Do you fry food at home? It makes a delicious meal, but when you clean up afterward, you have a lot of used cooking oil. And so you have the problem of how to dispose of it properly.
For the sake of convenience, I’m using “cooking oil” to describe both vegetable and animal fats you might use for frying or sauteing. Bacon fat, lard, butter, or hydrogenated vegetable shortenings present the same issues. They’ll just solidify at room temperature.
For that matter, salad dressings raise the same issues.
Whatever the choice matters for taste and nutrition, it doesn’t matter at all when it comes to proper disposal.
Rule number one: do not put used cooking oil down the drain
Do not flush it down the toilet, either.
Fat does not dissolve in water. Instead, it finds other fat and sticks together. It builds up on the inside of your pipes. Eventually, the pipe no longer has the capacity to drain water out to the sewer. Your sink backs up. Or worse yet, your toilet.
You can use a drain cleaner. The traditional ones use harsh chemicals. Newer enzyme drain cleaners are better for the environment and your health. But probably neither will unclog your pipes.
You can use a plumber’s snake, except the kind you can buy for yourself probably isn’t long enough.
So you have to call a plumber.
And that’s the least trouble putting fat down the drain causes.
If your used cooking oil gets out to the sewer, it will clump together with everyone else’s used cooking oil and start to coat the sewer pipes.
When the sewers get clogged, they can back up into people’s houses. The people whose fat caused the problem? Maybe, but the sewer doesn’t care. It creates an expensive plumber bill for someone.
Nearly half of all sewer backups in the US are caused by fat, oil, and grease (FOG in the lingo of the wastewater treatment community). And, of course, your city maintenance crews must work hard to clean out FOG before it causes a sewer backup.
Some people pour their used cooking oil out on the ground. Bad idea.
Fat is not only not water soluble, but it also repels water. Water plants in the soil need to grow. And I’ve read that it will eventually make its way into the sewer somehow.
Here are the safe and responsible ways to dispose of used cooking oil:
1. Best case scenario: take it to a disposal facility
Some municipalities offer drop-off facilities where residents can take their used cooking oil. Catawba County, North Carolina, for example. They will have instructions for how to get it there from your home. If you live in such a place, take advantage of the service.
Restaurants use a lot of oil, and so a whole industry exists to collect it from them. Even if you don’t have access to a drop-off facility, you may be able to find a restaurant that will accept your used cooking oil.
In any case, let the oil cool before you do anything else with it. Next, strain it to remove food particles. Cheesecloth, a coffee filter, or paper towel all work well for this purpose. You can probably mix different kinds of oil in the same container, but check with the facility where you take it first.
I mention paper towels for a good reason. Some people want to avoid paper towels entirely. They will say to use a rag to wipe your pan before washing it. But then if you put the rag in the laundry, all that FOG goes into the sewer. It doesn’t matter if it gets there from the kitchen sink, the dishwasher, or the laundry machine. So you will have to discard whatever you use to strain oil or clean it up after the meal.
2. Cook something else with your cooking oil
This suggestion only postpones the disposal problem, but you can cook with the same oil more than once. Just keep in mind that it’s smoke point is at a lower temperature each time you reuse it.
To reuse oil for frying, strain it while it’s still warm (but not hot) with cheese cloth, a coffee filter, or paper towel. Store it in the refrigerator (or other cool, dark place) in an air-tight glass jar.
Don’t attempt to reuse oil that has heated past its smoke point, though. Smell it before you reuse it to make sure it hasn’t gone bad.
3. Put used cooking oil in the trash
If you have no place to take used cooking oil, then you have to dispose of it in the trash. But there are right ways and wrong ways.
Don’t pour liquid oil into your garbage can. It will only make a mess. And unless it’s solid at room temperature, don’t try to put it in a plastic bag. It will only leak.
So pour it into a sealable container, preferably one that’s not recyclable, and put it in the trash. A paper milk carton with a plastic cap works nicely if you have one. Many places have stopped accepting glass for recycling. If you must put glass in the trash, you might as well fill it with other liquid trash, such as used cooking oil.
Or you can combine the used oil with something absorbent, such as used paper towels or napkins, sawdust, coffee grounds, or cat litter. You can put any of those items in a plastic bag and put it in the trash.
4. Compost a little used cooking oil
If you use paper towels or napkins to wipe up oil, you can add them to your compost. With some limitations.
First off, as I have said before, any kind or oil or fat repels water and inhibits air flow. Your compost pile needs both air and water to rot properly. So too heavy a concentration of oil will ruin it. Some oily paper towels or napkins mixed in with everything else shouldn’t hurt anything.
Second, don’t add any animal fat or vegetable oils used to cook meat to your compost. It will attract raccoons or other pests you don’t want.
You can use compostable trash bags, or for smaller amounts, compostable sandwich bags. In other words, you can now find bioplastic bags you can fill and toss on your compost pile. Everything should degrade in about six months.
5. Make soap with it
Housewives used to make their own soap for generations. Now, with commercial soaps easily available, only hobbyists make their own. You can be a hobbyist if you want!
Soap requires mixing fat, lye, and time. I have found a nicely written recipe for making soap with used cooking oil here.
You’ll recognize lye as a hazardous ingredient. Plenty of people these days have developed an unhealthy fear of hazardous ingredients. If you choose to make your own soap, you only need to have enough healthy fear of the lye to handle it intelligently. Any recipe you find online will give safety instructions.
6. Kill bugs and weeds
During growing season, bugs and weeds will attack what you have planted and carefully nurtured. A little oil can kill bugs. A lot of oil can kill plants. I confess I haven’t tried this, but it looks plausible.
Put some used cooking oil in a spray bottle and lightly spray any plants bothered by insects. Oil kills insects, or at least discourages them from returning. Spray it more heavily on weeds.
7. Check out these miscellaneous ways to reuse used cooking oil
There are all kinds of clever ways to reuse oil besides cooking with it.
- It makes a useful lubricant to fix squeaking hinges or sticking locks.
- If you have an oil lamp in your house, you can burn (filtered) cooking oil in it.
- Used cooking oil can also remoe paint from your hands. Just apply it, give it about five minutes, then wash your hands with soap.
- The oil will also remove all kinds of tough dirt and grime from the body of your car, or even your brakes. Put some on a rag or paper towel and scrub.
Your pets might like a little on their food
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