Cheat Sheet: Composting

emptying kitchen scraps in compost bin

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According to the EPA, in 2015, almost 24 percent of the U.S. municipal solid waste stream was composed of food remnants and yard trimmings. We could significantly reduce the amount of waste going to landfills by diverting these materials to another use.

Enter: composting. Grass clippings, food scraps, and yard waste are all ideal materials to add to a compost pile. Starting your own compost pile not only cuts down on your waste output, it creates a great soil booster for your garden as well.


Have you been thinking about composting, but unsure about taking on the challenge? Understanding the basics of composting can make it a less intimidating process.

What Is Composting?

Composting is the natural decomposition process of organic materials — including grass clippings, leaves, vegetable scraps, coffee grounds, and woodchips — sped up by a deliberate strategy in a concentrated environment. The resulting material (known as “humus”) provides a wonderful nutritional supplement for the soil.

For households: Composting allows you to reduce your waste output while turning your kitchen scraps and yard trimmings into a beneficial soil amendment for your garden.

For small-scale farms: Composting is a way to manage the residual plant and animal material the farm generates and put it to good use as a fertilizer and soil-builder for future crop production.

The Science of Composting


So, how does composting work? According to Nance Trautmann and Elaina Olynciw of Cornell University, microorganisms break down organic matter, producing heat, carbon dioxide, water, and humus in the process.

When composting is done correctly, a pile undergoes three optimal phases:

  1. The mesophilic, or moderate temperature phase, lasts two to three days.
  2. The thermophilic, or high temperature phase, lasts anywhere from three days to several months, depending on what is in the pile.
  3. The cooling and maturation phase lasts several months.

In the first stage, mesophilic microorganisms quickly break down the easily degradable materials in the pile. The microorganisms’ output of this breakdown is heat, so the temperature in the pile rises. High temperatures in a compost pile are necessary for the next phase — where thermophilic (meaning “heat loving”) microbes replace the mesophilic ones.

Thermophilic microbes then kill existing pathogens and accelerate the breakdown of complex carbohydrates, fats, and proteins that exist in the pile. Note that if temperatures in the pile rise above 149 degrees Fahrenheit, even the heat-loving microbes can be killed, slowing the rate of decomposition.


Because piles can get too hot, it’s essential to aerate, or turn the pile, for the cooling phase to be reached. The cooling phase is where the high microbial activity of the other two phases is reduced, allowing the compost to mature for use in your garden.

woman with shovel at outside compost bin

Regularly turn your compost to ensure all parts of the pile get enough oxygen. Image: Adobe Stock

What to Put in Your Compost Pile

Knowing what materials should go into your backyard compost pile is essential for a successful outcome.

You need a balance of “green” (nitrogen rich) and “brown” (carbon rich) materials to ensure a sufficient amount of oxygen the compost pile does not become anaerobic. Anaerobic decomposition occurs as a result of an improper chemical balance, mainly a lack of oxygen.

To ensure sufficient oxygen, it’s important to aerate, or turn the pile. If the pile is not properly aerated or has too much nitrogen and not enough carbon, it may develop a bad odor. A well-managed compost pile should not smell bad.


So, how do you achieve the proper chemical balance? Let’s start with the greens.

Green Materials

Green materials are rich in nitrogen. Some examples of green materials include:

  • Food scraps: Fruit and vegetable scraps are great for your compost pile. Never add animal-based leftovers (fat, meat, cheese, milk, etc.); the oils and fats are not conducive to a backyard composting operation.
  • Fresh grass clippings
  • Manure: If you have access to manure from horses, cows, sheep, goats, or chickens, it is a great compost ingredient; it speeds up the decomposition process. It is not a requisite for a successful compost pile, however. Never use manure from carnivores.
  • Plants and plant cuttings: Just-picked weeds from around the backyard (as long as there are no developed seeds or seed heads) are permissible, as are flower tops. Green leaves from a freshly cut branch work as well (just make sure to shred them).
  • Coffee grounds

Tip: Freeze Your Scraps!

To reduce the number of trips to the backyard to dispose of kitchen scraps, put them in an airtight container and freeze them. This also helps to avoid the smell of old food.


