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MATERIALS SYSTEM Introduction The conditions on Earth over the last four and half billion years, the energy flow from the sun, and the relative abundance of different elements form the basis of all phenomena on Earth, including life. Transformations of materials aided by energy from the sun and the Earth's core are at the basis of many environmental phenomena. In this unit, we examine some of the most basic systems of materials: elements and compounds. Most materials in nature, especially those in the biosphere (the part of the Earth which holds life) undergo chemical and physical changes constantly. Some materials, such as carbon and water, contribute to the cycle through various physical and chemical stages. Many of the environmental problems surrounding material use are actually disruptions of the cycles, which arise from taking or putting too much or too little material too fast or too slow into or from one or more of the phases in the material cycles. Solar energy in the form of electromagnetic radiation streams in through the atmosphere onto the surface of the Earth providing energy at the rate of about 1 kilowatt per square meter at places of peak intensity. In one hour, we receive more solar energy spread over the land area of the United States than we get from the fossil fuels we burn in one year! Except for this vast and continuous input of energy, most of the material on the Earth remains at a constant amount, changing forms in some cases, going through cycles that keep many of these in forms that are accessible to life. So, as far as most materials are concerned, the Earth is a "closed system". However, solar energy is the vital part – the input into this closed system – that maintains the material system suitable for life. Most of the matter on Earth generally remains on Earth, due to a continuous recycling of materials. Figure 1 shows the natural, large-scale processes that recycle materials.

Figure 1: Natural Recycling of Materials on Earth.

Through processes of transport and transformation in the atmosphere, absorption and settling in the oceans, and subduction and volcanism in the lithosphere, materials are recycled in nature through both physical and chemical changes. Residual heat in the core of the Earth and heat from radioactive processes provide energy from within the Earth. Solar energy drives the water cycle and the atmospheric currents, aided by the gases in the atmosphere. Water, carbon dioxide, nitrogen, chlorine, and sulfur are the main materials that cycle through atmosphere, oceans, and sediments. In this unit, we examine several material cycles including cycles of water, carbon, and nitrogen. As materials cycle through, we note that the total quantity of matter (mass) remains the same; energy that is put in changes to work, often to rearrange forms of matter; and is eventually lost to the surroundings. Human intervention has disrupted natural environmental processes. Later on in this unit, we look at some of these disruptions and the impacts, as well as the new paradigm of industrial ecology, which seeks to recycle rather than discard materials as part of the industrial processes. History of Materials on Earth

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The planets of the solar system are believed to have been formed from materials that broke off from the sun about 4.5 billion years ago. The Earth is presumed to have been in a completely gaseous state, cooling rapidly and gathering dust and smaller pieces of material, growing in size initially. Remains of pieces not coalescing initially with the planets remain as large rocky asteroids in orbits between Mars and Jupiter. One estimate is that a mass the size of the Earth originally at 6000° K (temperature of the sun's outer layer or photosphere) should have cooled to about 1500° in about 15,000 years. In about 25,000 years the temperature of the surface would have reached very nearly that of the Earth at present. At least sixty-six of the ninety-eight elements on Earth have been detected on the sun by means of spectroscopy. As the Earth cooled, the lighter atoms would tend to move away from the center more rapidly than the heavier ones, leading to a certain degree of layering. In the early period, significant amounts of hydrogen and helium--the main constituents of the solar nebula--remained on the planets. Some of the lightest atoms (hydrogen and helium for example) would escape into space, unless they combined chemically with other elements. Helium’s lack of ability to combine could be why we find little of this element on Earth, while the lighter but more reactive hydrogen -- which due to its weight should be able to escape with greater ease -- has been captured in the form of water and other compounds. To escape from the Earth's present gravitational pull, a molecule must have the "escape velocity" 11.3 km/second moving perpendicular to the Earth's surface. Table 1 shows the most abundant elements on Earth and a comparison of their estimated concentration in the sun.

Element Mass Number Atomic % in Sun's Photosphere Atomic % on Earth

H 1 8.76 2.7

He 4 18.7 (10-7)

C 12 0.003 0.1

N 14 0.01 0.0001

O 16 0.03 48.7

Na 23 0.0003 0.7

Mg 24 0.02 8.2

Al 28 0.0002 2.4

Si 28 0.006 14.3

S 32 0.006 14.3

K 39 0.00001 0.1

Ca 40 0.0003 2.0

Fe 56 0.0008 17.9

Cu 64 0.000002 1.4

Zn 65 0.00003 (small)

Atomic percent = % of total # of atoms

Table 1: Proportion of Elements in Earth and Sun.

Much of the Earth's material is in combination, as molecules. Even when the gases oxygen and nitrogen occur as elements in the atmosphere, they occur as molecular compounds O2 and N2, rather than in the atomic form (O and N). Seismology has given us much of our knowledge of the interior of the Earth. The core is approximately 3,500 km in radius with an average density 10.72 g/cc. The mean radius of the Earth is 6,371 km. The mantle, which is therefore about 2900 km thick has an average relative density of about 2.7 g/cc near the surface. The core, whose temperature is between 2000 and 4000° K, consists of molten heavy metals such as iron (Fe), nickel (Ni), and uranium (U), and minerals containing these metals as well as compounds of silicon (Si), aluminum (Al), and magnesium (Mg) with oxygen, carbon, and sulfur. Table 1 shows that the three most abundant elements on Earth are oxygen, iron, and silicon. However carbon, which is only 1 in every 1000 atoms, is the basic molecule of all life. The chemistry of carbon and its capacity to form numerous components are described in the Ecological System. It is interesting to note that silicon, in the same chemical family as carbon, abounds on Earth in the form of sand (SiO2) and other rocks. While carbon chemistry has given us live intelligence, we have used silicon chemistry for artificial intelligence -- as silicon is the basic material for computers. It is the coincidence of the strong hydrogen-oxygen bond and carbon chemistry, coupled with the abundance of these three elements and the Earth's gravity, distance from the sun (ensuring a particular temperature range), and speed of rotation (ensuring day and night) that gave us a water planet that could evolve our life forms!

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One of the basic tenets of nature is a recycling of materials that play a role in ecosystems--water, carbon, nitrogen, oxygen, and to a smaller extent, materials such sulfur and phosphorus. There are numerous other materials -- elements and compounds -- that we otherwise mine or extract and use in a variety of ways. They range from carbon-based materials, like oil, gas, and coal derived from carbon that has been sequestered by plants, or metals such as aluminum, iron, and uranium. Depending on the use, these materials may be dispersed into the atmosphere or Earth during processes like the burning of coal, or built into structures that slowly erode, such as buildings or monuments. The early atmosphere of the Earth contained water and other compounds including nitrogen, carbon dioxide (CO2), methane (CH4), and ammonia (NH3). The gases in our atmosphere - H2O, CO2, and N2 - have different primary reservoirs. Water is mostly in the ocean reservoir; CO2 in sedimentary rocks as carbonates, and N2 as gas in the atmosphere. In this unit we first describe the natural cycle of materials that pass through biological and geological cycles. Then we describe the use of materials in industrial processes, and how, over the last few decades, an examination of environmental impacts have led to some recycling of materials in the industrial setting. Mass Balance Technique The law of conservation of matter states that matter is conserved -- that is, neither created nor destroyed. Thus, if we know the amount of material that enters a chain of processes, and keep an account of all the amounts in different paths, we can calculate quantities of materials that are hard to measure. For example, we can calculate the amount of material discharged into the atmosphere if we know the amounts that went in, the transformations, and the waste streams to land and water. This method is called the Mass or Material Balance technique. An example of a process from everyday life is sewage treatment (see Figure 2). Wastewater is generated in your homes and is collected with the sewer system and transported to a treatment plant. When asked what happens to the sewage at the plant, most people say that the pollutants are removed from the water and the relatively "clean water" is then discharged to a water body. But what happens to the pollutants that are removed? In the treatment process, these pollutants are transferred from the water to the air, and to solid material known as sludge, or biosolids. And, a small amount remains in the "clean water." These waste products must be taken care of so that they do not affect the environment. A mass balance can be used to determine how much pollutant is emitted in each of its various forms.

Figure 2: Schemes of a waste water sewage treatment plant.

Another example (though historic) is the steel industry in Pittsburgh. The processing of steel requires vast amounts of water that then need disposal. As a result, many of the early "steel towns" were along rivers, since they provided both the water and the means for disposal. Prior to the environmental regulations in the USA, the “process water” was disposed directly to the rivers. However, one of the earliest regulations was the Clean Water Act, which prohibited such disposal without treatment to remove the process waste contained in that water. Since such treatment was expensive, the next option was to use the waste process water as cooling water since vast quantities of water were also needed for that purpose. However,

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this process led to air pollution as the water evaporated and transported the impurities into the air. After air pollution legislation was passed, the industry operators needed to remove the waste impurities. These are just two examples of the human search to find a sink for pollution that we are coming to realize does not exist. Many environmental problems have been caused by neglecting to think of the pollutants in terms of the conservation of matter and a mass balance.

