Mass Balance Technique
Material Cycles
Water Cycle
Carbon Cycle
Nitrogen Cycle
Sulfur Cycle
Oxygen Cycle
Industrial Use of Materials
Industrial Ecology
Industry as an Ecological System
Industry as an Economic System
Decision Making Techniques of Industrial Ecology
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Decision Making Techniques of Industrial Ecology

The basic premises of industrial ecology are resource conservation and pollution prevention, and achieving this on a system wide basis. Systems thinking means that we think of the product in terms of the materials extraction - refining - manufacturing - distribution - consumption - disposal scheme as we plan to produce it. We can then think of the different levels of the system at which industrial ecology could operate. Decision making techniques have been developed over the past decades that help to create a system wide industrial ecology in any community. There are four techniques that can be employed to create Industrial Ecology in any community.

I. Industry Level Exchange: An industry that has a large list of input materials, or industries among whom there is a scope for exchange of materials can build a network to exchange materials.

The automobile industry or a large producer of multiple products like 3M, IBM or General Electric can and do include their supplies in their plans on reusing and recycling materials. Large buyers of plastic like IBM, for example, get all their plastic from one supplier and buy such large quantities that they can set up a cycle of disassembling products and returning the plastic to the supplier. This type of "closing the loop" can also be of "economic" advantage to the firms or corporations.

Figure DM1. from a National academy of Engineering report illustrates a simplified process for automobile materials that show reuse and recycling of metallic and other parts. Automobile recycling has developed to be one of the most advanced systems, with only a fraction of the total materials going to landfills.

Figure DM1. Flowchart of materials in the automotive industry
Reprinted with the permission of Cambridge University Press

printable version

II. System of loosely coupled exchanges or a "community of exchange"

A firm may also look at its production system, and its input suppliers as well as other relevant organizations in its vicinity to see what kind of networks it can set up. A great example of this, cited often is the symbiotic relationship among a set of industries in Kalundborg, Denmark. A power plant, an oil refinery, a plasterboard manufacturing plant, a biotechnology plant, and a fish farm and ______________ all utilize material wastes from one another. Refined waste wastewater is used to cool the power plant. Excess gas from the refinery and sulfur obtained from the refinery are used to manufacture plaster board; biological sludge from the biotechnology plant is used by farmers; steam from the power plant is used by the biotechnology plant; waste heat from the power plant is used in fish farming and by the municipality for heating. One could conceivably design a community of process plants and other facilities to achieve similar symbiosis.


Figure DM2. Industrial Ecosystem.
Reprinted from Measures of Environmental Performance and Ecosystem Condition. Copyright 1999 by the National Academy of Sciences. Courtesy of the National Academy Press, Washington, D.C.


Reduce - Reuse - Recycle is a slogan that popularizes a waste management hierarchy of the "3R's" and is used widely for public awareness. This slogan was developed mainly for consumers as a way of thinking about their solid waste. But it could also be the cry for industry, especially in the U.S.

The U.S. uses more resources than any other country in the world. Though we represent 5% of the world's population, we use 24% of the world's energy and 20% of material resources such as copper, tin, and lead. (ZPG Fact Sheet) The United States "consumed" more minerals between 1940 and 1976 than did all humanity up to 1940.

The industrial ecology approach can be illustrated by a waste management system such as the sewage treatment system described above. Or, it can be applied to the larger scale design of a consumer product considering the pollution impacts across the entire life cycle of the product from raw materials to final disposal. This holistic "design for the environment" may not only minimize environmental impacts, but help improve the overall profitability of the product.

Figure DM3. Sewage Treatment System

Various public agencies have also attempted to set up material exchange programs. For example, in Sonoma County, California, the Public Education Conservation office in the county's Waste Management Agency facilitate exchanges through a quarterly newsletter as well as a website called SonoMax listing local materials AVAILABLE and WANTED for individuals and businesses.

III. Environmental Accounting

The ultimate "challenge for corporations is to fully integrate environmental thinking into corporate decision making - to, in other words, translate their environmental concerns into the language of business", writes Ditz, Rapanakia and Banks in their book, Green Ledgers (anobib)[link] . As stated earlier, we have long considered industry in solely economic terms and all business ledgers have been set up to reflect costs, expenditures, and profits. The different sectors of the economy; some environmental costs are reflected in a firm's accounts, for example, the costs to clean the wastewater or gaseous effluents before they are discharged to the environment, or the costs of solid waste disposal. These costs have become part of the accounting or "internalized" since the enactment of the various environmental laws especially since 1970.

