Carbon judgment.(FROM READERS)(Letter to the editor)

I strongly support your editorial in the March/April issue ("Carbon Crimes," p. 2). Building more conventional coal-fired plants is irresponsible. The coal industry will, however, try to reassure governments and citizens that "clean coal" plants will be built in the near future.

This has created debates on C[O.sub.2] capture and storage technologies. The debates have focused on two questions: 1) Is it possible to capture C[O.sub.2] and store it? (The answer is yes.) 2) Will the storage be reliable in the long term? (The answer is uncertain.)

These questions have put aside other major issues. In a perspective of life-cycle assessment, there are many reasons to conclude that so-called "clean coal" will never exist and should not receive huge subsidies: sulfur dioxide emissions; emissions of nitrogen oxides, particulates, volatile organic compounds, and heavy metals; and combustion ash and fly ash, which contain toxic metals. For each of these issues, the environmental impact is much higher for coal than for any other electricity generation options.

With respect to climate change, the appropriate question is not whether carbon capture technology can exist, but will it be implemented widely, at the global level? To this question, the answer is clearly no. Here's why:

Commercial technologies exist to reduce S[O.sub.2], N[O.sub.x] and mercury emissions, but these technologies have not been implemented widely. The technology of carbon capture is many times more expensive than any of these technologies.

Carbon capture is more energy-intensive than the scrubbing of sulfur dioxide. On a life-cycle basis, capturing sulfur reduces the efficiency of coal-fired generation by about 10 percent, while capturing carbon will reduce efficiency by about 25-40 percent, depending on the distance to a storage site.

Carbon capture imposes a waste management challenge that is about 50 times greater than the management of sulfur residues. The relative size of this challenge can be illustrated by the fact that sulfur normally constitutes 1 or 2 percent of coal, while carbon content is 70-80 percent.