Gardening How-to Articles

What and How to Compost

Left on its own, all organic matter will eventually break down into nutrients that can be absorbed by plants. Composting is simply a way of helping things along by including the right ingredients in the right proportions under optimal conditions. Follow these guidelines to produce compost faster and without odor or pest problems.

What can I compost?

Most plant-based organic material, including yard waste and fruit and vegetable scraps, can be composted at home under the right conditions.

You can put these materials in your backyard bin or pile:

  • leaves and brush
  • plant cuttings
  • grass clippings
  • fruit scraps
  • breads and grains
  • coffee grounds and filters
  • tea bags
  • eggshells
  • wood chips
  • sawdust
  • wood ash
  • old potting soil
  • cut flowers
  • food-soiled paper (napkins, paper towels)

Don't add these materials to your compost:

  • meat scraps
  • fish scraps
  • dairy products
  • fats or oils
  • grease
  • dog feces
  • kitty litter
  • weed seeds
  • charcoal ash
  • nonorganic materials

Layering and Mixing

Aim to have roughly equal parts “green” (nitrogen-rich) and "brown" (carbon-rich) materials. All organic materials contain carbon and nitrogen in varying proportions. In general, wet, or green, materials such as grass clippings, food scraps, and plant cuttings contain a higher proportion of nitrogen than dry, or brown, materials such as wood, paper, and autumn leaves.

Greens (high nitrogen):

  • grass clippings
  • plant cuttings
  • fruit and vegetable scraps
  • coffee grounds

Browns (high carbon):

  • fallen leaves
  • twigs
  • wood chips
  • sawdust
  • used napkins and paper towels
  • soil or finished compost

To create ideal conditions for composting, try to include roughly equal parts of both and layer or mix the materials in your pile. A pile with more browns will still turn into compost, but it will take longer. If you add too many greens, your pile may generate odors.

To avoid odors or pests, bury food scraps under browns such as leaves, brush, wood chips, or finished compost.

Air and Water

The microorganisms in compost need oxygen and water to survive.

To make sure that air can penetrate to the center of your pile, it should not be larger than 5 feet high by 5 feet wide. You can also layer your pile with coarse materials to help air circulation; or you can aerate it by turning or mixing it periodically. Turning requires extra effort, but will accelerate the compost process.

Your pile should be about as moist as a wrung-out sponge, not soggy. You may want to water it periodically during a dry spell or after adding large amounts of dry materials.

Time

You can make compost in as little as three months, or the process could take as long as one year. Each of the following measures will speed the composting process:

  • Layer your pile with the proper proportion of greens and browns.
  • Turn your pile and keep it moist but not soggy.
  • Chop materials such as branches and grapefruit rinds into small pieces before adding them to your pile.

Using Compost

If you have ever used peat moss, wood chips, manure, or topsoil to amend your garden, then you already know how to use compost. Mix compost into flower and vegetable beds; blend it with potting soil to revitalize indoor plants; or spread it on your lawn as a fertilizer. Use coarser compost as a mulch around trees and shrubs.

Note: If you make compost with plant cuttings or grass clippings that have been sprayed with pesticides, avoid using it on edible crops.


More: BBG's Guide to Composting 

    Discussion

  • BBG Staff August 16, 2017

    Aaron Lee writes: Leaves are an amazing brown for composters. Leaves from a tree growing in contaminated soil do not have lead in them from being grown there. Lead gets onto the leaves when they are raked up from the ground. The motion of raking scratches the soil and brings it up onto the leaves. Certain leafy greens can have lead in the plant tissue itself. This isn’t a concern with leaves from trees. Another entry point for lead into your compost is yard and garden waste that was growing in contaminated soil, and has soil attached to the root system.

    Factors that enable a composter to make an informed decision about using leaves from the yard: 1. Am I raking bare soil? Bare soil carries the most risk because you are more likely to scrape up soil while raking. Raking mulch or lawn carries a lower risk of getting lead into your leaves because you are not scraping up as much soil. 2. What are the lead levels in my soil? The higher the lead levels, the more risk involved. 3. Am I being careful to avoid scraping the ground while I rake? 4. Could I hand collect some leaves right after they fall to minimize soil getting onto them?