A mass balance is an accounting of material for a specific system boundary. In other words, you are keeping track of all sources of the material that enter the system, all sinks of the material that leave the system, and all storage of the material within the system. A mass balance can be done for four scenarios, or combinations of those scenarios as follows:

• Dynamic (flows change over time) • Steady State (flows do not change over time; the system is in equilibrium) • Conservative pollutants (the pollutant does not change form over time; no reactions) • Non-conservative pollutant (the pollutant changes form over time due to chemical, physical, or biological reactions)

The dynamic scenario is the most difficult to model mathematically. For our purpose, only the steady state conservative and steady state non-conservative scenarios are discussed to illustrate how the technique can be applied to environmental systems. Steady State Scenario The accounting system to track pollutants is as follows: input rate = output rate + reaction rate The reaction rate is equal to 0 if the pollutant is conservative. The reaction rate can be + or – if the pollutant is non-conservative.

EXAMPLE: Two streams enter a lake in the system represented below. The main stream has a flow of 10 m3/s, and a chloride concentration of 20 mg/L. The tributary stream has a flow of 5 m3/s and a chloride concentration of 40 mg/L. What is the chloride concentration leaving the lake system? Note that chloride is a conservative pollutant. The answer is obtained by balancing the sinks and sources of pollutants to the lake system as follows:

[10 m3/s]*[20 mg/L]

+ [5 m3/s]*[40

mg/L] = [C mg/L]*[10 m3/s + 5 m3/s]

200 + 200 = C*[15]

C = 400/15 = 26.7 mg/L

Often the reaction rate is due to biological degradation also known as a decay rate. The decay rate is often modeled as a first order reaction, which means that the amount that decays is proportional to the amount present at any time. In other words: Ct = [C0]*e-[k*t] Therefore for a steady state non-conservative pollutant, the equation needs and additional term to account for the decay as follows: Decay rate = -[k*C*V]

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k = reaction rate C = concentration at time V = volume of the system modeled

EXAMPLE: Assume the lake system has a volume of 10*106 m3, and the pollutant is non-conservative with a decay rate of 0.2 1/day. Flow and concentrations in the streams are as in the figure below. What is the concentration of the pollutant leaving the lake system? Input = [5 m3/s]*[10 mg/L] + [0.5 m3/s]*[100 mg/L] = 100 [m3.mg/L.sec] Output = [5 m3/s + 0.5 m3/s]* [C] = 5.5 * [C] Decay = -[0.2 1/day] * [C] * [10 * 106 m3] = -23.1 * [C] Input = Output + Decay

C = 3.5 mg/L

Material Cycles in Nature Biogeochemical Cycles In this section, we examine three material cycles of nature: cycles of water, carbon, and nitrogen--substances central to maintaining life on Earth. The three material cycles consist of the transfer of chemicals from biological systems to geological systems and are therefore called biogeochemical cycles. Processes that affect these transfers are biological processes such as respiration, transpiration, photosynthesis, and decomposition, as well as geological processes such as weathering, soil formation, and sedimentation. As materials cycle through, we note that the total quantity (mass) of matter remains the same, and energy that is put in changes to work (often to rearrange forms of matter) and is eventually lost to the surroundings.

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Figure 3: Map of Schematic Material Cycles.

Figure 3 shows several of the cycles that determine the balance between life (biosphere), the Earth (lithosphere), and air and water (atmosphere and hydrosphere). All of us are familiar with the water cycle. The major elements cycled in nature are carbon, phosphorus, nitrogen, and sulfur, along with oxygen which forms part of all the cycles. The diagram includes general material and energy flows. Nutrients of smaller systems also cycle--with carbon and oxygen being the main components. Figure 1 shows the interactions between material cycles, energy input and transfers. Various aspects such as the water cycle, state of the oceans, and the climate are all interrelated and the rate of human activities disturbs the natural flows of materials and energy. When the rates of the disruptions are larger than the capacity of the entire system to bounce back, the system begins to shift, affecting all levels of the ecosystems through local and global changes. Materials are transferred between the atmosphere, hydrosphere (oceans), lithosphere (land), and the biosphere. These various "spheres" act as "reservoirs" that keep materials for different amounts of time, called residence times. Each cycle forms a complicated system and the systems then interact with each other to produce weather and climate as well as the periodic fluctuations that maintain the dynamic balance on Earth, including all life. These cycles have evolved to the present rate over billions of years. Interruptions of these cycles at much larger rates by human endeavors such as fossil fuel burning produce several of the environmental problems we face. Four elements form the main components of biogeochemical cycles - S, N, O, and C. Table 2 shows the chemical species in terms of where these elements primarily occur and the relative amounts in the four major reservoirs -- atmosphere, oceans, biosphere, and lithosphere. Phosphorus is another element that is cycled in nature. We do not describe the phosphorus cycle here. In this unit, we describe three cycles in detail: the water (hydrologic) cycle, the carbon cycle, and the nitrogen cycle; we also give a brief descriptions of the sulfur and oxygen cycles. As we describe each cycle, we also describe the chemical and its sources.

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Element Atmosphere Oceans Biosphere Crust

S Sulfur

Minor SO2, COS, H2S, H2SO4 (CH3)2S

Large Small Large

N Nitrogen

Large N2, N2O, NO, (mostly NO & NO2)

Minor NO3

- Small NO-

Large SO4

2-

O Oxygen

Small 02, 03, CO2

Small O2

Minor Numerous Forms

Large Numerous Combinations

C Carbon

Minor CO2, H2, CO3

Small CH2O*

Minor CO3

2- CH2O*

Large CH2O* CO32-

* refers to organic matter in which carbon, hydrogen, and oxygen exist in numerous combinations

Table 2: Important chemical compounds and relative amounts in reservoirs.

Water and the Hydrologic Cycle Water is one of the central materials that determine the conditions on Earth -- and keeps it fit for life as we know it. Ancient Greek philosophers considered water to be one of four elements along with earth, wind, and fire. Water makes up seventy to ninety percent of all living organisms (70% of the human body). Most organisms can survive only in a limited range of temperatures. Water provides one of the main "buffers" between the living entity and the environment, preventing sudden changes in temperature. As it is a vital compound in life - our bodies are 70% water - and as the compound that keeps the Earth's environment fit for life, it is indeed an "element" of what makes up the conditions on Earth. The oceans and the water cycle were established early. Water appears to have been on the Earth throughout its 4.5 billion year history. We believe that water was part of the original "primordial" soup in which complex molecules including proteins were first formed, eventually leading to life. Most of the Earth's water resides in the oceans. The Earth is the only planet in our solar system with surface oceans. Mars and Venus, the once considered "identical" planets (so called because of similarity in size and composition to Earth), have dry surfaces. The "clouds" on Venus are not made up of H2O like the Earth's clouds; rather they are made up of CO2. The Water Molecule At the end of the eighteenth century, chemists were able to decompose water and show that it is made of oxygen and hydrogen. Water has several properties that make it a unique compound in its ability to support life. The properties are: its latent heat, its density, and its ability to dissolve so many substances. All of these properties come from the peculiar molecular composition and geometry of water. Because of the importance of the structure in determining the properties of water as liquid water and as ice, we describe the molecular structure and the liquid state in some detail. The peculiar geometry of water, with an angle of approximately 105° (104.5° to be precise) between the hydrogen bonds, turns out to be the basis of a miracle of our planet. First, let us look at how the molecule is formed when 2 hydrogen atoms and an oxygen atom combines. Figure 4 shows the valence electrons of H and O atoms, and the covalent bonding of H20.

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Figure 4. Scheme of formation of covalent bonds between H and O to form water. The two "open" pairs of electrons in oxygen are called the non-bonding pairs.

Note that with the sharing shown in Figure 4, H and O atoms compete their shells for part of the time. However, as oxygen has a higher positive charge in the nucleus, the shared electron in each bond spend a larger fraction of time in the oxygen orbital. This makes the oxygen side of the molecule more negative than the hydrogen sides. The actual reason that the molecule is bent rather than linear has to do with the mutual repulsion of the unshared pair of electrons in oxygen and is beyond our scope here. The shape of the molecule is shown schematically and in terms of the actual spatial configuration in Figures 5 a and b.

