Ever wondered what teh real eco-benefit is to using CFLs instead of incandescents, which are now being phased out completely for household applications? Here's my analysis. Feedback welcome. Also, if anyone want to work with me on producing a series of shorts along the lines of this paper, get in touch! There's a lot of magical thinking around people's "green" behavior. I'd love to dig into some of these areas a little and demystify things.
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To compare the now-familiar
compact fluorescent bulb to the traditional incandescent bulb, it is important
to look at more than just the obvious and much touted difference in energy
consumption between the two, which is a well-established difference. Worth
examining are not just the amount of electricity used and the amount of lumens
emitted per watt used, but also the money spent by the end-user over the life
of the bulb, what is necessary to make each of the two different types of bulb,
where that occurs, how they all get here, and what happens to them after
they’re no longer serviceable.
Here are the two bulbs in
question: a Sylvania #12750, 100 Watt, 120 volt frosted bulb, 1710 lumens, 750
hour estimated lifespan, priced at $0.65, and a
CFL Philips lighting #137158, 27 watts, 1750 lumens, 10000-hour
lifespan priced at $2.90.
The
incandescent gives us 17.1 lumens per watt versus the fluorescent’s 64.81
lumens per watt, a clear advantage in energy spent for light gained. This is not news.
Also
not news is that the incandescent has far superior color rendering. Incandescent light are what is termed a
“black-body lamp”, so called because the light is generated by heating matter,
the “black body” in question, up to the temperature at which it glows. Another
familiar black body is the sun.
These black body sources distribute light on a smooth curve across the
visible spectrum of radiation. The
Color Rendering index uses the light from this other blackbody, the sun, as the
source as the benchmark for what constitutes perfect color rendering. Fluorescents emit light with an uneven
distribution across the visible spectrum with spikes in certain frequencies,
which we humans find unnatural and unpleasant.
Assessing
the costs over ten thousand hours, the estimated lifespan of the longer-lived
bulb, gives us the following results.
Assuming a price of 10.9 cents per kWh, which is what I paid in October
2010, and that the replacement price for the incandescent stays the same as the
initial purchase price, .65, it works out to a financial savings of 105$ over
the 10,000 hour time span. The CFL uses 27w, working out to 270 kWh over its
life, whereas the incandescent uses 1000 kWh over the 10,000 hour time span and
needs to be replaced 13.33 times. This replacement factor comes up in every
area of examination, that however small the difference between the two bulbs
might seem initially, it becomes much greater when multiplied by 13.33.
As
far as the production of the two bulbs is concerned, there are several elements
to examine. The first is where are they made and what does it take to get them to
the end-user in Brooklyn. Both Philips and Sylvania make most of their bulbs in
China, not surprisingly, so one could consider that factor to be equal between
the two bulbs. It might even seem
to be an advantage for the incandescent bulb, since by the case, a 100w bulb
weighs .096 lb. including packaging, while a 27w cfl weighs .225 lb. including packaging, only 42% as much. However, once you include the number of
times the incandescent will be replaced, the numbers look much different. We have 1.28 pounds of incandescent transported
from China versus .225 pounds of compact fluorescent, 569% more.
The
next question is what does it take to make each of these bulbs. An incandescent
is a glass capsule, a tungsten filament, two nickel-iron lead wires, and a
glass-and-aluminum base. A
compact fluorescent is a glass tube, a phosphor coating, some mercury vapor, a
filament, circuit-board ballast, and a plastic and aluminum base.
The
process for making an incandescent bulb is as follows: the filament is made by
drawing heated tungsten wire through a die, after which it is annealed with
heat and wound into its characteristic spiral and treated with acid to remove
the mechanism used to make the spiral. The lead-in wires are inserted. The
glass casings are made by running a ribbon of heated glass along a conveyor
belt, where air nozzles blow the glass into molds that give them their shape.
The base is stamped in a mold, the whole thing is put together in a machine,
after which it is filled with argon and nitrogen and sealed shut mechanically.
Not nothing, but it doesn’t involve as many steps or as much energy as the
process for making a compact fluorescent bulb.
The
process to make a CFL is this: The glass is blown into long tubes, which are
then cut to length and twisted into a spiral while still heated. The inside of
the tube is rinsed with titanium dioxide, pretreated with another chemical,
then coated with phosphors on the inside and baked. The filament is assembled by a machine, then coated with
electromagnetic powder, and inserted into the glass tube. The tube is then
passed through a torch-like machine to remove impurities and the inside is
rinsed with argon. Then the mercury is vaporized and injected into the tube.
The circuit board ballast is printed, and then glass, filament and circuit
board are glued into a plastic and aluminum base.
The
manufacture of both bulbs is a complex industrial process, but from the
preceding paragraphs, it is clear that CFL manufacture has more steps and more
heat-based processes, not to mention a higher end-user price, showing us that
CFL manufacture is more energy- and material- intensive than incandescent
manufacture.
The
incandescent uses about a third less glass than a CFL, about 9 in2 versus about 25 in2, since
the simple bulb has much less surface area than the long corkscrew shape, and
they both use roughly the same amount of aluminum in the screw base, but the
incandescent loses out even in these areas because of the one-thirteenth length
lifespan. 119 in2 used
for the incandescents, 25 in2 for the CFLs.