    We also always recommend having your finished compost tested if possible. Testing empowers you to make the best decision about your compost feedstocks and give you certainty about its safety.

    The NYC Compost Project Hosted by Brooklyn Botanic Garden operates a compost hotline to answer additional questions you might have: Call us at 718-623-7290.

  • Danielle August 14, 2017

    I would like to use compost for my vegetable garden which is planted in a raised bed due to lead contamination in my backyard soil. Can I add leaves from trees growing in the contaminated soil to the compost I plan to apply to my vegetable bed?

  • cynthia September 10, 2016

    My dog got into my garden and went to the bathroom in it. My husband didn’t see it and watered the garden and it all went into the soil. What do I do now?

  • Diane Hansen July 10, 2016

    Is there any ingredient you can add that would speed up the composting process?

  • BBG Staff May 5, 2016

    Tony: Pressure-treated sawdust, boards, or other material should not be used in—or really, anywhere near—your compost pile. Although lumber has not been legally treated with arsenic and chromium compounds since 2003, wood intended for outdoor uses like decks and fencing is now often treated with copper and ammonium compounds. These preservatives could be hazardous if ingested and should therefore be kept away from soil-building materials that could potentially be used for agriculture (like your veggie garden). Furthermore, the preservatives in pressure-treated wood are designed to deter insects and bacterial and fungal growth and would therefore be harmful to the composting process itself.

  • BBG Staff May 5, 2016

    Pine needles sometimes get a bad rap for being acidic, but as they dry out and decompose, they quickly approach neutrality, so it’s fine to compost them.

  • Tony Germani April 29, 2016

    Is it okay to include, in the compost, sawdust which has come from pressure-treated wood?

  • Bill Hank October 18, 2015

    Is it ok to put some pine needles in the compost pile?

  • jblackburn October 14, 2015

    Meat, cheese, and oils will all eventually break down in a well-tended compost pile, but in the meantime, they can generate bad odors, which not only draw pests like flies, rats, and skunks but may also annoy your neighbors. If you avoid turning the pile to keep the rotting materials buried, you run the risk of creating conditions for breeding harmful (and methane-forming) anaerobic bacteria, the wrong kind for a healthy compost pile.

  • mel October 13, 2015

    Why can’t you add meat products to compost?

  • Betty September 22, 2015

    Thank you for the compost info. Question: Is it OK to add to my compost bin food from the table that has been cooked in oil i.e., EVOO, coconut oil? I have been composting for over 25 years and wonder if I’m doing the wrong thing.

  • Gina M. August 10, 2015

    I am new to composting and am looking forward to starting my first batch. I live in a condo with a fenced in patio (basically no backyard just a cement patio). Is it still feasible to start/maintain a compost bin without a yard to help encourage the compost process? Is there anything special I should do to facilitate the compost process since there won’t be any grass to surround the compost bin?

  • Candace July 26, 2015

    Can I put blackberry bush clippings in my compost barrel, or will that not break down?

  • Sandy G June 19, 2015

    I recently started composting. The problem I’m having are gnats! What am I doing wrong?

  • NYC Compost Project June 16, 2015

    Dear Laertner: It sounds like the setup you have is what we would call a tumbler. Tumblers are effective in creative relatively quick, small batches of compost. When using a tumbler, add equal amounts of browns and greens; otherwise you might end up with either a smelly or an inactive pile. Be sure to thoroughly chop them up to accelerate the decomposition process. When your container is full, you can let it sit and continue to turn the tumbler. (As tumblers become filled with material they can be a little difficult and heavy to turn.) Check on the material periodically until you have a dark, earthy smelly soil and voilà—you have compost!

  • Cheryle May 6, 2015

    I’m new to composting and am tight on $$. Can I place my green/brown mix on plastic outside and cover it with plastic (ex. garbage bags)? Or should I put in on the ground and cover with the bags?

  • laertner April 26, 2015

    I have made my own composter out of a 30-gallon barrel, and it can spin. I am not sure how to start it. We normally dig compost in the garden and have had problems with dogs and other animals digging things up. So we wanted to use a bin. Can you tell me how to get started?