Environmental costs in full, however, are more than what the firm remunerates. It is the cost of lost land and resources, loss of biodiversity, long term impacts of pollution, and health risks to the environment and people. Figure DM4 shows the representation in Ditz et al. of how the boundary of the private costs to industry are shifting. While some social costs of pollution have been internalized as cost of complying with regulation, other social costs, less easy to translate into monetary terms, remain outside the system boundary apparent to the corporation.

Figure DM4. The Shifting Boundary between Private and Social Costs
adapted from Green Ledgers: Case Studies in Corporate Environmental Accounting by the World Resources Institute. May 1995.

Several authors including Carnegie Mellon's economist Lester Lave have suggested ways to bring environmental costs into a corporation's ledger by applying the idea of "full-cost accounting". In the accounting profession, full-cost accounting is the practice where the complete costs of the firm are incorporated into the pricing of the products. These authors suggest that this idea could be used to add the now external environmental costs into the decision making of the corporation. This means that the price of the product should reflect the entire private and social costs throughout the life cycle of the product, from raw material extraction to product disposal.

What would happen if a firm did this? Their product would cost more. In the current way of thinking of the public, this might put the firm at a competitive disadvantage because only a few members of the public are willing to pay extra for a product whose manufacturer tries to compensate for the social and environmental costs due to the product's lifecycle. Full-cost accounting is, however, a method to explore as a way of including environmental costs in a company's ledger.

IV. Life Cycle Analysis

Life Cycle Analysis (LCA) is a technique used to assess the environmental impacts of a product over its entire life cycle. Figure DM5a depicts the stages in a product life cycle. Figure DM5b outlines a flow chart representing the same stages. As discussed in the section on industrial uses of materials, these life "cycles" have not really been cycles but linear changes.

Figure DM5a. Stages in a Product Life Cycle


Figure DM5b. General materials flow for "cradle-to-grave" analysis of a product system


LCAs are used to evaluate the environmental impacts of products at every stage from material extraction to disposal of the used product. In general, a LCA consists of three components.

  • 1) Life Cycle Inventory: An account of the inputs and outputs at each stage. This would quantify the energy and raw materials that go into each stage, including transportation and outputs of products as well as all environmental releases.
  • 2) Life Cycle Impact Analysis: This would characterize the environmental loading and assess what ecological and human health impacts each loading would cause.
  • 3) Life Cycle Improvement Analysis: This analysis would systematically assess how the environmental loading and impacts could be reduced, without losing the quality of the product.

The Society of Environmental Toxicology and Chemistry (SETAC) has provided an exhaustive description of the LCA methodology in their report, A Technical Framework for Life Cycle Assessment. Numerous authors including Robert Frosh and Deanna Richards, Robert Ayres, Robert Socolon, Brad Allenby and Tom Graedel have written extensively on the topic.

A LCA is hard to do because of all the data that are needed to do a complete job. The analysis can only be used for guidance rather than decision making because the available data might dominate the decision while the largest impacts might be from quantities for which the date are unavailable. All kinds of questions also arise such as where one starts the analysis, especially when comparing two alternatives. For example, when comparing glass bottles and plastic bottles, do we start the analysis with sand (raw material for glass) and oil platforms (as oil is the raw material for plastic), or assume that the glass and plastic are being manufactured anyway and to start with the glass and plastic as the "raw material"? Despite these problems, LCA provides a good framework for discussion of alternatives, and for detailed analysis when data are available.

The sections below elaborate the details of a LCA.

1. Life Cycle Inventory: Figure DM6 from the SETAC report shows the scheme of inputs and outputs for a LCA. The stages of LCA inventory are:

  • Definition of system and system boundaries
  • List of raw materials, their sources, energy involved in extraction, wastes and effluents produced
  • Steps of processing the raw materials, stages involving combination of raw materials and manufacturing process
  • Possibilities for recycling materials during processing and manufacture
  • Accounting of energy and effluents from each of these steps
  • Distribution and Transportation needed for the product to reach the consumer
  • Energy used and material waste and effluents produced during use and maintenance
  • Possibilities of reuse of whole product or parts
  • Possibilities of recycling of materials and the energy expenditure and effluent production in the recycling process.
Figure DM6. Life Cycle Stages
Reprinted with permission from The Ecology of Industry: Sectors and Linages.
Copyright 1998 by the National Academy of Sciences.
Courtesty of the National Academy Press, Washington, D.C.


