I have kept used grounds up to two or three weeks. After this time they smell sour and mold is growing on top. And they will dry out when stored in Rubbermaid containers. I try to mix the grounds into my compost piles as soon as possible.

One can made a fairly 'hot' or at least warm, compost pile in
40F weather. September thru November is my favorite time to create piles; with the availability of leaves.

I have saved grounds in 1 gallon covered buckets for months over the winter. I collected them daily from a coffee shop. They were fine in the spring, when I added them to beds and the lawn. Some were moldy, but so what.

I usually add UCGs to tumblers and cover with shredded leaves (no tumbling), they freeze within minutes, come spring, it (the stuff) heats up like normal. I'd guess they (UCGs) do not change much if they are frozen. Some people intentionally freeze their kitchen waste before composting, this would probably be no different.

Lloyd

P.S. What a great kid!! Kinda brings a tear to mine eyes. Send him/her up here, I'll train 'em as a mid-size composting facility operator. (Is that as creepy as it sounds!!??) ;-)

I saved a 5 gallon bucket of them last over winter, just make sure you have a good lid on your container. I was able to keep mine in a cool porch so smell and mold was no big problem. Like merrygardens posted, so what if they mold, that's the idea isn't it? It sure beats walking to the pile in 0 degree weather. This year they are worm food, I only need to go as far as the basement with them. I save a weeks supply of UCG and filters in the used plastic coffee container on the kitchen counter. MY worms seem to eat them with the other kitchen scraps just fine.

Curt

Could you please tell us what zone/state/province you're in ?

Thanks for your replies - I'm in Chicago - zone 5. I'm thinking of just leaving the can outside with the lid on for the winter. In the spring when I've used all the mulch that's in the bins now, and am ready to make the new piles, I'll have 55 gallons of coffee grounds ready to go - moldy or not. I'm getting the idea they'll still be more of a "green" than a "brown".

And yes..she is a great kid, and this is a terrific gift - and FREE!! We have 4 Starbucks within a few miles, so she'll just have them all save grounds over the holidays, and I'll be thanking her all year.

I use a big 7 gallon bucket or two and save them up all winter long. They are fine in spring when they thaw out to use. Even if there is mold growing on it, so what? That's part and parcel to breaking down like it will in your compost anyways. Yeah, it stinks to high heaven but it's all good.

If they're outside in Chicago in the winter, you won't need to worry about whether they'll start to stink. They'll freeze solid and next spring, you can start chipping off the edges to add to the compost.

You could put a flag to mark where the compost pile is, and just dump the grounds on top of the snow. Tidy up in spring.

If you have a "normal" Chicago winter and those coffee grounds are added slowly to the storage container they most likely will freeze and stay frozen most of the winter, as long as the average temperature stays below 32 degrees.