The comment by Krimpoff yesterday about hydroelectricity and nuclear fusion made me think that it might be a good idea to do a post about the polluting effect of each sources of energy we use or plan to use. Some of the "clean" sources are actually polluting and some of the "dirty" one are not that bad. So without further delay here is a little about the polluting effect of our energy sources.
Burning stuff (wood, coal, petroleum, ethanol, natural gas or anything else organic based you want to burn): produce green house gas: CO2 and H2O. The incomplete combustion of these products also release toxic volatile substance like carbon monoxide and nitrate oxide. And we must not forget to pollution brought about by the exploitation of these resources.
Hydrogen burning: Produce mainly H2O, which is a very efficient green house gas. The production of hydrogen requires great quantity of electricity, which might (depending on how the electricity is produced) further pollute the atmosphere.
Wind power: From what I know the only pollution wind power bring is in the form of the production of the turbine and the use of toxic lubricant to keep everything turning smoothly. It also requires a large flat windy place and to produce large amounts of energy from it we might have to destroy ecosystems and/or forest.
Solar power: Producing the solar panel imply very polluting reaction, to produce meaning full amongst of power require VERY large surfaces. The main problem with solar power is that even if we could extract every ounce of energy coming from the sun their is actually very little by cm^2 here on Earth. Because of that it suffer from the same problem as wind power in term of it impact on ecosystems, in fact it might even be worse since a "perfect" system would block sunlight from the ground and prevent plant life from growing under the panel.
Wave or tidal power: Producing the turbine and structure require a lot of energy, which implies pollution. The effect of placing a turbine in a wave heavy ocean or in a strong tidal area might impact the ecosystem by forcing water into the turbine.
Nuclear Fission: Producing the central require a lot of power, extracting and refining the fissionable material require polluting chemical. The exploitation of the power produces H2O and nuclear waste. However new models of reactor produce very little waste (recycling most of their nuclear fuel), another thing is that while most of the wastes are quite bad for our health, they are natural element and will eventually decompose into stable non-radioactive safe element.
Hydroelectricity: Like everything producing the dam requires lots of power and produce pollution, then producing the reservoir is an ecological disaster. Further more the decomposition of organic matter trapped under the reservoir and the organic matter brought into the reservoir by the rivers filling it produce a lot of methane. Then the production of electricity and expulsion of water release that methane into the atmosphere. Methane is a toxic gas and his also a green house gas, the good news (for Quebec at least) is that less methane is produced in the north (colder climate since less organic matter is brought in by the rivers.)
Nuclear Fusion: I'm going to skip the mention of producing the infrastructure problem. The first thing about nuclear fusion is that it produces hard radiation, which bring about the same problem as nuclear fission. While there is no direct radioactive nuclear waste (the product is harmless helium) the whole structure will become radioactive quite rapidly. Also we aren't able to produce electricity directly from nuclear fusion so we needs heat water and that produce H2O vapor.
So you see no energy production method is completely safe for the environment, some are better then other but there is no completely clean energy. We will need to find ways to make them as clean as possible, but we probably will never be able to produce electricity without having any impact on the environnement.