Burning Candles

CandleThe third Earth Hour takes place tomorrow night and once again I have been asked about carbon emissions from candles. So, without wanting to be a party-pooper, I thought I would dig up some calculations from a year ago, courtesy of the friendly family power engineer (you know who you are!).

Tomorrow night, many people will turn off the lights for an hour and light up candles instead. Since the candles themselves emit carbon dioxide (CO2), the question is will we end up reducing emissions for the hour or not? Of course, it all depends on how many candles you light up and what sorts of lights you turn off.

Since candles don’t actually emit very much light, the temptation (particularly in bars and restaurants) is to light lots of candles.  To make it concrete, think of a 40 Watt (W) traditional incandescent light-bulb. Although a 40W light bulb is not very bright, it actually emits the equivalent light of around 40 candles. The amount of CO2 emitted is equivalent to at most 5 or 6 candles. So if you turn off one light and replace it with enough candles to generate an equivalent amount of light, you’d be emitting at least 7 times as much CO2 as using the light-bulb. So, the moral of the story is not to light too many candles!

The comparison gets worse if you use energy-saving compact fluorescent lamps (CFL) rather than incandescent bulbs. A 7W CFL bulb gives about the same amount of light as a 40W incandescent bulb or around 40 candles. However, the carbon emissions from this bulb is equivalent to one candle. Admittedly, this is a fairly dim bulb, so you’d be more likely to be using a brighter bulb. But even if we considered a 14W CFL bulb (equivalent to a traditional 75W bulb) this produces emissions equivalent to two candles but the light output of almost 80 candles.

So if it was just about reducing emissions, you would be far better off leaving on CFL bulbs (and switching as many of your old bulbs to CFL as possible) than lighting candles at home or in bars and restaurants. Of course, it’s more about the symolism than anything else. Furthermore, there is a real saving in commercial premises like office blocks where the lights are turned off and nothing is turned on in their place.

One final point people make is the source of the CO2. Coal-burning power stations release carbon that has been buried in the ground for a very long time, while beeswax candles release carbon that has only recently been captured (of course paraffin candles are just as bad as coal-fired power stations!). While this is true, the end result in terms of CO2 in the atmosphere is the same. Perhaps the best thing to do is to buy the candles and keep them in the bottom drawer for emergencies and keep the carbon captured, while lighting your house with CFL bulbs!

The (Optional) Details

For the brave of heart, here are some of the details used to calculate the figures discussed above.

The aim of these calculations is to compare the carbon emissions of candles, traditional incandescent light-bulbs and energy-saving compact fluorescent lamps (CFL). To make this comparison fair, we should take into account the fact that candles emit much less light than light bulbs. The traditional unit of brightness for candles is candlepower, so I will start with a hypothetical candle that emits one candlepower of light. In more moden units, this is a luminous intensity of 0.981 candela.

Now, to complicate matters, the light output of bulbs is typically quoted in terms of lumens, a measure of luminous flux. The relationship between flux and total intensity depends on the area over which the light is emitted (e.g. a pinhole light might have high flux, but not much total intensity). For our purposes, I will assume that we have an unshaded bulb which emits light in just about every direction.

According to wikipedia, a 40 Watt (W) bulb has an output of 500 lumens, which converts to an intensity of 39.8 candela or 40.6 candlepower. So, our relatively dim 40W bulb generates as much light as about 40 candles. While there is a fair amount of variation amongst CFL bulbs, a typical 14W CFL is equivalent to a 75W incandescent light bulb. To get to the equivalent of our 40W bulb, we would need a CFL of about 7W. To achieve the equivalent light intensity of a 40W incandescent bulb, it would therefore require 40 candles or one 7W CFL.

Each hour a small candle burns at least 2.5 grams of candlewax (most candles would be worse than this), which contains a little over 2 grams of carbon, producing 7 grams of CO2 emissions.  So 40 candles would produce about 280 grams of CO2 each hour. These figures are based on the Hex Jar burn time in this table of candle burn times, which burns 1.5 oz of candlewax in 12 hours. Many others in the list burn at a faster rate.

