Class Session 21>
Welcome to week twelve. If you remember from previous notes, environmental impact is a function of population, consumption and technology. So far in the class, we’ve looked at consumption of biomass, chemical, energy, and land. In this week’s notes, we’ll focus on materials. Materials are everywhere. If you look around at where you are now sitting, you’ll probably see wood, glass, metal, plastic and a whole range of synthetic and composite materials. But where does all this stuff come from? Where does it go when we throw it out? Are their ways that we could be smarter about how we use materials?
It’s really tough to get a handle on all the different kinds of materials and what they’re used for, much less the types of environmental impacts that result from their use. Nonetheless, let’s try and get a handle on types of materials, consumption, environmental impact, and alternatives. Let’s begin by looking at the major types of materials.
For starters, materials can be divided into two major categories, non-renewable and renewable. Non-renewable materials are those for which there is a finite amount. Once they’re “harvested” or extracted, that’s it. There aren’t any more coming for a long, long time. Non-renewable materials include metals, industrial minerals, construction materials, and non-renewable organics.
Renewable materials are materials that can regenerate themselves. These include agricultural products, wood products and primary paper. From your readings of Bill McDonough’s work in week six, these are the kinds of materials that are part of the biological nutrient chain. There are grown from nature and can be sustainably harvested and there is no limit to the amount of this material, provided that the basic environmental conditions in which they exist are not destroyed.
II. Material Witness
Let’s now try and understand how
much of these materials we use. To begin with, the
To begin with, both the amount of materials, as well as the type of materials used by Americans changed a lot in the 20th century. In 1900, each American consumed about 2 metric tons of material per year for all uses, roads, transportation devices, houses, and personal belongings. By 1995, the amount of material consumed by each American had increased 500% to ten metric tons per person. Don’t believe it? Find a friend or relative that live in an old house, one that was constructed before or around 1900 and ask them how many closets the house had originally. Many old houses didn’t have any closets at all. Houses built today have large walk in (as well as walk through) closets. This is not a value judgement, but if environmental impact is a function of consumption, we need to look at this and see how consumption levels of materials are impacting our world.
Another way that American material consumption trends changed in the last 100 years is in the type of material consumed. In 1900, about half of all materials consumed were renewable materials such as wood, natural fiber, and agricultural products. By 1995, consumption of renewable materials had decreased to less than 10 percent of the total. Don’t believe it? Go to any antique store and look at the kind of material things were made of. Then go to Walmart. There is a huge difference in way things were made 100 years ago compared to the way they are made today.
The American economy as a whole consumed about 161 million metric tons of material in 1900. In 1995, the economy consumed 2.8 billion metric tons. Further, of all the materials consumed by Americans in the 20th century, more than half were consumed since 1970. So, you see, we are consuming more non-renewable materials.
Now, let’s try and get a handle on environmental impacts. Impacts from material use can occur during extraction of the resource, processing, use of the material, and disposal. Further the level of environmental impact is often associated with the type of material. So, let’s get started and sort through the material, so to speak.
Most of the material
we use, as we said, are non-renewable. So let’s get started there. The most
consumed material in the
The next most abundant material we Americans use are industrial minerals. Industrial minerals are minerals and rocks used in a wide range of manufacturing and other industries. These include cement, potash, phosphate, limestone, gypsum, flourspar, soda ash, sulphur, asbestos, abrasives, silica, talc and salts. Industrial minerals are used in many kinds of industries including paint, electronics, metal casting & foundry, paper, plastics, glass, ceramics, detergents, drugs & cosmetics, construction materials, manufacturing processing and environmental engineering. Industrial minerals account for about 12%, some 330 million metric tons, of our material consumption. Of this amount, about 7% comes from recycled material. Release of industrial mineral as waste residuals totaled 129 million metric tons in 1995. Some commodities in this group are harmful to the environment such as cadmium, asbestos, fertilizers, and road salt.
Next on the list are metals. Metals can be ferrous, meaning that they contain iron or elements alloyed with iron to make steel, or nonferrous, those that contain metallic elements not commonly alloyed with iron. Alloys are mixtures that contain at least one metal element. Steel, for example, is an alloy of iron and carbon. Other alloys include brass and bronze. Some of the better known metals include aluminum, cadmium, chromium, copper, gold, iron, lead, magnesium, manganese, mercury, nickel, platinum, potassium, silver, tin, titanium, tungsten, uranium, and zinc. Metals are used in a wide variety of household, commercial and industrial products including coins, jewelry, musical instruments, plumbing, cars, buildings, medical equipment, wheels, aircraft, kitchen utensils, coatings, tools, and many, many others.
It is important to remember that the use of minerals is inherently different from the use of carbon-based energy sources, which also come from the ground. When petroleum, natural gas, and coal are used, they no longer exist as fuels, and are converted to energy and other substances. They cannot be retrieved and reused for fuel. But when minerals are used, they usually continue to exist, in altered form to be sure, but in most cases the material has not disappeared. What does this mean? Minerals are inherently recyclable. So, why don’t we recycle more construction material? Good question. The answer lies in several places, literally. Certainly the cost of transporting these materials plays a factor. Construction materials are low value per unit of weight, which means that they don’t get transported very far and because they are relatively ubiquitous materials, it’s often easier and cheaper to find local, virgin sources of material than locate and transport used material from somewhere else.
