Esters – preparation, properties and disposal

This is a combination of several questions

• I have previously been asked to dispose of the chemical waste from the ester prac by evaporating it on an absorbent material and disposing of this to landfill. I have now been asked to store the waste in an organic waste bottle for collection at a later date. I have begun decanting this waste into a large glass bottle. However, when I opened the bottle, there was a large rush of gas from the bottle. Is this normal? It did concern me somewhat and I was pleased I had opened it in the fume cupboard. My question is: what is the correct way to dispose of this waste?
• Chemical waste disposal – from esterification activity: I would like to know how the waste generated from the Isopentyl acetate esterification process should be disposed of?
• I have a fair bit of waste collected. Is there any way I can reduce and dispose or may be use it for some other purpose?
• Could someone please advise about the safe storage and disposal of esters?