Compiled by Casey Williams and the New Mexico Compost Coalition

INTRODUCTION

This article is intended to give an overview of different styles of composting that work well in the high desert environment of New Mexico. We hope it will assist in deciding why you may want to use one composting method over another in a given situation.

Before delving into the styles outlined in this document, please note that none of the information listed is considered infallible or unchangeable. Also, this list is not exhaustive. There are countless ways to make compost and every way has specific benefits, nuances, and best practices. What is written here is meant to act as a general guide to compost methods while including some of the generalities of each method. It is intended to act as a springboard. Take the information and adapt it to your own needs. Finally, it is not within the scope of this document to discuss the specific details of each composting method listed. There are some resources provided to try to help readers further pursue specific styles. 


WHAT is compost?

  • Simply stated, compost is organic matter that has been decomposed by microorganisms in an aerobic environment (in the presence of oxygen) that has sufficient water.
    • Please note that there are some methods of decomposing organic matter in an anaerobic environment in order to make a compost product (for example, bokashi). Those methods will not be discussed here.

WHY do we compost?

  • There are multiple reasons for composting. Listed here are several of the more popular ones. Note that not every composting method listed in this article will address all of the following reasons for composting.
    • Decompose organic matter, turning waste streams into valuable resources, thereby keeping more materials out of the landfill, where they contribute to greenhouse gas emissions and climate change;
    • Provide a healthy soil inoculant for the land- spreading material with a diverse and abundant quantity of soil microorganisms;
    • Add organic matter to the land;
    • Sequester carbon in the soil;
    • Kill plant seed in the material;
    • Kill potential human and animal pathogens in the materials.

HOW does compost happen?

  • Time and sometimes heat. Some composting styles just take time and some take a combination of time and specific temperatures to reach the desired finished product.
Compost windrows at Santa Ana Pueblo

A note about high desert composting

While most of the general composting techniques hold true regardless of where one is in the world, the act of composting in each climatic region will have its own subtle variations. For the arid, southwest region of the United States, the main additional consideration is a quicker loss of moisture from compost piles compared to more humid and/or wetter areas of the world.

  • Several tips to help with pile moisture:
    • Keep a close eye on moisture levels. The simple act of paying attention to this facet will be a big help. You may need to check every day during the hottest times of the year. The “squeeze” test for moisture will tell you how wet the inside of your pile is.
    • Cover the pile! Using a breathable cover in the warm months will help keep more moisture in and still allow heat to dissipate and oxygen to enter. Using a non-porous cover in the cold months will help to keep both moisture and heat in the pile. Make sure that when using a non-porous cover, there is space at the top of the pile (and the bottom of the pile if possible) for oxygen exchange to continue.
    • A closed bin versus an open pile will also help keep moisture in.
    • Daily spraying or misting of the outside of the pile is an option in the heat. A thin layer of dry/crisp material on the outside of the pile is okay but a quick spray will help to keep it from getting too dry
    • If possible, consider setting up an automatic irrigation/watering system to lightly mist the outside of the pile at regularly scheduled times during the hottest months. Be careful with the setup, though, because the opposite problem, a pile that is too wet, is just as bad as a pile that is too dry.
    • Place the compost in the shade in summer months. If this is not possible then the pile or bin may be covered with two layers of shade fabric or cardboard.
    • For more information on high desert composting, visit the Bernalillo County Master Composters

Template:

  • Name and brief description of style
  • Scale of composting: Potential scales will be mentioned for each method. These are not hard rules.
    • Small- A standard homeowner or backyard gardener can make the compost without much specialized equipment.
    • Medium- A kind of in-between space where a fair amount of compost can be created, sometimes with less effort than working on a small scale. General farm equipment can be useful at times. Large specialized equipment is not necessary.
    • Large- Usually approached from a commercial production mindset. In other words, producing a lot of compost on an annual basis for use on large acreage or for sale to the public. Specialized equipment is not necessary with every style of composting that is large scale but it is often utilized to some degree.
  • Active vs passive composting
    • Active composting requires the person/people doing the composting to actively monitor the process, usually daily.
    • Passive composting is accomplished without any (or minimal) oversight after the pile is initially built. Another term for passive composting is “static.”
  • Batch vs continuous composting
    • Batch compost is made when all of the materials are added at one time, with nothing being added after the initial pile building phase.
    • Continuous composting involves materials being continuously added throughout the composting process (usually up until a certain point). 
    • Sometimes a style will fall in between. Some styles of composting can be done with either method mentioned but most styles of composting are generally carried out with one or the other.
  • Resources
    • Some useful links, for further exploration and learning potential.
    • The NM Compost Coalition is in no way affiliated with any of the organizations/companies that are mentioned in the resource sections.

