book_cover_big.gifLately the compact fluorescent lamp (CFL) is strongly recommended to replace the incandescent light bulbs (ILB). The main reason is because CFL’s can save a considerable amount of energy during their lifetime; at least that is what is claimed.

Before scrutenizing that claim closer, first a few facts about the lamps it self. The classical ILB, that has been with us basically since the invention of generating light out of electricity operates through a simple principle. A (tungsten) wire is heated through the passage of current to a temperature of about  3000 °C. At that temperature the wire (acting as a black body) emits almost white light. In contrast, the CFL is much more complicated and operates on the principle of a gas discharge. When a gas at lower pressure is subjected to the passage of a current a complex chain of events takes place that eventually results in the generation of UV radiation. When UV light hits a proper chosen phosphorous layer (coated on the inside of the glass tube) the UV light gets converted in visible light. The phosphorous layers are now so sophisticated that the color of the light of a CFL matches that of an ILB. CFL’s can live 4 times longer than ILB’s.

But there is more to tell. A CFL of  18W generates as much light as an ILB of 100W. Thus the amount of electricity needed to drive the lamp is a factor of 5 lower for the CFL and that is at first sight of course a big advantage. Certainly if you realize that about 25% of the electricity generated in the world is used for lighting purposes! However, if you hold an ILB in one hand and a CFL in the other hand you feel immediately a big difference in weight. This is because a CFL is much more complicated to operate than an ILB. A CFL needs an electronic circuit (called a ballast) to ignite and maintain the gas discharge in the tube. This ballast contains a substantial number of components. Thus the question arises if you take into account all the energy for manufacturing, shipping and dispose a CFL, will the energy balance then still be in favor of this lamp versus that of the ILB?

The answer to such a question can only be obtained by a careful Life Cycle Analysis (LCA). Several LCA’s have been done for CFL’s and ILB’s. A recent one is done by David Parsons[1] from the university of Southern Queensland, Australia. In the rest of this blog I quote a few of his conclusions. In an LCA many energy and environmental aspects of a given product are analyzed:

  • Components, processes, materials and quantities used
  • Manufacturing
  • Packaging
  • Transportation
  • Energy used in retailing and wholesale
  • Energy usage during usage
  • Energy losses in transmission lines
  • Impact assessment on environment
  • Disposal

Parsons does then a careful analysis of the two lamps for the items listed above. His conclusion is straightforward: “CFL’s are a significant better source of light from an environmental point of view than ILB’s maily because of their much more efficient use of energy”. He also touches on the problem that CFL’s contain a bit of mercury (about 3 mg)[2] that may pose a problem during disposal. However, he compares that with the amount of mercury that is emitted to the atmosphere by coal fired power plants. Again he comes to the conclusion that also on this aspect CFL’s outperform IBL’s with a factor of 5 in terms of environmental impact: “This analysis serves to confirm that the claimed environmental benefits of CFL’s over IBL’s is largely true and further that it is true on almost any measure…”

That is good news for the planet I think.

2008 © Copyright John Schmitz

[1] Parsons, David. “The Environmental Impact of Compact Fluorescent Lamps and Incandescent Lamps for Australian Conditions”, The Environmental Engineer 7(2): 8-14 (2006).

A link to this article:

[2] The mercury is needed to facilitate ignition of the gas.