 4.1. Cost index Fig. 1 shows total cost of three candidate technologies and the improved biopile scenario. Here, a cost was divided into four sectors, such as an energy consumption, machinery utilization, material consumption and labor. The cost of was less than the Excavation-disposal and HTTD. In the Excavation-disposal and HTTD, the cost of machinery utilization had high ratio. For a while, the cost of labor had higher ratio and cost of machineries utilization had lower ratio in the (36 months) scenario than the other technologies. These properties reflect on the difference in a physico-chemical technology and biological technology. Physico-chemical technologies have high energy consumed process, such as large ma- Table 2. Unit CO 2 emission rate of equipments and materials unit emission Item Unit emission of CO 2 Category [7] Temporary materials, iron pile sheet, pipes 6.55 Metal products for construction Backhoe, bulldozers Machinery and equipments for construction and mining Dump truck Trucks, buses and other cars Plastic sheets and pipes Plastic products Equipment for turbid water treatment Pumps and compressors Generator Engines Chemical analysis Research and development (intra-enterprise) Labor Diesel oil Electricity Unit: Mg-CO 2 /million yen, Labor unit: t-co 2 /man/day, diesel oil: kg-c/l, electricity: kg-c/kwh Remediation technology Remediation technology (24months) (36months) HTTD Disposal Cost (Million Yen) Fig.1. Total cost of the remediation technologies (24months) (36months) HTTD Disposal Fig.2. Amount of CO 2 of the remediation technologies 1373

4 chineries utilization or heating furnace to finish the remediation within a short period. On the other hand, the have no process which needs high energy consumption. However, it needs a longer period than a physico-chemical technology and needs a scheduled monitoring and sample analysis. This resulted in high labor cost. In the improved scenario of, the remediation period became 2/3 of that of normal scenario. Due to the reduction of the time necessary and work force for the site management, monitoring, cost reduction in 30% of the energy consumption, 23% of the machineries utilization and 23% of the labor force enabled. Total cost was reduced by 19% of the normal scenario. These results meant that the effect of improvement on the remediation was reflected on the cost index Environmental risk index Fig. 2 shows the amount of CO 2 emission of the remediation. The normal scenario of became 25% and 18% compared to the Excavation-disposal and HTTD, respectively. The difference in the CO 2 emission became bigger than the difference in the cost. High CO 2 emitted sector was the machineries utilization in the Excavation-disposal, the energy consumption and machineries utilization in the HTTD, and the energy consumption in the, respectively. The HTTD had two times more CO 2 emission caused by the energy consumption than the normal scenario of. This caused that the diesel oil had a larger unit CO 2 emission. The CO 2 emission from the labor force did not have so higher ratio. This trend caused by the smaller unit CO 2 emission. The energy, especially diesel oil had very large unit CO 2 emission. Therefore, the improvement to reduce the energy consumption would result in obtaining a great effect on reduction of CO 2 emission. In the improved scenario of, according to the shorter remediation period, the energy consumption, machineries utilization, labor and total CO 2 emission decreased by 30%, 10%, 13% and 17%, respectively. This caused the reduction of energy consumption for operating the aeration pump. As same as the cost index, these results meant that the effect of improvement on the remediation was reflected on the environmental risk index. Reflecting the properties of remediation technology, the had less cost and CO 2 emission than the HTTD and Excavation-disposal. The HTTD mainly consisted of processes consuming large quantity of energy, but the did not need so much energy. Larger machineries utilization made a technology more costly and larger energy consumption made it more CO 2 emitting. The improvement on time required was successfully reflected on the decrease of total cost and CO 2 emission Comprehensive evaluation index For 4 remediation technologies including the improved scenario of, the cost index, FUW Cost, the environmental risk index, FUW CO2 and the risk index, integrated FTP(t) were calculated. These indices were useful when shown as a relative value comparing to the value of the Excavation-disposal. Scenarios have an advantage comparing to Excavation-Disposal scenario when the value is less than 1. Meanwhile, it has a disadvantage when the value is more than 1. In contrast to the cost and environmental risk index, FTP(t) (integral of risk index with time) of was evaluated very low. On the cost and environmental risk index, there were advantages in the normal scenario (0.70, 0.25 times, respectively) and the improved scenario (0.56, 0.21 times, respectively) to the Excavation-disposal scenario. The improved scenario obtained more advantage than the normal scenario. On the other hand, the risk index of evaluated very low and became 37 times more in the normal scenario, 21 times more in the improved scenario to the Excavation-disposal scenario. A trade-off relationship between the risk index and cost or environmental risk index was indicated