Essential Oil Disposal
Within this article, all volatile oils including essential oils, absolutes and CO2s are collectively referred to as "essential oils."
Most consumers purchase and store essential oils in small 1/2 ounce bottles. When dealing with such small quantities of essential oils, it can be easy to forget that essential oils are highly concentrated, flammable substances that must be treated like other hazardous materials.
Although it's okay to freshen a drain by dripping a few drops of oil down the drain, don't dump large quantities down your drain.
As with pharmaceuticals, paint thinner, household chemicals and gasoline, essential oils should not be disposed of down drains or via other methods that can cause the substances to come into contact with water supplies, vegetation or animals.
Placing a few drops of essential oil down your drain to freshen bad drain odors, however, is acceptable. This small amount is equivalent to the quantity of essential oil that might be contained in a bar of cold pressed soap or shower gel that you'd use and rinse off in the shower.
Essential oils don't go rancid, but most essential oils do deteriorate with age and should be used up prior to that time or disposed of properly. See the Essential Oil Shelf Life article for more information.
If you have aging essential oils on hand that you no longer want to use in skin care or direct diffusion applications, refer to AromaWeb's How to Use Up Those Aging Essential Oils article for ideas on how to still get some use out of some of your deteriorating oils.
Disposing of small quantities of essential oils is especially easy. But if you're in the midst of cleaning out a large inventory of aging oils, proper disposal is even more important.
Most likely, your city/county/community has guidelines in place for the proper disposal of hazardous fluid ingredients. Call your vicinity's waste management department for details. Most guidelines aren't hard to comply with once you're familiar with the process. The procedure generally involves saturating the essential oil in an inert substance like sand and then sealing the mixture in an approved container.
Your retailer/supplier should also have a Material Safety Data Sheet (MSDS) available for each essential oil that you've purchased. The MSDS provides specific safety, storage, usage and disposal information for each oil.