Please keep related issues together on a single thread, I must have seen the evolution of your plot, over at least 6 different posts over a relatively short period of time... It creates a strange feeling of deja vu, but more importantly spreading out your questions and answers is inefficient, evidenced by the fact that earlier today I answered this question about whitespace ...
Earlier : Changing colours of bars in ggplot2 - #2 by nirgrahamuk
to remove the expansion around the axis limits change your scale_y_* to
scale_y_continuous(trans = "log10",expand = c(0,0))