I saved up a jug’s worth of cooking oil and grease and dropped it off at a collection site. What happens to it after that?
-Klaus W., Daphne, AL
Once you’ve dropped off your used cooking oil and grease at a collection site, it is probably picked up weekly by your city or your water utility. What happens after that differs from city to city. Some cities will send it to a processing facility with an anaerobic digester. Anaerobic digestion, the process of breaking down organic material without the use of oxygen, converts the cooking oil and other waste to an alternative fuel called biogas. Biogas can be used to generate electricity, heat water, or power cars.
Some cities will send it to a biodiesel plant, where the oil will be filtered and processed into a fuel that burns cleaner than regular petroleum diesel. Biodiesel can be used in most diesel engines today, and many diesel vehicles are rated to use B20, a blend of biodiesel and petroleum diesel.
While it’s fantastic to recycle a waste product into an energy source, the main reason cities collect grease is to divert it from water and sewage systems. When oil is washed down the drain (even with hot water), it can gunk up the pipes and cause expensive, wasteful clogs for you or your city. It can also cause environmental contamination and health hazards if raw sewage overflows. Municipalities and utility companies can spend thousands or hundreds of thousands of dollars on cleaning and repairing water and sewage systems backed up with grease.
Cooking oil recycling programs accept all kinds of oils: butter, olive oil, canola oil, corn oil, and the fat rendered from animal products such as bacon, turkey, and sausage. If your city doesn’t have an oil recycling program, you can dispose of used oil and leftover grease by sealing it in a container (such as an empty milk jug) and putting it in the trash. But of course it’s better to recycle it if you can!
Have a question about recycling, sustainability, or green living in general? Send it to firstname.lastname@example.org and we might answer it in a future column!