Figure 5a Figure 5b

The shape of the water molecule is an isosceles triangle in which the H-O-H bond angle is approximately 105°. The illustration on the right shows the scheme of covalent bonds in water. Altogether, there are 8 valence electrons in the water molecule: six originally belonging to the oxygen atom and one each to hydrogen. Four electrons are involved in the O-H bonds, two in each. The remaining four electrons belong to oxygen, and are in nonbonding orbitals. This gives water its peculiar geometry and charge character. The molecule is electrically polar, that is, it has a net positive charge nature at the hydrogen end of the triangle, and a net negative character at the oxygen atom. In a group of water molecules clustered together, a positively charged region in one molecule tends to be attracted to the negatively charged region in another. There are two positive regions in each water molecule - the two hydrogen atoms. There are two negative regions projected by the nonbonding electrons. Each of the nonbonding pairs of electrons attract a positive hydrogen atom on a neighboring water molecule, and each of the hydrogen ends attracts an oxygen end of a neighboring water molecule. This results in each water molecule having four nearest neighbors. This type of bonding between molecules, due to hydrogen atoms forming a "bridge," is called a hydrogen bond. Figures 6 a and b show a scheme of a hydrogen bond, and the spatial configuration of H2O molecules in the liquid form. Figure 6c shows how the continuously moving liquid water molecules make transient hydrogen bonds with one another, forming a fluid network.

Figure 6a: The hydrogen bond is the weak covalent bond between the hydrogen in one water molecule with the two electrons in the non-bonding orbital of oxygen in another water molecule. The hydrogen bond is very weak (about 5 kcal/mole) compared to the H-O bond in its original molecule (about 110 kcal/mole).

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Figure 6b: Space configuration results from the hydrogen bonding in liquid water, magnified about a million times the original size. The shadows suggest the constant motion of the molecules.

Figure 6c. Models of the three-dimensional network formed by the liquid water molecules, creating a fluid network.

At low temperatures, this structure is highly geometrical and coordinated. This ordered structure is the structure of ice, which in effect gives the hexagonal shape to snowflakes. At a temperature close to the freezing point, the kinetic energy of the water molecules is small and the hydrogen bonds keep the molecules in place, but still not very closely packed. This is sketched in Figure 7.

Figure 7. The structure of ice, magnified a million times. The atoms come together in a hexagonal pattern.

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The weak hydrogen bonding means that ice has a lot of empty space. When ice melts, the "frozen" geometry is removed, but not all the hydrogen bonds are broken. The molecules begin to pack more closely together so as to fill some of the empty space. Thus liquid water is denser than ice. Water has its greatest density at 4°C, which is why the top of a lake freezes before the bottom. The cooler part freezes and the more dense water (at a slightly higher temperature) sinks to the bottom. The bottom freezing last helps protect organisms that live in the bottom. The empty space between molecules also means that ice does not conduct heat very well. So, the frozen top of the lake keeps the heat from the water below from escaping too readily, maintaining it as liquid. This characteristic is central to maintaining aquatic life during winter. Even when ice converts to water at 0°C, only about 15% of the bonds are broken, so cold water molecules are still relatively bound together. Although molecules are constantly in motion, local order is still mostly maintained, as molecules remain bound to one another even as they move fast. Thus, water is able to absorb a lot of heat without significant change in temperature. The heat capacity of water is higher than most substances, including air. Oceans do not suffer from sudden changes in temperature, which is important for living systems in the oceans. The ocean also buffers the climate on its shore. The large quantity of water on Earth serves to prevent sudden rises of temperature, between night and day for example . A lot of heat and thermal motion of the molecules are necessary to finally break all the bonds, and to vaporize the water. All of this means that it takes high amounts of energy to change the states of water from solid to liquid and liquid to gas. Water has a high latent heat of fusion (energy required for melting) and a high latent heat of vaporization (energy required to vaporize). Land plants and animals are able to dissipate a lot of heat simply by the evaporation of water through transpiration or by sweating, in the case of plants and animals respectively. Under extreme conditions, such as in a desert, a human body may evaporate as much as one liter of water per hour by sweating to rid itself of heat. The polar nature and empty spaces in water also make it a good solvent. The polar nature gives rise to the high surface tension of water. This high surface tension makes water capable of rising in capillary structures of roots and stems. It also gives firmness to the surface of lakes so that light insects can actually sit and move about on the surface. Water vapor is a greenhouse gas. Both the capability to keep heat in and to transfer heat from the tropics serve to moderate temperatures on Earth. For example, as one half of the Earth rotates away from the sun, the fall in temperature is much more gradual than it would have been if there were no water vapor in the atmosphere. Thus water has a combination of properties that accounts for its central role in preserving life on Earth: liquid more dense than solid; high surface tension; high heat capacity; and high solubility.

The Hydrologic Cycle and Water Balance Water is a fundamental necessity for all ecological systems, as it is a cornerstone of life. Estuaries (where river and sea meet) are an aquatic environment that is important to the life cycle of many species. Water is cycled through evaporation and transpiration from plants into the atmosphere, and precipitation back to Earth. Four-fifths of the water in the global water cycle comes from the oceans. Of a total of about 1.36 billion cubic kilometers of water, about 97% is in oceans. An additional 2% is locked up in glaciers and icecaps, and 0.31% is stored in deep groundwater reserves. This leaves only about 4.2 million cubic kilometers of relatively accessible fresh water. Water evaporates from the large surfaces of the Earth's oceans. It is estimated that 41,000 cubic kilometers of water returns to the sea from the land per year, balancing the transport of water from sea to land through the atmosphere as precipitation. About 32,000 cubic kilometers return to the sea as runoff that cannot be captured. The remaining 9,000 km3, is potentially available as water supply for humans and animals. This could theoretically supply 20 billion people. During the past 300 years, human water use has increased 35-fold. But the availability is far from uniform on the Earth's continents. There are places in the Middle East and Africa which have no access to natural fresh water. In addition, some people have lifestyles that consume much more water than others. The average U.S. resident consumes 70 times as much water per year as an average resident of Ghana. The United States Geological Survey website has a section completely devoted to the water resources of the United States (http://water.usgs.gov/). The water withdrawn for public supply during 1995 was an estimated 40,200 Mgal/d. Public suppliers served about 225 million people during 1995. Total public supply withdrawals in 1995 averaged 1979 gal/d for each person served. The hydrologic cycle also cleans the environment. Clouds and run-off transport and deposit pollutants into lakes and oceans. The transport and deposition of SO2 and NOx in pollution is the environmental problem known as acid rain. SO2 and NOx come from sources such as fossil fuel burning as well as from some natural sources such as volcanoes. The amount of water cycled per day is enormous and highly variable. One thousand gigatonnes of water evaporate from the oceans each day. In some places like the southern coastal regions of Peru, decades may pass with no rain at all. The water cycle is one cycle that has been manipulated extensively by human technology through irrigation, building dams, and hydroelectric energy plants.

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Figure 9: Hydrologic Cycle in Quantities.

Availability and Pollution of Water Although water is so abundant on Earth that we call the Earth a "water planet," 97% of this water is salt water. Only about 3% of water is fresh water, and less than 0.01% is readily available from rivers and lakes. Problems of availability of fresh water arise from agriculture (both the vast amounts used in irrigation and the pollution arising from pesticides and fertilizers), industrial pollution, and pollution from sewage. Some types of industrial pollution of water (like heavy metal pollution) have been realized only relatively recently. Water had historically been thought of as a "bottomless" sink for pollutants. A statement often used by industry as recently as a couple of decades ago was "dilution is the solution to pollution." These attitudes, and the fact that water is relatively plenty in highly industrialized nations, delayed our recognition and addressing of water pollution. While the hydrologic cycle is continuously at work globally, local conditions of rain and fresh water supply vary tremendously. This uneven distribution of water determines the nature of many of the problems related to fresh water management and use. The average residence time of a molecule of water in the atmosphere is about eight days. The residence time of water in deep ground water aquifers, or large glaciers, may be hundreds, thousands, or hundreds of thousands of years. Table 3 shows the major salt and freshwater stocks on Earth, and the small amount of freshwater available. Less than 1% of this water is actually usable.

Table 3. Volume (million km3) % of total water

Saltwater Stocks

Oceans 1,338,000 96.54

Salty ground water 12,870 .0.93

Saltwater lakes 85 0.006

Freshwater Stocks

Glaciers, permanent snow 24,064 1.24

Fresh ground water 10,530 0.76

ground ice 300 0.022

Freshwater lakes 91 0.007

Soil moisture 16.5 0.001

Atmospheric water vapor

Marshes, wetlands 11.5 0.001

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Rivers 2.12 0.0002

In live organisms 1.12 0.0001

Table 3: Water stocks on Earth.

Figure 10 shows the annual fresh water availability for selected countries.

Figure 10: Average amount of fresh water available for various countries, in cubic kilometers per year, as measured over the period 1921 to 1985. This figure shows the vast differences in

the natural distribution of fresh water among different regions. Source: The World's Water 2000-2001: The Biennial Report on Freshwater Resources.

