Short note for today

Yesterday I purchased Lester Brown's "Plan B 3.0", and quickly realized that his book covers a lot of the same material as my book. However, his emphasis is on society, failing states and the potential collapse of modern civilization. Much more of his book is dedicated to Response (Plan B) than understanding the problems, i.e., he is more focused on policy change than on science. Also, he does not use equations or charts in his book. So I think our books will complement each other. My book focuses less on government and policy than Brown's because I think that the system is broken, and the only way we can affect change is to work outside the system. Perhaps power is centralized in an ascending state but becomes decentralized in a declining state. The approach to change that I am advocating is decentralized - it depends on individuals changing their lifestyles. The U.S. government is beholden to corporate interests and addicted to economic growth, so I believe it will never institutionalize the necessary changes.

Check out today's new blog "Reduce Your Waste".  Also, I forgot to mention in my consumption/consumerism blog yesterday that a good online video to watch (20 minutes), if a bit liberal biased, is "The Story of Stuff" by Annie Leonard. Note: Tomorrow I will be a faculty marshall at commencement, so there will be no blog entry.

Reduce Your Waste

In 1990 U.S. citizens generated over 4 pounds of solid waste per day, or over 1500 pounds per year. Individuals in most other developed countries generate only half that amount. Over 39% of municipal solid waste is paper, something we can easily reduce. Most communities dispose of solid waste in sanitary landfills by dumping it on the ground and covering it each night with a fresh layer of soil. Rainwater can infiltrate the waste and dissolve material to form a “leachate” solution, so modern landfills have liners and leachate collection systems that prevent the leachate from contaminating the underlying groundwater. However, unregulated and pre-regulation landfills have extensively contaminated groundwater aquifers. There are about 3,000 landfills in the U.S.. Most people don’t want a landfill sited near their home, an example of the NIMBY (Not In My Back Yard) syndrome. Also, because expansion of urban centers and overall population growth make it difficult to find suitable locations for landfills, the number of landfills and the capacity of landfills in the U.S. have been decreasing, and some cities are finding it hard to find places that can accept their waste. The most famous example was of a garbage barge that in 1987 could not find a facility to accept their waste, and after traveling over 5,000 miles over 112 days it finally unloaded its waste at an incinerator in Brooklyn, New York (http://www.nytimes.com/1987/07/11/nyregion/trash-barge-to-end-trip-in-brooklyn.html).

Two alternative approaches are to recycle and to incinerate waste. Until 2007, the city of Nashville burned their garbage and used the released energy to heat and cool metro buildings downtown. However, the smell of the garbage, the increasing value of the riverside property that the incinerator was located on, and the fear that the incinerator released heavy metals from its’ smokestack, led the city to close the operation.

Your effort to reduce waste must start at the beginning, when you are in the purchasing phase [1]. First, don’t buy a product unless you need it. Never buy disposable products or junk that will need to be replaced frequently. Next, buy products with minimal packaging, avoiding those that are “individually wrapped”.

Choose products that are made from recyclable materials, not plastics that can’t be recycled . When possible, buy products with provisions for returning or recycling the used product. Always remember to bring your reusable bags when you go shopping, and place fruit and vegetables directly in the bag rather than using the plastic bags in the produce department. Save some trees and use less paper: don’t subscribe to newspapers or magazines, since most of the information they contain can be obtained online. This semester I taught a class on Sustainability, and we went almost completely paperless (e.g., term papers were turned in, graded, and returned electronically). When you use paper in the office, always print double-sided, or reuse paper that has been printed on only one side.

The mantra for reducing waste is the 3 R’s: Reduce, Reuse, and Recycle, in that order (http://en.wikipedia.org/wiki/Waste_hierarchy). It’s best to reduce by consuming less. For example, I run a chemical laboratory at Vanderbilt University. We used to buy chemicals in bulk to reduce the cost per unit volume. However, we rarely ended up using all of the chemicals. When labs are closed down (when Professors retire), large amounts of chemicals, some hazardous, must be disposed of at great expense. When you consider that the environment was degraded twice, both in the production and disposal of the waste, and the fact that the chemicals were never used, it all seems very wasteful. Now we buy small quantities of chemicals, and purchase replacements when needed.