Coal-burning power stations typically emit CO2 at the rate of 1kg/kWh or 1 g/Wh (need to dig up a reference on this one) (US National Renewable Energy Laboratory figures of 1.114kg/lWh are quoted here). This means that the 40W incandescent bulb produces around 40 grams of CO2 emissions each hour, while the equivalent CFL bulb is only 7W, and so it produces only 7 grams of CO2 emissions each hour. Of course, if your power comes from renewable sources, the emissions of these bulbs may be lower.

Photo credit: Rickydavid on flickr (Creative Commons).

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24 thoughts on “Burning Candles

  1. Matt Moore

    Hmmm – I’m a bit cynical about Earth Hour. Nice calculating BTW.

    I’d rather have an evening where everyone bought a CFL for someone is their life – and then you got to turn it on for that hour. Or else you got to do something real rather than playing at being “environmental”.

  2. Mark L

    Hi Sean,

    Yes, the use of candles certainly should be avoided. And I applaud your analysis — we need to make sure our efforts are having the effects we intend. Also, it is good to see that your sensible concluding advice is “not to light too many candles”. Bjorn Lomborg has used the same facts to argue in The Australian newspaper that we should give up on Earth Hour altogether, which is the kind of abuse of statistics for which he has become famous. Funny to note that he has changed his tune since his book The Skeptical Environmentalist, in which he argues that any response to climate change is a waste of effort.

    Another thing to note is that many participants in Earth Hour will have 100% Green Electricity, in which case turning off the lights has minimal impact, and burning candles is then definitely a bad idea.

    I’m not sure I agree though with your conclusion on the difference between carbon in coal and that in candles, namely that “the end result in terms of CO2 in the atmosphere is the same”. If the wax comes from organic sources, such as beeswax, and not as a by-product of the oil extraction chain, and if the candles would not have been produced if you didn’t purchase them, then the net effect on the atmosphere of you choosing to burn the candle is zero (ignoring the energy used in production, transport, etc.). The production of the wax trapped carbon from the atmosphere in the candle, and you are just releasing it again. This is unlike coal, where the production of it drew nothing from the atmosphere.

    Of course, you could have bought the candle and then buried it, thus causing a net withdrawal of C02 from the atmosphere — but that would be an active C02 reduction strategy, much like any carbon capture and storage program, and really has nothing to do with your consumption of lighting. You could have done the same thing if you hadn’t switched off your electric lights.

    For a reference on the emissions of coal-fired power stations, you could use
    http://www.repp.org/repp_pubs/articles/envImp/06analysis.htm which gives the life-cycle emissions of current US coal-fired power as 1,114 g/kWh.


  3. Sara

    “a small candle … producing 7 grams of CO2 emissions”
    “40W incandescent bulb … 40 grams of CO2 emissions”
    “equivalent CFL bulb … 7 grams of CO2 emissions”

    Ok, so a CFL bulb produces the same emissions as a small candle. If we’re going for equivalent lighting, then the bulb makes sense. However, most people are running MANY lights in their home in addition to electronics, etc. If they use only one small candle for the hour, it’s still much better. And really this is about lowering CO2 emissions. One candle, one hour.

  4. stubbornmule Post author

    @Sara: If only people were lighting just one candle! Articles like this one show that people assume that any number of candles are better than light-bulbs. Since most candles you buy are paraffin, a fossil fuel, lighting up half a dozen candles is almost certainly going to put you behind in terms of emissions. Also, I would question how many people would turn off their electronics along with the lights. I suspect many computers, TVs, stereos, etc were on while the lights were off.

    Of course, as I note in the post, the point is more symbolic than anything else and so I turned off my lights along with everyone else, but tried to keep the candles to a minimum. The real benefits from Earth Hour are firstly raising awareness and secondly the savings from switching off lights in office blocks rather than homes. What annoys me the most, prompting this article, are the restaurants and bars which make a point of participating but by lighting dozens of candles (almost certainly paraffin). They are almost certainly emitting more than they would if they left the lights on.