While the amount of water available is low, we further compound the problem by polluting our groundwater. Groundwater lies mainly deep underground in aquifers, which are geological niches of porous materials or space between rocks. Farms, cities, and factories all have run-off that can seep down into the ground, and pollute even deep aquifers. Industrialized agriculture has also been responsible for digging deep into the water resources. Pollution of Ground Water Fertilizers and pesticides applied to cropland, organic wastes from farmlands, and sewage from cities all pollute ground water. Nitrate pollution of groundwater due to these sources has become very severe. In California's central valley, nitrate level in ground water almost tripled between 1895 and 1980. One of the effects of nitrates in groundwater is the so-called blue-baby syndrome, or methenoglobinemia, in which the oxygen-carrying capacity of the baby's blood decreases. Pesticides of various kinds have entered many aquifers and are one pathway for organo-chlorine compounds -- also known as endocrine disrupters -- to enter our systems. The effects of organo-chlorines are discussed in the unit on Risk & Human Health. Even when the problem of water pollution was first realized, the remedies sought were end-of-pipe -- cleaning up polluted water -- rather than conservation of fresh water or prevention of pollution. Water purification technologies were developed. Creative re-design of industrial processes and water conservation technologies like low-flush toilets have begun to get serious attention only recently. Industry is just beginning to design and implement methods that reduce water pollution. The use of "grey water" (water that has only been partially re-cleaned) for high water use applications such as agriculture has not received much attention in the U.S.

Carbon Cycle It is believed that most of the carbon now on Earth was originally released from the interior of the Earth as CO2, a gas which now makes up about 0.03 to 0.04 percent by volume of air, and is primarily responsible for maintaining the Earth as a greenhouse with temperature conditions suitable for life. CO2 is the most available form of carbon for living organisms. Molecules containing carbon may keep the carbon fixed over millions of years or may cycle the carbon through quickly. The

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atmospheric cycling and effects of CO2 on climate are discussed in the Atmospheric System. The versatility of carbon compounds and the vital role of carbon as the basis of life is described in the Ecological System. Thus, carbon exists in the biosphere as the central element of life, in the lithosphere as coal (carbon) or limestone (calcium carbonate, CaCO3), in the atmosphere as CO2, in the hydrosphere as dissolved CO2 , as well as in other complex forms. The atmosphere contains about 750 billion tons of carbon in the form of CO2. Photosynthesis by plants removes about 120 billion tons of carbon from the air per year, but plant decomposition returns about the same amount. Living plants and animals contain 560 billion tons of carbon (mostly forest trees). Plant remains and organic matter buried in the soil contain about 1400 billion tons. About 11,000 billion tons are trapped in compounds which are complexes of methane (CH4) and water, found on ocean floor. The oceans contain another 38,000 billion tons of carbon, most of it in the form of dissolved CO2. With the onset of the Industrial Revolution about 200 years ago, we began burning massive amounts of fossil fuels and releasing large amounts of the earthbound carbon into the atmosphere, primarily as CO2. The burning of fossil fuels adds about 22 billion tons of CO2 per year, containing about 6 billion tons of carbon. Deforestation adds a further 1.6 to 2.7 billion tons, by not removing this amount. The rapid growth of synthetic organic chemicals also contributes to the amount of CO2 released. The main reservoirs for carbon are sedimentary rocks, fossilized organic carbon (including the fossil fuels), the oceans, and the biosphere. Carbon goes primarily through three cycles with different time constraints:

1. A long-term cycle involving sediments and the depths of the lithosphere. 2. A cycle between the atmosphere and the land. 3. A cycle between the atmosphere and the oceans.

The last two cycles are faster and subject to human intervention. Carbon Cycle One: Long-term Cycle The cycling of carbon between atmosphere, oceans, and sediments involve a slow dissolution of atmospheric carbon and carbon from rocks via weathering into the oceans. In turn, the oceans deposit sediments, and some of the sediments are thrown back into the atmosphere through volcanic action.

Figure 11: Carbon Cycle One.

The cycle depicted in Figure 11 occurs over hundreds of millions of years. Calcium carbonate (CaCO3) is a larger portion of sediments because the ocean contains large amounts of calcium. Carbon Cycle Two: Air and Land Cycle The second cycle between the atmosphere and biosphere, occurs over different time scales ranging from days to decades. Carbon dioxide is the basic "food" of the biosphere and thus the biosphere is the primary agent for this cycling. Photosynthesis (synthesizing starches and sugars using light) is a main mechanism for cycling carbon by the biosphere. The chemical reaction of photosynthesis may be represented as:

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CH2O represents a unit of organic matter; six of the CH2O unit would be C6H1206 which makes the simple sugar (glucose or fructose). Eleven of these units make sucrose (C11H22O11), a more complex sugar formed by the combination of one glucose and one fructose. Thousands of glucose molecules combine to form a molecule of starch, or of cellulose. Thus photosynthesis takes the atmospheric carbon in CO2 and "fixes" it into the biosphere. The subsequent cycling of the carbon in the biomass is created.

Figure 12: Carbon Cycle Two.

Thus 750 Gt-C in the atmosphere cycling at the rate of 80 Gt C/yr means that the lifetime of the carbon in the atmosphere reservoir is about 9 years. When the organic matter is oxidized through respiration, the reverse of photosynthesis takes place.

Respiration releases CO2 into the atmosphere. Respiration and photosynthesis occur at nearly equal rates over one year. Buried biomass -- eventually becoming fossil fuels, including coal -- has historically had the effect of keeping the carbon in the land. The accelerated burning of fossil fuels is, however, releasing these large stores into the atmosphere as combustion products. Burning of biomass-based fuels such as methanol and ethanol has been suggested an alternate to fossil fuel combustion. Biomass fuels have no net release of carbon dioxide. The effects of fossil fuel burning are discussed in the Atmospheric System. Carbon Cycle Three: Air and Sea Cycle The oceans contain much more carbon than the atmosphere. Carbonates washed down from rocks over thousands of years, dissolved CO2, and carbon in the oceanic biomass constitutes this reservoir. The carbon from the top layers of the ocean cycles faster, whereas the carbon in deep waters may take thousands of years. The summary of the three cycles is shown in Figure 13.

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Figure 13: Three Carbon Cycles combined.

Nitrogen Cycle The nitrogen cycle is dominated by the N2 gas in the atmosphere. Nitrous oxide, N2O, is the second most common form. Nitrous oxide (commonly known as laughing gas) is a greenhouse gas. Seventy-nine percent of the atmosphere is nitrogen in the form of N2 gas. Because N2 has low reactivity, it offsets the high reactivity of oxygen, O2, the other major constituent of the atmosphere. For example when we light a match, the nitrogen does not burn with the oxygen. It does not react with any other element or common compound under ordinary conditions. This property of nitrogen has been called the "fire insurance" of our atmosphere. If the nitrogen was not "diluting" the flammability of 02, every spark from a match could lead to a large fire! Due to its different valences (3,4,5,), nitrogen can form a multiplicity of compounds with a single element. For example, it can combine with oxygen to form N2O, NO, NO2, or N2O5! As a group, these oxides (except for N2O5) are denoted by NOx. NOx compounds form an important category of air pollutants. They can result, for example, from nitrogen and oxygen combining in the extremely hot environment of an automobile engine. Nitrogen oxides and hydrocarbons, in the presence of sunlight, give rise to photochemical smog and tropospheric ozone problems, which are described in the Atmospheric System. Natural and anthropogenic nitrogen oxides also contribute to acid rain. Nitrogen - Essential for Life Nitrogen is an essential element for life. Amino acids, which are the building blocks of proteins, contain nitrogen as NH2, the "amino" part of the molecule. The four building blocks of DNA [Adenine (A), Cytosine (C), Guanine (G), and Thymine (T)] consist of single or double rings of carbon and nitrogen atoms, with various side chains. Nitric oxide is a neurotransmitter. Thus all living organisms require large amounts of nitrogen. However, in the form of N2, nitrogen is unusable by all organisms with the exception of diazotrophs (or more simply, nitrogen-fixers). Diazatrophs are primitive bacteria that possess an enzyme which makes them capable of converting N2 gas to ammonia Diazotrophs may be symbiotic, living as nodules in roots of plants such as legumes. A type of bacterial called cyanobacteria live on lichens, mosses, and ferns. Some cyanobacteria are free-living and capable of photosynthesis.

