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NHA Responds to CalTech Study
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By Brian Schorr, Project Coordinator, National Hydrogen Association


Last month, researchers at the California Institute of Technology released a report in which they warned that increased leakage of hydrogen as a result of a switch to a global hydrogen economy has the potential to cause stratospheric cooling and indirect thinning of the ozone layer by as much as 10%.  This report appeared in the June 2003 issue of Science magazine.

The NHA believes that the analyses in this report were misrepresented, giving a false impression of what to expect in a global hydrogen economy.  NHA members were asked to provide their thoughts on the article and specific points they would like to see addressed in this response.  Key points are included below:

It is the position of a majority of members that the CalTech report misrepresented the leakage rates of hydrogen to be between 10-20% in a global hydrogen economy.  Actual leakage will be 10-400 times less than that, and will be reinforced by a hydrogen economy’s displacement of many of the fossil-fuel activities that release significant amounts of hydrogen today.  Current leakage rates run around 2%, and in a global hydrogen economy, a more realistic estimate of leakage would range from 2-3% for liquid hydrogen.  In addition, a reasonable increase in the total hydrogen concentration would be at least one order of magnitude less than the researchers assume, resulting in less than a 1% increase in ozone depletion, in the worst case scenario.

It should also be noted that an article published by Dr. Nejat Veziroglu was referenced in this report to back up the 10-20% leakage rate claims.  However, Dr. Veziraglu and his students published that article several years ago and it appears to be pertinent mostly to NASA’s space launch program.   It is not appropriate for the present effort, which uses mostly compressed hydrogen storage.

The researchers determined that a 3-4 fold increase in total hydrogen emissions would result from a 10-20% leakage rate.  They then used a 4-5 fold hydrogen increase in near-surface hydrogen emissions in their base case.  A 4-5 fold increase in hydrogen concentration appears to correspond to more than 20% leakage.  This is clearly at least one order of magnitude high for anything but a worldwide liquid hydrogen economy with poor handling practices.

Finally, the researchers measured the ozone depletion rates at both poles.  In gathering their data, they used the high depletion results for the North Pole (the highest depletion rates of the higher of the poles) and drew their conclusions of ozone depletion based upon extreme results, not mean results.

The report does raise an important issue.  Proper investigation and accurate data collection and interpretation are not only warranted, but vital in the early stages of the transition to a hydrogen economy.  The NHA supports further study into the environmental benefits and impacts of hydrogen, and will work closely with those engaged in this type of study to ensure that hydrogen fuel is as safe for the environment as it is safe for consumers.

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