I don't often deep fry, or have bacon in the mornings, but when I do, I always have the same question of what to do with the grease. Usually, I just put it in the city compost bin, figuring all the raked leaves, etc from others will dilute it enough for the city to handle it. But can I compost it? Or is there a yeast, a fungus, beetle, worm, or something that I could feed it to that would turn it into something useful? And how could doing so be relatively straightforward for someone like me with kids and a job and not a lot of time and money to experiment with?

I found a neat q&a about grease and oyster mushrooms which seems relevant, but I'm guessing I'd have to adopt mushroom farming as a hobby to be able to use that advice.

  • do you have any community composting available? perhaps you can contact them and find out if they have a collection point. old fats can be turned into biodiesel so there is a demand for them if they can be collected economically.
    – flowerbug
    Commented May 5, 2020 at 23:57

4 Answers 4


Since you have a city compost bin the best thing for you to do is keep putting it in there. Grease is not particularly helpful to the compost process. By shipping it off you are not starving your pile of a great input.

I visited a commercial composting operation. They got a lot of different inputs including large quantities of wood chips and oil. They would soak some of their wood chips in oil as a way to incorporate the oil into the windrows. They had acres and acres of windrows that were turned and hydrated with large tractors. They also have big fences and lots to keep animals out and traps inside the space to catch any animals that get in. In that environment, where the piles are managed with large equipment in a tightly controlled manner, oil can be thoroughly composted.

In a home environment, trying to compost oils and fats is just begging for trouble.


In their book 'Gardener's Lore' (Also published as 'Old Wives'Lore') the authors, Maureen and Bridget Boland, tell a charming wartime tale. They buried the solidified fat they'd collected from their drain, at the dead of night, under an ailing climbing rose (since it was wartime London they were concerned that people would think they were wasting food if they just binned it). To their surprise, the rose that had never bloomed, flourished from then on. They used fat this way ever afterwards until they had a garden accessible to foxes, who would dig it up. In those days the fat they referred to was 'dripping' whether the same benefit is obtained from modern vegetable oils I wouldn't know - but the bacon fat may work if you've got a suitable rose that might benefit.

  • How would one bury bacon grease under a plant without distressing it? Especially if the rose is ailing, I would worry about damaging its roots with a typical trowel. Poke or drill a hole deep enough for the volume of grease? Commented Mar 4, 2021 at 19:37

These are some alternatives I can think of:

If you have a burn pile outdoors once in a while you can burn it. Start small, be careful, not during a drought, check the weather forecast for strong winds and have a burn permit. Grease fires are not easy to put out (they have to be smothered).

For liquid vegetable fats used for deep frying, if you don't mind the smell the oil can be used in an old oil lamp. Might mean you get hungry from smelling french fries. :)

For animal and vegetable fats, in some amounts, they can be added to animal feeds (ask your neighbors if they keep pigs, etc. who would be glad to take it).

If it is a once a year thing you need to do, I would dig a trench down deep enough that the oils would not be dug up by animals, and bury it. Eventually the soil creatures will do something with it. As bodies of animals contain fats, nature does know how to deal with it. Every year choose a different spot.

The best thing we have done here to eliminate having to deal with bacon grease is that we buy precooked crumbled bacon. After calculating the cost of bacon and how much you actually get from it after being cooked it works out to be a reasonable cost.

Some people cook with bacon grease; in small amounts, it is OK, and it is how I always remember Grandma's bread. She said during the Great Depression they used bacon grease instead of butter on bread.

  • I can vouch for spreading bacon grease on bread. Surprisingly, unless you heat it up, it's not that much more flavorful than butter, but it is filling. Commented Jul 20, 2020 at 19:46

You can compost, or add to a compost pile, very small amounts of vegetable oil, but not animal oil. If you want to dispose of the oil, its best to mop it up with paper towels and drop those in the household rubbish rather than adding to the compost. Further information and advice on disposing of oil and grease here https://www.gardeningknowhow.com/composting/ingredients/vegetable-oil-in-compost.htm

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