One of the mayors is very ill so he decided to smash open the box of instructions. He is showing greed because he is taking the box for himself because he believes that it may have a cure.
Lizzie and Lopper take the canned foods for themselves instead of sharing it with the rest of the town. They are being greedy and selfish. Lizzie ends up dropping the whole bag of food. She then offers it to Lina but she doesn't take it because she feels it is unfair to the rest of the citizens in Ember. Lizzie and Lopper are showing greed because they aren't telling the rest of citizens of Ember that they have found food, that had run out awhile ago.
The Mayor takes all of the food for himself. He hides in the pipe-works and takes all of the food for himself. He doesn't tell the citizens of Ember about the extra food. He also has extra light bulbs in the pipe-works closet as well.