What you can and cannot compost

Things you can compost!

Materials Carbon or Nitrogen Details
Alfalfa meal and hay
Algae, seaweed and lake moss
Nitrogen
Good source of nutrients and minerals.
Apple pomace (cider press waste)
Ashes (wood, not coal)
Neutral
Use only wood ashes since coal ashes can be toxic to plants. Use sparingly as a pest deterant.
Beverages, kitchen rinse water
Neutral
Help keep the pile moist, but don’t over do it.
Buckwheat straw or hulls
Cardboard
Carbon
If you have lots of this, consider recycling it. Otherwise, shred into small pieces in pile.
Cat litter (unused!)
Clover
Cocoa hulls
Coffee grounds (and filters)
Nitrogen
Great source of nitrogen and worms love coffee grounds!
Cornstalks, corn cobs A little tricky, so shred and/or break down and mix well into pile.
Cottonseed hulls
Cowpeas
Dog food
Nitrogen
Dryer lint
Carbon
Yum, lint. Make sure you moisten it a little before you add it.
Eelgrass
Egg shells
Neutral
These break down slowly, so make sure to crush these before adding.
Feathers
Nitrogen
Flowers
Fruit peels (not limes)
Grape pomace (winery waste)
Grass clippings
Carbon
Make sure they are not too wet and mix with dry leaves for best results.
Hair
Nitrogen
Good source of nitrogen. Make sure you scatter, so it doesn’t clump.
Hay
Nitrogen
The best kind is hay that is not suitable for livestock and is starting to decay on its own. Make sure it is dry and weathered.
Hedge Clippings
Hops (brewery waste)
Kelp (seaweed) Good source of potassium (perfect for growing potatoes!). Use sparingly or sprinkle kelp meal in to get your pile cooking.
Leather (leather waste)
Nitrogen
Leaves
Nitrogen
Manure from herbivores (cow, horse, pig, sheep, chicken, rabbit)
Nitrogen
Newspaper
Carbon
Nut shells
Oak leaves
Carbon
Oat straw
Sawdust and wood shavings
Carbon
Paper
Peanut hulls
Peat moss
Pine needles and cones
Carbon
Tea leaves
Vegetable peels and scraps
Vetch
Weeds
Carbon
Wheat straw

Things you should NOT compost!


Materials
Carbon or Nitrogen
Details
Ashes (coal or charcoal)
n/a
May contain materials that are toxic to plants.
Cat droppings/litter
n/a
These may contain disease organisms and should always be avoided for composting.
Colored paper
Dog droppings
n/a
Same as cats.
Lime
n/a
Acidity can kill composting action.
Meat, fat, grease, oils, bones
n/a
Do not break down, can coat materials and “preserve” them, can attract pests.
Nonbiodegradable materials
Toxic materials

Things that MAY be composted, but only with caution and skill


Materials C/N Details
Bird droppings
Nitrogen
Some bird droppings may contain disease or weed seeds
Diseased Plants
Nitrogen
Make sure your pile gets to at least 135 degrees Fahrenheit for a few days to let it “therma kill” the disease
Milk, yogurt, cheese
Neutral
May attract pests, so put it in the middle to deep into the pile
Weeds
Nitrogen
For best results, dry them out until crunchy, then add them to your compost pile
Sod
Nitrogen
Like diseased plants, make sure your pile gets hot enough to make sure the grass doesn’t keep growing in your pile.

{ 42 comments… read them below or add one }

laura braggioti March 29, 2009 at 3:53 pm

hi
thanks
i wonder about beans….are they like meat? i cook beans for two and inevitably have left over, can i compost? will they attract rats etc I live in the city…up til now i only am using raw fruit and veggie and grass leaves ….thanks (ex: pea soup, no oil, lental soup etc no oil)
thank you

_____________________________________________________

Hey there, Laura. Thanks so much for your question, it’s a good one! We’ve taken the time to answer it for you in the form of a video and blog post. Hope this helps. Have a great weekend, and good luck with your compost pile. Thanks for reading!