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The conversion of N2 gas to ammonia is called nitrogen fixation, and makes the nitrogen available for use by organisms. In the atmosphere, nitrogen is fixed (i.e. N2 is converted to NH3) in three ways: (1) bacteria, (2) by humans through a manufacturing process called Haber process used in fertilizer production, and (3) through a chemical process initiated by lightning. Thus nitrogen fixation is an important process for biological functioning. Legumes such as peas, clover, and beans have nitrogen-fixing bacteria in their roots. This enables them to grow in nitrogen-poor soil. Plants take up nitrates through their roots, and convert them into proteins and other compounds. Animals get their nitrogen from plants. Wastes and remains of animals and plants contain organic nitrogen compounds which are then broken down by bacteria and converted into compounds such as ammonia (NH3). Other bacteria (denitrifying bacteria), found especially in waterlogged soils, convert nitrates back into nitrogen gas and make it unavailable again. Plants can not use N2, and the N2 can therefore escape into the atmosphere. Farmers normally try to prevent the soil from becoming waterlogged. This is the problem with over-watering houseplants as well. Lightning is an electrical discharge through the air, and can cause N2 and O2 molecules to change into the atomic form, combine with water to form weak nitric acid (HNO3), and precipitate atmospheric nitrogen to the Earth, adding nitrogen to the soil in a usable form (nitrate, NO3). Inside plants and other organisms, the nitrates are converted into amino-acids and other vital compounds. Modern agriculture uses artificial fertilizers such as ammonium nitrate (NH4NO3) to capture nitrogen. For example, if you examine the box of "plant food" that is a fertilizer designed for "acid-loving" plants such as azaleas or rhododendrons, you see the numbers 30-10-10, where the 30 stands for N, the first 10 for phosphorus, and the second 10 for potassium. This fertilizer then contains 30% of a nitrogen compound, mostly ammonium nitrate (NH4NO3) with some urea. While this improves yield, it upsets the natural balance of nitrogen in the ecosystem. Too much of nitrogen added to the soil through fertilizers washes out into ponds and rivers and causes overgrowth of algae in large patches. These algae blooms prevent light from entering the water and smother other aquatic life. The Nitrogen Cycle is shown in Figure 14.

Figure 14: The Nitrogen Cycle.

Combustion and lightning fix nitrogen in the atmosphere. When plant matter (biomass) is burned, the organic fixed nitrogen is converted into nitrogen oxides and released. The clearing of forests by fire and burning of leftover debris from farmland creates large emissions of nitrogen oxide. The oceans and sediments also contain large amounts of nitrogen as nitrates. Ammonia (NH3) is another form of fixed nitrogen. Ammonia is produced by bacteria after they consume organic matter. This accounts for the ammonia smell from the cat's litter-box resulting from the bacterial emissions. Before chloroflourocarbons were invented, ammonia was the most common refrigerant. While the figure shows the main global routes of cycling nitrogen, in some locations (for example the Los Angeles basin, Mexico City, and in other industrial cities), nitrogen oxides (NOx) and nitric acid (HNO3) form a significant fraction of the local tropospheric environment. Sulfur Cycle

Nitrogen-fixing bacteria

on soybean roots

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Sulfur is mainly found on Earth as sulfates in rocks or as free sulfur. The largest deposits of sulfur in the United States are in Louisiana and Texas. Sulfur also occurs in combination with several metals such as lead and mercury, as PbS and HgS. Sulfur appears as the yellow aspects of soil in many regions. Sulfur was mined early in the form of the yellow element and used for gunpowder and fireworks. While bacteria digest plant matter, they emit H2S, hydrogen sulfide, a gas that has the "rotten egg" smell characteristic of swamps and sewage. Sulfur is an essential element of biological molecules in small quantities. Sulfur and its compounds are important elements of industrial processes. Sulfur dioxide (SO2) is a bleaching agent and is used to bleach wood pulp for paper and fiber for various textiles such as wool, silk, or linen. SO2 is a colorless gas that creates a choking sensation when breathed. It kills molds and bacteria. It is also used to preserve dry fruits, like apples, apricots, and figs, and to clean out vats used for preparing fermented foods such as cheese and wine. Sulfuric acid, H2SO4, is a very widely used chemical. Over 30 million tonnes of sulfuric acid are produced every year in the U.S. alone. The acid has a very strong affinity for water. It absorbs water and is used in various industrial processes as a dehydrating agent. The acid in the automobile battery is H2SO4. It is used for "pickling" steel, that is, removing the oxide coating from the steel surface before coating it with tin or electroplated with zinc. Sulfur is also a biologically important atom. Although only small amounts of sulfur are necessary for biological systems, disulfide bridges form a critical function in giving biological important molecules specific shapes and properties. (see Ecological System.) Sulfur is released into the atmosphere through the burning of fossil fuels --especially high sulfur coal--and is a primary constituent of acid rain. Sulfuric acid (H2SO4) is the primary constituent of acid rain (see Atmospheric System) in about all regions other than California. Sulfur dioxide and carbonyl sulfide (COS) occur in small quantities in the atmosphere; but due to its high reactivity, sulfur is quickly deposited as compound (sulfates) on land and other surfaces.

Figure 15: The Sulfur Cycle.

Figure 15 shows the biogeochemical cycle of sulfur. As in the case of nitrogen, the figure shows the large quantities. Local activities such as coal burning can release large amounts in a small area. Sulfur compounds can also be transported from the higher altitudes from tall "smoke stacks" and contribute to acid rain far from the sources. Oxygen Cycle Oxygen, like carbon and hydrogen, is a basic element of life. In addition, in the form of O3, ozone, it provides protection of life by filtering out the sun's UV rays as they enter the stratosphere. In addition to constituting about 20% of the atmosphere, oxygen is ubiquitous. It also occurs in combination as oxides in the Earth's crust and mantle, and as water in the oceans. Early in the evolution of the Earth, oxygen is believed to have been released from water vapor by UV radiation and accumulated in the atmosphere as the hydrogen escaped into the Earth's gravity. Later, photosynthesis became a source of

Source: Uni-bremen.

http://www.min.uni-bremen.de/

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oxygen. Oxygen is also released as organic carbon in CHO, and gets buried in sediments. The role of oxygen in life is describe in the Ecological Systems.

Figure 16: The Oxygen Cycle

Oxygen is highly reactive. A colorless, odorless gas at ordinary temperatures, it turns to a bluish liquid at -183° C. Burning or combustion is essentially oxidation, or combination with atmospheric oxygen. Figure 16 shows a very broad overview of oxygen cycling in nature. The involvement of oxygen in numerous reactions makes it hard to present a complete picture. Oxygen is vital to us in many ways (beside the most obvious--for breathing). Water can dissolve oxygen and it is this dissolved oxygen that supports aquatic life. Oxygen is also needed for the decomposition of organic waste. Wastes from living organisms are "biodegradable" because there are aerobic bacteria that convert organic waste materials into stable inorganic materials. If enough oxygen is not available for these bacteria, for example, because of enormous quantities of wastes in a body of water, they die and anaerobic bacteria (that do not need oxygen) take over. These bacteria change waste material into H2S and other poisonous and foul-smelling substances. For this reason, the content of biodegradable substances in waste waters is expressed by a special index called "biological oxygen demand" (BOD), representing the amount of oxygen needed by aerobic bacteria to decompose the waste. The result of not meeting the oxygen demand was described earlier in the section on the water cycle. Industrial Use of Materials

"If man began with speech, and civilization with agriculture, industry began with fire. Man did not invent it, probably nature produced the marvel for him...He put the wonder to a thousand uses. First, perhaps... to conquer his fearsome enemy, the dark; then...for warmth,...then he applied it to metals, tempering them, and combining them into stronger and suppler than those in which they had come to his hand..."

-Will and Ariel Durant The Story of Civilization, Volume I: Our Oriental Heritage, p 11.

Beginning with fire, "industry" (or in these early days, humans) learned to use energy to manipulate materials, transforming them to suit our purposes. These rearrangements, while bringing great progress, have also left us with large prices to pay. These prices come mostly because of our disregard or ignorance of evolving the material use on a scale of time and space that learned its lessons from natural material cycles. The natural material cycles described in the previous sections are a part of our ecosystem. Over billions of years, materials, energy and life have all evolved with mutual interactions to become part of a natural ecology. Most materials that form part of the biosphere occur in cycles, especially those that play central roles in biological systems. The use of materials by humans has changed over time in quantity and quality, and especially over the last century. The early use of materials for food, shelter and energy required small amounts of materials for each person and were conserved to large extent because it was hard to get, shape and work with materials. Often, materials remained as part of a product such as a tool or a plough for decades and were reused or recycled. The trends of material use in products have changed significantly with the technological age – particularly in the 20th century. Plastics are perhaps the most radical material