The two brief examples below point our some of the difficulties in doing the LCA to compare the environmental performance of two products. The first demonstration of the life cycle approach for a consumer product is the comparison of a paper cup and a Styrofoam cup described by Martin Hocking in his 1991 paper.(reference/bib) The use of Styrofoam for fast foods and hot beverages became a debate issue in the mid to late 1980s. The issue was that many people felt that Styrofoam would not degrade as easily as paper, and therefore was more of an environmental problem. Here, the primary focus was on the disposal stage of that particular consumer product. Hocking performed a life cycle analysis on the hot beverage cup and showed that the environmental issue is more complicated than just the disposal stage as follows:

  • Styrofoam relies on a non renewable resource (petroleum) for raw materials, paper use a renewable resource if the trees are from a sustainable tree farm
  • Similar high energy use for both products in the processing stage
  • Similar high water use for both in the processing stage
  • Paper was slightly heavier than styrofoam in terms of packaging and subsequent transportation
  • No differences in terms of use
  • In terms of disposal, paper has more mass than Styrofoam. Though paper is biodegradable, that biodegradability decreases significantly because of conditions in a landfill and because the paper has to be coated with wax for this use. In terms of incineration, Styrofoam has a greater energy potential.
  • Final analysis is that it is hard to determine which is the better environmental choice since it is dependent of programs that are in place for the raw materials, use, and disposal.

Another classic example is related to the energy source for automobiles i.e., electric versus gasoline engines. The 1990 amendments to the Clean Air Act required that several regions (such as Southern California, etc.) that were not meeting the tropospheric ozone standard, needed programs in place to ensure 2% of cars in 1998 were zero emission. The requirements increase over time. The trend has been towards the development of cars that are powered by electric batteries. These cars do not emit any emissions from the tailpipe and are declared zero emission vehicles.

  • However, the "xero emission" is only because the focus of the regulatory strategy was on the use stage of the life cycle. The issue becomes more complicated when the entire life cycle is evaluated as several researchers have done. A simplified analysis is as follows:
  • Raw materials for electric cars depend on the electricity source but is primarily coal. The electric cars also need a substantial battery that is currently made out of lead. Gasoline vehicles rely on petroleum. All of these raw materials are non renewable, though they may have different lifetimes. Lead emissions from lead processing plants cause air pollution with severe toxic effects (reference Hendrickson, Lave, and McMillian.
  • Both power sources for the vehicles include high energy needs and water/air emissions during the refining of the raw materials, and the processing of the final product.
  • Packaging systems differ drastically from transmission lines and batteries to tanker trucks, pipelines, and underground storage tanks. All have their associated environmental negatives.
  • In terms of use, the electric car has zero emissions compared to the significant tailpipe emissions from current gasoline vehicles that are highly inefficient. However, there are emissions at the centralized electricity power plant that provides the electric vehicle with energy.
  • In terms of disposal, there is the issue of battery disposal versus oil disposal.
  • The better environmental product depends on several management choices concerning the energy source for the electricity, the battery material used, the location of the motor vehicles versus the centralized power plants, and so on. The issue is complicated.

2. Life Cycle Impacts

Following an inventory we could, in theory, assess what impacts the product will have in it's life cycle. Again this poses a number of problems as discussed in the two examples above.

In assessing impacts, we need to list and prioritize the impacts of concern - is it land loss, water pollution, global climate change, deforestation, human or ecological health hazards or all of these that make our list of concerns?

For each type of emission or loading to the environment from the inventory analysis one could think of mapping the type of effects and the extent of the problem. A brief sketch of this is shown in Figure DM5. Note that this is just a representation to provide one way of depicting inventory and impact for a LCA.


Figure DM7. Example representing Inventory and Impact variable


A serious problem in calculating impacts is that the quantity of a material does not fully represent the human health or ecological impacts. Small amounts of dioxin are much more lethal than tons of a relatively benign substance like calcium oxide. The Green Design Initiative at Carnegie Mellon has addressed this by a clever scheme called the "CMU-ET" method.

{missing part 3 - 3) Life Cycle Improvement Analysis:


Green Design: Doing a LCA and it's use in Decision Making

Green Design maybe be defined as "Design that attempts to minimize environmental burdens without compromising functionality". The principle underlying green design is to assess life cycle impacts of the product during the design phase and add the minimization of environmental burdens as a design criteria to the usual design criteria such as performance, economy, reliability and safety. Aspects of green design include selecting materials that are more environmentally friendly (easy to recycle, little to no toxic byproducts), design for disassembly to facilitate reuse and recycling and designing for energy efficiency.

Several modeling systems including the EPS or Environmental Priority Strategies System for products design initiated by the research institute of the Volvo Car Company in Sweden in 1990 have sought to construct databases to enable LCA calculations. There are numerous problems with getting exact numbers because of reasons such as incomplete accounting, material losses and proprietary nature of data. The Handbook of Industrial Energy Analysis by Ian Bokstead and G. F. Hancock of the Open University in England (John Wiley, 1979) and their database is probably the most extensive source. Many industries keep their own databases, and are sometimes willing to share information.

