Connections for the STEM Classroom
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Making Our Consumption of Geologic Materials Visible
by Steve Mattox, GVSU Geology Department
Recently, a couple events prompted me to think about my consumption of geologic materials. A friend had posted a photo of the Bingham Copper Mine near Salt Lake City. Many people commented on the how ugly or bad the mine looked. Another friend posted that we all use copper. I wondered how much of that big hole I was responsible for. My second experience was with 120 general education students in my Environmental Geology class at GVSU. My old lecture was focused too much on mineral identification and too little on why minerals mattered. This article outlines how I changed my class to increase engagement with my students.
How much do I need in my lifetime? Looking around I see cement, roadways, metal, glass, electronic devices, drywall, ceramics, even some wiring in Christmas lights. My car is parked out front. The lights are on and the furnace is keeping me warm. It seems like a lot of stuff. How much iron, copper, salt, rare earth elements, gasoline and coal do you need in a lifetime (I’m assuming 80 years). Take a moment and jot down some estimates. The quick answer is the Mineral Education Coalition’s “Every American Born Will Need…” cartoon. It’s a line drawing of a baby surrounded by a satellite of geologic commodities in units of pounds and gallons. The quick answer is 3.5 million pounds of metals, minerals, and fuels in a lifetime. It sounds crazy until you start digging into the numbers which is exactly what I did with my students.
Aerial view of the Bingham Copper mine. The pit is about four miles across and over 1,000 feet deep.
Let’s start with copper. According to the Mineral Education Coalition (MEC) an American born in 2016 will need 945 lbs of copper per lifetime. Rio Tinto reports an ore grade of 10.6 lbs of copper per ton of rock. I assumed a rock density of 2.8 gm/cc (low). I estimate an American will need about 28.8 cubic meters of copper ore (rock of economic mineral) in a lifetime. My classroom is about 200 cubic meters. Seven Americans need that much volume per lifetime. The Copper Development Association (https://www.copper.org/ ) states that half the copper we use is from recycled material and half is newly mined in the United States. The newly mined copper is mostly used for wiring. The Keweenaw Historic Park (https://www.nps.gov/kewe/index.htm) would be a great way to connect our consumption to Michigan geology and history.
Aerial view of the Empire iron mine near Ishpeming, Michigan. The pit in the foreground is about a mile across.
The MEC states I’ll need 45,225 lbs of iron in my life time. Iron ore is commonly 60% iron and 40% silica (quartz). The iron minerals are hematite and magnetite (about 5 gm/cc). The quartz is 2.7 gm/cc. The ore is from a rock called banded iron formation. So, we can use a density of about 4 gm/cc. To convert the weight to volume I guided my students through some dimensional analysis:
1 cubic cm/4 gm X 1 gm/0.0022 lbs X 45,225 lbs/lifetime X 1 cubic meter/1,000,000 cubic cm = 5.1 cubic meters/lifetime
The U.S. Geological Survey publishes detailed annual reports on mineral commodities. The 2017 report highlighted Michigan’s critical role in supplying the nation. At $82.41 per metric ton we calculated we’d only spend $1,689 for a lifetime of iron. However, a link to a local newspaper showed the 400 mining jobs are tenuous. Using Google Earth we estimated the volume of the mine, 640 million cubic meters. Dividing the volume of the mine by our individual volume per lifetime we determined the mine supplied 124 million Americans.
Rare Earth Elements
Rare Earth Elements (REE) aren’t shown on the “Every American Born Will Need” cartoon so we used the U.S. Geological Survey’s commodity data. About 35.2 million pounds of REE were consumed in the states in 2016, primarily for electronics, magnets, and batteries. With some basic assumptions about population we estimated a minimum of 8 pounds of REE for a lifetime. The students realized the REE are critical for their cell phones but didn’t know of their critical need by the military. There are no operating REE mines in the US; most of our supply is imported from China. In 2010, China withheld exports to punish Japan over territorial rights. Additional REE resources will be needed to grow a green economy and domestic sources must be developed to reduce our nearly 100% reliance on imports.
