According to Carla from Trashmagination:
Wine corks are a socially acceptable item to collect. Some people even save corks from special occasions. They label corks with the date and occasion and keep them in a glass jar. Wine corks have a faint smell, but it’s not a bad smell… Of all the items I have ever collected, wine corks was the easiest to get in quantity fast! People don’t have to clean wine corks. If people have to clean the item, that’s a stumbling block to gathering it in quantity.
Although environmentalists lament the loss of cork forests to commercial crops such as eucalyptus, advocates of artificial corks claim that “natural corks” are just “granules and dust bonded with solvents”, and no more biodegradable than the artificial product. “Granules and dust bonded with solvents” describes “agglomerate corks.” These differ from “natural corks” that are one piece made out of cork bark.
Source