Washington, 17 Jun 2003
While the proposed hydrogen-fueled cars of the future are generally considered to be environmentally friendly because they emit only water vapor, a new study says that leakage of the hydrogen gas that would fuel such cars might cause problems in the Earth's protective ozone layer.
A June 12 press release says that researchers at the California Institute of Technology report that the leaked hydrogen gas resulting from a hydrogen economy, if it accumulates, could indirectly cause as much as a 10-percent decrease in atmospheric ozone. The stratospheric ozone layer protects the Earth from the sun's ultraviolet radiation, which causes skin cancer and weakened immune systems in humans.
If hydrogen were to replace all fossil fuels used in transportation and to power buildings, the scientists estimate that four to eight times more hydrogen would be released into the atmosphere than is currently released by human activity. In an article appearing in the journal Science, the researchers assumed a 10 to 20 percent loss rate due to leakage. Because molecular hydrogen freely moves up and mixes with stratospheric air, the result would be the creation of additional water at high altitudes and an increased dampening of the stratosphere, and, indirectly, destruction of ozone.
In this respect, hydrogen leakage would be similar to chlorofluorocarbons (CFCs) -- once the standard substances used for air conditioning and refrigeration. They were intended to be contained within their devices, but in practice CFCs leaked into the atmosphere and attacked the ozone layer. CFCs have been widely replaced by alternative substances and are set for a complete phase out under an international agreement.
However, the authors of the report say uncertainty remains about the effects of hydrogen on the atmosphere because scientists still have a limited understanding of the hydrogen cycle. They also note that, unlike the case with CFCs and other atmospheric pollutants like carbon dioxide, the current situation is unique in that society has the opportunity to understand the potential environmental impact well ahead of the growth of a hydrogen economy.