Every kitchen tradition has a way of dealing with used fat, and almost none of them involve a sink. Cooks kept dripping in a stone crock by the stove and used it again, or rendered fat was strained through muslin and saved for the next batch of frying. The habit of pouring oil down the drain is a recent one, arriving with indoor plumbing and the assumption that anything which flows away has been dealt with.
It hasn’t been dealt with. It’s moved a few metres and stopped. Understanding how to get rid of cooking oil properly is one of those small pieces of household knowledge that saves a great deal of money and inconvenience later, and it takes about a minute to learn.
What happens after the oil leaves the pan
Hot oil pours like water but behaves nothing like it. Kitchen drains are cool, so the oil begins solidifying almost immediately, coating the inside of the pipe in a thin layer. Each subsequent pour adds to it. Over months the channel narrows until a piece of food waste catches, and then everything behind it stops moving.
At the municipal scale this produces the masses that water engineers call fatbergs. One removed from beneath Whitechapel in London weighed roughly the same as eleven double-decker buses and took a crew of eight several weeks to break apart. Domestic blockages are smaller and considerably more personal, because clearing them is billed to the household.
How to get rid of cooking oil the simple way
Let the oil cool in the pan until it is safe to handle. Pour it into a container you were going to throw away anyway: a glass jar, a plastic tub, an empty tin. Seal it and put it in the general waste bin. That is the whole of it.
Two habits improve the results. Wipe the pan with kitchen roll or newspaper before it reaches the sink, because the residue left after pouring is the part that does the coating. And keep oil away from the compost heap, where it starves the pile of air and draws vermin. Straightforward used cooking oil disposal asks nothing more than a container and a moment of patience.
Filtering oil for a second use
Frying oil is not necessarily finished after one use. Let it cool, pour it through a fine sieve lined with muslin or a coffee filter to remove the solids, and store it somewhere dark in a sealed jar. Oil used for fish will taste of fish, so keep it separate.
Watch for the signs that it is done: darkening colour, a thicker texture, smoking at a lower temperature than it should, or a sharp smell when it heats. At that point how to get rid of cooking oil matters more than how to save it.
Larger volumes need a different answer
Households frying regularly, and anyone cooking for a business, generate more oil than a jar can absorb. Specialist collectors, Quatra among them, take used cooking oil directly from businesses and process it into biodiesel.
The older way of thinking, in which fat was a resource to be kept rather than a nuisance to be flushed, turns out to have been the more accurate one all along.
