Nearly all of us use some kind of cooking oil, and most of us eat meat (still) and produce what we think of as waste fats. By conserving and using this “waste” fat, we can save money and avoid additional harm to the environment.
In the United States, until the mid and late 20th centuries, people regularly collected and reused fat. This seemed to go by the wayside as people started to throw away fats, usually into the garbage.
Advice for Meat Eaters
Contemporary practice is to trim the fat, perhaps remove the skin, and then throw them away. This makes sense, because these are generally considered unhealthy fats, but it represents an expense: you paid for that fat at the price of the meat.
What you should do is render the fat, and then collect the liquefied fat into a jar. This fat can then be used to grease up skillets, and used to fry food. It can also be used as a substitute for butter.
To render fat: put around 1/2 cup of water into a pot, and then add the skins and fat trimmings. Bring it to a low simmer, and cook, covered, stirring occasionally, until the skins and fat become brown and harden. Spoon off the fat into a jar. Store in a refrigerator. It can also be stored at room temperature for a while, because saturated fats tend to go rancid slowly.
You can also collect fat that’s drained from ground beef.
The names for some fats: beef milk fat is called butter, beef fat is called tallow, chicken fat is called schmaltz, pig fat is called lard, lamb fat is called suet. I think turkey fat is also called schmaltz.
As always, reducing meat consumption is good for the environment, and your health. If you find yourself with a surplus of gathered fat, consider eating less meat.
Advice for Vegetarians
Vegetable oil goes rancid, so you should keep it in the refrigerator. Collected fat should also be kept refrigerated.
Used vegetable oil used for deep frying is called “brown oil” and can be collected after it’s been used for frying. Let the oil cool and settle. Then, using a funnel and a paper towel folded into a filter, pour the oil into a glass jar.
The filter will catch the browned crumbs, and the used oil will go into the jar. This oil can be reused for frying. Brown oil tends to help battered and breaded foods fry up harder and darker. You can also just use it for skillet frying.
If you fry a lot, and end up with brown oil that’s going black, you should get rid of it. Unfortunately, there aren’t many options for recycling the oil, unless you can find a restaurant that will allow you to dump oil. One partial use for the oil is to help ignite charcoal for grilling. It burns nothing at all like lighter fluid, and is safer, but it does provide enough heat to get the coals started.
Oil can also be filtered and then burned in a furnace to provide heat.
Used vegetable oil can also be processed to make biodiesel fuel. This is a process of combining the oil with a methanol-and-lye solution to produce diesel fuel and glycerine soap.
You can also filter and then reuse the oil to make soap without the biodiesel. The main problem is that this soap, if formulated to be gentle for your skin, will smell like fried food. Soap that’s made “hot” with a little excess lye is good for cleaning floors, and will not smell bad.