Choosing light bulbs

As part of my ongoing mission to reduce our electricity consumption, I've been using low-energy light bulbs for years. We still have a few of the old-style incandescent bulbs in rooms where we switch the light on only briefly (i.e. the loo and bathroom) because the low-energy ones take a while to get going (actually, the newer ones probably aren't too bad. Ours are mostly quite old). This chimed nicely with last week's Change the World Wednesday challenge, which was to replace at least one incandescent bulb in the house with a low-energy bulb.

Having said that we only have old fashioned bulbs in rooms where they're switched on briefly, I have to confess I wasn't telling the whole truth there: We still had halogen bulbs in the kitchen. We'd been meaning to replace them with LED bulbs, but had had trouble finding any in local shops. By coincidence, in the same week as the challenge, one of the halogens blew and Ian ordered a set of four LED bulbs online (they're nowhere near as expensive as they used to be, by the way).

LED bulbs replacing halogens in our kitchen

So, challenge met with zero effort on my part! I have to say, we don't like the new bulbs very much. They're a very cold light and, being so directional, make the kitchen seem much darker than with the same amount of light more evenly spread around. I'm sure we'll get used to them in time.

This isn't the end of the story, though. The challenge prompted some very interesting discussions of the pros and cons of different types of light bulb, both in comments on the original blog post, and in linked blogs. In particular, Argentum Vulgaris had quite a lot to say about the cons of CFLs (compact fluorescent lights - like the old fluorescent tubes, but smaller), following up his earlier post on the same subject. I was quite shocked to learn that there are lots of reasons not to like these increasingly ubiquitous bulbs, and set about doing some research. Here are the various objections and what I've learned about each one.

1. They contain mercury. Do they? Well I never knew that. Not only do they contain mercury, but the way they produce light it by vapourising mercury. This poisonous chemical is their very essence! While the mercury is safely contained within the bulb, this may not be a very great concern, but what if one breaks? Mercury vapour is not something you want to be inhaling. Luckily, it turns out that the concentrations of mercury vapour in the air that might result from breakage are nowhere near high enough to do you any harm (though I probably still wouldn't bend over to clear one up straight after it had broken, just to be on the safe side).
   
   That's not the only concern, though. It seems that the main worry about mercury is that, once released into the environment, it gets into the food chain and particularly builds up in fish (presumably not good for the fish, though no-one seems terribly worried about this), which we then eat (not good for us - a major concern). So if all these CFLs that we're now fitting in our houses end up in landfill, will they release a lot of mercury pollution into the environment? One answer that I came across in various places is that the amount of mercury they'll release is outweighed by the savings in emissions of mercury from coal-fired power stations. That claim has to be worth a bit of investigation.
   
   First fact: Coal burning is the biggest human-generated source of mercury in the atmosphere. There are non-trivial amounts of mercury involved here. Estimating how much is tricky, though, because coal is not a pure substance - it's a mixture of all sorts of stuff, varying from place to place. The amount of mercury in coal varies enormously. I did manage to find some estimates, though: The amount of mercury in coal varies from 0.012 mg/g to 33 mg/g, of which 90% is released into the atmosphere. The next question is: How much coal is burned to generate one kWh of electricity? That answer is fairly easy to find: It's 0.36 kg, or 360 g of coal. Using the very lowest figure for amount of mercury in coal, we can calculate that generating 1 kWh of electricity by burning coal releases 3.9 mg of mercury into the atmosphere. Coincidentally, that's almost exactly the same as the amount of mercury in a CFL bulb.
   
   That means that if you can save just one kWh of electricity with your CFL bulb, and if your electricity comes from a coal-burning power station burning the very cleanest coal, then the CFL is releasing less mercury than the incandescent bulb. I feel a graph coming on...
   
   
   
   Electricity used by incandescent and CFL bulbs
   
   If you replaced a 100W incandescent light bulb with a 30W CFL (and that's a fairly high powered CFL on the usual equivalents), by the time you'd used the light for 15 hours you would have saved the same amount of mercury in power station emissions as the mercury you might release when you eventually throw the bulb away. Remember, that's with the very cleanest coal; the dirtiest coal contains several thousand times as much mercury as that. Of course, this only applies if your electricity is produced by a coal-fired power station. I'm not sure whether mine is or not, but this analysis persuades me that mercury is a non-issue.
2. CFLs emit electromagnetic radiation. Well if they didn't, they wouldn't be much use. Light is electromagnetic radiation!
3. CFLs emit UV radiation. OK, this is a bit more specific, and yes, they do. So does the sun. It's possible to get sunburn from CFLs if they're within about 30 cm of your skin, so you may want to consider how close you put your desk lamp.
4. In a cradle to grave analysis, CFLs use more energy than incandescent bulbs. I have to quote this one: An International Association for Energy-Efficient Lighting (IAEEL) study conducted in Denmark, explored some carbon footprint factors, but not all, showing it took 1.8 Kwh of electricity to assemble a CFL compared to 0.11 Kwh to assemble an incandescent bulb. That means it took 16 times more energy to produce a CFL. Yes, but we've already seen how quickly a kWh or two can be saved when using these bulbs. The study did not include the fact that a CFL is much heavier and is more dangerous to handle, and will thus cost more to package, to ship, and to sell. Um, much heavier and more dangerous? I don't think so. Maybe a little bit heavier, but it's not going to make that much difference. This research also did not calculate the energy required to safely dispose of a CFL and reclaim the mercury. The cost of removing mercury from the landfills was also not considered. As already discussed, the quantities of mercury involved are trivially small compared with that released by burning coal. There will be no cost of removing it from landfill. If such a study could be done, and considered all the negative contributing factors, it would show a CFL has a massive carbon footprint, one that would dwarf a regular incandescent light bulb. I doubt it.
5. The waste heat produced by incandescent bulbs makes a valuable contribution to heating our homes. Heat rises. Do you really want to heat your ceilings?
6. CFLs emit ultrasound. This is interesting. (Actually, most of the article is really annoying, but the bit at the end is interesting). Yes, it seems that CFLs have something known as electronic ballast, which turns the power on and off very rapidly to stop a runaway reaction in the bulbs, which would destroy them very quickly. This operates at a very high frequency, too high for humans to hear but within hearing of just about every other animal. Well, all I can say to this is that my cat doesn't seem overly bothered by it. On the other hand, older fluorescent tubes, which operate at a lower frequency, can be unpleasant to work under, and Mrs Green reports that they give her insomnia and dizzy spells. In my opinion, this is the only good reason for not using CFLs.

After all this research, I've found only one good reason (and there were others that I can't be bothered to go into here) for not using CFLs, and I'm lucky enough not to be affected by this. Don't fall for the scare stories!