Bob Doyle, Columnist
My last column mentioned the energy of our bodies, gasoline and coal burning power plants.
Today I would like to develop a few more interesting numbers to help us understand the impact of our civilization on the environment. At the Renewable Energy Conference last September, one of the speakers mentioned that the carbon dioxide emitted by an SUV would require 75 trees (to absorb) each year.
Let’s suppose that an SUV (or the equivalent truck) gets 15 miles per gallon. Then if one drives such a vehicle 12,000 miles a year, then that vehicle would use 800 gallons of fuel (12,000/15 = 800). Now a gallon of gasoline when burned in an engine gives off 20 pounds of carbon dioxide.
(This is not the weight of the gasoline but the carbon from the gasoline combined with the oxygen in the air. In carbon dioxide, 73 percent of the mass or weight of the molecule is oxygen. There are two oxygen atoms, each with a mass number of 16 to the single carbon atom with a mass number of 12.)
So if an SUV or equivalent vehicle consumes 800 gallons of gasoline, it puts 16,000 pounds or eight tons of carbon dioxide (800 x 20 = 16,000) into the air each year.
If 75 trees can absorb this amount of carbon dioxide, then each tree can absorb about 200 pounds of carbon dioxide. (16,000/75 = 213). So every time, you pump 10 gallons of gasoline into your vehicle, you have put 200 pounds of carbon dioxide into the atmosphere through your driving. (It doesn’t matter whether you have a gas guzzler or a hybrid, all motor vehicles make the same amount of carbon dioxide per gallon.) This is the amount of carbon dioxide that a medium sized tree can absorb during a year. (The tree absorbs its carbon dioxide through its leaves when they are growing in the spring and summer.)
The biggest generators of carbon dioxide are the coal burning power plants. Each day a 1,000 megawatt or 1 gigawatt plant consumes 9,000 tons of coal. (This is a long trainload of coal each day, 365 days a year.) Using metric tons, it can be shown that these plants consume 375,000 kilograms per hour. (9,000,000/24 = 375,000). Now in one hour, such a plant would create a million kilowatt hours.
So each kilowatt hour requires .375 kg of coal (375,000/1,000,000). Assuming that the coal has 10 percent unburned material (the amount of ash generated is 1,000 tons per day), about 1/3 of a kilogram actually combines with oxygen to make carbon dioxide. Since we need 12 grams of carbon to make 44 grams of carbon dioxide, the actual amount of carbon dioxide per kilowatt hour will be 1.24 kilograms or a little over 2.7 pounds of carbon dioxide per kilowatt hour. (1 kilogram weighs 2.2 pounds)
Suppose your household in a month consumes electricity at an average rate of 1,000 watts, you would expend 720 kilowatt hours each month (30 days x 24 hours in a day).
Considering the 10 percent loss in electrical transmission, a coal burning power plant would have to burn 300 kilograms of coal each month for your house electric needs. This amount of coal upon being burned would create 1000 kilograms or one metric ton of carbon dioxide per month.
So if you have a house whose electric comes from a coal burning power plant and an SUV, your house and driving would likely be adding 20 tons of carbon dioxide to the air each year (12 tons for your house and eight tons for the SUV)
In fact, the average carbon dioxide emission per American is 20 tons per year, the world’s highest among large countries. (This figure also includes carbon dioxide emitted by heavy trucks, manufacturing, airplanes, shopping malls, office buildings, sports arenas, NASCAR, school buildings, etc.).
Caesar’s month
We get our month names from the Romans. July comes from the Roman month Julius, a month renamed in honor of Julius Caesar in 44 B.C. Two years earlier, Caesar had overhauled the old lunar Roman calendar that was being manipulated by the Roman high priests or pontiffs, who were being bribed by corrupt officeholders. (If you wanted to prolong your term of office, pay off the Roman priests to add an extra month to the calendar.)
Caesar’s reforms gave us our current 12 months with their varying day lengths and a leap year day added to the end of February every fourth year. Before Caesar’s assassination, the Roman Senate changed the month of Quintilis (fifth month) to Julius in honor of Caesar, whose birthday was the 12th of the month.
In 8 BC, the Roman month Sextilis (sixth month) was renamed Augustus for the Roman emperor Augustus, who was the adopted son of Julius Caesar. Both of these months are 31 days in length, the only two consecutive 31 day months in the calendar.
The moon will be nearly full on Friday, then appearing to the right of the bright planet Jupiter. The next evening features the full moon, which will then be to the left of Jupiter. Just as in June, this month’s full moon has a low path across the southern sky, often appearing yellowish due to its shining through haze and emissions from trees.
Call (301) 687-7799 to request a free planetarium/Science Discovery Center bookmark (shows and tours resume on Sunday, Sept. 7).
Bob Doyle is available for brief talks and discussions for clubs or groups (call above phone number). He invites comments and questions from readers. Contact Bob Doyle at rdoyle@frostburg.edu.