Additionally, freezing will assist in achieving chemical balance in your compost pile. For example, if you have an overload of “green” food scraps from last night’s dinner party and you do not have the necessary “brown” materials to balance out the pile, freeze the scraps for a while until you have enough “brown” to add to the pile.

Brown Materials

Brown materials, on the other hand, are rich in another crucial ingredient, carbon. Carbon gives the microbes the energy they need to work. It is useful to shred most brown ingredients to reduce the workload for microbes and enable decomposition to happen more quickly.

Some examples of brown materials include:

  • Dead, dry leaves
  • Hay and straw
  • Simple paper products: Newspaper, paper, and cardboard
  • Crushed eggshells
  • Tea bags and loose-leaf tea
  • Wood ashes and sawdust: Use sparingly. Wood ashes can make the pile very alkaline, which limits microbial activity. And sawdust can take a long time to break down.

Moisture in Your Compost Pile

According to the EPA, another important factor to keep in mind is the moisture content of the pile, since the hard-at-work microorganisms need an adequate amount to survive. Water also transports nutrients and organic matter throughout a compost pile, which keeps the pile from becoming stagnant.


But how do you tell if you need to add water? According to the New York City Compost Project, “Optimal moisture levels for composting occur when materials are about as moist as a wrung-out sponge — obviously moist to the touch, but yielding no liquid when squeezed.”

For advanced-level composting, you can get a compost moisture meter to measure your pile’s moisture level more precisely, but this isn’t necessary. If you get regular rainfall, it will often do the trick, as it provides a slow soak that is optimal for infiltrating a compost pile. However, if you live in a drier climate, you will probably need to water your pile. Make sure to add water slowly and to turn the pile to incorporate the water so it reaches all sections.

Where you live and your particular climate will have a significant effect on your pile; you may need to do some experimenting. 

Editor’s note: Originally published on August 31, 2009, this article was updated in July 2019.

 

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Comments

  1. Brilliant article detailing the benefits of compost heaps. Didn’t know that so many different things were going on inside composts. Might try building one myself but I’m really worried that I won’t do it right and it might smell too much.
    Fantastic keep it up!!

  2. Dry leaves can shed water, so compost piles built in the fall can be too dry. Soap can be used as a surfactant to keep leaves moist and hasten the decomposition process. Dissolve your leftover natural soap remains or add biodegradable liquid soap in a few gallons of water and use it to wet the leaves as you build your pile.

    If you are mostly looking to divert your kitchen waste and do not care much about the sicence of composting, then a standard 3’x3’x3′ bin (either a commercial black plastic bin or a homemade wood bin) is very low maintenance. We just throw in our kitchen waste alternating with some dry leaves and it composts just fine without turning, watering or monitoring. I add manure and/or finished compost now and again to keep things going.

  3. Just a tip grass clippings are good however if you use ex: weed feed on your lawn it should not go into the compost as told to me at a compost seminar , also egg shells should be rinsed/

  4. Your presentation on “cheat sheet”, is so revealing to me. I appreciate this environment and soil protection knowledge. I am surely going to put it to use because am quite at home with this theory.
    Thanks.

  5. Yes K J, take a look at the “vermicomposting” link at the top of the article for more information about composting with the help of earthworms!

  6. I agree that this is a great article about traditional composting. I think that if you have a big enough yard that you can compost traditionally without experiencing unpleasant smells in your living area. If you do not have a yard or live in a cold climate, you can compost indoors using worms with no bad smells.

  7. Pingback: 8 Easy Green Thanksgiving Tips | eko park apartments

  8. Pingback: Are Biodegradable Bags a Viable Option for Composting? - Earth911.com

  9. loved this article! still a little confused about how exactly do you get started like the whole “hole” thing! my backyard is kind of small….like 2m x 8m its a little more longer than wider. what can i do? does it matter if my backyard is a bit small? really looking forward to start this compost, im just a girl trying to promote greeness in my city and school!

