ENVIRONMENTAL POLICYANALYSIS
POLLUTION
PREVENTION
Matrix Approaches to Abridged Life Cycle Assessment T. E. G R A E D E L AT&T Bell Laboratories Murray Hill, NJ 07974 B. R. A L L E N B Y AT&T Technology and Environment Organization Princeton, NJ 08542 P. R. C Ο M RI Ε AT&T Technology and Environment Organization Whippany, NJ 07981
Experience demonstrates that the life cycle as sessment (LCA) for a complex manufactured product or an industrial manufacturing process works most effectively when it is done semiquantitatively and in modest depth. To facilitate such assessments, we have devised an abridged LCA matrix. We discuss the concepts leading to this matrix and give examples of check lists and evaluations to guide assessors in valuing the matrix elements. The matrix scor ing system provides a straightforward means of comparing options, and we recommend "target plots" as convenient and visually arresting ways of calling attention to those design and imple mentation aspects whose modification could most dramatically improve the assessment rat ing. We demonstrate these tools by performing assessments on familiar products: generic auto mobiles of the 1950s and 1990s.
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Of the three formal stages of life cycle assessment (LCA) (/), the first stage, inventory analysis, is rea sonably well conceptualized, and the second, im pact analysis, is in the early stages of conceptual ization. In the third stage, improvement analysis, the results of the first two life cycle stages are trans lated into specific actions that benefit the industryenvironment relationship (2). Despite their concep tual utility, it has proven difficult in practice for corporations to carry out detailed life cycle inven tories, more difficult to relate those inventories to a défendable impact analysis, and still more difficult to translate the results of those LCA stages into appropriate actions [3-6). Among the reasons for these problems are that comprehensive LCAs are expensive and time consuming, partly because the acquisition of quantitative information may require onsite analytical measurements or detailed reviews of sensitive files and records. In addition, many LCA methodologies in use are applicable to only a limited subset of commercial products, and even then the impact analyses are inevitably contentious, in part because they involve value judgments in comparing and balancing different impacts. Accordingly, numerical assignments of impact are often not accepted as adequate guidance. Dealing with these problems and at the same time producing improvement analyses that are useful to decision makers are difficult tasks at best. Experience seems to demonstrate that the LCA process works most effectively when it is done in modest depth and qualitatively by an industrial ecology expert. As a result, abridged assessment protocols are beginning to be developed (7, 8). The goal is to do the LCA rapidly—say, two days for a typical product or one week for a typical facility—while identifying the principal environmental effects across the life cycle of the option evaluated. We describe techniques that can accomplish this goal and produce improvement analyses that could be expeditiously implemented. The product assessment A suitable assessment system for environmentally responsible products (ERPs) should have the following characteristics: it should enable direct comparisons among rated products, be usable and consistent across different assessment teams, encompass all stages of product life cycles and all relevant environmental concerns, and be simple enough to permit relatively quick and inexpensive assessments. Clearly, it must explicitly treat the five life cycle stages in a typical complex manufactured product. Stage 1 is premanufacturing and is performed by suppliers, drawing on (generally) virgin resources and producing materials and components. Stage 2 is the 0013-936X/95/0929-134A$09.00/0 © 1995 American Chemical Society
manufacturing operation. Stage 3 FIGURE 1 is packaging and shipping and is directly under corporate control. Environmentally responsible product assessment matrix Stage 4 is the customer use stage Matrix elements are assigned a number ranging from 0 (highest impact on the and is not directly controlled by the environment) to 4 (lowest impact). The numbers in each box are the matrix element manufacturer but is influenced by indices. how products are designed and by the degree of continuing manu Environmental concern facturer interaction. Stage 5 is ter mination of a product's life, in Life cycle stage Materials Energy Solid Liquid Gaseous which a product is no longer sat residues residues residues choice use isfactory because of obsoles cence, component degradation, or Premanufacture (1,2) (1,3) (1,4) (1,5) (1,1) changed business or personal de Product manufacture (2,1) (2,2) (2,4) (2,5) (2,3) cisions; the product is refur bished or discarded. Product packaging The central feature of the assess (3,4) and