Jo An, you've got the biology correct (won't cross skin barrier, builds up plaques), but you've got the chemistry way wrong. As GrandmaArial said, in saponification the strong base (NaOH) attacks the ester group that links the fatty acid to the glycerol (also known as glycerin). This releases glycerol, and the sodium carboxylate of the fatty acid. Any hydrogens that have been added on to the long-chain fatty acid previous to the saponification reaction are not affected by the NaOH, so they remain intact. The heat generated by this process is not enough to break the chemical bonds that hold the hydrogens on to the long-chain. Also, hydrogen, or diatomic hydrogen, is not a greenhouse gas.