Looking at a life cycle, one can think of generic strategies to adopt during design. In a World Resources Institute publication Ditz and Ranganathan (1997) developed four categories of measures that can be used to characterized a product:

(1) Materials Use: quantities and types
(2) Energy Consumption: quantities and types used or generated
(3) Nonproduct output
(4) Pollutant releases

Calculating these per unit of product is at the basis of every LCA. Design for the environment or Green Design then uses this data to evaluate and improve designs by several possible strategies:

(1) Materials reduction or substitution and recycling
(2) Energy reduction or substitution
(3) Pollutant reduction and change in their nature

Examples of this could be substitution of materials by those that would do the job with less toxic emissions in the production and use phases and designs that would use less energy in the use phase. Figure DM8 from the Richards and Frosch article cited before shows how the environmental considerations of lifecycle stages can lead to Green Design.

insert DM8. Environmental considerations of lifecycle stages

The student exercise on LCA [link] is an example of how despite the uncertainties a LCA could be used to compare alternative consumer products for making the "environmentally friendly decision on what products to buy. The exercise also points up the difficulties in such analysis.

The Environmentally Responsible Product Assessment Matrick (Figure DM9) has been suggested by Laudise and Gaedel as a formulation for doing an evaluation. Each square of the Figure DM9 would have a checklist from which an impact analysis as in Figure DM7 could be done.

Figure DM9. Environmentally Responsible Product Assessment Matrick
Reprinted with permission from The Ecology of Industry: Sectors and Linages.
Copyright 1998 by the National Academy of Sciences.
Courtesty of the National Academy Press, Washington, D.C.

Design for the environment (DFE) or Green Design as formulated by the electronics industry considered the following aspects in the design of electonic products such as computers:

  • design for disassembly or separability: how easy (and economical) are the components to separate for reuse or recovery of materials?
  • design for recyclability: Is there potential for maximum recycling of component after use of the product?
  • design for reusability: can components be reused in different product lines after recovering and refurbishing them? (Kovlak's reusable camera is an example of where this is practiced by the manufacturer)
  • design for remanufacture: can materials be recovered and recycled after use? this might include - setting up a system for consumers to send back used items.
  • design for disposability: can all materials and component be disposed of safely?

Other aspects of DFC are discussed by Hutchinson, et al. at Green Design

Finally, we provide two examples to illustrate some of the ideas discussed above. Table DM1 is an inventory of the major raw materials, products, and product uses of the chemical industry as a whole. The graphs in Figure DM10 provide an example of the environmental profile of a computer workstation. These are both examples from the National Academy of Engineering Report, "Industrial Environmental Performance Metrics (NAE Press, 1999).

Raw Materials




Natural Gas




Caustic soda



Synthetic rubber


Product End Users
Food ingredients
Fuel additives
Household materials
Safety glass
Construction materials
Paint and coatings
Soaps and detergents
Sports equipment
Personal Care



Table DM1. Major Raw Materials, Products and Product End Uses of the Chemical Industry
Reprinted with permission from Industrial Environmental Performance Metrics
Copyright 1998 by the National Academy of Sciences.
Courtesty of the National Academy Press, Washington, D.C.


Environmental Profile of a Computer Workstation

Results of a life cycle study of the computer workstation are summarized in the graphs above. The computer workstations studies was assumed to contain one 1/6 inch thick silicon wafer (about 28 square inches), 220 integrated circuits (213 in plastic and 7 in ceramic packages), about 500 square inches (3.6 square feet) of single and multilayer printed wiring board, and a 20 inch monitor. The subcomponents included in the study were semiconductor devices (SD), semiconductor packaging (SP), printed wiring boards and computer assemblies (PWB/CA), and display units (Dis). The profiles of energy, material, and water use and waste reveal some aspects of the environmental impacts of an electronics product.

Figure DM10. environmental profile of a computer workstation



Figure DM9 from Frosch and Richards provides an overview of the progress being made by industry in environmental design and management. As discussed in the Unit on the Ethical System, the sustainability ethic is a goal towards which this figure optimistically points.

As consumers, we have a responsibility to choose products that ensure a better environment and this implies an understanding of the complex system of natural and artificial materials that provide our needs, wants, and comforts.


Figure DM11. Industry's environmental design and management learning curve
Reprinted with permission from Industrial Environmental Performance Metrics
Copyright 1998 by the National Academy of Sciences.
Courtesty of the National Academy Press, Washington, D.C.



  ©Copyright 2003 Carnegie Mellon University
This material is based upon work supported by the National Science Foundation under Grant Number 9653194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.