How much less pollutants does nuclear fusion emit compared to the burning of fossil fuels?

Answer 1

The answer depends on what you call pollutants.

Natural gas, which is rather clean and contributes mostly carbon dioxide to the global warming problem, can be made 65% efficient when a gas turbine is used to generate electricity and waste heat is used to heat buildings. This is about as well as fossil fuels can do.

By comparison, nuclear power produces no carbon dioxide at the reactor. It nonetheless has a carbon footprint in the mining, refining, transportation and enrichment of fuel. Its carbon footprint has to include carbon emissions from construction of the plant, and from decommissioning the plant. Carbon emissions connected to dealing with long-term waste are unknown. Nevertheless, when all this is considered, the carbon footprint of nuclear power appears to be about 40% of the highly efficient gas-powered plant mentioned. (Nuclear plants would be useful to heat buildings, but they are never built in cities.)

This would seem to speak strongly in favor of nuclear power, but it does not take into consideration the possibility of nuclear disaster, which can be extremely costly environmentally (estimates for the Chernobyl disaster go as high as a trillion 1995 dollars worth of Ukrainian real estate - of course this is economic, not environmental), and also does not consider the fact that nuclear waste will have to go into storage that will be known to be safe for over a million years before its radioactivity is down to the accepted limit of being equal to that of naturally occurring uranium ore. Radioactivity is always damaging to life in any quantity, the question is what we are going to allow - remember it occurs naturally, so we have to allow some.