There are numerous references that give ideas on how to reuse and repurpose materials. For example, Jeffery et al. [1] suggests that we reuse plastic bags after washing, use empty glass jars as storage containers (it’s nice to see what’s inside a container without opening it), shop at second-hand clothing and book stores, and reuse wrapping paper. Reusing and repurposing items is also an opportunity for you to think “outside the box” and be creative. I personally always reuse disposable paper and plastic shopping bags. I store recyclables in the paper bags until they become unusable, and line garbage cans with the plastic bags. We forgo our reusable shopping bags only when we run out of disposable paper or plastic shopping bags. We donate our used clothes to Goodwill unless they are in bad shape, in which case we cut them up and use them as rags. Though I love books, I now avoid purchasing them, and instead sign them out of the library to save both money and paper.

Many charities accept used goods for reuse. This year we donated a computer to the National Christina Foundation. I personally found it rewarding to fix the computer up and then drop it off at a school for children from low-income families. Goodwill accepts many types of items and resells them in their stores. We have donated furniture and electronics to Amvets, and many charitable organizations are in need of used cars – you can claim a nice tax deduction for donating an old car instead of taking it to the dump.

Recycling is often the first concept that comes to mind when people discuss green living. That’s because we can recycle without really changing our lifestyle, so it is comparatively easy. Just throw the item in a recycle bin rather than a trash can. However, not everything can be recycled, especially when we consider cost. Moreover, not everything needs to be recycled, as I will now demonstrate. Students in my Sustainability class were upset when they learned that Vanderbilt recycles paper, plastic, and aluminum, but not glass. That got us talking about reasons for and costs of recycling. I noted that glass is a harmless material that is costly to recycle. Glass is made by melting beach sand containing silicate minerals like quartz (SiO₂). The sand melts over a range of temperatures, and isn’t completely molten until temperatures of around 1200°C (this temperature is lowered by addition of fluxes such as lime CaO, soda Na₂O, and sometimes Borate B₂O₃). To heat it to such high temperatures requires a lot of energy. It takes a lot of energy to remelt the glass during recycling, and because glass is relatively inert and won’t cause environmental damage when disposed of in a landfill, forgoing recycling was not as evil as they perceived. On the other hand, glass recycling uses less energy than manufacturing glass from sand, saving 315 kg of CO₂ for every ton of waste glass recycled (http://en.wikipedia.org/wiki/Glass_recycling), so recycling glass is still preferable. The best option is to reuse the glass, so it doesn’t have to be remelted.

The material that saves the most energy by recycling is aluminum. Aluminum ore is called bauxite, and it contains aluminum oxides that must be converted to metal. This means the Al³⁺ in the oxide must be reduced to metallic Al⁰ by adding three electrons, which requires a lot of energy because Aluminum prefers to be in the +3 state. This also means that Al metal will oxidize when in contact with oxygen in the atmosphere, but fortunately the process is very slow. Al metal has a very low melting temperature, so it takes a lot less energy to recycle the aluminum by heating and melting it than it would to mine more bauxite and convert the oxide to the metal.

The other thing to keep in mind is that it only makes sense to recycle materials when there is a market for the recycled product. For example, recycled paper is generally inferior to first-use paper, so different uses must be found for it. Fortunately, clever people are thinking of many new uses for reused and recycled products.

Whenever you are about to throw something in the garbage, think about whether that item can be reused or recycled. Repair it, or find someone who could use it, perhaps by selling it on eBay. Consider whether the waste is hazardous, which would require special disposal (we will discuss this in the next section). Don't just throw it in the garbage without thinking!

