The Fresh Loaf

A Community of Amateur Bakers and Artisan Bread Enthusiasts.

Can you compost unused starter?

medora66's picture

Can you compost unused starter?

I hate the thought of throwing out my unused starter -- but I simply can't keep up with it.  So ... can I compost it?

Thanks for your help, 


gaaarp's picture


Yerffej's picture

Yes you can and you make me wonder...How much starter are you throwing away?


LindyD's picture

Discarded starter is great for the compost pile.  It won't be wasted since it eventually will wind up feeding your garden which in turn feeds you and your family.

proth5's picture

I'll give you mine and perhaps you can give me some composting tips for starter.

When I'm at home, I compost the standard leaves, fruit/vegetable scraps, etc in two rather small composters.  One is a batch composter - a plastic drum like thing that can be rotated to mix the compost.  The other is a Sun Mar continuous composter where I seem to put things in, but for some reason - it never fills up. (I think it's the theiving squirrels who will chew through just about anything to get into it, but I digress...)

I've thought about composting the starter, but the small volume and plastic enclosure nature of the composters have always given me pause.  You know, stuff like upsetting the moisture level, starter oozing from vents and drainage openings, starter drying like cement on the composter walls, further encouragement of theiving varmints, etc.

If I had a large compost pile, I don't think I would think twice, but with my little urban setup, I would appreciate some "how to's"


jj1109's picture

It's a little OT but I'll chip in :)

Your starter is basically purely starch, which the microbes in it love, and every microbe in your compost bin will love too. The starter will only be there a day or two at the most before it's disappeared, in any decent composting system (nice and hot, composting happily).

If your compost is too wet, add shredded newspaper and turn it more often. If your compost is too dry, add some moisture when you turn it. The right moisture level is such that when you squeeze a handful of compost, a few drops of water dribble out of your fingers.

If you put a lot of kitchen scraps in your composting system (relative to everything else you put in) you'll need more yard waste eg dried leaves, shredded newspaper to get that carbon / nitrogen ratio up a bit.

A little bit of starter (i'm guessing a couple of hundred grams at the absolute most is all you'd need to throw away if you have good starter management!) will simply provide some pure carbon source for the compost. A lot (eg kilograms!) could change the pH balance of the system, but we're talking a LOT of starter to do that.


medora66's picture

Wow, you guys are fast ... !!

Jeff, I'm wondering about all this unused starter so I'm very glad you asked.

I'm very new to this.  I'm using Peter R's new book, and refreshing my mother starter every 5 days (which I have to admit is a little much for me).

So, two followup questions: do I REALLY have to refresh that often?  What would happen if I just did this once a week?

And ... do I need to keep as much as he suggests in his book going?  Or could I cut this back a little?  The total weight of the refreshed starter is 24 oz ... and you only use 4 oz in his method to refresh, so basically if I can't make bread every 5 days (a pipe dream) ... I'm going to throw away 15-20 oz of starter every 5 days.  (I hope this makes sense ...)

And even if I DO make bread ... his sourdough recipe only calls for 2 oz of starter.  So I'd have to make a whole lot of bread to get through this mother, y'know?

I know I can make other stuff with the starter, but again, I'm not living a "bake every 5 days" kinda life, if you know what I mean ... 

Any advice you can offer would be so greatly appreciated.

Yumarama's picture

First, since we're talking a Reinhart formula I'll presume that we're dealing with weights here, not liquid/volume ounces and also point out the following is in regards to a 100% hydration starter, equal weight flour and water.

So no, you do not need to keep 24 oz of active starter unless you're running a bakery. For weekend bakers at home, you can cut that back drastically. In your case you mention that the recipe calls for just 2 oz of starter, so let's assume that after some playing with several recipes, you keep coming back to this one as your favorite. So that's the quantity you want to have available. If your normal "go to" recipe uses more or less, then change the quantities to suit.

You can keep a starter that will give you 2 oz (57g) in excess/discard whenever you feed it. And if it happens that you're not baking that weekend, you'll only be discarding 2 oz of starter which is really just 1 oz of flour (28g). 

So assuming you're feeding your starter on a 1:2:2 ratio, that 2 oz you want as "excess" to either bake or discard, means your old starter needs only be 1/2 oz. or 14g. 

So 1:2:2 here would translate as .5 oz old starter, 1 oz water, 1 oz flour for a total of 2.5 oz of "mother" starter. In grams, that's (rounding up for easier counting) 15g old starter, 30g water, 30g of flour for a total of 75g. That's a under a half cup in volume. You can easily keep this volume of starter in a half-pint mason jar and it will take up almost no room in the fridge.

If you ever do a recipe that wants more starter, you can easily "feed up" your 2 oz (60g) of starter without discarding so in one feed you'd have 2oz:4oz:4oz [S:W:F] for 10 oz of starter (283g). Need 13 oz? Easy: feed 2oz:5.5oz:5.5oz. It will just take a wee bit longer to peak. (And a bigger jar.)

You can even let the starter stay in your fridge for 2 weeks (maybe more) without too much problem if you simply can't feed it weekly. Feeding should take less than 5 minutes to measure and mix, then an hour or two on the counter to perk up before going back in the fridge so even a weekly feed should usually be possible with a busy schedule.

Yerffej's picture

You have already received the answer you need.  Keep just a couple of ounces of starter and increase that when and if you bake.  I would refresh the refrigerator starter weekly to keep it active.


rick.c's picture


The answer is that you can keep as much or little starter as you want.  I don't know your baking schedule, but, if you are making one batch a week, it doesn't make sense to keep 1.5 lb of starter going.

You could try keeping 1oz of starter and putting it in the fridge, then, a day before you are going to use it, refresh it to 3oz and leave out of fridge until ready to use, then use your 2oz for the recipe and return 1oz again to the fridge.  The exact timing is something you will have to get used to, when I say a day, it could be 12-36 hours for your refreshed starter to become active to a usable level.

Another option is to keep like 1# of starter in the fridge and remove small amounts at a time until you are almost out of the fridge reserve, then refresh that to 1# again.  In essence, whatever works for you!