obviously. Then, the RN SOIL of became larger and had no advantage comparing with the others. The improvement of efficiency on the was successfully reflected on the RN SOIL of smaller value than that of the normal. However, despite of the improvement on the, there could be no competitiveness among candidates because of larger RN SOIL value comparing with the other remediation technologies. Using the eq. (4), the RN SOIL,cost and RN SOIL,CO2 also were calculated. On a comprehensive index, there were disadvantages in the HTTD scenario (1.7 times more (cost), 1.4 times more (CO 2 )) to the Excavation-disposal scenario. There were large disadvantage in the normal scenario (26 times more (cost), 9.0 times more (CO 2 )) to the Excavation-disposal scenario. This meant that an advantage on the cost or environmental risk index was lost because of a disadvantage on the risk index. In the improved scenario, there were a disadvantage of 12 times more (cost) and 4.2 times more (CO 2 ) to the Excavation-disposal scenario. Significant improvement on the comprehensive indices was found, however, it can not reach to be competitive to the Excavation-disposal. Comparing to the HTTD, the improved scenario had 6.8 times more (cost), 3.0 times more (CO 2 ) in the comprehensive indices. Judging from these results, to obtain enough technological competitiveness to physico-chemical technologies, the technology should improve more to raise a performance level. Applying the LCA approach to evaluation of the remediation technologies by dividing whole remediation process into sub processes and integrating all sub cost and CO 2 emission, a cost and environmental risk index were evaluated in detail. Then, the modification of the RN SOIL was successfully carried out to introduce the redefined FUW index. Furthermore, reflecting a technological improvement on a cost or environmental risk index, a technology under development can be evaluated whether it has competitiveness to other remediation technologies. In other words, applying the LCA, a relationship between the RN SOIL and sub process efficiency of remediation technologies in the development stage can be estimated. 5. CONSLUSIONS A comprehensive evaluation index, the RN SOIL was successfully modified by applying a risk assessment and LCA. Taking the as an example, the effect of improvement was reflected on the environmental risk and the comprehensive evaluation index, the RN SOIL. Introducing LCA for estimating an environmental risk index, the effect of improvement is evaluated precisely in a comprehensive manner. It would be helped to develop a competitive technology, and select an appropriate tech- 1374

5 nology. ACKNOWLEDGMENT Authors would like to thank Mrs. Chisa Hiyama for her help to collect and organize data. This work was supported in part by a Grant-in-aid (Hazardous Chemicals) from the Ministry of Agriculture, Forestry and Fisheries of Japan (HC ). REFERENCES 1. C. Yamauchi, H. Ito, T. Fujisawa, H. Matsuda, A. Katayama, T. Tsunekawa, T. Saito, T. Kitsuka, T. Tanaka and K. Ishihara: Waste Manag Res, 12, (2001), p Y. Inoue and A. Katayama: J. of Mater Cycles Waste Manag, 6, (2004), p Federal Remediation Technologies Roundtable: Remediation Technologies Screening Matrix and Reference Guide, Version 4.0, 4. Naval Facilities Engineering Service Center, US Navy: Technologies information database, (2004) 5. Kennedy, Aust and Bumpus: Applied and Environmental Microbiology, Vol.56, 8, (1990), pp Ministry of Agriculture, Forestry and Fisheries in Japan: World agricultural census 2000, Vol.9, Report on rural communities, (2000) 7. National Institute for Environmental Studies, Center for Global Environmental Research: Embodied Energy and Emission Intensity Data for Japan Using Input-Output Tables, (2002), 8. Ministry of Land, Infrastructure and Transport: civil engineering work estimation standard year 2004, (2004), Construction Research Institute, 9. Construction Research Institute: 2004 standard estimation on civil engineering work, (2004), Construction Research Institute, 10. Construction Research Institute: Manuals for estimation standard of civil engineering works in 2004, Construction Research Institute, (2004) 11. Construction Research Institute: Construction price , Construction Research Institute, (2005), (in Japanese). 12. Naval Facilities Engineering Service Center, US Navy: Application Guide for Thermal Desorption Systems, Technical Report TR-2090-ENV, (1998) 13. Naval Facilities Engineering Service Center, US Navy: Cost Estimating Program Version 3, hnologies/remed/bio/bpce%20.xls, (2000) 14. Japan Construction Mechanization Association: List of depreciation of machineries for construction in 2005, Japan Construction Mechanization Association, (2005) 15. Ministry of Land, Infrastructure and Transport: Standard labor cost of public work in 2005, (2005), html, 16. Japanese Society of Civil Engineering, Committee of Global Environment: Report on investigation and research in 1995 Committee on investigating of LCA on civil engineering, (1995) 17. T. Kusuda: LCA on public water supply system, ed. H. Imura, LCA on construction, II-7, Ohmsha, (2001), pp Ministry of the Environment, Global Environment Bureau: Preliminary figures of Global warming gas emission in 2004, Press release, (2005) 19. Ministry of Internal Affairs and Communications, Statistics Bureau: Statistical data/ demographic shifts, (2004),