Greenhouse gases – more than just carbon dioxide
Climate change and carbon dioxide have certainly gained increased awareness over the last year, but there’s also other gases that contribute to global warming – some of them can trap more for far longer than CO2. What are these gases, what’s their impact and what are their sources?
“Anthropogenic” might be a term that you see around a lot now when the boffins are talking about global warming and greenhouse gases. Anthropogenic simply means originating from human activities, as opposed to those occurring in natural world.
(GWP) Global Warming Potential
This is another term you may see when greenhouse gases are being discussed – GWP.
As carbon dioxide isn’t the only greenhouse gas, but the one of primary concern presently, other gases that can contribute to global warming are compared to it. Gases also have differing lifespans to, so GWP is the ratio of heat trapped by one unit of a greenhouse gas compared to one unit of CO2 over a specified time period.
The hidden danger
Some of the gases below aren’t part of the Kyoto Protocol, therefore, their production doesn’t need to be reported. The danger is that any inroads made on reportable gases could lead to a false sense of security while being eroded by some of these other compounds.
Other greenhouse gases
Methane is a naturally occurring gas, but the Intergovernmental Panel for Climate Change estimates that 60% of global methane emissions are from anthropogenic activities which include:
- Fossil fuel production
- Cultivation of crops such as rice
- Clearing of forests
Livestock are notorious for methane production – particularly cattle. That’s part of the reason why reducing meat in your diet is beneficial for the environment. Methane from animals is the result of bacteria acting on food consumed.
Some humans also emit methane in limited quantities. I don’t think I need to explain that, but contrary to popular belief, only about a third of us emit methane when, you know – and it’s a very small amount :).
All jokes aside, methane is a potent greenhouse gas. While it has a shorter atmospheric lifespan than carbon dioxide, in the first 20 years it has a GWP (see definition above) of 62 – that’s 62 times the heat trapping capacity of CO2. And here’s the double whammy – methane breaks down to water and… CO2 (carbon dioxide). It’s the gas that keeps on giving.
Compared to carbon dioxide and methane, anthropogenic related nitrous oxide emissions are quite small, but this greenhouse gas has a GWP of 296 over *100* years
Anthropogenic sources of emissions include:
- Exhaust from cars, trucks etc.
- Coal fired electricity production
- Agricultural fertilizers
- Industrial production of adipic acid and nitric acid
So, to cut down on nitrous oxide emissions, we need to drive less and use less electricity (and switch to greener alternatives). We should also seek out fruits and vegetables that have been grown on organic farms – better still, more of us need to return to the old habit of having our own vegetable gardens!
Nitrogen trifluoride (NF3)
Nitrogen trifluoride production so far in 2008 is around the 4,000 ton mark and is projected to double in the next year. That mightn’t sound like much, but NF3 has an incredible 17,000 times the global warming potential of carbon dioxide. To date, no studies have been performed to determine the level of NF3 in the atmosphere. As it’s not covered under the Kyoto Protocol as being a reportable gas, NF3 is one of the compounds that threatens to bite deeply into any improvements in other greenhouse gas reduction efforts.
Nitrogen trifluoride is used in the manufacturing of LCD and plasma screens.
CFC-12 is a type of Chlorofluorocarbon, more accurately Dichlorodifluoromethane, which does not occur in nature. It’s an artificially produced greenhouse gas which was used extensively as coolant in refrigerators and air conditioners and was usually sold under the brand name Freon-12. It’s manufacture was discontinued in 1995 after it was found to cause terrible damage to the ozone layer. While it has been discontinued, be wary of old appliances such as refrigerators that may still contain freon gas. Call your local waste disposal authority to get advice on how to dispose of it.
CFC-12 has a GWP of 8500
HCFC-22 is a hydrochlorofluorocarbon, aka Chlorodifluoromethane or R22. It was also sold under a Freon brand name – Freon-22. It’s been used mainly in air conditioning applications, but is also being phased out due to environmental concerns, among them its impact on the ozone as a greenhouse gas. Air conditioning manufacturers will no longer be permitted to produce R22 equipment from 2010. If you’re buying an air conditioning system either new or second hand, check that it doesn’t use this gas.
It’s not only bad for the ozone layer, but HCFC-22 has a GWP of 1500
Hydroflourocarbon HFC-134a is one of of the most widely used refrigerant blends, fire suppressant and propellants – it’s pretty much taken the place of CFC’s and HCFC’s. However, it has a atmospheric life of 14 years and a Global Warming Potential 1,320 times that of carbon dioxide.
Tetrafluoromethane is another artificial compound – no natural sources have been found. It’s main source is primarily as a by-products of aluminum and magnesium smelting, but it’s also used as a refrigerant, in circuit board manufacture and some insulating materials. It’s also found in some stain protectors for fabric and carpet. Once released into the atmosphere, it’s greenhouse impact is basically irreversible – so recycle those aluminium cans and avoid using stain protectors if possible. I’ve also read that Tetrafluoromethane is used in some pizza boxes to stop the pizza from sticking to the cardboard – scary.
Tetrafluoromethane is a greenhouse gas with an atmospheric lifetime of a staggering 50,000 years and a GWP over 100 years of 5700!
Sulfur hexafluoride is used as an insulator in circuit breakers and other electrical hardware and is also a by-product of creating magnesium. It’s a greenhouse gas with a GWP of 22,200 times that of CO2 over a 100 year period. The demand for die-cast magnesium parts by the automotive industry is responsible for a major increase in emissions. Ironically, the auto industry is wanting more magnesium based components as they are lighter and therefore contribute to better fuel economy.
Carbon dioxide gets a pretty bad rap when it comes to greenhouse gases, and rightly so – but it’s certainly not the only culprit that’s causing our climate to change through global warming. It’s also important to remember that CO2 has a crucial role in the ecosystem. Without it, plants would die and most life on the planet would then follow suit. Plants need carbon dioxide in combination with light and water to create organic material. It’s the extreme level of CO2 we’re producing and there not being enough plants on the planet to cope with it that’s the problem. Other natural “carbon sinks” such as our oceans are rapidly becoming saturated with the stuff, to the point some are becoming acidic.
But carbon dioxide aside, awareness of other greenhouse gases such as the above can help give us extra impetus to green our lives wherever we can and to call on companies we buy from to do the same in order to minimize the amount of havoc we wreak on our fragile atmosphere. It’s rather frightening to think that the products we buy today may still have an atmospheric impact tens of thousands of years from now.
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