Composting with this method requires any container with holes in it that is 5-gallons or larger. Some carbonaceous (“brown”) material is placed in the bottom of the container and then food scraps (or other “green” material) are spread on the top. The layering of brown and green material continues, similar to lasagna gardening or sheet mulching, until the container is full. Top with a carbon layer and move on to the next container. Turning and adding worms are optional. The entire process from start to finished product takes about 1 year.

  • small scale
  • passive
  • continuous

Resources: Make Compost Not Garbage

Can be made or purchased. Common styles are the cylindrical tumbler that is hand-cranked and the rectangular prism shape that is fed from the top and harvested from the bottom. Also, a single bay system similar to that in the three bin/bay section can be used. Material is usually added to the bin until it is full and then it is left to sit (with some possible tumbling, depending on the bin) until it has broken down.

  • small scale
  • passive
  • continuous or batch

A common backyard style where three bins/bays are set up side by side. One method with this system is to turn material from the first bay, when it fills up, into the second. Then the first bay is filled again. At this point, the middle (second) bay is turned into the third and final bay and the first is turned into the second. This process repeats in the same manner. Another method with this system is for one bay to have material added to it until it is full, at which time the next bay is filled. When the second bay is full the third bay is utilized. The idea is that by the time the third bay is full, the first bay is ready to harvest and can start to be filled up again. Temperatures usually do not get to thermophilic composting temps with this design. It might be a good idea to check the temperature anyway, depending on what kind of materials are added to the bays.

  • small/medium scale
  • active or passive
  • continuous

This is a nice and simple way to deal with the continuous production of a small amount of food scraps. Medium-sized logs/branches are laid out on the ground, followed by the mounding of mixed shredded “green” and “brown” material. A small hole is dug into the side of the mound, about 2’ from the ground and a batch (5-10 lb) of food scraps are buried there, being covered up with the green/brown mixed material so that it is not exposed. The next deposit is made several feet to the right of the first deposit and this pattern is repeated until the full circumference of the mound has been filled. Next, deposits are made approximately 3’ from the ground in a circle (above the first line of deposits). Finally, deposits are made in a circle 4’ from the base of the mound. At this time high nitrogen material is added and the pile is turned and composted like a thermophilic pile (see section below).

  • small scale
  • passive to active
  • continuous to batch

These units have recently become available. They work with a combination of drying/heating the material and then grinding it into smaller particles. With this type of machine being newer, there is not as much information out there about them. However, it could be a good option to look into for those that have limited space/time and still want to process their own food waste.

  • small scale
  • passive
  • continuous
  • Resources
    • FoodCycler by Vitamix, Lomi by Pela

Thermophilic composting involves high temperatures, ranging from 132-170°F. Piles are managed for temperature and moisture and turned according to specific guidelines. The turning of the material is for the purpose of adding oxygen back into the pile, getting a new part of the pile into the “hot center,” and to be able to add moisture to the organic matter more uniformly. If done correctly, this is a good composting style for killing human and animal pathogens and seeds of plants.

Hand turn piles require a fair amount of physical labor. They can be built on a pallet inside of a cylindrical cage, on the ground in a mound or windrow, or inside a large compost bin. The smallest recommended size for a hand turn pile is about 1 cubic yard. This size pile has a large enough thermal mass to stay hot through the whole composting process, given that the recipe is right.

  • small/medium scale
  • active
  • batch

Much less physical labor is involved, as a machine is used to turn the piles. It can be tricky to produce high quality compost with a front end loader because the turning process is less precise but it can be done. Watering of the pile is still usually done by hand.

  • medium scale
  • active
  • batch

Tractor pulled/PTO driven, skid-steer, self-contained compost turner

The least labor-intensive thermophilic style per volume of compost produced. Requires expensive machinery. Also requires some forethought and possibly some infrastructure for initially wetting up materials and pile building. These units usually have an option to mount a water tank in order to re-hydrate the materials at the same time that they are being turned during the composting process. The best units have teeth aligned in such a way as to turn the compost pile similarly to how it would be done by hand, moving the hot center toward the outside while tucking the outer layers into the middle of the pile. Compost turners can be made instead of purchased, though it is not very common to do so.