Catskinner July 17, 2009 at 7:47 pm

Terra Preta [black earth], found in the Amazon basin, is essentially compost with large quantities of charcoal. It creates very productive topsoil that is difficult to wear out. I’d like to attempt duplicating it; any recommendations?

———

I heard some NPR story or something about that, I think. I was not familiar with the concept at all until very recently, and I don’t know much about it.

I don’t know how to produce it, but I found this: http://en.wikipedia.org/wiki/Biochar

Oh, and I found the NPR story: http://www.npr.org/templates/story/story.php?storyId=92455289

Good luck!

Lois July 19, 2009 at 9:37 pm

Just starting wanting to do a compost bin. I made mine just out of chicken fencing wire. It is place under some trees so would not get real wet, nor real dry. Live in Iowa and have lots of corn shucks and cobs etc. Also, wanted to use it for my kitchen food waste, Did not realize until now that I could shred news print in with it to help.
Is there some kind of soil or stuff to mix in with it to get it started? Lois

————

There are plenty of compost starters or compost activators that you can use, but they are not required.

http://www.cleanairgardening.com/compoststarter.html
http://www.cleanairgardening.com/coac.html
http://www.cleanairgardening.com/compost-thrive.html

Corn cobs and shucks break down faster when you shred them before adding them to the pile.

Monica July 22, 2009 at 5:44 pm

Just want to check on using lake weeds in our compost pile! we live on Lake St. Clair and have lots of weeds growing up from the bottom of the lake. Can these be harvested and put into our compost pile? I know they are a good source of nitrogen. ALSO, we have a large community garden where we live…does the seaweed have to be composted before it is put in the beds? (Probably a dumb question, but thought I’d ask anyway!) Our veggie garden soil is low in nitrogen and phosphorus, which we can most likely amend next spring with organic fertilizers. Meanwhile, though, we do need to get those nutrients into the soil to help the poor plants which are struggling to survive! Ph yeah, and a coffee roaster friend of ours gave us a lot of coffee hulls, can they go directly into the soil? Any advice will be most appreciated!!!

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Yes, you can compost those lake weeds. You should definitely compost them before adding them to your beds. Or at the very least, bury them at the beginning of the winter, so that they have all winter to decompose before you plant in the spring.

It seems that you can use coffee hulls as a soil amendment. It wouldn’t hurt to add some to your compost, too.

http://www.oisat.org/crops/economic_crops/coffee.html

“Return coffee pulps and hulls as organic fertilizer in coffee fields. These are rich in nutrients. A 60 kg bag of coffee pulps/hulls contains: 1 kg N; 0.60 kg P; .09 kg K and other trace elements. The pulp resulting from processing contains: 1 kg N; 0.84 kg P; 2.25 kg K and trace elements (Coffee Research Institute, 2001). “

Audrey August 1, 2009 at 8:17 pm

I’m wondering about bread?

I’ve seen lists online that say both that it’s ok and that it’s not. Any recommendations?

————-

Bread is definitely ok to compost.

The only reason I could possibly think of someone saying don’t compost it is that it might attract animals that want to eat it. But if you’re adding it to a closed bin, or you bury under the top layer in your compost pile, that would solve that problem.

Roy August 9, 2009 at 10:39 pm

If you compost bread, what about the old bread on top of the fridge that has got moldy? Would this ruin the compost?

————-

It’s perfectly fine to add moldy bread to your compost pile. It won’t hurt anything.

Tim August 17, 2009 at 5:18 pm

Thank you for all your helpful advise

I’ve read cooked potatoes and citrus rinds should not be used in compost. Mostly because of the chemicals used to protect or feed them. Beside the potential rodent/vermin issues can I use cooked potatoes and citrus rinds in my compost?

Regards

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I would say yes to both things.

I’ve also read that in a few places about avoiding citrus rinds, but I compost them all the time and have never had trouble. The majority of composting books say that it’s fine to compost citrus.

The exception to that would be with vermicomposting. Worms don’t do well with a lot of citrus rinds. Regular composting is fine.