  5. stubbornmule Post author

    I wouldn’t judge paraffin versus soy based purely on cost. In terms of carbon emissions, both would emit carbon. An argument can be made that candles from renewable sources (including beeswax and soy) are preferable to those from non-renewable sources (paraffin). While this would not reduce the emissions from burning a single candle, at least the carbon release, capture cycle is shorter: the existence of the industry making these candles could be argued to increase the rate of carbon capture at the margins. I also found a discussion about the two types of candles that you may find interesting.

  6. harry

    My opinion is, its better to use energy saving bulbs than going to all this kinds. Using oils for lighting may also affect health. Thanks for sharing with us.

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  9. nicky

    I just have to say that I don’t know anyone who would expect to get the same amount of light from candles as bulbs during earth hour. This article was well done but it assumes that you would need to have full light. And it didn’t take into account alternative materials for candles. I would like to see a comparison of those. What this comes down to is that we are so american that we can’t live without a highly lite room for one hour. Why can’t we give up a little light? Is it really that bad? Lighting 2 or 3 candles for an hour is nothing.The fun is sitting in low light and telling stories or playing music or games or talking or enjoying the stars with your friends and family.

  10. Stubborn Mule Post author

    I have no problem at all with people lighting 2 or 3 candles, the post was really motivated by the pictures in newspapers and on television reports after previous Earth Hours of restaurants and bars with hundreds of candles burning on every flat surface.

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  16. Ram Mohan

    Hi Sean, stumbled on your blogpost on candles while trying to read up on emissions and carbon from candles! Great perspective. What I’d like to say is we advocate swapping CFLs with LED light bulbs as Mercury contamination is getting worse in villages in Africa where they’re disposed in garbage heaps near water sources. We also advocate aginst the use of candles as they’re dangerous in villages as well in urban homes in Africa.
    And they’re also expensive with a candle that burns for 6 hours costing 20-25 USD cents. Do you have any comparative figures for LED Bulbs?
    I can link you on to Dr Kushant Uppal who manufactures these LED solar bulbs in India. We are on a drive to replace Kerosene lanterns and Candles with Hi quality Solar LED lights.
    Strangely enough my mascot is an Ass I call Jack that lives a retired life on my farm in The Gambia.

  17. Alcidas

    There is a fallacy in your argument. You assume that the person who does not switch on a 40W electric light bulb must use 40 candles in place of the bulb. This is not a valid assumption.

    A person who is replacing an electric light with candles for reading might have to do this, but for those who simply want some illumination, it may only be necessary to use one or two candles in lieu of the electric bulb.

    My wife and I often dine by candlelight, and when we do so we use a maximum of two candles.

    Therefore, assuming that your figures are accurate, we would only be emitting 14 g of CO2 per hour, instead of 40 g with the electric bulb. Of course, our two candles do not give us as much illumination as the one electric bulb, but the whole point is that, unless you are reading, it is usually not necessary to have that much light in the first place.

  18. Ram Mohan

    Hi Alcidas & Stubborn Mule

    We come from a completely different world. Every villager here eats
    virtually a candle lit dinner. Lit in small dark huts, children study
    around this little candle.
    Inhalation of the fumes from the proximity of their faces to the
    candles is certainly a cause for frequent respiratory illnesses
    A simple study done in the region estimates that the saving from not
    buying a candle, spread over just 500 villages results in a saving of
    15,000,000 USD every six years. What the carbon emissions are , heaven
    and experts like you would only know.
    Put together with the loss of property and lives in Africa , caused by
    the candle, one can only hope that we see sense and eradicate the
    candle from villages in Africa.


  19. tapaninyc

    In a public spaces such as restaurants, candles are permitted for decoration only, so adequate lighting must be left on regardless.

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