Composting with the use of worms. At this point in time, seven different species have been deemed suitable for vermicomposting, with Eisenia fetida beingmost commonly used. Worms have a good diversity of microorganisms within their digestive tracts so they add additional organisms to the material being composted. They also do a great job of getting rid of human and animal pathogens but do not eat/kill plant seeds. At large scales, vermicomposters usually pretreat/precompost material to kill plant seed and to make the materials easier for the worms to break down in a shorter period of time. Also common at larger scales is using a machine to sift the finished product to remove any larger organic matter that has not yet been broken down.

Worm bin

Easy to do inside of a home or on a back porch. There are countless designs out there, from DIY homemade bins to prefabricated units to purchase. There are also numerous ways to feed the worms and harvest the casts (finished vermicompost/worm poop). Top feeding in a thin layer or feeding in different corners/sections of the bin are popular methods. Getting the worms to move upward to a new bin so that the lower one(s) can be harvested, harvesting from one side of the bin at a time, or getting the worms to move downward (with light) so that the top layer/bin can be harvested are all popular ways to collect finished worm compost. Many home-scale vermicomposters make the mistake of feeding exclusively or mostly food scraps to their worms. It is a good idea to feed a large portion of carbonaceous material (paper, cardboard, leaves, etc.) to the worms in addition to those materials higher in nitrogen (food scraps, grass clippings, etc). Larger above-ground “bins” can be built out of a multitude of materials. These are generally shaped to make a long, relatively narrow line per bin (ex: 4’ wide x 24-36” tall x desired length).

Can be done by hand or with the help of some machinery. Piles are usually 4’-8’ wide and 24”-30” tall. Piles are fed on one end so that as the worms are working through the organic matter, the pile gets longer. Harvest happens at the end furthest from the actively feeding worms.

  • medium/large scale
  • passive
  • continuous

This is a specific design/style of vermicomposting. The pile is in a triangle or wedge shape. A back wall (temporary or permanent) is used as a starting place, with two side walls running alongside the pile. Worms are fed on the front face of the wedge and when the desired length is reached, they can be fed in a manner that essentially “turns” the wedge around to feed back in the opposite direction. Harvest happens at the end furthest away from the feeding face of the wedge.

Simple holes that are dug in the ground, often in a line that is longer than it is wide (ex: 4’ wide x 24” deep x desired length). Sometimes the sides of the pit are left bare and other times they are lined (ex: with cinder blocks). There is a lot of bending and/or kneeling involved, as the composting process is happening below ground.

  • medium/large scale
  • passive
  • continuous

These are bins that look kind of like raised garden beds. Widths can vary but 4’ is common. Lengths can run from 8’ to 40’. There are DIY designs out there as well as units that are available for purchase. Worms are fed across the whole surface area of the bin and the material is harvested from the bottom, either manually by knocking the casts to the ground or with a cutting bar. Feeding is done by hand on smaller scales and can be done with machinery on larger scales. The same goes for gathering the cut casts.


Developed by Dr. David Johnson and Hui Chun Su at Chico State University. This method is good for the “set it and forget it” enthusiasts out there. Once the material is loaded into the cage and an automatic watering system is set up, all you have to do is add worms when the pile cools down and monitor the moisture level of the pile. It can take 9-12 months from start to finish with the JSB.

Made by assembling a system of pipes with holes in them that wood chips are laid over, followed by the material to be composted. Air is forced through the pipes in order to oxygenate the material. Temperature is monitored to make sure that the pile does not heat up to dangerous levels. Material is harvested when the pile cools back down to ambient temperature.

**Care must be taken when dealing with human waste.** Common for people that want to dispose of their waste by composting it. There are numerous styles of composting toilets. Usually, “deposits” are made in the same bucket or bin with finely textured high carbon material sprinkled over the top (sawdust, shredded hay, etc). When the container is full, a lid is placed over the top and the material is left to “cure” for a year or two before being used. Human waste can also be composted using thermophilic processes (see section above) if a high amount of care is taken during the process. It is not recommended to use composted human manure on any edible plant material that could come into contact with the ground that the compost was applied to. Another consideration is that there are some concerns with drugs and other potentially harmful chemicals ending up in the finished product (as a result of passing through the human body first). A term for human waste being composted on a large scale (sometimes by municipalities) is “biosolids.” Take care if using this material and consider getting it tested for contaminants and heavy metals.


Happy composting!