1. Jeffery, Y., L. Barclay, and M. Grosvenor, Green Living for Dummies. 2008: For Dummies.

Change the Way You Live: Sustainable Living

"The diligent farmer plants trees, of which he himself will never see the fruit." — Cicero

You go into a community and they will vote 80 percent to 20 percent in favor of a tougher Clean Air Act, but if you ask them to devote 20 minutes a year to having their car emissions inspected, they will vote 80 to 20 against it.  We are a long way in this country from taking individual responsibility for the environmental problem.  -William D. Ruckelshaus, former EPA administrator, New York Times, 30 November 1988

The activist is not the man who says the river is dirty.  The activist is the man who cleans up the river.  -Ross Perot

Materialism is widespread in our culture. It is perhaps the most important social force in our society. It drives our economy, fuels our desires, and preoccupies our minds. Americans are addicted to shopping and self-indulgence. We continue to spend even when we don’t have any money, which is part of the reason why our country is now in the throes of an economic crisis (another reason is that we are bumping up against the physical limits to growth where our demand (ecological footprint) exceeds the supply (biocapacity)). That we continue to purchase products that we don’t need and can’t afford, when we buy them when we know we shouldn’t, when the anxiety caused by accumulating financial debt does not prevent us from purchasing more, then we have an addiction, a disease of the mind. The symptoms are an uncontrolled compulsion to shop and purchase items and the habit of “going shopping” whenever we have free time even when we don’t need anything. There is also a buildup of tolerance to the pleasure of shopping but decreasing satisfaction with continuing purchases, so we must buy more to get the same “high”, a sure sign of addiction. The following sections contain prescriptions to the disease of consumerism. Many of these prescriptions are common sense, and they don’t require the knowledge of a scientist to explain or elaborate. However, I am reminded of the numerous books and magazines sold daily that tell the reader how to lose weight. The answer is obvious (stop eating!), but sometimes we need encouragement. Also, I would argue that here we are dealing with a much larger problem than obesity, and unlike obesity there is more than one way to reduce the problem.

How Should I Start Living Sustainably?

We have to shift our emphasis from economic efficiency and materialism towards a sustainable quality of life and to healing of our society, of our people and our ecological systems.  -Janet Holmes à Court

Reduce Your Consumption

We’ve reviewed a lot of evidence that consumption has the biggest impact on the environment. I hope it has convinced you to change your lifestyle. But how? What changes will have the greatest effect? To reduce consumption requires changing the way you think and how you spend your time, which is not easy. So be patient, and take small steps. Don’t get frustrated. It will probably take a few years of effort before you become satisfied. Start small, or start with the “low-hanging fruit”, the easy changes that have a big impact.

First, you must divorce yourself from materialism. Look around your home. How much do you own? How much of it do you really need? When looking at past and potential purchases, ask yourself if you would be less happy if you didn’t own it. If you are still tempted to make an unwise purchase, remind yourself that it is unsustainable, and picture what it will look like in a landfill a few years in the future. Remind yourself that the peace of mind you gain from keeping that money in the bank, or avoiding another credit card purchase you can’t afford, is worth more than the item. Pat yourself on the back for not letting advertisers manipulate your behavior. If you stop and think this way before making any purchase, you will avoid the trap of impulse buying that comes naturally in a materialistic world.

When trying to reduce consumption, one of the easiest guidelines to remember is to avoid disposable products. I’ve followed this guideline for most of my life, because it always seemed so obvious to me: products are designed to be disposable so that we will spend much more money continuously replacing them. Disposable products may seem more convenient, but often they are marginally so, and using them generates huge amounts of waste. Water bottles have become a symbol of our wasteful society, and rightly so. It’s so easy to avoid using disposable water bottles: buy a BPA-free water bottle, carry it with you wherever you go, refill it for free, and wash it every day. You can save yourself lots of money by doing this.

It’s useful to keep in mind that corporations always try to sell as much product as possible. They do this by convincing you through advertising that you need something that you don’t really need. There are endless examples of ways that advertisers try to get consumers to consume more, e.g., Taco Bell serves a "4th meal", and movie theaters have increased the size of their drinks to the point that they no longer fit in the drinkholders, both obvious examples of why America has an obesity epidemic – we are victims of advertising. Some advertisers suggest that you can’t be happy without their product; for example, Best Buys motto is: "You. Happy."

