NEVER ... NEVER PRESERVE GARLIC IN OIL.
When raw garlic is stored in oil, Clostridium botulinum bacteria can grow. Low-acid foods like garlic are a good source of these bacteria which are found in soil, water, and air. Oil's oxygen-free environment is perfect for growth of this anaerobic bacteria. It is slowed down, somewhat, if stored in the refrigerator but ... after a few weeks, the bacteria grows and becomes dangerous. And we're talking botulism food poisoning here.
So ... don't store garlic in oil.
OK ... it's not an environmental thing but ... I thought it was worth sharing.
As always ... send in your comments.