Test your knowledge of climate change, and see what educators have to say about it, at The New York Times. You may have to sign up for a free New York Times membership to see the story. The educators discuss the natural greenhouse effect and how it is essential for our planet to support life; they distinguish the natural effect from the industrial greenhouse effect. Other frequently-confused matters are clarified, such as the relationship between depletion of the ozone layer and global warming (they are not related in a significant way).

Note that one of the answers given mentions that ethanol burns more cleanly than fossil fuels. This is very true in the sense that fossil fuels contain not only hydrocarbons, they have “impurities” that are nitrogen- and sulfur-containing organic compounds. The nitrogen and sulfur end up as well known air pollution components NOx and SOx after combustion.

However, as previously mentioned on this site on Oct. 8th, predictions of air quality in Los Angeles based on a switch to E85 ethanol-based fuel, and studies of air quality from Brazil, where some cars run on pure ethanol, all show increased amounts of highly-toxic acetaldehyde, formaldehyde and ozone and related species in the air. Formaldehyde and similar compounds damage the lungs, causing inflammation and other problems, and cause serious problems for both healthy people and especially people with asthma. Ozone is a major, direct cause of pollution-related respiratory distress. Formaldehyde is commonly used as a preservative for specimens in biology and medical labs.

If you wish to see the original scientific papers, they are cited here.

As possible explanations for the generation of harmful species from ethanol, I offer the following suggestions:

  • The oxygen in ethanol could, under circumstances of less than ideal combustion, result in formaldehyde and other aldehyde formation.
  • The ready manner in which ethanol absorbs water from the atmosphere interferes with combustion efficiency.

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