Oh, no, not another greenhouse gas!

Thirteen years ago the Kyoto Protocol attempted to limit emissions of six types of greenhouse gases; these are carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride. You can see the effect of these if you put “Global Warming Potential Index” into the search facility that good folk at WordPress have kindly provided near the top of this web page.

There are other greenhouse gases, which have only fairly recently been found to have heat trapping qualities. These are not covered by any international treaty. The most damaging of the greenhouse gases unaffected by Kyoto is nitrogen trifluoride (NF₃), which looks set to become a rapidly growing greenhouse gas problem.

 You might be relieved that this obscure chemical is not an ingredient in any of the cleaning products is not under your kitchen sink or in your garage or workshop, but it is cleaning agent: nitrogen trifluoride is mainly used in equipment cleaning, but also as a plasma etchant for thin-film liquid crystal displays and thin-film photovoltaics. Ironically, thin film photovoltaics, designed to avoid emissions produced by fossil fuel burning may end up causing just as bad a greenhouse effect as carbon dioxide does unless the use of nitrogen trifluoride is properly controlled, or better still an alternative is found which does not damage the environment.

Nitrogen trifluoride is also widely used in electronics. If you have cellular telephone, an MP3 player and a flat screen television or a computer, or anything else that contains semiconductors the nitrogen trifluoride will have almost certainly been used in its production. The production of semiconductors across the world is a massive industry. Semiconductors are usually made of silicon, a very common element and work devices such as flat screen televisions by allowing electronic conduction in a solid state.

Solid state electronics manipulate current to create the messages that cause the letters of my the words to appear on my screen when I hit my keyboard as I type this post. Nitrogen trifluoride has been used to enable me to write these essay that can be read virtually anywhere in the world (and they seem to be) as well as to enable the readers to read my essays.

Nitrogen trifluoride was first introduced in the semiconductor industry as an alternative to the perfluorocarbon (C₂F₆) which has an atmospheric lifetime of 10,000 years and is about 9,000 times more powerful a greenhouse gas than carbon dioxide. Fortunately for everyone perfluorocarbon is emitted into the atmosphere at a tiny rate, compared with the dreaded CO_2.

Whereas the 100 year global warming potential of carbon dioxide is 1, the 100-year global warming potential of Nitrogen trifluoride is 16,800. Its shelf life – the “best before date” or rather the “worst before date” is 550 years compared with 100 years for carbon dioxide.  

Increasing demand saw worldwide production of nitrogen trifluoride rise by about 50% from 2008 to 2007 and the signs are that it continues to rise.  Of course, manufacturers and users of nitrogen trifluoride do try not to waste any or allow any to escape into the atmosphere. However it is startling to learn from Michael Prather’s work that if all the nitrogen trifluoride produced this year were to be released into the atmosphere, it would have a global warming effect as severe as 67 million tonnes of carbon dioxide in the air, a small amount compared with the 7.5 billion tonnes that goes and stays in the air, without being recycled by plants and the soil and the oceans.  

There is no monitoring of nitrogen trifluoride in the atmosphere. Its control is largely left to local health and safety regulations –an often under resourced inspectorate in many places. Most of the nitrogen trifluoride produced is destroyed and never reaches the atmosphere. Two studies have found that only two to three per cent of the gas escapes destruction after its use. If you rely on manufacturer’s estimates of the escape of the gas you are relying on self reporting by the very industry that benefits form the production of nitrogen trifluoride; that is not generally satisfactory for something with such a high level of danger, in terms of its shelf life and its massive global warming potential.

Mr Prather intends to monitor the levels of nitrogen trifluoride in the air. It seems odd that we need to rely on one scientist to do this and odder still that there is no international regulation of nitrogen trifluoride, but then again, no odder than the Kyoto, an inadequate mechanism to control climate change.