Posted on 02/07/2002 7:33:24 PM PST by John Jamieson
Which Pollutes the Atmosphere More, a Gallon of Gasoline or a Gallon of Milk?
John R. Jamieson
MIT67, NASA67-94 retired
EPA current regulations require that passenger cars generate no more than .09 grams/mile of hydrocarbons, 3.4 grams/mile of CO, and .4 grams/mile of NOX. In addition, cars must average at least 27.5 mpg. A 6 pound gallon of gasoline (plus 90 pounds of air) then is allowed to produce about (.09+3.4+.4)*27.5/454) pounds of pollutants. Or about a total of about a quarter of a pound (individually: .006 pounds hydrocarbon, .21 pound of CO, and .025 NOX). California’s and future national regulations are much tougher (2 to 10 times).
Figuring out the pollution associated with a gallon of milk is much harder. Extensive Internet searches provided the following information:
There are about the same number of cars and cows (cattle) in the US, roughly 110 million each.
A good dairy cow produces about 2,000 gallons of milk a year. Wow!
A producing dairy cow consumes about 80 bushels of corn, 8 tons of corn silage, 6 tons of hay, 200 pounds of salt and minerals, 900 pounds of protein supplements and 200 pounds of cottonseed per year. Total feed cost is about $1000. Additional farm energy costs per cow is about $100. The farmer sells the milk for about $2,400.
Cows like people, generate virtually all their energy from the slow combustion of carbon in their diet. 2 atoms of carbon combine with 2 molecules of water to produce a molecule of CO2 and a molecule of CH4 (a hydrocarbon called Methane). The literature is quite clear that these gases are “belched” not “farted”. Methane production per cow is specified at 264 pounds per year. This would be a great fuel source, if it could be collected.
Therefore the production of a gallon of milk produces .132 pounds of hydrocarbon pollution, much more than the hydrocarbon generated by the gallon of gasoline alone but only about half of the total pollution generated by the gasoline.
NOX is caused by high combustion temperatures in the car's engine and is not likely to be generated in significant quantities by the slow, low temperature combustion in animals. CO production in cows is also probably quite low. But, there is a major factor, we’ve left out. What about the energy in the form of hydrocarbons used to produce the feed and run the farm?
Here I have to take a SWAG. If half the food costs and all the energy costs from the farm came from hydrocarbons, there is more pollution to consider. $600 worth of fuel is about 600 gallons (probably mostly diesel, and farmers pay no road tax). The EPA has no pollution or mileage standard for farm equipment, but if we assume that this fuel generates about the same pollution as automotive fuel, we have to add another 600/2000*.25 pounds of pollution. About .075 pounds.
Now we have cars generating .25 pounds of pollution per gallon. And milk generating about .207 pounds per gallon.
Conclusions:
1) If you live in most states, the total pollution generated by a gallon of gasoline is about 25% higher than that generated by a gallon of milk.
2) If you live in California or one of the other states that use the same requirements, the gallon of milk is probably polluting more.
3) In the very near future, when the tougher standards kick in, the production of a gallon of milk will pollute more than the use of a gallon of automotive fuel.
4) IN ALL STATES, NOW, AND IN THE FUTURE, THE PRODUCTION OF A GALLON OF MILK POLLUTES THE ATMOSPHERE WITH HYDROCARBONS EQUAL TO THE BURNING OF 14+ GALLONS OF GASOLINE.
Drink up, and drive.
That's a very human-centric view. I bet the cows consider it farting.
If only I did'nt have to pay for recycling.
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