In the ChemEng 2F04 class this morning, however, the professor told the class that recycle does not help the planet. He introduced second law of thermodynamics and this law says that heat transfer from high temperature to low temperature. It's easy for heat to transfer from high temperature to low temperature. However, to transfer heat from low temperature to high temperature requires external energy (heat).
In the recycling process, for example, cans, we must melt the cans before they can be reproduced. The heat used for melting is released to the atmosphere, thus increasing the temperature of the surrounding atmosphere.
So how does recycle help the planet? Yes, indeed we reduce garbage. But heat is continuosly being released to the atmosphere. Besides, concentration of carbon dioxide in the air dramatically increase since 1900s'. I think the ratio of 21% oxygen and 79 % nitrogen in the air is not true anymore.
Technologies of biofuels do not move advance as fast as the global temperature and concentration of greenhouse gases in the air. When year 2012 comes, will the earth be destroyed? Or will the earth destroy himself in 50 billion years when the energy of the Sun exhausted? I don't know, you don't know, no one knows.
In fact, when I was typing these words, I am killing the planet. Because computer produces carbon dioxide, although in a minute amount.