It sounds like a fantastic deal. Here you are with your 8000 pound car to transport a single 150 pound person. These 8150 pounds need that 6 liter, 300 hp engine to get the thing rolling, burning one gallon every 10 miles or so. Of course in the back of your mind you have this nagging feeling that you contribute with such a car tremendously to the CO2 in the atmosphere. But, hey there is a solution for that too. You can participate in one of these “Carbon Neutral” approaches where you (or a company or organisation for you) plant a bunch of trees that will take up the amount of CO2 that your car generated (read the article of Andrew Revkin in the New York Times of April 29, 2007). Thus, the dilemma is solved, you can drive your car and the world will not suffer. Is it?
Of course planting trees is in itself not a bad thing. But, traffic pollutes the air with many other chemicals than just CO2. For example, there are also massive ammounts of nitrogen oxides and hydrocarbons (also called Volatile Organic Compounds, VOC’s) released. Under the influence of sunlight, nitrogen oxides and VOC’s can give smog (increased ground levels of ozone, O3) that can be extremely unhealthy and especially for people that suffer from asthma. In addition to these chemicals there is generation of particles (soot). These particles can block sunlight which in turn can lead to local climate changes (less rain for example).
Hey but wait. Did we forget about the holy grail perhaps? How about these bio-fuels? They are “carbon neutral” too, isn’t? Let’s have a closer look to one of the bio-fuels, ethanol, that can be produced from corn. It is indeed true that corn while growing will fixate an amount of CO2 (from which carbohydrates are synthesized in the photosynthesis process). Of course burning ethanol in the engine will release again the CO2 bound earlier in the atmosphere. Two important aspects need to be considered:
- Detailed studies have shown that the energy balance to produce ethanol from corn is negative. It appears that about 30% more fossil fuelis needed than ethanol fuel can produce. Sounds like carrying water to the sea. [Pimentel and Patzek, Nat. Resour. Res., Vol 14, No1, March 2005]
- A recent study at Stanford university shows that E85 (a mixture of 85% ethanol and 15% gasoline) generates also other chemicals than just CO2. Among those are aldehydes (compounds that contain carbon, hydrogen and oxygen) that also contribute to smog formation. Thus we solve perhaps one problem but get back another one.
The fact that the ethanol production has a net negative energy balance is a serious one. But it is not unexpected if we keep in mind the Second Law of thermodynamics that says us that you will get nothing for free. The production process of ethanol requires at several stages (for instance during the distilling process) energy inputs and those inputs come typically from fossil fuels (used in power plants for instance). The Second Law teaches us that every-time we require energy, that a certain amount of the energy degrades in quality and is no longer available to do work.
Folks, the message is clear. Reducing the fuel needed for traffic can be reduced substantially by some very simple measures: stop driving the 8000 pound vehicles, reduce your speed, keep your tyres properly inflated and make sure your engine is tuned. This will save you money and will reduce the green house gases emissions. But it is us who have to take action, writing checks will just not cut it.
And by the way……. continue to plant trees!
© Copyright 2007, John E.J. Schmitz