In
the area of side effects of manufacturing, the incandescent rises slightly in
comparison. There is nothing
particularly toxic in incandescent bulb manufacture, other than the processes
necessary to get the raw materials of aluminum, glass, nickel, iron, tungsten,
argon and nitrogen, many of which materials are also used in the CFL. The process of manufacturing CFLs is
certainly more of an environmental concern based on the following data.
Not all CFL bulbs comply with
the E.U. Restriction of Hazardous Substances of 2006 standard for manufacture
of electronics, which bans the use of lead, mercury, cadmium, hexavalent
chromium, polybrominated biphenyls, and polybrominated biphenyl ether. Therefore, some of them are still made
using these extremely toxic and long-lasting chemicals. Another piece of
evidence, albeit circumstantial, is that compact fluorescents are almost
entirely manufactured in developing nations with lax environmental regulations,
such as China and India. One reason they are cheaper to make them there is the
lack of environmental laws. So as
far as toxicity of manufacturing process is concerned, the incandescent is the
clear winner.
Toxicity
brings us to the topic of mercury, which is the one negative issue people may
have heard raised in connection with compact fluorescents. Mercury is a
high-profile toxin. Many U.S. states have a fish consumption advisory due to
the presence of mercury in fish. Mercury is highly toxic to the central nervous
system and the kidneys and it is estimated that up to 10% of all children born
in this
country are at risking of having impaired neurological
development due to
mercury. It is no longer mined in most industrialized
countries because it is too locally toxic, too expensive on account of environmental
protection laws, politically unpopular, or all of the above. Currently, the main producers of
mercury are China, Kyrgyzstan, Mexico, and Algeria, none of whom is noted for
having strong environmental protection laws. Spain, formerly a major producer, has recently discontinued
mercury mining.
5 mg of mercury per bulb is the
current DOE Energy Star rating guideline for mercury content of compact
fluorescent bulbs, but that is only for bulbs compliant with that standard, and
some other CFLs claim to have significantly less than 5 mg mercury in them. The bulb we are using as our example is
Energy Star compliant, so we will assume that it contains 5 mg of mercury. At this point, it looks like the
incandescent is clearly ahead of the CFL because no mercury is involved at all
in its manufacture versus 5 mg for the CFL.
Important to take into account
here is that mining for industrial use is not the only source of environmental
mercury. Emissions from coal-fired power plants are a major source,
approximately .0234 mg of mercury per kWh of electricity generated. America
gets approximately 45% of its electricity from burning coal, so if we take 45%
of the 1000 kWh to be used by the incandescent, we get 23.4 mg of mercury
lofted into the atmosphere by our incandescent. For the CFL, the number is 6.318 mg of mercury released by
the electricity consumption and 5 mg contained in the bulb, totaling 11.318 mg
of mercury. Again, the CFL is
ahead, even on mercury.
There is the question of how
much the CFL is ahead on mercury, because we don’t know if the 5 mg inside the
bulb will be released into the environment or recycled. When compact fluorescents are thrown
away with regular garbage, they are generally tossed in a landfill, where they
break, or are incinerated, where they also break. Obviously when they are incinerated, their mercury enters
the atmosphere, but when they are landfilled, some of the mercury still leaches
out horizontally in gaseous form.
Let us consider landfills to be part of our environment in the long
term, and say that when mercury is thrown in a landfill, that mercury can be
considered to be in the environment.
Three studies done in Maine
brought back CFL recycling rates of 2%, 6.7%, and 23.5%. Until better data becomes available,
we’ll use the average of those three results, about 10%. Subtracting 10% from the 5 mg contained
in the CFL bulb, we have a final mercury scoring of 10.818 mg mercury for the
CFL and 23.4 mg of mercury for the incandescent, (provided that the end user is
not one of those people who pays the extra money to get all of their
electricity from renewable sources) still a clear advantage to the compact
fluorescent.
Beyond mercury, we have to
consider mass entering the landfill, which is similar to the earlier
transportation topic. After the
mercury from a CFL is reclaimed, the rest of it goes into a landfill, as does a
traditional incandescent bulb at the end of its life. Per ten thousand hours of illumination, we now have .225
pounds of compact fluorescent going into a landfill or incinerator, less a
negligible amount for the 5 mg mercury removed, versus 1.28 pounds of
incandescent.
To summarize, here are the
differences between the two bulbs. Incandescents look nicer and are cheaper and
less toxic to make, but not when you consider that you need thirteen times more
of them. Compact fluorescents have
a more complex, toxic and energy-intensive manufacture process, and do contain
mercury that could end up in the end-user’s immediate environment, but because
they last so much longer than incandescents, they come out ahead on all
counts. When that lifespan
multiplier, a factor of more than thirteen, is taken into account, they cost
the user less in the long run, they give more light for the amount of energy
used, they use less resources in their manufacture and transport, and they take
up less space in landfills or capacity in incinerators.
The concerns with compact
fluorescents that must be kept in mind are ones of toxicity. One should make sure to buy compliant
CFLs (the TCP brand is an example), and be sure to recycle bulbs that no longer
work to avoid depositing that mercury in one’s own immediate environment. Energy Star’s savings calculation
spreadsheet also has some nice green bromides further encouraging you to use
them. They state that replacing
one 100w incandescent with a 27w CFL is the equivalent of taking one tenth of
one car off the road for a year, has the equivalent air pollution reduction of
1/8 of an acre of forest, and will save putting 1150 lbs of carbon dioxide into
the atmosphere.
yours
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