We consume 30,300 lbs of salt per lifetime, mostly for highway deicing and by the chemical industry. To convert the weight to volume I guided my students through some dimensional analysis:
1 cubic cm/2.16 gm X 1 gm/0.0022 lbs X 30,300 lbs/lifetime X 1 cubic meter/1,000,000 cubic cm =
6.4 cubic meters/lifetime
The volume of a small U-Haul trailer, like the one pulled by a car, is 3.6 cubic meters. I’d need just shy of two for the salt I consume. Again, the U.S. Geological Survey published detailed annual reports on uses, consumption, and sources. Michigan produces rock salt and salt from brine. Nationally, there are about 4,000 salt miners and, although we have adequate reserves, we import about 23% of the salt we use. Depending on the type consumed, you will spend $150 to $750 on salt over your lifetime. The severity of winter influences society’s salt consumption and the cost. In 2016, Kent County bought $2 million of salt. The County Commissioner noted that $250,000 of salt might be used in a single day during a bad storm.
The salt storage shelter pictures above has a volume of about 2,500 cubic meters, enough for about 400 people over a lifetime.
Stone, Sand, and Gravel
The Mineral Education Coalition shows we consume 1.4 million pounds of stone, sand, and gravel per lifetime, mostly for construction aggregate, road base, and asphalt.
Again, some dimensional analysis:
1 cubic cm/2.6 gm X 1 gm/0.0022 lbs X 1.4 million lbs/lifetime X 1 cubic meter/1,000,000 cubic cm = 244.7 cubic meters/lifetime
The volume of a 50 foot rail boxcar is 155 cubic meters. I need almost two boxcars filled with my sand and gravel. The U.S. Geological Survey tracks our consumption of this commodity. As a nation we spent $8.9 billion on stone, sand, and gravel in 2016 and, over a lifetime, you’ll spend about $5,600. Michigan’s abundant glacial and river deposits serve our needs. But some towns are pushing back about gravel quarries near them. For example, in Chelsea, mine expansion could supply about 15,000 people for their lifetime.
The MEC reports about 585,000 pounds of coal per lifetime. Nearly all of the coal is burned to generate electricity. This converts to about 20 pounds per day or a volume of about 2.8 cubic meters per year. Thinking more broadly, one rail car could supply 30 people per year. About 365 rail cars of coal were needed to supply the needs of the city of Grand Haven each year (prior to the new natural gas plant) and 6,400 rail cars for Grand Rapids (each year). For Grand Rapidians that’s a train 100 miles long heading to our local power plants each year. Hazel and Mattox (2009) calculated that each American releases one cubic centimeter of mercury into the environment over their lifetime by using coal.
The American level of consumption is not sustainable. Scheer and Moss (2017) summarize our oversized per capita needs relative to the rest of the world. I hope that making my consumption evident, with a few explicit examples, and making volume of materials relatable to daily life triggers some reflection and change of behavior.
A science teacher with about 20 pounds of coal, the typical daily consumption for an American.
The author beside a typical gasoline tanker.
The Mineral Education Coalition shows we consume over 78,000 gallons of petroleum in our life. Major uses are transportation, heating, and materials. At a capacity of 8,200 gallons each of us would need about 9.5 tankers per lifetime.
Please email me if you’d like a classroom exercise aligned to this Connections. I welcome suggestions, corrections, and additional ideas.
Steve Mattox email@example.com
Hazel, M., and Mattox, S., 2009, Visualizing the Impact of Burning Coal, Michigan Science Teachers Association Journal, p. 42-55.
Mineral Education Coalition, 2017, 2017 Mineral Baby at https://mineralseducationcoalition.org/mining-minerals-information/mining-mineral-statistics/
Scheer, R., and Moss. D. , 2017, Use It and Lose It: The Outsize Effect of U.S. Consumption on the Environment, EarthTalk, Scientific American (link to https://www.scientificamerican.com/article/american-consumption-habits/