Green lightbulbs cut atmospheric mercury levels

You know that scaremongering that goes on about mercury and how cracking a low-wattage CFL (compact fluorescent lightbulb), is supposed to be so dangerous? Well, Popular Mechanics has done a little Fermi estimate (a back of an envelope calculation) to show that actually using CFLs (despite their mercury content) will ultimately reduce the amount of mercury in the Earth’s atmosphere:

CFLs contain about five milligrams of mercury, that’s a very small amount, about enough to cover the dot at the end of this sentence. A watch battery contains 25 milligrams and a manual home thermostat has hundreds of times as much at about 3 grams. Even breaking a CFL bulb is not likely to expose people to enough mercury to hurt them. Now, consider that burning fossil fuels is the main source of mercury in the environment.

A conventional smoke-belching powerplant will release about 10 milligrams of mercury into the atmosphere to power an incandescent light bulb but the energy needed for a CFL is a fraction of that at about 2.5 milligrams. Multiply those numbers by the numbers of lightbulbs around the globe (millions, billions?) and that’s a fourfold difference in mercury released to power incandescent versus CFL.

Of course, PM doesn’t discuss the many other factors that might have to be taken into account such as the higher production energy, materials costs of CFLs versus incandescents, and whether or not those are offset by the longer life of CFLs. It could be more interesting to compare conventional incandescent filament bulbs with their equivalent lumen value in LED bulbs…

5 thoughts on “Green lightbulbs cut atmospheric mercury levels”

  1. You miss the point. Coal-fired power plants spew a form of mercury into the atmosphere and that has distinctly adverse health consequences. You seem to think that using one type of light source rather than another will make a difference in total energy consumption and therefore reduce the pollution. You base this on the reduced wattage required by CFL bulbs. But this premise is flawed because electricity production is not really sensitive to electic light use. A neighbor turning on her air conditioning next door will require more electricity than is saved by my installing CFL bulbs.

    The real problem is coal-fired polution always includes mercury and excessive green house emissions. The better way to reduce atmospheric pollution is not through changing light bulbs but changing the electricity production technology to nuclear power, which eliminates all air-borne pollutants.

  2. While you are right about the prevelence of air conditioning, you still do not understand the point. If your goal is to reduce mercury emissions, the best strategy is to switch electricity production technology, not light bulb types. If the rest of the world could afford it, there are obviously huge population centers where air conditioning would be adopted if it were available since so many people live in hot climates for at least part of the year. But that has little to do with the question: electricity production is not driven by choice of lightbulb even in countries where there is no air conditioning.

    Electricity use for household lighting is never going to drive baseload demand in population centers. Therefore you can switch from any type of lightbulb to any other without any significant effect on required baseload production capacity. So if you are using coal as a generating source, it just won’t matter what lightbulb you use. Mercury pollution will still be a big problem.

    So your advice is essentially irrelevant worldwide.

    1. By the way, it’s not my advice. I think the PM article is less than an in-depth thesis too. I think the clue is in the name of the magazine and the name of the magazine from which their item appears to be cribbed. I assumed that the article is more about raising awareness of the point that you have to look at any “solution” from various perspectives. Use of CFLs won’t lower atmospheric Hg concentrations, but it may have a small impact on how much electricity needs to be generated. Other things would have a much bigger impact, of course. Teach certain nations to work without A/C and to use their legs instead of cars and that might help. (Hybrids don’t solve anything, by the way, just relocate the pollution).

      I certainly don’t think nuclear is without its own issues, even the most ardent advocates I’ve spoken to recognise that it has an environmental footprint. It is just that the nuclear footprint is so very different from coal-fired (comparing the risks is like comparing car travel to flight). Social power generation and micro-grids have potential with everyone generating their power and heat using kitchen and toilet waste (necessarily supplemented with a natural or biomass hydrocarbon pumped into homes and building) and with some on-roof solar and wind where it works and in hotter climes cooking with solar cookers).

  3. David, the Popular Mechanics argument doesn’t sound very strong. There is no per-country quantification of the percentage of electrical power currently used to light incandescent lights. I could find no percentage of homes using AC. I did see that usage is rapidly rising in China, India, and even the UK.

    I’m skeptical that converting to CFs will actually lower atmospheric mercury. I see no numbers showing that the use of more-efficient light would actually lower usage of coal-fired facilities.

    Mercury contamination from broken CF bulbs are probably not dangerous for most of us. I would recommend caution for pregnant women.

    This argument about CFs will only disappear when they are made shatterproof or are eventually replaced by LEDs or other new lighting technologies.

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