Composting in Hot & Arid Environments

Hello Everyone!

I am about to start working on a series of projects out here in the rather harsh arizona desert.

Composting is probably going to be a bit different out here than what I'm used to, and if I am going to construct anything it needs to have some innate fire proofing capabilities.

I've seen a few of the methane-digester canisters out here so I know those probably won't catch fire, but I'm hoping to find a better and quicker way of creating good and ready plant food to add to the soil. A worm tower of a sort seems like it might be ideal - I should be able to access a steady stream of organic waste in the form of dried manure (dog, donkey) and some kitchen scraps. Possibly even from a small restaurant as well.

Unfortunately a worm tower stands up and into the hot air. I'm afraid one would dry up quickly and constantly, though burying it slightly and excavating a small area next to it to scoop out and into might work...

Besides this, I'm considering simply digging a small pit and covering it well to combat evaporation, then digging it up later.

Do you have any tips or tried methods for composting in extremely dry and hot climates? thanks!

- Graham

Do you have any heavy equipment ,or just digging by hand?

I was thinking a root celler type of setup might be just the ticket?

By hand.

If I can get my hands on an old wooden barrel it should serve nicely as a worm tower, I'm thinking. And it wouldn't look bad either!

It's too hot in Bullhead City to compost.

The dry environment is great for making hay though. When I was growing up in the low desert, I once helped a neighbor load all of his grass clippings that had been piling up for several years so he could haul it to the dump. In all that time, there was no decomposition, it was just too hot and dry. What we shoveled into the truck was Bermuda grass hay, not compost, not humus, nothing that could enrich the soil, just dessicated hay.

But were you to water it, wet it down enough so that the composting process could start and all sorts of bugs could begin to digest it, I think you would find that the decomposition process would be very quick. In the hot and wet climate that I live in now, small pieces like grass and leaf litter take months to decompose, wood chips a little longer. Composting is great in climates where decomposition stops for the winter months and slowly resumes in the spring as things thaw out. As the weather warms up and plants need more nutrients to grow, they are there, because the decomposition has speeded up as well. But in a climate with no winter, you need to be continually adding biomass all year long.

I think you would get much better results by using mostly biochar to amend your soil, and just chop up your composting materials fine to use as mulch. Are you on sand or caliche or do you have some other soil type?

On edit: Pits aren't going to be that much better at keeping things moist. Those desert soils are SO moisture deficient that they are going to suck water out of anything you bury. There is a reason things are preserved by dessication in the desert.

Desert soil are normally very fertile and dont need much compost, They do benefit from an over-story.
I would do a an indoor worm composting. I you have 20lbs of worm they can process 10lbs to 20lbs of worm per day.
And they will double their population every 3 months. So it doen't take too long to get to 20lbs.

Are you on sand or caliche or do you have some other soil type?

I'm not sure how the locals would describe it, just moved here - its a rocky desert, lots of different sizes of rocks where development is. Instead of lawns people have rock lawns or gravel yards. Fine sand and dirt lies just under it - well compacted but i need to look again for caliche. Above ground I haven't found a whole lot of rocks that resemble this, only a few. I don't recall seeing anything like this in the cliff layers.

you need to be continually adding biomass all year long

That is something I'm interested in doing.

Desert soil are normally very fertile and dont need much compost, They do benefit from an over-story.

Yes I am going to use shadecloth on hoops and otherwise migrate out from shade heavy areas. I'm interested to see how the sun here differs in its effects vs in Florida.

I mostly want the compost so that I can have a way into cycling nutrients as well as adding them, and between the animal and kitchen waste produced about everywhere here, I think there is an untapped valuable resource if I can manage to include certain amounts of wetter items into a low evaporation environment with the worms and not need to add water.

Inside seems the most reasonable if I really want worms.

biochar would work, although usually that is a technique more designed for humid tropics where everything else breaks down so fast soil microbes need a more permanent place to live

compost will work, but should be kept moist, shaded, out of the wind, anything to prevent dehydration--sometimes covered with canvas or plastic, but make sure oxygen can get to it-- dog manure is ok to use, but in smaller quantities, and active monitoring and keeping good temps in the pile will eliminate possible parasites and pathogens

worms like cooler temps(60s -70s) as well as moisture (and dark) probably just keeping the tower in the coolest place you have inside like you suggested would keep them actively munching and having babies

noted about the dog manure

Perhaps I won't use it or where it could transfer worms. Zone 4 mulching or some such.

