This article is reproduced with the permission of New Scientist for exclusive use by Nova users.

TV boom may boost greenhouse effect
02 July 2008
From New Scientist Print Edition.
Fred Pearce

An industrial chemical being used in ever larger quantities to make flat-screen TVs may be making global warming worse. However, because it's not covered by the Kyoto protocol, nobody knows by how much. The gas was first introduced as a measure to cut greenhouse gas emissions, but a prominent atmospheric chemist this week warned it could now be having the opposite effect.

The gas is nitrogen trifluoride (NF3). As a greenhouse gas it is 17,000 times as potent as carbon dioxide, molecule-for-molecule, yet is not covered by Kyoto because it was made in tiny amounts when the protocol was agreed in 1997.

Even today, no one is measuring how much reaches the atmosphere. The one certainty is that it is accumulating. In a new study, Michael Prather of the University of California, Irvine, calculates that it has a half-life in the atmosphere of 550 years.

NF3 production is "exploding", says Prather, because of escalating demand from the electronics industry. It is used mainly to flush out the by-products of chemical vapour deposition, a process which deposits thin films onto glass surfaces for liquid crystal displays (LCDs), and onto silicon wafers for semiconductors.

Prather puts the first global estimate of NF3 production at about 4000 tonnes this year, and double that for next year. Its largest maker, the US company Air Products, based in Allentown, Pennsylvania, is building two new factories to produce the gas, in the US and South Korea. Others are setting up in China.

If it were all released into the atmosphere, this year's production would have a warming effect equivalent to about 67 million tonnes of CO2, the same as the annual CO2 emissions of Austria.

Ironically, the surge in demand followed Air Products' development of NF3 as an alternative to perfluorocarbons (PFCs) - greenhouse gases subject to the Kyoto protocol. In 2002, the company won a climate protection award from the US Environmental Protection Agency for "replacing PFCs in the semiconductor industry, resulting in a significant net reduction of greenhouse gas emissions". But since then any gains are likely to have been wiped out by emissions from the soaring use of NF3 by the booming electronics industry.

The Kyoto protocol covers six man-made greenhouse gases: CO2, methane, nitrous oxide, hydrofluorocarbons, PFCs and sulphur hexafluoride. NF3 was one of more than a dozen less prominent man-made greenhouse gases that were excluded.

Now Prather's analysis, online at Geophysical Research Letters (DOI: 10.1029/2008GL034542), calculates the potential warming effect of currently manufactured NF3 is greater than both sulphur hexafluoride and PFCs individually. The problem is that nobody knows how much NF3 is being released.

Air Products told New Scientist that, compared with PFCs, only a small proportion of the NF3 used by electronics companies is released into the air. Indeed, Prather agrees that switching to NF3 "probably was an improvement" for this reason, but he warns that NF3 is twice as potent as perfluorocarbons. The gas is not controlled in the same way as PFCs, he says, and as a result manufacturers may be careless with it. "There is optimal, and there is real life," he says. "The chemicals industry does not traditionally do a good job controlling emissions."

Fears are increased because users of NF3 get little warning that they should prevent the gas being released. For example, Air Products' online summary of NF3 mentions its "negligible" impact on ozone depletion, but not its greenhouse gas properties.

At least one manufacturer of LCDs is concerned about the greenhouse effect of its NF3 emissions. Toshiba Matsushita Display Technology says it has developed a process that uses pure fluorine instead of NF3, resulting in "zero greenhouse gas emissions".

Prather wants NF3 to be included in national inventories of greenhouse gases, and says it would be "prudent" for the gas to be covered by the successor to the Kyoto protocol.

From issue 2663 of New Scientist magazine, 02 July 2008, page 10

For the latest from New Scientiist visit www.newscientist.com