Monday, April 02, 2007

Was Earth Hour a candle in the wind?

Sydney's Earth Hour was an unconditional success in raising awareness about what we can do to fight global warming, with well over fifty percent of the population participating : :::[SMH]

MORE than half of Sydneysiders - as many as 2.2 million - switched off their lights to celebrate Earth Hour on Saturday night, a poll has found.

No one saw this avalanche of support coming - only 65,000 households had pledged to support the event.

However, a few have raised valid questions about the merits of the exercise in reducing carbon dioxide emissions, despite that this was always an ancillary objective. The most obvious one is that the emissions that were generated by the vehicle traffic that came to see Sydney dowsed, and to picnic along the foreshore bathed in flickering shadows, would have detracted from the total emissions reductions.

Another interesting point was raised by Sylvie Else, a contributor to Jennifer Marohasy's politics and environment blog, who suggests that those that turned to candles (I am guilty as charged) were generating more CO2 than they would have otherwise. She bases her assumptions on the guess that Energy Australia uses gas to supplement coal during peak hour usage: :::[Jennifer Marohasy: Earth Hour and candles: A note from Sylvie]

Leaving aside whether CO2 emissions are really a problem, if these people thought they were reducing CO2 emissions by their actions, then I rather think they were deluding themselves. Earth Hour was held during a time of peak electrical load, so any electricity generation displaced would be peak load, probably running on natural gas. Such generation produces about 500 grams of CO2 for every kilowatt-hour.

So turning a 100 watt light bulb off for an hour saves 50 grams of CO2, or 13 grams of carbon. A candle is mostly carbon by weight, and candle wax is only moderately less dense than water at room temperature. This means that burning just 5 cm of a typical 2 cm diameter candle will produce more CO2 than running the 100 watt light bulb for an hour. If the light that was turned off is fluorescent, then even less candle can be burned if there's to be a net reduction in CO2.

She is theoretically right - wax is a hydrocarbon chain - when you burn it, carbon dioxide is formed. So I undertook further research and posted back to her:


It's not as clear cut as you would imagine; The greenhouse friendliness of your candles depends on what wax they are made of.

Paraffin wax is derived from crude oil, and as we know that is carbon that has long ago been taken out the atmosphere and sequestered deep underground by nature. It also does not burn very cleanly, pumping soot particles into the air and causing discomfort for asthmatics.

However candles made from wax derived from beeswax or bayberry wax and other renewable sources are environmentally friendlier. As are candle wax made from other plant oils, such as soya oil, by a process called hydrogenation. Because the carbon in these oils was originally in the atmosphere before being taken up by the plant from which the oil is made, the effect on the environment is small.

But 'candle-miles' also need to be taken into account.

If everyone used soya oil candles as a light source instead of electricity, this would cut the need to burn fossil fuels to generate the electricity, therefore reducing carbon emissions into the atmosphere from fossil-fuelled power stations. But if the environmental impact of producing and transporting the candles is taken into account, then electricity (especially if it is generated from renewable sources) is a more environmentally friendly option.

If you want to act more effectively and not just be symbolic, source locally produced candles derived from renewable wax such as beeswax.

Technorati Tags