transport (3,1) (3,2) (3,3) (3,5) ment system that we recommend is (4,5) Product use (4,1) (4,2) (4,3) (4,4) a 5 χ 5 assessment matrix, the En vironmentally Responsible Prod Refurbishment(5,5) uct Assessment Matrix, one dimen (5,4) recycling-disposal (5,2) (5,3) (5,1) sion of which is life cycle stage and the other is environmental con cern (Figure 1). In use, the Design for Environment (DFE) assessor studies the product de TABLE 1 sign, manufacture, packaging, in-use environment, and likely disposal scenario and assigns to each ele Automobile characteristics that affect the ment of the matrix an integer rating from 0 (high environment, for 1950s vs. 1990s generic autos est impact, a very negative evaluation) to 4 (lowest Environmentally responsible product assessments of generic autos impact, an exemplary evaluation). In essence, the as show that the 1950s vehicles were heavier, less fuel efficient, prone sessor is providing a figure of merit to represent the to dissipation of fluids and exhaust pollutants, and had less durable estimated result of the more formal LCA inventory components. analysis and impact analysis stages. She or he is guided in this task by experience, a design and man 1950s 1990s ufacturing survey, appropriate checklists, and other Automobile Characteristic Automobile information. (Although the assignment of integer rat ings seems quite subjective, we have performed ex Materials (kg) periments in which comparative assessments of prod 0 101 Plastics ucts are made by several different industrial and 0 68 Aluminum environmental engineers. When provided with check 22 Copper 25 lists and protocols as in Reference 9, Appendix G, Lead 23 15 overall product ratings differ by less than about 15% 25 10 Zinc among groups of four assessors.) The process de Iron 207 220 scribed here is purposely qualitative and utilitar 793 Steel 1290 ian, but does provide a numerical end point against Glass 54 38 which to measure improvement. Rubber 85 61 96 81 Fluids Once an evaluation has been made for each ma Other 38 83 trix element, the overall Environmentally Responsi 1434 Total weight 1901 ble Product Rating (RERP ), is computed as the sum 27 15 Fuel efficiency of the matrix element values: (miles per gallon) RERP = Σ, Σ, My (1) Yes Exhaust catalyst No Because there are 25 matrix elements, a maxi CFC-12a Air conditioning CFC-134a mum product rating is 100. The assignment of a discrete value from zero to Air conditioning entered the automobile market in the late 1950s on top-of-the-line vehicles. four for each matrix element implicitly assumes that the DFE implications of each element are equally ima
VOL. 29, NO. 3, 1995/ENVIRONMENTAL SCIENCE & TECHNOLOGY • 1 3 5 A
TABLE 2
Environmentally responsible product assessment ratings, by life cycle stage
element
Element
indices 9
value''
Premanufacture Materials choice
(1,1)
2
Energy use
(1,2)
2
Solid residue
(1,3)
3
Liquid residue
(1,4)
3
Gas residue
(1,5)
2
Product m a n u f a c t u r e Materials choice (2,1)
0
Energy use
(2,2)
1
Solid residue
(2,3)
2
Liquid residue
(2,4)
2
Gas residue
(2,5)
1
Element designation
1990s
1950s
Matrix
Packaging a n d transportation Materials choice (3,1) 3 Energy use
(3,2)
2
Solid residue
(3,3)
3
Liquid residue
(3,4)
4
Gas residue
(3,5)
2
Customer use Materials choice
(4,1)
1
Energy use
(4,2)
0
Solid residue
(4,3)
1
Liquid residue
(4,4)
1
Gas residue
(4,5)
0
Refurbishment-recycling-disposal Materials choice (5,1) 3
Energy use
(5,2)
2
Solid residue
(5,3)
2
Liquid residue
(5,4)
3
Gas residue
(5,5)
1
Element Explanation
Few toxics are used, but most materials are virgin Virgin material shipping is energy-intensive Iron and copper ore mining generates substantial solid waste Resource extraction generates moderate amounts of liquid waste Ore smelting generates significant amounts of gaseous waste
value*
3 3 3
3
3
CFCs used for metal parts cleaning Energy use during manufacture is high Lots of metal scrap and packaging scrap produced Substantial liquid residues from cleaning and painting Volatile hydrocarbons emitted from paint shop
3
Sparse, recyclable materials used during packaging and shipping Over-the-road truck shipping is energy-intensive Small amounts of packaging during shipment could be further minimized Negligible amounts of liquids are generated by packaging and shipping Substantial fluxes of greenhouse gases are produced during shipping
3
Petroleum is a resource in limited supply Fossil fuel energy use is very large Signficant residues of tires, defective or obsolete parts Fluid systems are very leaky
2 3 3 3
3 3
4
3
1 2 2 3
No exhaust gas scrubbing: high emissions
2
Most materials used are recyclable
3
Moderate energy use required to disassemble and recycle materials A number of components are difficult to recycle Liquid residues from recycling are minimal Recycling commonly involves open buring of residues
2
3
3 3 2
Shown in Figure 1. "Matrix elements are assigned an integer ranging from 0 (highest impact on the environment) to 4 (lowest impact).