I’ve personally never read anything about not composting cooked or uncooked potatoes. Seeing how I sometimes eat the skin of a cooked potato, I can’t imagine that the leftover potato could be that bad for the compost if it doesn’t hurt me.

Kristi August 18, 2009 at 2:17 pm

We’ve started composting recently and despite not adding any meat or dairy products, we have tons of maggots. It seems like they’re just eating everything and leaving very little but themselves behind. What to do?

Thanks!

————–

It’s normal for bugs and larvae to get into the compost. It’s not a big deal, and they aren’t hurting anything. They are helping the materials break down. Kitchen scraps often attract bugs more than yard waste, so I’m guessing you might be adding a lot of vegetable and fruit scraps and things like that.

Burying that stuff under more carbon rich materials like leaves will keep a lot of bugs from flying into the bin and finding the stuff, so that might help if you really don’t want to see any larvae.

katrina August 30, 2009 at 7:05 pm

Can I compost leaves from a black walnut tree? The leaves and nuts that fall from the one in our backyard seem to inhibit anything else from growing so I’m hesitant to add it to our compost pile.

———–

Please do not compost anything that comes from a black walnut tree, because it is toxic to plants, horses and even humans.

http://ohioline.osu.edu/hyg-fact/1000/1148.html

BJ September 12, 2009 at 3:37 pm

Great tips! Can diatomaceous earth be used to control insects in a compost pile? We currently use it in the hen house to diminish odor and flies. We also sprinkle a little around trees and plants but not sure how it might affect compost materials.

———-

My understanding is that diatomaceous earth doesn’t work very well when it is damp. And compost should be about the dampness of a wrung out sponge. So I’m not sure if it would be very effective.

I don’t think it would hurt anything to try it though.

HERTA September 14, 2009 at 2:27 am

I love to compost and have two active compost containers, which are doing very well, plus several large bins just for the end of the season garden cuttings. I was hoping that over the years it would turn into some nice usable compost, but it looks and feels more like dried straw material. My question is: will this ever amount to anything?

————

Sounds like you have the “too much of a single type of material” problem.

I would take some of that straw-like material and start adding it to your other active compost bins, a bit at a time. I think it will break down nicely if you mixed it in with other stuff.

Another tip is that if you have tough stalks of something that you want to compost, it helps to cut those stalks into smaller pieces. You can run over them with a lawnmower, or cut them with scissors, or run them through a chipper / shredder. Smaller pieces break down better and faster than large pieces.

HERTA September 14, 2009 at 11:30 pm

Thank you for your response. Do you think its ok to use it to cover my plants for the winter. It all has been shredded with a chipper.

Thank you for your reply

SB October 3, 2009 at 12:46 am

I have been working with my red worms for 2 years and have had wonderful success with my garden using my worm’s castings for fertilizer. My husband saw a TV show about worms and wants to see if he can feed worms asphalt shingles, metal and wood. I am afraid that the compost would be toxic. I saw an article about super worms in Wales and it asks some of those same questions. Can you discuss this?

————–

Thanks for your question. I am only an intermediate vermicomposter at best. We have one worm bin going at work.

But I am skeptical that you could feed the worms asphalt shingles, metal and wood. Pressurized wood, for instance, is sometimes treated with arsenic. So although it doesn’t hurt to test, I would be careful with overloading your worm bin with a bunch of stuff that might be potentially toxic and might end up killing all your worms. In small amounts though, I guess you could try and see what happens.

natalie wilson October 5, 2009 at 7:58 am

what about onions?????

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Yes, onions are fine. Onions are covered under the category of “fruit and vegetable scraps.”

natalie wilson October 5, 2009 at 9:23 pm

ah!! thankyou so much!!! have found your site to be extremely helpful and interesting!!!! thanks heaps!!

cheryl cary October 15, 2009 at 6:33 pm

Can you compose in the winter? If so how do you turn it when it freezes? Thank you Cheryl

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We have a page about composting in winter here!

http://compostinstructions.com/composting-year-round

Falkor December 9, 2009 at 3:47 am

What about Eucalyptus leaves? We have a tree in the front yard, the only one in the yard that shed leaves, and I think it is a Eucalyptus globulus tree(at least thats the best I can tell from the pictures online). Are the leaves safe to put in the compost? They are kind of thick(not succulants though), and have a potent smell when rubbed or broken.