Another way that corporations get you to buy more is through the use of planned and perceived obsolescence. Everyone born before the 1970’s has the perception that the quality of products has declined, and that products are now designed to be disposable. I remember that my grandfather spent a lot of his time fixing things, and as a result, he seldom had to purchase replacements. In fact, I still have some of my grandfather’s tools, which are now between 50 and 100 years old. How many of today’s products last that long? Few do because most products now are designed with planned obsolescence in mind. Again, the goal of the manufacturer is to get you to buy as much of their product as possible, so they design the product to fail after a planned amount of time, usually just after the warranty lapses. In fact, most consumers now accept that they will have to buy a replacement shortly after the warranty expires, but it wasn’t like that in the past. My parents and grandparents each owned only one vacuum in their lifetimes, but today people frequently replace their vacuums after only one or two years of service. The vacuums are made so cheaply that they are not even worth repairing. Do you remember TV and appliance repair shops? You almost never see them now, because it usually is more expensive to repair a product than to replace it. Now the old product goes into the landfill as waste, and we waste more time shopping for and more money purchasing replacements.

Corporations and advertisers also rely on perceived obsolescence when they try to convince you to replace a product that still works perfectly well. By emphasizing a fancy feature in each new version of a product, usually a feature that you are unlikely to use and definitely don’t need, they convince you to buy replacements on a regular basis. This strategy has always worked well for car sales, but it works even better for new electronic devices that perform better tricks every year. I know people who buy annual upgrades of products such as the IPod nano or the IPhone because Apple is so remarkably good at marketing. I personally am a technophile, so I enjoy playing with gadgets and figuring out how to use all of their features (I even read the manuals!), but I still use less than half of the features bundled in most of my electronic gadgets. Yes, I am tempted to buy the newest versions of these products, but I know I don’t need them. From my experience, the constant upgrading is time-consuming and expensive, and I have more enjoyable and less expensive things to do. To convince myself not to buy them, I find the best strategy is to remind myself how much time it will take to figure out how to use them and to configure them properly. I now strive to simplify my life and eliminate clutter, a topic to which we will return.

Sometimes it’s not easy identifying the cheaply made junk. A good source of information on product reliability is the magazine Consumer Reports. Over time, you will learn which brands and countries sell junk, and which make reliable products. My grandfather used to say decades ago that anything marked “made in China” was junk, and that may be even truer today (and we now know that they frequently make their products using materials that are bad for our health).

Besides avoiding purchases of disposable products and junk that is designed to break, and repairing rather than replacing, you should try to purchase products that are made from renewable resources and that are made locally (to reduce carbon emissions from transportation and to help your local economy). Always keep in mind that your goal is to reduce your footprint. Does your footprint look like that of an elephant, or of a mouse? Stop living so large!

Is Our Current Lifestyle Unsustainable?

Human population is estimated to increase from 6 to 9 billion by 2050, but humans already use over half of accessible runoff and about 40% of plant growth for the energy stored in plants by photosynthesis [1]. We have created large holes in the ozone layer and increased the concentration of CO2 in the atmosphere by more than a third. The rate of species extinctions is growing exponentially (we are actually in the midst of earth's 5th mass extinction event, primarily caused by humans), and the percentage of fisheries fully exploited is nearly 80%. How many humans can Earth support? In this chapter, we look at sustainability as a balance between ecological resource supply and demand.

The ecological footprint is a measure of your resource demand. It is an attempt to estimate how much of earth’s resources you consume, and how much of an impact you have on the environment. There are many ways of calculating the size of your footprint, as you will find if you search the Internet for ecological footprint calculators. One way to express the size of a footprint is as the number of Earths that would be required to support the world’s population if all humans consumed resources at the same rate, i.e., the global ecological footprint. One problem with this approach is that the number of Earths then depends on the global population, which is exponentially increasing. It is thus a moving target. In spite of this problem, it is still a useful way to compare qualitatively the environmental impact of different lifestyles. Another more accurate method is to estimate the area of earth and sea that are required to support an individual’s lifestyle by regenerating renewable resources and absorbing wastes. If measured in productive land area, the global ecological footprint in acres per capita is 6.8, while citizens of the U.S. require 23.5 [2]. I like to think that I could sustain my family of four on our relatively large suburban yard of 1 acre, but to live like average U.S. citizens we would need 4*23.5 = 94 acres!