1 3 6 A • VOL. 29, NO. 3, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
Explanation
Few toxics are used; much recycled material is used Virgin materials shipping is energy-intensive Metal mining generates solid waste Resource extraction generates moderate amounts of liquid waste Ore processing generates moderate amounts of gaseous waste Good materials choices, except for lead solder waste Energy use during manufacture is fairly high Some metal scrap and packaging scrap produced Some liquid residues from cleaning and painting Small amounts of volatile hydrocarbons emitted Sparse, recyclable materials used during packaging and shipping Long-distance land and sea shipping is energy-intensive Small amounts of packaging during shipment could be further minimized Negligible amounts of liquids are generated by packaging and shipping Moderate fluxes of greenhouse gases are produced during shipping Petroleum is a resource in limited supply Fossil fuel energy use is large Modest residues of tires, defective or obsolete parts Fluid systems are somewhat dissipative C0 2 , lead (in some locales)
Most materials recyclable, but sodium azide presents difficulty Moderate energy use required to disassemble and recycle materials Some components are difficult to recycle Liquid residues from recycling are minimal Recycling involves some open burning of residues
portant. The use of detailed environmental impact information to apply weighting factors to the matrix elements would slightly increase the complexity of the assessment, but perhaps increase its utility. For example, a certain product line might be thought to generate most of its impacts during manufacture and few during customer use, so the manufacturing row could be weighted more heavily than before and the customer use row weighted correspondingly lighter. Similarly, a judgment that global warming constituted more of a risk than did liquid residues might dictate an enhanced weighting of the energy use column and a corresponding decreased weighting of the liquid residue column. To the extent that an appropriate weighting scheme is obvious and noncontentious, its use will provide an improved perspective on the environmental burden of the product being evaluated.
Assessing generic automobiles
FIGURE 2
Environmentally responsible product assessments Comparative assessment matrices of environmental impacts of the generic automobile of the 1950s and 1990s. Environmental concern Life cycle stage
Materials choice
Energy use
Solid residues
Liquid residues
Gaseous residues
Total
Premanufacture 1950s
2
2
3
3
2
12/20
1990s
3
3
3
3
3
15/20
Product manufacture 1950s
0
1
2
2
1
6/20
1990s
3
2
3
3
3
14/20
Product packaging and transport 1950s
3
2
3
4
2
14/20
1990s
3
3
3
4
3
16/20
1950s
1
0
1
1
0
3/20
1990s
1
2
2
3
2
10/20
Product use
Refurbishment-recycling-disposal
Automobiles have both manufac1950s turing and in-use impacts on the 1990s environment, unlike many products such as furniture or roofing Total materials. The greatest impacts re1950s sult from the combustion of gasoline and the release of tailpipe 1990s emissions during the driving cycle. However, there are other aspects of the product that affect the environment, such as the dissipative use of oil and other lubricants, the discarding of tires and other spent parts, and the ultimate retirement of the vehicle. As a demonstration of the operation of the tools described above, we performed environmentally responsible product assessments on generic automobiles of the 1950s and 1990s. Some of the relevant characteristics of the vehicles are given in Table 1. Compared with the 1990s model, the 1950s vehicle was substantially heavier, less fuel efficient, prone to greater dissipation of working fluids and exhaust gas pollutants, and had components such as tires that were less durable. From a systems perspective, however, there were far fewer automobiles, and each was driven far fewer miles per year. Premanufacturing, the first life cycle stage, treats impacts on the environment as a consequence of the actions needed to extract materials from their natural reservoirs, transport them to processing facilities, purify or separate them by operations such as ore smelting and petroleum refining, and transport them to the manufacturing facility. Where components are sourced from outside suppliers, this life cycle stage also incorporates assessment of the im-
3
2
2
3
1
11/20
3
2
3
3
2
13/20
9/20
7/20
11/20
13/20
6/20
46/100
13/20
12/20
14/20
16/20
13/20
68/100
pacts of component manufacture. The ratings that we assign to this life cycle stage of generic vehicles from each period are given in Table 2 where the two numbers in parentheses refer to the matrix element indices shown in Figure 1. The higher (that is, more favorable) ratings for the 1990 vehicle are mainly the result of improvements in the environmental aspects of mining and smelting technologies, improved efficiency of the equipment and machinery used, and the increased use of recycled material. The second life cycle stage is product manufacture (Table 2). The basic automotive manufacturing process has changed little over the years, but much has been done to lessen its impact on the environment. Of potentially high impact is the paint shop, where various chemicals are used to clean parts and volatile organic emissions are generated. There is now greater emphasis on treatment and recovery of waste water from the paint shop, and the switch from low-solids to high-solids paint has greatly reduced the amount of material emitted. Materials are used better during fabrication (partially because of better analytical techniques for designing component parts), and reuse of scraps and trimmings from the fabrication processes is emphasized. Finally, the VOL. 29, NO. 3, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY • 1 3 7 A