———–

Great question! I didn’t know the answer to this one, and had to look it up.

It turns out that University of California Davis has studied this issue and determined that Eucalyptus leaves are safe to compost, but very slow to break down because of their oily leaves.

So I wouldn’t try to compost too many of them at once, because it might be a challenge to get them to break down well. But in limited amounts, you should be fine. And they are safe.

Sierra February 12, 2010 at 12:42 pm

My husband and I are renting our first home and I’m excited to start composting as about 70% of our weekly garbage is compostable. It appears as if the family who lived in the house before us set up a wire composting bin directly behind the children’s swingset in the back yard. I was wondering if that was in any way dangerous in terms of toxic fumes, children eating the dirt, etc.

supercomposter February 12, 2010 at 1:02 pm

Thanks for your question.

I answered it here with a blog post:
http://compostinstructions.com/composting-toxic/

Darrel March 6, 2010 at 3:19 pm

I saw peanut hulls on your chart but it doesnt specify weather its carbon or nitrogen? please let me know.
Thanks

Falkor March 10, 2010 at 3:31 am

What about sugar? We have a box of confectioners powder sugar that the ants got to and want to know if we can compost it. The box says “w/out preservatives or trans fat”, ingrediants are “sugar, cornstarch”, and the brand is “C&H”.

lars March 11, 2010 at 3:30 pm

Yes, it’s fine to compost, although it might attract ants.

Best to bury it in the center of the pile or bin.

lars March 11, 2010 at 3:32 pm

Good question!

I’m not entirely sure of the answer, to be honest. It won’t be nitrogen rich though.

I’m guessing either carbon rich, or neutral. I would lean toward calling it carbon rich.

Apryl April 2, 2010 at 7:55 am

I am currently composting using a rolling drum in my backyard. It was 50% full of kitchen waste. I dethatched my lawn and put all of the dry dead grass and moss in the bin. I just read that it isn’t ok to compost yard waste treated with weed-b-gone. I used Scotts fertilizer with moss control and now I’m worried that the whole bin of compost is toast. Any insight?

lars April 2, 2010 at 8:28 am

@Apryl,

I guess it depends on how long ago you used the moss control product on your grass.

The issue in question is that if you are composting something that has been treated with an herbicide and it hasn’t broken down completely, your finished compost might still have herbicide in it, which could harm vegetables, flowers or shrubs.

There is a solution though! Only use this batch of compost on your grass, where you already used that treatment anyway, and you’ll be fine.

michele April 15, 2010 at 12:10 am

I am tired of wrapping organic matter from the kitchen in plastic and sending it to the landfill. Can I just sprinkle my peels and celery tops etc around my acreage. Will it attract animals? I really don’t want another thing to maintain around here so a compost bin doesn’t appeal to me. Thanks

lars April 15, 2010 at 7:42 am

@michele,

Although just throwing it on the ground will indeed work, it can attract rodents and pests.

A better option would be to simply bury your materials if you don’t want to mess with a bin or a compost pile.

Michelle May 5, 2010 at 12:37 pm

I have a few questions. I am a very beginner to composting, and I saw this online: http://dinnergarden.blogspot.com/2009/05/dinner-garden-learns-to-compost.html
I wondered if something like this bin thing would work? I have a very small garden, so we decided to try this bin thing.
We set up this bin thing like they said on their website, but I see from your information that I should probably drill some holes in the bottom, too, for drainage. Also, we put in a lot of dandelions and some thistles, with some leaves and some soil to get it going. What else should I use? How often should I turn something like this? We have a pet house rabbit (herbivore of course), and I see I can use his litter as well. Oh, and I see you have weeds in the “ok to compost” and in the “May be composted but with skill” section. Since we are definitely not skilled at this, is using the dandelions and thistles a problem?

