Dear Umbra,

It’s always nice to look through cookbooks and to watch cooking shows that feature yummy deep-fried food, and I have often been tempted to try and cook my own creations. However, no one ever seems to mention what they do with the used cooking oil, especially after deep-frying. What is the best way of disposing the oil? I do not want to tip it down the sink, and adding it to compost will suffocate the earthworms. Perhaps it’s better all round not to deep-fry anything?

Liz
Atherton, Australia

Dearest Liz,

Over here in America, people deep-fry entire turkeys for the late-November Thanksgiving holiday. We believe anything can be deep-fried. Recent years have seen various deep-fried candy bars appear at country fairs, and I think one can deep-fry ice cream. These occasional revolting yet compelling treats — and our obesity epidemic — aside, deep-frying is a tasty, time-honored cooking technique. Do not eschew it afore you even do it.

Grease frightening.

Photo: misterbisson

You are correct, though, the leftover oil should not be poured down the sink drain. It will create an ungodly mess, clog the drain, and run up your plumbing bill. Any grease that makes it through to the sewer must be treated at the wastewater plant, and they don’t want to deal with your grease. If you have a septic tank, it’ll just help shorten the life of the tank.

Cooking oil can be reused, although it degrades with each use and will eventually need to be disposed of. To reuse it, filter it through a fine sieve or layers of cheesecloth to remove food bits, then store it in a closed container in a cool, dark place. Apparently you’ll know when it’s too old or degraded, because it will appear dark and viscous, and smoke when it reaches 190 degrees F or lower. The “dark” aspect seems unmistakable, as would out-and-out rancidity, and I think after putting in some practice you’ll recognize an oil that smokes before it should.

When the oil’s time has come, you may just need to call your local garbage folks (your city or province) and ask what the rules are about used cooking oil. In the U.S. I’ve found that municipalities differ as to their preferred technique. A Maryland county directs people to bring large amounts to the transfer station instead of leaving it with curbside pickup. In parts of Alaska, folks can put only a gallon in the trash at a time; one suggestion for those with a larger amount was to find a pet-food manufacturer who needed used oil. Who knows what for — better not to ask. A Washington county suggested mixing large amounts of oil with cat litter or sawdust to make a solid, putting it all in a tightly sealed container and only then putting it in the trash.

You see what I mean — each locality seems to have a different preference. I think containers of oil exploding in trash trucks may be one issue, and another might be how oil behaves in a landfill or incinerator. I direct you to your local trash informants because I think they will have an opinion, not because I’m passing the buck. If they have no opinion, let your oil solidify, and/or mix it with sawdust, wrap it up tightly, and place a gallon or less per week in the trash. Enjoy your cooking adventures.

Tempuraly,
Umbra