FIGURE 3
Target plots of Design for Environment design attributes for generic automobiles
productivity of the entire manufacturing process has been improved; substantially less energy and time are required now to produce each automobile. The environmental concerns at the third life cycle stage, product packaging and transport (Table 2), include the manufacture of the packaging material, its transport to the manufacturing facility, residues generated during the packaging process, transportation of the finished and packaged product to the customer, and product installation where applicable. This aspect of the automobile's life cycle is benign relative to the vast majority of products sold today because automobiles are delivered with negligible packaging material. Nonetheless, some environmental burden is associated with the transport of a large, 1 3 8 A • VOL. 29, NO. 3, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
heavy product. The slightly higher rating for the 1990s automobile is the result mainly of the better design of auto carriers (more vehicles per load) and the increase in fuel efficiency of the transporters. The fourth life cycle stage, product use, includes impacts from consumables or maintenance materials, if any, that are expended during customer use (Table 2). Cars are significantly more efficient and reliable, but their use continues to have high impacts on the environment. Increased fuel efficiency and more effective conditioning of exhaust gases account for the 1990s automobile achieving higher ratings, but clearly there is room for improvement. The fifth life cycle stage assessment includes impacts during product refurbishment and those resulting from the discarding of modules or components deemed impossible or too costly to recycle (Table 2). Most modern automobiles are recycled (some 95% currently enter the recycling system), and from these approximately 75% by weight is recovered for used parts or returned to the secondary metals market (10). There is a viable used parts market, and most cars are stripped of reusable parts before they are discarded. Improvements in recovery technology have made it easier and more profitable to separate the automobile into its component materials. In contrast to the 1950s, at least two aspects of modern automobile design and construction are retrogressive from the standpoint of their environmental implications. One is the increased diversity of materials used, mainly the increased use of plastics. The second aspect is the increased use of welding in the manufacturing process. In the vehicles of the 1950s, a body-on-frame construction was used. This approach was later switched to a unibody construction technique in which the body panels are integrated with the chassis. Unibody construction requires about four times as much welding as does body-on-frame construction, plus substantially increased use of adhesives. The result is a vehicle that is stronger, safer, and uses less structural material, but is much harder to disassemble. The completed matrices for the generic 1950s and 1990s automobile are illustrated in Figure 2. Examine first the values for the 1950s vehicle at the various life cycle stages. The numbers in the "Total" column show moderate environmental stewardship during resource extraction, packaging and shipping, and refurbishment-recycling-disposal. The ratings during manufacturing are poor and during customer use are abysmal. The overall rating of 46 is far below what might be desired. In contrast, the overall rating for the 1990s vehicle is 68, much better than that of the earlier vehicle, but still with plenty of room for improvement. The matrices provide a useful overall assessment of a design, but a more succinct display of DFE design attributes is provided by the "target plots" shown in Figure 3. To construct the plots, the value of each element of the matrix is plotted at a specific angle. (For a 25-element matrix, the angle spacing is 36%5 = 14.4°.) A good product or process shows up as a series of dots bunched in the center, as would occur on a rifle target in which each shot was aimed accurately. The plot makes it easy to single out points
far removed from the bulls-eye and to mark their topics for special attention. Furthermore, the comparison of target plots for alternative designs of the same product permits quick comparisons of environmental responsibility. The product and process design teams can then select among design options and can consult the checklists and protocols for information on improving individual matrix element ratings.
