Newtonian traffic safety
I've been exploring for oil and gas for so long now (and reading OGJ for just as long) that my college physics courses are pretty much forgotten. However, you are familiar with Einstein's E=mc2 which is related to the Newtonian K=1/2mv2. That is to say the kinetic energy K of a moving body is proportional to its mass but also to the square of its velocity. The big problem in a collision (Journally Speaking, Jan. 5, 2004, p. 15) is not the momentum (the product of mass x velocity) of the colliding bodies but the energy transfer.
The modifier that prevents an SUV from being as devasting to a small car as it is to another SUV is the efficiency of energy transfer. In a direct (nonglancing) impact, energy transfer is proportional to the ratio of the colliding masses. If a ping-pong ball hits the floor, almost none of the ball's energy transfers to the earth and it rebounds nicely. Remember those executive time wasters like the five metal balls hanging on strings? Because the balls were all the same mass, the energy transfer from one to the next was nearly perfect. Two equal SUVs will likewise transfer nearly 100% of the available energy resulting in major damage. A small compact car would only have to absorb half or less of the energy of an incoming SUV. What all this means is that you should include the square of velocity (speed) as a factor in your hypothetical penalty since it is even more important than mass.
William Dickson
Dickson International Geosciences
Stafford, Tex.
Correction: ethanol letter
Editor's note: The author's name was inadvertently omitted from this letter when it first appeared (OGJ, Jan. 19, 2004, p. 10).
In his letter, "Ethanol's Net Energy Balance" (OGJ, Nov. 10, 2003, p. 10), Steve Plotkin seems to have some misconceptions not only of energy balances, but more importantly, of environmental costs and benefits. He argues that ethanol's negative net energy balance means very little and that petroleum fuels also have negative net energy balances.
As Gavin Longmuir succinctly explained in his letter (OGJ, Sept. 22, 2003, p. 10), in the case of fossil fuels we invest some energy in development, extraction, transportation, and processing in order to obtain more energy than we expended in these processes.1 In the case of ethanol, even with the input of "free" solar energy, the energy content of the ethanol is no greater than the fossil energy input. Therefore, ethanol is not a "renewable" energy source.
So why should we use fuel ethanol? Plotkin says, "What does matter is cost and environmental impact, and net energy balance is one tool that helps us to estimate these." The fact that ethanol has a negative net energy balance is, of course, a major contributor to its high cost. Plotkin argues that ethanol's greenhouse gas emissions are less than those of gasoline, so its use as a gasoline substitute would be beneficial from the standpoint of climate change.
Let's look at some environmental impacts. In essence, corn ethanol is made by cycling fossil fuels (in the form of gasoline, diesel, fertilizer, pesticides, and propane for drying the grain) through cropland and then refining the corn. Over the past 4 years (1999-2002) US corn production has averaged about 9.5 billion bushels from about 70.3 million acres.2 About 23% of the US corn crop is produced in the Great Plains states of South Dakota, Nebraska, Kansas, Wyoming, Colorado, Oklahoma, Texas, and New Mexico. The acreage devoted to corn in these states is about 18 million acres or about 26% of the US corn acreage.3 Much of this land is easily erodable, and numerous studies have conclusively demonstrated that row crops—such as corn—result in much higher erosion rates than cereal grains or forage crops. For example, on a silt loam soil with a 12% slope and an average rainfall of 38.5 in. near Zanesville, Ohio, a continuous corn-cropping sequence resulted in an average soil loss of 99.6 tons/acre over a 9-year period. Wheat grown in a rotation sequence with corn yielded a soil loss of 11.4 tons/acre, while permanent pasture had a soil loss of only 0.2 tons/acre.4
Furthermore, 45% of the corn acreage in these Great Plains states, or about 8 million acres, is irrigated with water that is being overdrafted [mined] from the Ogallala aquifer.3 Since corn requires approximately 2 acre-ft of applied irrigation water per acre, the corn acreage in the Great Plains requires close to 16 million acre-ft/year of irrigation water. To put this in some perspective, the average annual flow of the Colorado River (measured at Lee's Ferry) is about 14 million acre-ft/year.
Growing a crop that results in soil erosion nine-fold greater than wheat or with overdrafted groundwater in order to produce ethanol that contains less energy than the fossil inputs to produce it hardly qualifies as either sustainable or environmentally beneficial. Basically corn ethanol is a nonrenewable energy source, and its environmental costs outweigh whatever meager benefits it may possess.
References
1. Gavin Longmuir, "Alternate energy," OGJ, Sept. 22, 2003, p. 10.
2. State level data for field crops, Agricultural statistics data base, National Agricultural Statistics Service, US Dept. of Agriculture [www.nass.usda.gov].
3. County level data by state for crops, Agricultural statistics data base, National Agricultural Statistics Service, US Dept. of Agriculture [www.nass.usda.gov].
4. J.P. Zublena, "Corn Cropping Sequences," NCH-50, National Corn Handbook, Purdue University Cooperative Extension Service, West Lafayette, Ind., 1987.
Donald F. Anthrop
Professor
Department of Environmental Studies
San Jose State University, Calif.
Concerning SUVs
I enjoyed your piece on Newtonian mechanics as applied to mass of typical SUVs (OGJ, Jan. 5, 2004, p. 15). I don't agree with you about the perceived safety parameter associated with increased mass being the primary justification given by SUV buyers for owning an SUV. Most of them that I've ever talked to (and, no, I don't own one or would ever want to, either) cite the on-demand four wheel drive capability and their elevated driver-viewpoint relative to low-clearance cars as the primary reasons.
In light of this, it would make more sense to create incentives for the car manufacturers to cut down on the overall vehicle weight by utilizing new, lightweight materials while maintaining the current overall interior dimensions and raised driver seating along with the four-wheel drive capability.
Trying to link vehicle mass with severity of fines for traffic violations presumes fairly consistent enforcement of the associated fines upon every SUV owner caught speeding. In the real world, many of the SUV owners are topnotch lawyers who can get speeding tickets totally dismissed or at least get the fine greatly reduced! Many others are close friends of such lawyers!
I agree that Americans who want to drive SUVs should be permitted to do so with payment of the associated increased upkeep going along with that ownership. But, it may be possible to mandate greater fuel efficiency while not shrinking the overall size of the typical SUV—just its vehicle weight and, thence, its fuel consumption.
If you want to simply cut down the probability of an SUV being involved in traffic accidents, why not offer a government-provided "bounty" to SUV owners for every mile or every hour of vehicle operation that they forego by either hitching a ride with someone else, by walking to their destination, or by staying at home?
I would leave the safety issue totally out of the argument revolving around raising fuel efficiency standards. It doesn't really come into play.
Jim Hemmen
Oil & Gas Research Analyst
Wichita, Kan.
More on SUVs
I read your editorial (Jan. 5, 2004, p. 15) in Oil & Gas Journal pertaining to SUVs. There is another criteria besides safety and economy.
I always drove station wagons, which were gas guzzlers, simply because I required space for hauling items and yet have a safe place in which to lock luggage if traveling. When I reached the age of 60, a new requirement had to be considered. That was ease of entry and exit. Low slung autos are more difficult for these two operations. So, I went to SUVs, of the Explorer size, to solve this problem. Actually, a vehicle about 4-in. lower base than an Explorer and with a lower backseat entry would be perfect for the over-60 crowd. Instead, the auto makers build them bigger, requiring step ladders, or very low-slung, requiring a crane to board and disembark. This has nothing to do with fuel economy or safety, just convenience.
Luis R. Celerier
Judson, Tex.
