ARB Scientists Dispute Lead Acid Battery Report
For immediate release
California Air Resources Board scientists have sent a letter to Carnegie-Mellon University (CMU) rebutting a report that warns of added lead pollution from the increased use of electric-powered vehicles.
According to the letter signed by Tom Cackette, ARB chief deputy executive officer, the report compares the total discharges of lead to air emissions resulting in an overestimation from lead smelting and battery development facilities of between 44 and 1000 times. In addition, the Carnegie-Mellon report incorrectly portrays the development of electric-powered vehicles as dependent on today's lead-acid battery as the power source of tomorrow's cars.
"While lead-acid batteries have been the dominant power source for electricity in motor vehicles since before World War II, few experts expect them to be widely used in future electric vehicles," said John Dunlap, Air Resources Board chairman.
ARB staff determined that Carnegie-Mellon researchers used questionable assumptions and outdated data to determine battery recycling and lead smelting emissions. For example, ARB researchers point to CMU assertions which rely on US Bureau of Mines data that includes 20 years of uncontrolled emission rates. Using that complete data set CMU concluded that emissions from smelting operations were 44 times greater than those actually emitted by a modern facility.
In addition, ARB scientists claim that CMU may be as much as 1000 times off in their estimate of lead emissions from early EVs. Most early EV batteries will be recycled in California where secondary smelters that emit only about 0.002 percent of the lead used instead of the 2 percent of the total rate estimated by CMU.
The use of recycled lead is also important when measuring emissions because about 45 times less lead is released when recycled lead is used to build batteries than when newly mined lead is used. Presently, California recycles about 95 percent of all batteries and 85 percent of a new battery consists of recycled lead.
ARB scientists also found that Carnegie-Mellon employed pessimistic assumptions about present and future electric vehicle battery performance and usage. The ARB letter cites information from the Acurex Corporation and CalStart that estimates that about one-half of all electric vehicles built in 2000 will use lead-acid batteries. That figure drops to only about 10 percent of all batteries being lead-acid in 2010.
The ARB's concerns were also expressed by scientists from Argonne National Laboratories in a May 30, 1995 letter to Science Magazine. The Argonne letter cites errors in the CMU study that overestimate airborne lead emissions by up to six times and the amount of lead needed in modern batteries by about three times.
The Argonne letter signed by Linda Gaines, Ph.D and Michael Wang, Ph.D states that, "The conclusions reached in this article (the CMU report) are gross overstatements and based on obsolete data and extremely pessimistic technology assumptions."
The ARB staff has invited Carnegie-Mellon University researchers to its July 12, 1995 workshop on electric vehicle infrastructure at the ARB Mobile Source Laboratories in El Monte, CA to comment on its report and to discuss other viewpoints. This workshop is one of a series of public forums to be held over the next year to provide public input on the ARB's Zero-Emission-Vehicle rule.