The concept of the ecological footprint is clearly Malthusian. It assumes that there is a fixed amount of resources available. It raises an important question: What is the carrying capacity of the Earth, the number of humans that Earth can support sustainably? Estimates range between 4 and 10 billion, depending on the average environmental impact of humans [3]. Remember that I = P*C*T. Assuming T is equal to one (*elsewhere we will debate whether T is smaller or greater than one, i.e., whether technology increases or decreases our environmental impact), then one Earth can sustainably withstand a maximum level of human impact Imax = P*C. If we reduce consumption C, we can increase population P and still maintain the equality. If all humans minimized C by becoming vegetarians and we farmed all arable land, then the maximum population that Earth could support Pmax = Imax/Cmin = 10 billion people. However, currently our consumption rate is closer to Cmax, and in this case Pmin = Imax/Cmax is about 4 billion. The current global population is 6 billion. According to the Living Planet Report 2008 [2], the current global ecological footprint of that 6 billion people is 1.3 planet Earths (See Fig. Global ecological footprint from [2]). This means that humanity uses ecological services 1.3 times faster than Earth can renew them. We are in “ecological overshoot”, i.e., our population and impact have grown so much that the earth can no longer support us sustainably. In order to live sustainably, humanity must reduce its total ecological footprint to one earth, either by reducing consumption or population. We can choose now to reduce consumption, but if we don’t act then eventually nature will make the choice for us and without mercy, and global population will decrease until it reaches a sustainable level.

The maximum amount of ecological services and resources that Earth can provide is termed the biocapacity. It is a measure of supply, expressed as the amount of land available for production per capita. The global biocapacity is -0.6 hectares per capita, again indicating that we have a global ecological overshoot (see Fig. Footprint and Biocapacity factors that influence overshoot from [2]). For the U.S. it is -4.4 hectares per capita [2], which explains why the U.S. has to import so many goods. Our use of ecosystem services and resources is sustainable when we demand less than the Earth can supply, i.e., when the global ecological footprint equals or is less than the global biocapacity. Unfortunately, the footprint now exceeds the biocapacity, and the gap between the two is increasing. The Figure Ecological footprint Biocapacity Overshoot [2] illustrates an optimistic scenario in which we act quickly to close the gap between supply and demand. In the unsustainable situation when demand is greater than supply, as it is now, we build up an ecological debt. If we decrease the demand until it is less than the supply, then we can build up a reserve.

Cornucopianists argue that advances in technology could make the term T in I = P*C*T vanishingly small, so that both population and consumption are relatively unconstrained. To understand their reasoning I give the following quote from Edward O. Wilson’s Consilience, in which Wilson uses the term “Exemptionalist” synonymously with Cornucopianist: “Of course the exemptionalists will say that new technology and the rising tide of the free-market economy can solve the problem. The solution, they explain, is straightforward: Just use more land, fertilizer, and high-yield crops, and work harder to improve distribution. And, of course, encourage more education, technology transfer, and free trade. Oh, and discourage ethnic strife and political corruption. All that will certainly help, and should have high priority, but it cannot solve the main problem, which is the finite resources of planet Earth. It is true that only 11 percent of the world’s land surface is under cultivation. But that already includes the most arable part. The bulk of the remaining 89 percent has limited use, or none at all.” [3]

1. Speth, J.G., The Bridge at the Edge of the World: Capitalism, the Environment, and Crossing from Crisis to Sustainability. 2008, New Haven, CT: Yale University Press. 295.