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invention, in the way that material permeated society. In 1900, 75% of products used renewable materials (that is, agricultural and forest materials, such as wood and natural fibers). By 1980, 70% of materials used were from non-renewable sources such as ores, minerals, and petroleum. In 1955, 8% of materials in products were petroleum-based (plastics). By 1980, 32% of materials in products were petroleum-based. Wood and stone were the earliest "materials" to be shaped and used by humans. In the course of time, natural materials such as clay and mud were used for cooking and building. With the advance of technology, discoveries of ways to extract metals from ores, methods to shape and transform materials, and eventually with the knowledge afforded by synthetic, organic, and nuclear chemistry, we have made numerous combinations of materials that have never existed in nature. The age of "synthetic" materials started with forming alloys of metals. Bronze (an alloy of tin and copper), brass (an alloy of zinc and copper), and gold alloys (14 carat gold is 14 parts of gold and 10 parts of copper; 24 carat gold is pure gold metal) have all been used since ancient civilization. The first transformations of materials gave humans the ability to shape materials into forms they wanted. As pure gold is too soft and pliable, the addition of copper was an early innovation to make gold stronger. Metallic elements were alloyed to increase strength to make strong and lasting tools, structures and weapons. Iron, copper, sulfur and phosphorus were probably the materials that received the greatest attention for these uses as "industry" emerged. Of course, stones of various kinds, including marble (CaCO3), granite, gypsum (MgSO4), sand (SiO2) were all used since early times for building. There were also fuel materials such as wood, coal, and oil, which were first used to build fires, then for controlled extraction of energy. With increasing technological capabilities, human ingenuity and art (“techne” in Greek means “artful” or "cunning," as in Charles Dickens' Artful Dodger) combined with scientific understanding led to unprecedented arrangements and transformations of materials. In pressing to get the functionality of various desirable properties and technological progress in designing and producing new materials, we did not know or think of these materials as part of our natural environmental system. In extracting them from the natural system, and combining them into new forms, we began concentrating materials, producing materials that did not exist in nature, and extracting or "purifying" into elemental form large quantities of elements that existed in nature only in chemical combinations with others. In these processes, there was no awareness of how much "useless" material (waste) was produced as we extracted the "useful" material, or of the role that "indestructible" synthetic or even natural materials may play when released into the environment after their use in unprecedented quantities over relatively short periods of time. The greatest ignorance we exhibit as an industrialized "civilization" is perhaps a lack of respect or even a total ignorance - of the role of time and of cycles in providing system balance. In pressing on with our economy, we lost sight of our ecology! Robert Ayres, one of the originators of the idea of industrial ecology summarizes the crux of our material use in the beginning paragraph of his book Industrial Ecology, co-authored with Leslie Ayres:

"...every substance extracted from the Earth's crust, or harvested from a forest, a fishery or from agriculture, is a potential waste, it soon becomes an actual waste in almost all cases, with a delay of a few weeks to a few years at most. The only exception worth mentioning are long-lived construction materials. In other words, materials consumed by the industrial economic system do not physically disappear. They are merely transformed to less useful forms. In some cases (as with fuels) they are considerably transformed by combination with atmospheric oxygen. In other cases (such as solvents and packaging materials) they are discarded in more or less the same form as they are used. It follows from this simple relationship between inputs and outputs - a consequence of the law of conservation of mass - that economic growth tends to be accompanied by equivalent growth in waste generation and pollution." (Ayres 1)

Though this realization has not fully hit most parts of our society even today, the 1960's environmental consciousness articulated three features or problems of the industrial rearrangement of material: resource depletion, increasing waste materials, and the presence of toxic materials in the environment. The first idea, resource depletion (which came from industry), was the realization that the Earth does not have an infinite bank of materials. The second idea of increasing amounts waste came from people noticing the ugliness of waste -- as garbage on highways, junked cars, the "blooms" of algae in lakes from over-nitrificiation from detergents and pesticides, or mounds of mining overburden. The presence of toxic materials in the environment was a slower realization, spurred most notably by Rachel Carson’s Silent Spring which has a chapter titled "And the Birds Sing No More" to signify the impact of the pesticide DDT which weakened the eggshells of birds. Prior to this century, industrial countries did not consider pollution or resource shortage a serious problem. When resources in the home countries were hard to access, trade or conquests were used to procure material. Historians Will and Ariel Durant make the point that the Industrial Revolution came to England first because of the long history of British command of the seas, because science in England was mainly "directed by men of practical bent", and because England had a constitutional government sensitive to business interests. The reaction to resource depletion in this century was a foray into ideas of conservation and resource management, finding out how the economies of recycling would compare with the economies of resource extraction from nature. Thus early in this century, the aluminum industry began its quest for recycling. Aluminum recycling is one of the most advanced processes of

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recycling because of decades of learning. Conservation ideas also developed through the desire to conserve the natural beauty of forests and other landscapes. In the 1970's, economic and political pressures such as the oil cartel and depletion of coal led to ideas of energy conservation in the United States. Energy-intensive, material-producing industries such as aluminum, and paper started to look seriously into recycling. Energy conservation measures in the U.S. also led to smaller sized cars, which had hitherto gone on with the philosophy of "the bigger, the better." Station wagons for family uses and recreational vehicles for vacations were a common sight during the economic upsurge of the 1950's and early 1960's. Automobile recycling gained favor and achieved 90% material recovery in the 1980's. In 1994, the National Environmental Technology Act was passed to encourage the government to work with industry to promote technologies that will have positive environmental impact. Particularly, the government was interested in and more efficient and non-polluting technologies so that we can maintain our current standard of living in light of population growth. In the Senate, those supporting the measure contended that “coming up with new, nonpolluting technologies will ultimately help efficiency and the economy.”1 All of these conservation measures were, of course, totally anthropocentric, with an objective of preserving our conveniences, and meeting our wants and desires. It was not the ethos of conservation practiced by older civilizations with a respect for value and an eye to the future, or to the "seventh generation," as described in the Ethical System. Faced with resource depletion, we began defining materials as renewable and nonrenewable resources. Materials like coal that can only be replaced over long periods of time (compared to the time periods of human activities involving their use), are called nonrenewable resources. Materials such as wood which can be replenished in reasonable periods of time are called renewable resources. Note that these are renewable only if we replant trees at a rate that keeps up with use. Thus the Redwoods or old-growths forest trees should not be looked on as "renewable" resources because of the time it would take to replace them. Increasing amounts of waste and its disposal was the second mounting problem. Europe, having an older industrial base and limited land area, felt the waste disposal problem sooner and more acutely than the United States. The concentration of people and hence of quantities of waste are higher in the urban areas. In his book The Search for the Ultimate Sink, historian Joel Tarr writes that urban pollution is the "product of the interaction among technology, scientific knowledge, human culture and values and the environment," reduced or exacerbated at times with environmental policy and control technology. Sinking of waste and recycling of usable items have been a part of all cultures. But an economy that marketed convenience items as necessary to quality of life, and the accompanying perception that we have of an inexhaustible resource supply, have led to a throw-away society, especially in the U.S. Often, in analyzing environmental problems, we focus on industrial generation of waste, without a full realization that industry generates waste to meet consumer demands. In 1976, an average consumer spent 15% of his/her income on "durable goods" -- automobiles and parts, furniture and other appliances, 18.5% on food, and 22% on "nondurable goods" such as clothing and shoes, gasoline, and alcoholic beverages! (U.S. Bureau of Economic Analysis) In addition to garbage and sewage, industrial wastes in air, water, and land have also posed formidable problems. Toxic materials in the environment are a much subtler problem. Basically, the problem arises when we produce new compounds or isolate elements in configurations not found in nature, with properties such as a resistance to degradation. Many of these materials do not decompose on exposure to the usual agents that nature uses to decompose -- air, light, water, or bacteria. Persistent substances, such as plastics and chlorofluorocarbons, produce cumulative, long-term, and long-range effects on plant, animal, and human health. In many cases the effects are not predictable because of our lack of knowledge and the absence of consideration of systemic, long-term impacts. Joe Thornton writes in Pandora's Poison, a book on the impacts of chlorine compounds, "the chemistry of the chlorine atom gives chlorine gas and organochlorines useful properties, but these same qualities (high reactivity and chemical stability) create enormous environmental problems...Organochlorines that are stable in their intended use, however, are also persistent in the environment." Organochlorines and other organic compounds and metals give rise to health hazards such as cancer and endocrine disruptions discussed in the unit on Human Heath and Risk. The U.S. Bureau of Mines maintains an account of the world production and flows of metals and other primary materials such as coal and other fossil fuels. Table 4 shows the amount of some metal ores extracted in 1988.

Metal Weight of Ore

(KMT) Weight of Metal

(KMT) Mine & Mill Waste

Aluminum 97,660 36,400 61,260

1 Source: http://www.senate.gov/~rpc/rva/1032/1032108.htm

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Copper 750,000 8,450 740,000

Iron 953,000 564,400 390,000

Uranium 1,900,000 36 1,900,000

Lead 101,000 3,380 98,000

Table 4: World Production of some metals and mine waste in 1000 metric tonnes (KMT) (adapted from Ayres 1996)

Table 4 shows that each pound of aluminum extracted produces 1-7 pounds of waste at the mine, and almost all of the uranium ore is waste! The main intent of the table is to show the amounts of waste at the very first stage -- mining and milling -- in the production of a metal. Note that in all cases, we produce much more waste than metal. This is only the beginning. Each stage of production of a consumer good such as an automobile or a toaster requires many more stages of manufacturing, each with its own wastes discarded to air, land, and water. The Flows of Copper and Aluminum Figures 17 and 18 are flowcharts showing the stages in the use of two metals-- copper and aluminum. The flow of copper is shown only from the mine to the point of input into an industrial process. The figure for aluminum is drawn to represent the whole sequence of use, including recycling. These flow charts are the beginning stages of doing a life cycle analysis, which we describe in the next section on Industrial Ecology. In the Energy System, we have shown similar diagrams for the production of energy from different sources. Copper

Figure 17: Scheme of copper metal flow from mine to entry into manufacturing process.