Discussion A corporation designing its products with the DFE philosophy in mind should apply a similar approach to its processes and facilities. The product assessment system that we presented above can be readily adapted to these cases. For processes, considerations include the environmental impacts arising from construction and eventual disposal of the process equipment, the materials used during process operation, and the consequences of associated processes that assume and depend upon the existence of the process being assessed (9). For facilities, considerations include site selection and development, facility operations, refurbishment, transfer, and closure, as well as the products made and processes used therein (11). Unlike classical inventory analysis and perhaps impact analysis, overall LCA as presented here is less quantifiable and less thorough. It is also inestimably more practical and utilitarian; it is far better to conduct a number of abridged LCAs by these or similar techniques than to conduct one or two comprehensive LCAs. A survey of the modest depth that we advocate, performed by an objective professional, will identify perhaps 80% of the useful DFE actions that
could be taken in connection with corporate activities, and the amounts of time and money consumed will be small enough that the assessment has a good chance of being carried out and its recommendations implemented. References (1) Vigon, B. W. et al. Life-Cycle Assessment: Inventory Guidelines and Principles-, U.S. Environmental Protection Agency: Cincinnati, OH, 1992; EPA/600/R-92/036. (2) A Technical Framework for Life-Cycle Assessment, Society of Environmental Toxicology and Chemistry: Washington, DC, 1991. (3) Pittinger, C. A. et al. /. Am. Oil Chem. Soc. 1993, 70, 1-15. (4) Brinkley, A. et al. In Proceedings of the 2nd IEEE International Symposium on Electronics & Environment, Institute of Electrical and Electronics Engineers: Piscataway, NJ, 1994; Report 94CH3386-9, pp. 299-306. (5) Snowdon, K. G. In Proceedings of the 2nd IEEE International Symposium on Electronics & Environment, Institute of Electrical and Electronics Engineers: Piscataway, NJ, 1994; Report 94CH3386-9, pp. 293-98. (6) Horkeby, I. In Proceedings of the International Conference on Industrial Ecology, Richards, D. ]., Ed.; Washington, DC: National Academy Press, 1995. (7) Callahan, M. S. In Proceedings of the 2nd IEEE International Symposium on Electronics & Environment, Institute of Electrical and Electronics Engineers: Piscataway, NJ, 1994; Report 94CH3386-9, pp. 215-19. (8) Toile, D. et al. In Proceedings of the 2nd IEEE International Symposium on Electronics & Environment, Institute of Electrical and Electronics Engineers: Piscataway, NJ, 1994; Report 94CH3386-9, pp. 201-06. (9) Graedel, T. E.; Allenby, B. R. Industrial Ecology, PrenticeHall: Englewood Cliffs, NJ, 1995. (10) Field, F. R. et al. Automobile Recycling Policy: Findings and Recommendations; Prepared for the Automotive Industry Board of Governors: Massachusetts Institute of Technology: Cambridge, MA, February 1994. (11) Allenby, B. R.; Graedel, T. E. In Proceedings of the Third National Academy of Engineering Workshop on Industrial Ecology, Washington, DC: National Academy Press, 1995.
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