2. Hails, C., ed. Living Planet Report. 2008, WWF, ZSL, and the Global Footprint Network. 48. http://www.footprintnetwork.org/download.php?id=505

3. Wilson, E.O., Consilience: The Unity of Knowledge. 1998, New York, NY: Vintage Books. 367.

Case study: DuPont Plant, New Johnsonville, TN

For a number of years I took students in my graduate course Aqueous Geochemistry to tour the DuPont Plant in New Johnsonville, TN, about two hours west of Nashville. The plant manufactures Titanium Dioxide TiO₂ by mining the mineral ilmenite FeTiO₃ and reacting it Hydrochloric acid HCl as follows: FeTiO₃ + 2HCl = FeCl₂ (aq) + TiO₂ + H₂O. The Titanium dioxide is a pigment that gives Kilz paint, Oreos, and many types of toothpaste their brilliant white color. There are two problems with this process. One is that the product solution is still very acidic. The other problem is that ilmenite contains many toxic heavy metals that are soluble in the acidic solution. In the 1960’s when people didn’t know better, DuPont was allowed to dispose of hundreds of thousands of gallons of this toxic acid solution directly into the Tennessee River, which of course killed all fish and bottom feeders downstream. Later they switched to the more environmentally friendly but more expensive process of deep-well injection. They drilled wells between 1000-2000 feet deep and then pumped the acidic waste into a confined, deep limestone layer. The thinking was that the limestone (which contains calcite CaCO₃ and dolomite CaMg(CO₃)₂) would neutralize the acid: CaCO₃ + 2H⁺ = Ca²⁺ + H₂O + CO₂. The confining (impermeable) layer above would keep the waste isolated from shallow aquifers that supplied drinking water. Once again, there were two problems with this plan, which my class would remind the DuPont engineers of every year, and every year they would claim ignorance. First, the acidic solution dissolves the limestone, which results in the formation of large caves deep underground. Eventually the weight of the overlying rock layers causes them to collapse, breaking into pieces, falling, and filling the caves. This shatters the confining layer and makes it permeable, so that the wastes can rise up into the aquifers. The other problem is that, as shown in the reaction, limestone dissolution produces CO₂ gas, and the pressure of that gas can build until it shatters the overlying rock and escapes. Either way, it seemed likely that the confining layer would eventually be compromised. So, to their credit, DuPont came up with a new solution that was even more environmentally friendly but (they claimed) even more expensive. Since around the year 2000 DuPont has been reacting the ilmenite with sodium carbonate, and according to the DuPont engineers the only by-product is harmless FeCO₃ (the mineral siderite), which is used to make bricks for construction. However, recently it was learned that this process produces dioxin as a by-product. Pure Dioxin is the strongest poison known to man (it is the neurotoxin in Agent Orange), and the New Johnsonville Plant is the fourth-largest producer of dioxin in the U.S..

This case study illustrates many different points. First, it is difficult to anticipate all of the potential outcomes of a complex industrial process. That is why ecologists advocate the precautionary principle. Second, industrial chemistry sorely needs to be “greened”. Green chemistry is a field just now coming into its own, and it has the potential to reduce greatly the environmental impact of the chemical industry. Third, despite repeated attempts at trying to “green” the chemical process, the production of Titanium Dioxide still causes serious environmental problems. DuPont is being sued by numerous plaintiffs who live near or work at their Titanium Dioxide plant in DeLisle, Mississippi, who claim that dioxin has seriously damaged their health or caused the death of loved ones (http://video.google.com/videoplay?docid=-7693391300780002092). At New Johnsonville, TN, many citizens are afraid to talk about the health risks posed by the DuPont plant because they work for the plant, their livelihood depends on its success, and they fear retaliation (http://www.dupontsafetyrevealed.org/newjohnsonville.htm). This raises many questions: Should we allow chemical companies to manufacture goods like Titanium Dioxide that are nonessential (it is simply used for aesthetic reasons) but that cause great harm to human health and the environment? Or should we close the plants, even if it meant that thousands of people would lose their jobs? The plants in New Johnsonville DeLisle are by far the largest local employers, so closing them would be an economic disaster for those communities. In fact, years ago when DuPont reapplied to the State of Tennessee for a permit for deep well injection, a representative of the Tennessee Environmental Council asked me if I would testify against the application. I refused, saying that deep well injection seemed to be the best of the alternatives known at the time, and that I couldn’t bear the thought of helping to put all of those people in New Johnsonville out of work. Yes, I am pro-environment, so I believe we should always be looking for ways to protect the environment, but the overall benefits of change have to outweigh the overall negatives, and in this case, the economic vitality of New Johnsonville seemed to me to outweigh the potential risks of deep-well injection.

