How to Recycle Used Cooking Oil
You probably already know that you should never pour fats and oils down the sink - they will congeal with water and cause backups in your plumbing and public sewer system. So, what's the most eco-friendly way to dispose of spent oil?
Detroit Grease, located next to Detroit's recycling drop-off center Recycle Here, accepts used oil from both food service establishments and residential customers. According to their website, all of the oil they collect is "recycled locally, for use as recycled biodiesel, compost for local farms, and for use in natural gas-creating biodigesters for 100% carbon footprint-free recycling." They accept oil from Metro Detroit, Ann Arbor, and surrounding areas.
Store your oil in a glass jar or large metal can, such as a coffee can. These can be hard to find, as coffee is usually sold in non-recyclable bags composed of a mixture of aluminum and plastic. Here in the Detroit area, you can contact Arts & Scraps to see if they have any on hand. You can also contact a local soup kitchen or food service establishment, as they often purchase food in large cans. If you're asking a soup kitchen for their cans, consider making a donation at the same time!
Your city may have a drop-off date for used cooking oil; these drop-off days often occur around the holidays to accommodate all the extra cooking. Visit your city's website for more information.
Given that Reduce and Reuse are higher up on the scale of waste reduction than recycling, how often should you reuse cooking oil before recycling it? There is much debate here! According to Cook's Illustrated Magazine, "With breaded and battered foods, reuse oil three or four times. With cleaner-frying items such as potato chips, it’s fine to reuse oil at least eight times—and likely far longer, especially if you’re replenishing it with some fresh oil." And, according to the USDA, "If you are planning to reuse the oil, strain it through a cheese cloth or sieve. Store the used oil in a sealed and light-proof container for up to 3 months. For best quality, refrigerate used frying oil that you want to use again."
However, keep in mind that there are some real health concerns with using improperly stored used cooking oil. Rancid -- meaning old and stale -- oil contains free radicals, molecules that can damage cells and lead to increased cancer risk, as well as affect the quality of your food. Oil is not infinitely reusable for cooking - every time you reuse oil, its smoke point drops. Smoke point is the temperature at which an oil starts to smoke and burn. Frying in an oil that has reached its smoke point does more than just make your food taste 'off' - fats in burnt oil start to break down, releasing toxic free radicals. You can find a chart of smoking points for various oils here.
According to a recent study published in the American Cancer Research Association's Cancer Prevention Research journal, reheated oil undergoes chemical alterations, including the formation of a toxin called acrolein, a known carcinogen. The study found that 'thermally abused cooking oil' consumption resulted in a marked increase of metastatic lung tumor formation compared to fresh oil consumption in laboratory mice.