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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.

    Discussion

  • diane-adams October 13, 2021

    Can moss from scarification be added to compost heap?

  • Ro May 27, 2021

    I’m just starting for the first time and have a tub with a door at the bottom to remove compost when ready. Can I add cooked vegetables to it? Thanks

  • laure3808 April 6, 2021

    To avoid odors or pests bury food scraps under browns, leaves, wood chips, or finished compost I gather those scraps should not be meat, fish fats etc. Is there any way of composting these safe from pests and odors? I already have a compost bin as I live in a village others might want to use the bin too. I did once shred paper but found that some contains plastic—is newspaper still safe? And can I get replacement parts for the compost bin as mine is now missing one of its little doors.

  • [email protected] March 19, 2021

    I have a decomposing walnut tree stump at the bottom of my garden, the dead wood is soft and dry. Can I use this as a soil additive, or should I add it ti my compost bin?

  • Chris Owen January 1, 2021

    1) When my bin gets too full, can I move compost that hasn’t yet matured into another container that I don’t add to or turn?
    2) Can I add material if the material is freezing?

  • geoff davies December 5, 2020

    I run 3 compost bins. I have put in clean cardboard in the past. But can newspaper be used in small amounts?

  • holly September 17, 2020

    Can I add paper and cardboard to my compost pile? Thanks

  • Ata Teiaua August 26, 2020

    I have never done composting but this site touched my heart and inspired me to try and see what the result it is. Thank you for sharing this article.

  • Jonathan Andrews December 6, 2018

    You say I can add coffee grinds and filters. But my building drinks a lot of coffee. Are there limits?

  • randy February 25, 2018

    Are wood ashes OK in a garden?

  • 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?

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Image, top of page: NYC Compost Project Hosted by Brooklyn Botanic Garden