Environmental Risk

Here’s an example of how knowledge can sometimes make life more difficult. In the morning, I am often confronted with the question of whether to empty the water out of the teapot and refill it with fresh water. It seems wasteful to dump the water in the pot down the drain, and furthermore that water has degassed its fluorine (although all fluorine probably degasses during boiling anyway). However, the water may have leached heavy metals from the pot while in contact with it for several days, or perhaps bacteria have begun to grow in the water. Also, I am impatient, and prefer to fill the pot with hot water so it takes less time to boil. So I dump the water out and then run the tap water for one minute before filling the pot because water standing in our pipes overnight may have leached metals from our pipes (this is unlikely to be a problem for us, though, because the practice is designed to avoid lead that leaches from solder that connects Copper pipes, and most of our pipes are galvanized steel). Is it better to save energy by using the water already heated in my hot water heater rather than heating cold water on my stove until it boils? Or is it better to save water by not running it until the water gets hot, which in my house takes roughly one minute? There are so many considerations that go into making such a simple decision, that complex decisions can seem overwhelming. Am I overanalyzing every situation? Wouldn’t life be simpler if I always did what was easiest, but perhaps at a slightly higher level of risk? Are the perceived dangers great enough to warrant my concern? Won’t I become unhappy if I have to assess a list of threats for every decision I make? Thinking about the world this way does make it seem to be a dangerous place.

The best approach to this problem of “too much information” is to only concern yourself with the greatest potential threats. The problem is that human perception of risk in the modern world is notoriously inaccurate. Stone Age humans faced essentially the same risks that their ancestors faced may thousands of years previously. Natural selection caused humans to evolve, preparing them to better deal with these risks and reducing their chances of succumbing to those risks. Also, they could pass on survival strategies orally from generation to generation. My guess is that Stone Age humans’ perception of risks in their environment was largely accurate. However, our society and environment is now changing so rapidly that evolution does not have time to prepare us for the many new risks we are faced with. Furthermore, the risks our generation faces are different from the risks faced by our parents, so the wisdom they impart to us is not sufficient, and we have to rely on other sources of information to adequately deal with these new risks. In this new world, how well do our new coping strategies prepare us for risk? Not very well. A famous study published in Science (*v. 236, 1987) examined the perception of risk by groups such as college students and The League of Women Voters. They were asked to rank risk associated with twenty different activities. Their rankings were then compared with the actual risks, defined as the mortality rate for that activity (number of deaths per year associated with that activity, probably normalized to the number of people participating in that activity *check). These two groups rated “nuclear power” as the highest risk, when in reality it was the lowest risk. Studies like this have led to several generalizations about risk perception:

1. We are genetically predisposed to worry about risks, because worrying about risk increases our chances of survival. However, it is possible to worry too much.

2. We tend to overestimate the risk associated with high-impact, low probability events (e.g., nuclear power plant disasters)

3. Man-made risks worry us more than natural ones (e.g., radiation from power lines & cell phones are less dangerous than radiation from the sun)

4. New (unfamiliar) risks worry us more than old risks.

A good example of point 2 is air travel. Many people are so afraid of traveling on airplanes that they refuse to fly. However, per mile traveled, the risk of dying in an automobile is much greater than in an airplane.

So what are the risks associated with global warming, peak oil, and water pollution? We will examine that question in the following chapters.