The problem is that mining for
minerals can have substantial environmental impact. To capture the raw
material, metal bearing rock, called "ore", and rock and dirt that
covers the ore must be removed. The rock and dirt that covers ore is called
"overburden" and very little of this material is used. In addition,
great quantities of overburden must be removed and processed to capture the
mineral. For example, to produce a ton of copper requires the removal of over
100 tons of overburden.
Many different types of chemicals are also used by mining operations to separate metals from the ore. These include acid, mercury and cyanide. Once the metals have been removed, the chemical impregnated ore remains behind. This reside is referred to as "tailings". Often, both the overburden and tailings discarded during ore processing are often left near the mine source. When it rains, the material from these waste piles can runoff into waterways.
Tailings are also dumped directly into lakes or rivers or stored in reservoirs that can flood or gradually leach into waterways.Often this material is highly acidic in nature and this runoff affects land surfaces around the mine. These acidic landscapes often can not support plant life and can also result in displacement of animal life, resulting in a relatively sterile environment. Acid mine drainage needs to be prevented or neutralized before it is discharged into the environment. Lands disrupted by surface mining or strip mining operations can be reclaimed and replanted.
The last non-renewable material category are non-renewable organics. Though material which is both organic and non-renewable may seem counter intuitive, remember that what makes a molecule organic is that it contains carbon. Carbon based fuels, such as coal, oil, and natural gas are organic materials that are non-renewable. However, when we are talking about materials, we are not talking about fossil energy for fuel. Rather, coal, oil and natural gas are used for many types of products. Non-renewable organic materials, then, are those which are derived from petroleum, liquefied natural gas, natural gas, and coal but which are used for applications other than energy. These include resins used in the production of plastic, synthetic fibers and textiles, synthetic rubber, solvents, lubricants and waxes, and ashphalt and road oil.
Consumption of nonrenewable organic materials totaled 113 million metric tons, with only 2.7 percent produced from recycled materials. A total of 21 million metric tons was released back into the environment as waste. As for environmental impact, processing and manufacturing of nonrenewable organics can create waste that lead to wastes can create local environmental problems. Of particular concern is plastic. The amount of plastic we use is increasing rapidly and plastic are an increasing problem for landfill. Plastics contain ingredients that may contain toxic constituents such as cadmium and lead, as well as heavy metals. Because only 2 percent of plastics are recycled, virtually all of these materials are landfilled or incinerated.
III. Renewable Materials
Renewable organic materials include:
1. agricultural non-food products such as cotton, wool, and tobacco;
2. wood products such as lumber, plywood, and veneer, and;
3. paper products.
In 1995, Americans consumed 231 million metric tons of renewable organic material. Of this amount, about 8% came from recycled material, most of which was paper. About 80 million metric tons was released as waste back to the environment. Renewable organics can create environmental impacts mostly from paper in the wastestream as well well as pulp processing.
The final material category is
nonfood animal products, such as fishery products like fish meal, leather and
IV. Around the World
Now that we’ve looked at the
As the world’s economies grew between 1975 and 1996, the amount of material used rose relatively little overall, on a per person basis. As the world’s population increased from a shade under 4 billion in 1976 to 5.8 billion in 1996 – an increase of 45% -- the amount of materials used increased at more or less the same rate. People, on average, didn’t use much more or less stuff. So, we can extrapolate from this and say that total material use increased by about 45% as well and kept pace with population.
However, over that same time period, economic growth outpaced population. The world gross national product (GNP) increased faster than population over the same time period. Global GNP went from $14,300 billion in 1970 to $29,995 in 1999, an increase of 109%. So, compared to economic growth on a per unit basis, the amount of material used per unit of economic growth fell dramatically. What this means is that in general, industrial economies are becoming more efficient in their use of materials. The terms economists and ecologists use to describe economies using less material per unit of economic output is “decoupling” or “dematerilization”.
So, the world’s economy is continuing to grow and becoming more efficient with how it uses materials. What do these trends mean for environmental impact? For starters, just because decoupling or dematerialization is occurring, doesn’t mean that there are fewer materials being consumed, just fewer materials per unit of economic output produced. In overall, we’ve already see that the total amount of materials used increased about 45% between 1976 and 1996. So, with regards to the environment both overall consumption of natural resources, as well as waste generated continued to increase. Further, the World Resources Institute estimates that “one half to three quarters of annual resource inputs to industrial economies are returned to the environment as wastes within a year.” Let’s look at this more closely. What this is saying that some 50% to 75% of the materials consumed in a year end up in the waste stream within that same year.
There is also great disparity
around the world in terms of levels of material consumption. We know this
already from the pictures from the “Material World” website that we looked at
in week five. The average American, for example, releases about 2 ˝ times the
amount of waste material into the environment as a person in
Further, while outputs of some
hazardous waste materials have been controlled, stabilized, or reduced, outputs
of many potentially harmful materials continue to increase. The World Resources
Institute estimates that “many potentially hazardous flows