  • BBG Staff February 26, 2015

    Vijaya: Here, “organic” means anything derived from living matter. Any such materials that will decay during the composting process will work. That being said, the fewer residual pesticides from garden clippings or kitchen waste the better for your compost, especially if it is intended for growing edibles.

  • Vijaya February 24, 2015

    In the article, it says put organic fruit and veggie scraps—does that mean we can only compost organically grown veggies and fruit waste?

  • Vijaya February 24, 2015

    Nice article. I have started indoor composting with a Kambha composter bin with pots, one above the other, in southern India. Weather is quite hot here. I usually put fruit, veggie scraps, and leftovers along with homemade yogurt occasionally and through thin layer of paper cuttings above every layer of green. My top pot seem moist enough and shrinks down the waste pretty good. The two bottom pots, which have half-composted material, dry out very quickly, hence, the composting process takes longer. Is it recommended to spray some water to bottom two pots occasionally, or should they be left to take their own time to compost? Is there any other way to speed up composting?

  • Peggy Carrigan November 16, 2014

    My parents actually put all our scraps and coffee grounds, etc., in our garden, so I have always been a composter. I never knew about layering with the green/brown etc.. so that is good to know. I want to start a bin outside so I can plant a nice garden next spring. What is the best kind of container? Plastic? Also, one more question, if it is an outside bin, you mentioned the worms and bugs get in on their own—how do they get through plastic or aluminum? Thank you!

  • BBG Staff September 24, 2014

    Kirsti, cat feces are definitely a composting no-no. Cats, dogs, and other animals—pets or otherwise—may carry parasites and other pathogens that can be harmful to humans if ingested.

  • Lorien Deats September 24, 2014

    I am starting my first compost. I would like to start indoors, but it seems outdoors would be the easiest by the comments. Just not quite sure how to get the composting started. I have a small container in mind. If I put this outside, should it be covered or protected from weather, or should I start inside as I originally intended (I’m afraid it will smell too much)?

  • Kirsti August 17, 2014

    You only mentioned dog feces being a problem. Are cat feces OK to put in compost? Great articles; I have learned so much! Thanks.

  • Terry July 19, 2014

    This is my first time doing composting. Do you have to have a lid on your container? Can you put in all skins from all fruit?

  • BBG Staff October 1, 2013

    No need to add worms to an outside bin, Carmen: If the browns, greens, and moisture levels are right, the worms will move in on their own and help the composting process.

  • carmen engel September 30, 2013

    I am making my first compost. It is in a bin but outside. Do I need worms also? Thanks.

  • BBG Staff September 18, 2013

    Sure, Kim: As long as they aren’t animal-based material, the moldy scraps are fine. The mold means they are already decomposing, and turning them into the pile with the rest of the compost will speed up the process.

  • kim campbell September 18, 2013

    Is it ok to put moldy scraps into the compost pile?

  • Lucia Pascone June 7, 2011

    We started a pile of autumn leaves mixed with some grass clippings and kitchen scraps in a large area in our yard in Delaware County hoping it would decompose in time for late spring planting. The proportion of brown to green was not right and then the snow of winter months made it a wet mass. Can we still save our attempt and speed up the decomposition process?

    Thanks,
    Lucia

  • Eliz Peters July 1, 2010

    If you’ve created an indoor system, you’ll want redworms to break up the biggest bits of organic material. If you rely just on the microorganisms to do the work, it will take a long time and likely be a smelly process! The best worms for indoors are different than your garden worms; they can easily be purchased online. For more info on an indoor system, see http://v4.bbg.org/gardening/article/indoor_composting/  For sources of worms and more, visit http://www.nyc.gov/html/nycwasteless/html/resources/prod_serv_composting_worms.shtml

  • Rose Taps June 24, 2010

    Recently set up my first compost bin. 20 gallon plastic bin with holes punched on all 4 sides. Have been layering a few weeks. Do I need to add worms? If so can I take them from my garden? Slightly confused on the worm issue. Please advise.

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