The Behavior of Water Pollutants

In their textbook "Ecological Economics" (2004), Herman Daly and Joshua Farley say that the limits to human population growth may lie not in resource depletion, but in the waste absorption capacity of the environment. This can be understood with the following analogy. Water purification filters usually contain a resin that turns color when it becomes saturated, i.e., it cannot absorb any more pollutants. The interface between the two colors of resin (the reaction front) will migrate through the column from the inlet towards the outlet. Water flowing from the outlet will be purified until the interface reaches the end of the column, at which point the column resin is saturated in pollutants and cannot absorb any more. From that time on the outlet water will be just as polluted as the input water. In this case, the waste absorption capacity of the filter has been exceeded. Our environment acts as a filter, purifying water that passes through it, but eventually the filter will become saturated.

Let’s examine this in a little more detail. What happens when the concentration of a pollutant in a sediment-water system (lake or stream) keeps increasing? Examine langmuir 10-007. Imagine that we pour uranium U into a beaker containing water and sediment. Some of the U will dissolve in the solution, but some will adsorb onto the surface of mineral grains in the sediment. At first the proportions of U in solution and adsorbed to sediment will be constant as the total U concentration increases (move along a straight line away from the origin). As concentrations get higher the number of available sites for U to sorb onto mineral surfaces begins to decrease, and a greater proportion of U enters the fluid, causing the adsorption isotherm to level off and approach a slope of zero when the adsorption sites become “saturated”. Eventually even the solution becomes saturated, i.e., it can’t dissolve any more U. What happens then? Any additional U added to the system will precipitate out as a U-rich mineral (in this case Schoepite) that is added to the sediment and therefore causes the sediment concentration of uranium to begin increasing again. Note that as long as the solutions remains saturated in Schoepite, any additional U we add will go into the sediment, increasing the U concentration in the sediment. Conversely, no matter how much additional U we add, the concentration of U in the solution is fixed at its highest possible concentration. In this case, we have saturated our filter.

Let’s look at some slightly more complicated models in which the sediment but not the solution becomes saturated. Polluted water enters a beaker with sediment, equilibrates with the sediment, and then is replaced with another batch of polluted water. At first, a large proportion of the pollutant will sorb onto the sediment, causing the concentration in the solution to decrease substantially. As more batches of polluted water equilibrate with the sediment, the concentration of pollutant in the sediment will increase, and therefore the concentration of pollutant in the water that exits the beaker will increase in direct proportion. As the sediment approaches “saturation”, it can sorb less pollutant, so most of the pollutant remains in solution, and our sediment filter become increasingly ineffective.

What if we stop polluting? Can the system recover? Start adding batches of fresh water. You would observe that the water that exits the beaker would at first have high concentrations of pollutant because our sediment filter was saturated in pollutants. But with time, the concentration of pollutant in the sediment and in the exiting fluid would decrease and eventually go to zero. Thus, we can “flush” pollutants out of a sediment-water system such as a stream or lake, but it may take a long time and a lot of fresh water to remove all of the pollutant, especially if the pollutant strongly sorbs to the sediment (which is why PCB’s are still in Hudson River sediments after many decades).

Now imagine a reservoir such as a swamp with one stream entering and one stream exiting. If the stream entering the swamp is polluted, sediments near its entrance point will strip pollutants out of solution. With time, a concentration gradient will develop across the swamp, with high pollutant levels near the input stream and low levels near the output stream. As polluted water flows across the swamp, it encounters sediments with decreasing pollutant concentrations, so the concentration of the pollutant in the solution will continuously decrease. The water becomes increasingly pure as it traverses the swamp. In nature, swamps do an excellent job of filtering pollutants from water. However, if pollutants continue to enter the swamp, the total pollutant concentration in the swamp will keep increasing. Eventually sediments near the input stream will become saturated, and that “saturation front” will slowly migrate across the swamp until it reaches the output stream. At that point the entire swamp system has become saturated, and the output water will be just as polluted as the input water. As in our beaker example, if we stop polluting and the water in the input stream becomes pure again, then over time the process will be reversed, and the pollutants will slowly be flushed out of the swamp.