  10. Also in my 1st year to compost. I started with a tumbler last fall which maybe wasn’t the optimal time of year. Over the Winter I have resisted (mostly) the temptation to turn it and now it seems to be dry and dead. Besides water, what should I do to re-start the process, or should I just start over? lost in TX t

  11. I thought you would want to avoid using newspapers because the chemical ink will get into the ground and contaminate things no?

    Wow didnt know composting is such a procedure.

    My grandfather planted flowers and vegs in his front and back yards.

    He simply got fish from the market that was about to be thrown out, chopped them up, mixed it with food scraps and just tossed it over and into the soil where he planted things.

    Granted it all stunk real bad for about a week but no one ever complained about the luscious vegetables and flowers he had. It was so bountiful that he gave away quite a lot of his bounty and people would come back for more.

    But he never followed any of this. He did say he woudl just use food scraps if he didnt have or was unable to get the fish. He said that in the fall he would just turn over the soil again which would cover all the composting.

    He never had a bin. I dont know where he kept all that food scraps though . I think he kept them in bags. maybe thats what the stench in the basement was during the cold winters.

  12. Kudos to Earth911 for promoting organic waste recycling over the internet and through other new communication modalities. In Canada homes, schools, businesses and government offices are learning the valuable benefits of worm composting through our environmental education extention services and we are happy to announce that awareness and participation is rapidly growing. We can look to a future when every citizen takes personal responsibility for their own organic waste recycling at home and in the community. There will be ZERO waste going to the archaic curbside waste collection system. A garbage truck will be museum memoriabillia. Landfill will take on new meaning. Simple, inexpensive, natural solutions that successfully support sustainable systems. Is it possible? YES. Lots of Love, Gerrie Baker, aka The Worm Lady, Foley Mountain, Westport, Ontario

  13. Hey guys im trying to start a composting hole in my backyard but im wondering: is it okay if i turn it two days a week like monday and then thursday or something like that? and if not what is the appropriate times of turning it ?

  14. I’ve found the cheapest way to build a compost bin is to use pallets. You can get pallets for free all over town. Just use three to make the back and sides and a fourth to make the door (if you want it “gated”). For the door make sure you lift off the ground when fastening so it swings clear of the ground (use hinges from local hardware store). If you live in the cold put a roof on it. Down here in South Coastal GA there is no need to have a roof. Use old wire coat hangers to wrap around the posts to secure sides and back pallets. (that’s the cheap way). If you want to put chickenwire around it put it on the outside so it will not get in the way when turning compost. Happy ‘posting everyone.

    Got any questions or comments hit me up at DanCigarMan@yahoo.com. I’m just getting started myself.

    Dan

  15. These are all helpful hits in creating a good compost pile. Thanks for the artical. As I get mine going, if I come up with any new tips I will be sure to let all of you know.

  16. Coffee grounds are not a brown (carbon) material. They are a green material, being rich in nitrogen. They can heat a pile hotter than manure.

  17. The you tube video has the proportions backwards–it should be one part GREEN to 3 parts BROWN.
    Also, once you are experienced, it is perfectly OK to add some animal-based leftovers. A little cheese or shrimp shells will dissappear quickly. Just remember to ALWAYS bury the food scraps INTO the pile and mix it around so everything is coated with active compost. You should see almost all browns at the surface.

  18. Hi Haley, thanks for sharing your link with me. I have a high altitude living blog and we have lots of trouble because of the arid nature of the environment.

    Wondering if you’d be interested in guest blogging a version of this geared toward high altitude issues in our mountain lake resort.

    Take a look and let me know. You know me as @arklady but I am also @fawnskinflyer

  19. Hi,

    I just started composting and my tumbler is working great, looks exactly like it is supposed to, very exciting! One question though, I have been shredding our cereal boxes and putting them in there. It sounds like those have been treated and should not go in, is that correct? If so, that is such a shame, we go through so many boxes…

    Thanks for the help!
    Lee

  20. Odd, I tried finding the article that brought me here through links, but I can’t right now, but it seems there is quite a bit of contridictory information provided here. Coffee grounds are brown, then they’re green, and piles should be 1/3 geen and 2/3 brown, then the opposite. I’m far less technical with my composting and never seem to have problems getting above 140, but THIS is why people get confused with composting.

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