There is also a fair amount of donkey manure in the area that seems it would be valuable for mixed nutrients. I believe I can recall Mollison or Lawton mentioning in a lecture that running wood and manure through a wood chipper makes a fine mulch in desert environments and rocky deserts.

right, they talk about dehydration, but things never decompose, look a little harder you may find the donkey

I'm finding compost processes slow and difficult also since moving here to a drier climate. Cardboard sheetmulch is still in evidence 2 and 3 years later (while in GA it would be gone in a single season). Research and observation tell me that organic matter breaks down in two ways in a dry climate....1. in the guts of a ruminant animal; and 2. in a fire. Other than that, it hangs out for a long time. One advantage of this is that it is much easier to build soil or amend soil texture by the direct application of organic amendments.
For food waste sorts of materials, perhaps you can consider passing these through animals of some sorts before taking the resulting manures and litter and using them on the soil, with composting ahead of time or simply directly, allowing the composting to take place in place. This includes black soldier flies and earthworms....which can be kept in bins and well watered, and will break off feed yields from material not directly usable by other animals.
Another lesson I'm learning the slow way is that organic matter doesn't incorporate itself like it does in a wetter climate.....it may just sit there as a mulch indefinitely. So some of the material, especially nutrient rich material such as manure, might be best incorporated into/ under the soil surface somehow, so that it stays moister, has more chance to decompose, and releases it's nutrients to the roots.

Not quite as hot and dry here in Colorado, but it took me years to figure out how to get stuff to decompose quickly.

My process uses a 4'x4' 2' high wooden perimeter box in which I wet, compact and cover with plastic. When dry ingredients are added like fall leaves, I compact it all really well by walking on the heap and then wet it, making sure to only add a few compacted inches at a time. Kitchen waste is usually wet enough to toss right on. When I do turn it (usually only once), the pile has held quite a bit of the moisture without any maintenance watering, but I do water it again during the turn and pee on it occasionally if its high in carbon. This one box handles all the yard debris for a 1/5th acre treed suburban lot.

Hi Graham:

I'm in Phoenix so I can relate!

Composting in a hot dry area is quite a bit different than in other areas. Here are some things to watch out for:

--exposing more mass to the elements will make a pile dry out faster. Dryness is the enemy here. You definitely need a tarp to cover an exposed pile. Or if you can dig an impression in the soil to start your compost, that will help too.
--type of bin matters. Concrete block bins (common in AZ) will exacerbate the hot, dry conditions. The cement will leach water and heat up as well. Open mesh bins don't hold moisture well enough - the exposed sides dry out within hours. I've had good luck with wooden bins made from pallets or other wood.
--you will need to water your compost regularly. I water mine with greywater as much as I can. I'm just about to install a Laundry to Landscape greywater project at a friend's house, he will use the water on his compost. He will also pee on the compost. Peeing in a bucket half filled with water will dilute it. You can get bucket water by setting a bucket under your AC condensate line - no need to turn on the hose in the summer! (Note: If you have a swamp cooler, keep in mind that this water is much more saline than AC water and should only be used on plants with high salt tolerance, but limit it's use in the compost bin).
--Friends of mine had great success by "spot composting". They layered their entire yard with woodchips from tree trimmers (about 6" thick) and then pulled back a bit of the mulch, dug a hole big enough to hold a week's worth of compost, and proceeded to fill it (including pee buckets). When it was full, they covered the hole with the soil and put back the woodchips and dug a fresh hole. They did this in a methodical manner so they knew where they had already composted. They had an AMAZING garden.
--Worm towers. It does get too hot to keep them outside unless you insulate them really, really well. I have created worm jerky a time or two It was sad. There is also a type of worm bin you can make using a degassed fridge. The fridge is insulated so it *may* work for us. Have yet to find a place in Phoenix who will sell me a degassed fridge - apparently degassing is a job for a professional.


You CAN make awesome soil in the desert. I've done it, tons of other people do it and it is really satisfying to know that you have used up all this "waste" to produce something glorious!

Here's a picture of some compost from my chicken composting bin - this was just snatched from the top of the pile because the girls are molting and CRABBY. The inside stuff is usually teaming with little critters. On the surface, the hens get most of the critters. Notice the difference in texture too. The compost material has little balls in it (bacteria doing it's thing) but the less amended soil is angular and chunky.

This is compared to less amended soil in my yard. Now no area of my yard has not seen some kind of amending over the past 6 years. At the very least, all parts have been mulched with woodchips.

You can see white pieces in the less amended soil that is organic matter (sticks/wood mostly) that is SLOWLY breaking down. I actually dug that sample with a trowel. When I first moved here, I had to use a pickaxe.