Over nine million metric tons (18,000 million lbs.) of copper is mined annually. The two main countries producing copper are Chile and the U.S., each producing about 2 million MT annually. Canada, the former USSR, Zaire, Zambia, and Poland are the other countries. Copper is usually mined via open pits. After a large amount of processing, each process with its other inputs and wastes, copper metal is delivered to the various industries that use it. Because copper is used in alloys such as brass and wires, it is difficult to extract and reuse the metal economically. Separation is one of the major obstacles in the attempt to recycle copper. Copper is the oldest known metal to be extracted and used by humans. There are signs of copper use as early as 6000 B.C. toward the end of the Neolithic Age, considered by historians as the beginning of the Age of Metals. Alloying copper with tin or zinc to form bronze and brass seems to have happened by 3000 B.C., and other metallurgical heat-treatment processes like casting seem to have started by 1500 B.C. (Durant, Vol. I, p. 103). Aluminum

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Figure 18: Aluminum flowchart

Aluminum plays a very crucial role in modern society. Its light weight and durability make it the basis of aircraft and large mirrors used in telescopes! It is a versatile metal. The extraction and processing of aluminum from its ore -- bauxite (Al2O3) -- is environmentally destructive. Aluminum is not abundant in the Earth's crust (14.3 atomic % or 8% by mass compared to 27.7% for Si (Silicon) and 5% for Fe (Iron), but it is abundant in combination with oxygen. This strong combination requires a lot of energy to break! The main producers of aluminum are Australia, Guinea, Jamaica, and Brazil, with much smaller amounts from Greece, France, and Hungary. To separate aluminum (pure Al2O3) from the bauxite ore that also contains Fe2O3, SiO2, TiO2, and other minerals, a significant amount of electricity, water, and chemicals (such as limestone (CaCO3) and Caustic Soda (NaOH)) are needed. Separation of the metal Al from Al2O3 is done by means of an electrolytic process that consumes large amounts of electricity. Because of this, the companies producing aluminum had, in the early days, also developed hydroelectric power plants close to the mines. Thus the Tacurai Dam in Brazil sends one-third of its output electricity to aluminum smelters! Because the extraction of aluminum from the alumina (Al2O3) ore requires an enormous amount of electrical energy, the aluminum industry initiated processes to recycle the used aluminum and was one of the first industries to do so. For many other materials, the sequence is not closed: that is, the used product is not processed to get the original material back.

Student Exercise: List the materials in a familiar consumer product such as toaster, clothes, soap, and cleaners. Find the source of the material and where it ends up finally.

Flows in the Case of a Consumer "Material”: Packaging In the previous two cases, and in the material cycles earlier in the unit, we looked at the flows and cycles of materials that occur in nature. A large and diverse group of materials central to the consumer economy of today is all the material that can be categorized as packaging. The amounts and flows of packaging materials are important aspects to consider because of their large effect on the environment. Packaging including cartons, cans, and bottles used for consumer items that are individually small, but contribute to resource use and waste because of the sheer number of units we use. Packaging also has an often overlooked aspect; their centralized production and large distribution systems mean that we transport a large amount of consumer items over long distances, each with its own packaging. Thus transportation involves large expenditures of energy. Packaging includes containers (made of glass, metals, or plastics), one-use containers (paper, plastic bags, cartons, and toothpaste tubes) and wrapping materials (paper, plastic, Aluminum foil). Recycling of packaging materials is very limited in the U.S. In 1993, we used about 310 kg (or 700 lbs.) per person of paper and paperboard for packaging, leading to a total of 80 million metric tons. Europe uses more plastics than paper because of the relative scarcity of land to grow wood.

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As two examples of packaging materials, we now briefly describe the schemes of flow of paper and plastic. Paper and paperboard products are made mostly from wood pulp, and some paper from plant fibers such as cotton, linen, and grasses. Five thousand tons of paper is made per day in the U.S. to satisfy the 700 lbs per person per day demand. In 1996, 45% of post consumer waste paper was recycled, and the industry has set a 50% paper recovery goal.2 Increasingly, the industry in the U.S. is attempting to obtain wood grown on plantations or intensively managed forests rather than use wood from natural forests. Still, some of the tropical forests in South America and South East Asia are being harvested at alarming rates to provide wood for paper. Paper pulping process uses high amounts of electricity and water -- 2000 Kwh and 8000 gallons of water per ton of pulp produced. A large amount of energy is also used when "pulp mats" are dried over hot rolls to become paper. The processing of paper (especially the bleaching) consumes large amounts of chemicals. In particular, several million tons of chlorine are used, which combines with the organic material in the process waste to produce over 1,000 types of organochlorine by-products. About 50 tons of organochlorines are released into water and air by an average size paper mill. Organochlorine byproducts are also concentrated in the sludge, 80% of which is buried in landfill. Environmental damage to plants, aquatic life, and health risks to workers are well-documented effects of paper mill effluents. The byproducts include dioxins, which are both hazardous and bioaccumlative. Health and water pollution concerns have led the paper industry to look into chlorine-free bleaching processes, such as using ozone. Professor Terry Collins of Carnegie Mellon University has developed a new family of bleaching compounds that decompose into water and oxygen. Pollution of the different media -- air, water, and land -- are discussed in the Atmospheric System, in the section on water cycle in this unit, and in the following section on solid and hazardous waste. Rethinking the use of materials using principles of ecology and "closing the circle" (a term used first by Barry Commoner) is the topic of the next section on Industrial Ecology.

Student Exercise: Quantitative LCA • 1. Choose an appliance you use daily. • 2. List as accurately as possible, the materials in the appliance

(excluding energy source). Consider how long you would keep it and what happens to it after you no longer use it. Draw a flow chart of the system of production, use, and the after-use of the appliance. Consider barriers and incentives to recycling the materials.

• 3. Add to the flow chart arrows to indicate energy inputs and water inputs.

• 4. Try to describe as closely as possible the "final" fate of each material. What are the differences from the way they existed originally and their final form?

Industrial Ecology Industry is characterized as an economic activity in which materials are taken in, transformed, and disbursed as products and dispensed of as waste. Over the last two centuries, technology has afforded us many ways of transforming materials so we have new, long-lived materials both as products, and as waste. The natural material cycles described in a previous section are part of our ecosystem. Over billions of years, materials, energy, and life have all evolved to part of a natural ecology. In recent years, environmental problems and resource depletion have led to the rethinking of industrial uses of materials. The previous section gives some details of material use in industry. Whereas it has been customary to dispose of materials at the end of their use, industry (especially in the U.S. and Europe) has begun to move toward a better accounting of material use, to exploring ways of using less energy and materials in production, and how to recycle materials and energy. The scheme of industrial use of materials, which tries to conserve and recycle materials, is called Industrial Ecology. Industrial Ecology represents significant changes of mindset -- or paradigm shift -- from the previous centuries since the Industrial Revolution. Prior to this philosophy, we extracted and disposed of materials from nature as though nature provided us with an inexhaustible supply and as though nature could simply absorb increasingly large quantities of waste materials, some of which could not be degraded by natural processes. The first move was to remove pollutants from the environment or to reduce pollutant emissions rather than to effect whole systemic changes. Resource depletion, air pollution, and the shortage of land and energy led to the first examination by industry of how to recover material from used items rather than keep extracting new material from Earth.

2 "Industrial Environmental Performance Metrics," NAE Press, 1999.

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A short review of Industry from the early economic vantage point and from the new ecological vantage point will give more background to the development of Industrial Ecology, and decision making techniques that have evolved from the new paradigm of Industrial Ecology. Throughout the next sections, Industrial Ecology may be referred to as I.E. Industry as an Ecological System As the environmental objective changed from waste management to pollution prevention, looking at the "ecology" of an industry or group of industries became more common. Graedel and Allenby, (1994) in the first textbook published on Industrial Ecology, write:

"Industrial Ecology is the means by which humanity can deliberately and rationally approach and maintain a desirable carrying capacity, given continued economic, cultural, and technological evolution. The concept requires that an industrial system be viewed not in isolation from its surrounding systems, but in context with them. It is a systems view in which one seeks to optimize the total materials cycle from virgin material, to finished material, to component, to obsolete product, and to ultimate disposal. Factors to be optimized include resources, energy, and capital." (Graedel and Allenby)

The "deliberate," "internal" approach means that we need to understand the underlying science, technology, and decision-making aspects so that each of these can be adjusted and the whole system optimized, not just for performance of the product to meet the needs of the user, but also to minimize the environmental damage caused by the life cycle of the product. The systems approach would help us make a transition from thinking of industry solely as an economic system to a more holistic framing of the industry as an ecology, compatible with the ecology of nature. In the unit on Ethical Systems, we discuss the gradual dawning of the philosophy of Industrial Ecology. The main focus of I.E. is to look at the whole system of production, use and disposal. The major focus of I.E., writes Ayres, is to:

"identify opportunities for reducing wastes and pollution in the materials-intensive sections by exploiting opportunities for using the low-value byproducts (i.e. wastes) of certain processes as raw materials for others. Technical feasibility is the primary criterion for initial consideration." (Ayres 6). This view is an engineering perspective.