Rachel May 13, 2010 at 1:59 pm

I’ve been wanting to compost, and I am just beginning are u not suppose to compost cooked food….if they’re scraps.I know u can’t compost meat, but what about shells (specific) to sunflower seeds, or any other nut for that matter? Also bread…..Is it pretty uch anything that has not been cooked?Thanx

Patti May 23, 2010 at 6:48 am

I’ve read that eggshells are great for composting, but what about the whole egg?

lars May 23, 2010 at 6:58 am

@Patti

Eggs (as opposed to just eggshells) can become putrid and stink and/or attract rodents if you add them to your compost pile or bin. So I do not recommend adding whole eggs.

Maurice May 23, 2010 at 11:15 am

Please read this article on the use of eucalyptus in composting: http://slosson.ucdavis.edu/documents/1993-19942140.pdf

More on the benefits of Eucalyptus in composting for plants and vegetables… A California research project on Eucalyptus leaves in compost:

http://ucanr.org/repository/CAO/landingpage.cfm?article=ca.v047n03p22&fulltext=yes

The finding that both sludge products similarly affect crop growth indicates Eucalyptus trimmings (present in the compost, but not in the heat-dried sludge) do not suppress crop growth at the rates being evaluated in this study. This is an important point because it was initially feared that allelopathic compounds in the Eucalyptus would inhibit crop growth. The authors hypothesize that the composting process degrades the allelopathic compounds into harmless products.

In summary, the field experiment showed that incorporating sewage sludge compost 4 inches deep as a soil amendment in spring plantings significantly increased yields of onion, snapdragon, turf and spinach. Greenhouse experiments produced similar results and demonstrated that the presence of Eucalyptus trimmings in compost does not depress yields.

Renee June 26, 2010 at 10:32 pm

I live in Alaska and just started my compost pile today. Is there anything I need to do to protect my bin and composting material in the winter? I live in an area that can get to -35 F.

lars June 28, 2010 at 5:08 pm

@Renee

Anything that you do, the pile will still freeze solid during the winter. But it’s no big deal. The composting process will stop when it’s freezing, but it will start back up again naturally when the snow melts away next year.

I’d be worried more about the bin itself than the materials, but I’m not really an expert on super cold weather like that, so I don’t think I’d have anything constructive to recommend.

HannahDaizy July 3, 2010 at 8:54 pm

Wait, can you compost nitrogen items and carbon items together?

lars July 5, 2010 at 2:49 pm

@HannahDaizy

Yes, absolutely. You are supposed to have a mix of carbon rich and nitrogen rich materials for optimal composting. Too much of one or the other will cause problems and slow things down.

Renee in Katy July 29, 2010 at 3:47 pm

Hi Lars!

I LOVE this SITE!!!! So helpful!!! I’m new at composting… I took a Plastic plant container, cut out the bottom, turned it upside down on the turned over Soil, and put my kitchen scraps in it to start. What should I do next? Should I add anything to it to get started in breaking down, or should I just wait? Thank you so much!

Renee in Katy July 29, 2010 at 3:49 pm

Oh, I put a wire cage around it and on top of it to keep out Cats in the neighborhood… So, my Container is technically “open” and moist…there is a Water Source nearby…

Renee in Katy July 31, 2010 at 9:00 am

O.k…I bought a compost bin yesterday and put it together! It came with come Composting “Seed” I think is supposed to help it along… I put some Grass shavings on top of my Kitchen Scraps and poured H2O on it… Do I need to do anything else to it? I did give it a toss. I put it in a great area that gets lots of sunlight. Thanks!

Will August 13, 2010 at 1:12 pm

When the composting process is finished and you have your product compost, do you have to use it right away or can you store it until you are ready to use it for your garden?

LEE IN VA. August 14, 2010 at 10:16 pm

Can you compost left overs from the kitchen such as spaghetti or casserole dishes?

DJK August 16, 2010 at 9:38 am

I like to go to Starbucks and get the spent coffee grounds to add to my compost. It seems to really heat up after I add a fresh batch…

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