A more global approach to Industrial Ecology would be to plan and carry out all industrial and related activities including consumer use, in a way as to minimize environmental harm, to think of ecology as a guiding principle for our economic-technological systems. Very briefly, the principles of nature's ecology are: cycling, a web of interaction and interdependence among parts, stability, and diffuse boundaries. These are discussed in more detail in the Ecological System.

Student Exercise: What do these principles of ecology mean if we are to apply it to a particular industry? Take the example of paper or plastic and outline how that industry could go about applying these principles of nature's ecology.

Figure 19 shows a scheme of the entire industrial - ecological system as represented by Bob Ayres and Kneese in the early 1970's. It is a beautiful representation of this system. It shows the two basic inputs: sunlight incorporated into natural materials through photosynthesis, and minerals from the Earth. Starting with those two inputs, and adding air and water, we get quite a complex system of materials and energy in our industrial society. Note the large amounts of "residuals", or wastes.

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Figure 9: Scheme of Industrial - Ecological System

This flow of materials and energy is called Industrial Metabolism, taking the analogy from biology. "Metabolism" of materials in industry uses energy, labor, capital, and information or knowledge. Putting all these ideas together, we have a new framework for the ecology of industry. In the book Ecology of Industry, Deanna Richards and Robert Frosh introduce this idea with the following statement.

"...industry's ecology is defined by the metabolism of materials (the flow of materials through industrial systems, including their transformations during flow); the use of energy, labor and capital; and the application of information or knowledge. A characteristic of ecological systems is that they evolve. The evolution of industrial systems and their use (and storage) of resources are affected by the introduction of new technologies, decisions made in design, preferences of consumers, regulating dictates, and the like...Indeed "industrial ecology" has become jargon for describing systems of production and consumption networks that have a minimal impact on the environment as a primary objective and have an overarching objective of environmentally sustainable economic expansion."

-Deanna J. Richards and Robert A. Frosch in The Ecology of Industry

Industry as an Economic System Industrial development, especially in the 19th and 20th centuries, assumed an inexhaustible supply of materials, energy, air, and water (the Earth as an endless source). Constant growth in the production of goods was valued and waste production was not even considered a problem. Production measured by the GNP (Gross National Product), or the total value of goods and services produced during a given time period were taken as the indicators of progress, development, and a nation's well-being. Figure 20 shows the societal and industrial attitude toward the use of the Earth for human activities, which led to a loading of air, water, and land by various materials, both toxic and nontoxic.

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Figure20: Scheme of material flow in early Industry.

The sequence of production and use of consumer products generally consists of energy inputs and waste outputs at each stage, with some industries (such as paper production) showing limited energy recovery from waste, and some industries (such as aluminum) showing recycling of materials. Because economic rather than environmental concerns were at the forefront, and gasoline and diesel for transportation was available cheaply, many production facilities were centralized to take advantage of economies of scale. Large factories produced large quantities of material and products, and a highway and rail system network distributed these to points of use. Thus each transportation stage in the Figure 20 consisted of an energy expenditure. Traditional economics has considered an industry, corporation, or business firm as a system, defined by their inputs and products. In this view, inputs are capital, materials (including energy), and labor -- things paid for by the corporation. Outputs are products -- goods and services the corporation produces. In this view, a view of what the corporation had to account for in its expenditures, waste and byproducts (especially pollution) were considered externalities -- "external" to the system, since the corporation did not have to pay for it. This myopic view led to behaviors such as discarding waste materials into air, land, and water without much thought. The U.S. Environmental Protection Agency, created in 1970 by the National Environmental Protection Act of 1969, forced industries to consider their waste streams as something they would have to pay for and add to their list of expenditures or inputs. This began to "internalize" some of the externalities. Pollution became a "cost" to the corporation, because it would have to pay for remediation and disposal of waste and pollution. This expanded the notion of the industrial system to include waste management at the site of production. It took a while for this notion to extend to "wastes" like the overburdening left at coal mines, land use, and other "costs" to the environment and risks to the health (of people and of nature) such as loss of biodiversity or incident of chronic disease. The burdening of land, air, and water, especially near large population centers such as cities or large industrial zones led to shortages of land and pollution of air and water. With some of the waste material and emissions being toxic, the nineteenth and twentieth centuries began seeing new "plagues" such as black lung, asbestosis, emphysema, various forms of cancer, hormone disruptions, nervous system effects, and reproductive effects. It is a well known fact that lead paint has had detrimental effects on children, but it wasn't until the 1980's that exposure to lead in the air from gasoline was proven to caused IQ deficits in children. [Needleman] The high cost of caring for these new plagues and health related problems generated interest in Industrial Ecology by many unrelated industries. It is now starting to hit home that health care providers must pay the costs of injured or ill workers due to toxic exposure to pollution. Resource depletion, air pollution, and the shortage of land and energy led to the first examination by industry of how to recover material from used items rather than continuing to extract new material from Earth. The 1970's also saw "embedded energy analysis", a technique to see how much energy was used in our activities including product manufacture and use. A closer look at "life cycle of products" began in the mid-1980's. Figure 21 shows a slightly altered scheme of production that began to emerge, with some attempts at material recovery.

Figure 21: Life Cycle of Durable Products into Recycling of Material

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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. 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 22 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 22: Flowchart of materials in the automotive industry. Reprinted with the permission of Cambridge University Press.

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 and often-cited example 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 all utilize material wastes from one another. Refined 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.

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Figure23: 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 "Three R'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. The United States "consumed" more minerals between 1940 and 1976 than did all humanity up to 1940. (http://www.zpg.org/Communications/earthday/Demo.pdf) The industrial ecology approach can be illustrated by a waste management system such as manufacturing 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 24: Sewage Treatment System

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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 (http://www.recyclenow.org/sonomax/), listing available and wanted local materials 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," write Ditz, Rapanakia, and Banks in their book, Green Ledgers. 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. In 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 25 shows the representation in Ditz et al. of how the boundary of the private costs to industry is 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 25: 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 26a depicts the stages in a product life cycle. Figure 26b outlines a flow chart representing the same stages. As discussed in the section on industrial uses of materials, these life "cycles" historically have not really been cycles but linear changes.

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Figure 26a: Stages in a Product Life Cycle

Figure 26b: 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, an 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 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. An 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 data 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

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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 an LCA.

1. Life Cycle Inventory: Figure 27 from the SETAC report shows the scheme of inputs and outputs for an 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 27: Life Cycle Stages Reprinted with permission from The Ecology of Industry: Sectors and Linages.

Copyright 1998 by the National Academy of Sciences. Courtesy 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.

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• 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 "zero 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 its 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 28. Note that this is just a representation to provide one way of depicting inventory and impact for an LCA.

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Figure 28: 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. 3) Life Cycle Improvement Analysis:

Green Design: Doing an LCA and its use in Decision Making Green Design may 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 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

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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. The student exercise on LCA is an example of how, despite the uncertainties, an 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 Matrix (Figure 29) has been suggested by Laudise and Gaedel as a formulation for doing an evaluation. Each square of the Figure 29 would have a checklist from which an impact analysis as in Figure 28 could be done.

Figure 29: Environmentally Responsible Product Assessment Matrick

Reprinted with permission from The Ecology of Industry: Sectors and Linkages. Copyright 1998 by the National Academy of Sciences.

Courtesy 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 electronic 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 DFE are discussed by Hutchinson, et al. in Green Design.

Finally, we provide two examples to illustrate some of the ideas discussed above. Table 4 is an inventory of the major raw materials, products, and product uses of the chemical industry as a whole. The graphs in Figure 30 provide an example of

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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

Air Oil

Coal Wood

Energy Sulfur

Minerals Seawater

Natural Gas

Products

Acids Nylon

Alcohols Pigments/dyes

Benzene Polyester

Caustic soda Polyethylene

Esters Polyvinylchloride

Ethylene Solvents

Fibers Synthetic rubber

Xylene

Product End Users

Adhesives Food ingredients Pharmaceuticals

Automobiles Fuel additives Piping

Boats Household materials Preservatives

Carpets Insulation Roofing

Computers Packaging Safety glass

Construction materials Paint and coatings Soaps and detergents

Containers Paper Sports equipment

Cosmetics Personal Care Textiles

Fertilizers Pesticides Toys

Tires

Table 5: 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. Courtesy of the National Academy Press, Washington, D.C.

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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 30: environmental profile of a computer workstation

Conclusions Figure 31 from Frosch and Richards provides an overview of the progress being made by industry in environmental design and management. As discussed in 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.

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Figure 31: Industry's environmental design and management learning curve Reprinted with permission from Industrial Environmental Performance Metrics

Copyright 1998 by the National Academy of Sciences. Courtesy of the National Academy Press, Washington, D.C.