As we start the Garden Series discussions, one of the first things that we need to discuss is compost, because this will be on of the basic building blocks of the garden.
Compost is a natural result of the breakdown of organic material as it degrades. All organic matter will break down over time and become compost, however it is possible for us to speed up and control how that breakdown occurs. That is basically the difference between cold-composting and hot-composting, which is what we want to discuss today.
Composting that happens in nature when leaves fall from a tree and slowly degrade over a long amount of time laying on the ground is what we mean by cold-composting because the temperature inside the material being composted does not rise very high. Cold-composting relies on anaerobic bacteria. Anaerobic bacteria are forms of bacteria that do not live or grow when oxygen is present Because cold-composting relies on anaerobic bacteria you will notice a slimy feel to leaves being composted this way and you will also notice a rotten smell as the material decomposes. Believe me, a cold-compost pile is NOT something you want anywhere close to, or upwind from your house, or your neighbors house if you want to remain on friendly terms with them.
Hot-composting on the other hand happens relatively quickly due to the high heat generated in the compost pile that breaks the materials down. A typical hot-compost pile will get up to a range of between 140 to 160 degrees Fahrenheit. Hot-composting relies on aerobic bacteria, or bacteria which rely on and thrive in oxygen. The heat generated inside the compost pile is because of the aerobic bacteria deep inside the pile working hard to break the material down quickly.
I know I keep saying quickly when referring to hot-compost and over time when referring to a cold-compost. Let's put them into some kind of perspective so you can see the difference. A cold-compost will take many months, or even up to a couple years to completely break down the organic material whereas a hot-compost pile can break down the material within about three to four weeks. Now you understand what a huge time difference there is between the two different forms of composting.
As part of this series I have started a new compost pile in my yard in which I will be using the hot-compost method to break down organic matter and get it ready to use on my garden.
To keep things simple, I will be using materials and items that are readily available either through Amazon or at your local home improvement store like Home Depot or Lowes. I chose to go with the 36"' x 36" x 30" wire compost cage shown below which is available from Amazon. You can also find similar compost cages at home improvement or gardening centers.
The heavy gauge steel wire is powder coated for long life outdoors in your yard and will last you many years. They are available in both green and black colors and are available in two sizes, however for a hot-compost pile, the larger 36" x 36" x 30" size is necessary to obtain the amount of biomass necessary to generate the required heat in the center of the pile for hot-composting which we will discuss later. The open mesh panel sides allow for proper airflow which is crucial in a compost pile.
Cages like this are not absolutely required for a compost pile, it just makes it more convenient to keep the compost contained to one spot in your yard and helps to keep rodents and other animals out of the compost pile. If you are not concerned with rodents or animals getting into your compost pile, you can simply create a compost pile on the ground without anything around it. Most people just find the cages, or something similar much easier to compost in.
I have even built my own composting area before by attaching used wooden pallets together like in the photo below. If I had pallets available, I would do that again as it is cheaper, but since I do not have any available to me, I chose the wire cages. Also, since I am now in an urban setting, I didn't want it to look too "redneck" for my neighbors who will be seeing it.
This system above simply used 7 full-sized wooden pallets for the sides, 3 half-pallets for the fronts, and a bunch of plastic zip-ties to hold them all together. I used this setup for about 10 years until I moved to my current house.
The wire composting cages are extremely easy to assemble without any tools in just a couple minutes. Simply decide where you want to have your compost pile and attach the flat panel sides together by guiding one of the long anchor spikes down through the connecting loops on the sides of each panel. Once the bin is in the position where you want it to be, the anchor spikes can then be pushed down into the ground to hold the compost bin in place to keep it from moving.
You will also need a tarp that you can lay over the top of your compost pile. This helps to retain the moisture inside it and keep it from drying out as quickly. It also protects it from getting too wet in the rain. A third thing that it does it help to hold in the heat generated from the compost pile.
I purchased three identical 3'x3' wire cages and set them up side-by-side that will be used for the compost as it goes through its various stages from a beginning pile of yard waste, grass clippings, and other organic material to finished compost that is ready to use in the garden.
Since I attached the cages to each other using one of the side panels of the existing cage to create the side of the next cage I ended up with two extra side panels and extra anchor spikes from my three cages which I used to create a fourth bin which I will utilize to store the finished compost product.
You never, ever want to add composting materials to a hot-compost pile that is already working. This can cause the entire composting ecosystem which has been formed inside the pile to be thrown off-balance and will stop the composting from happening, or at least drastically slow its progress down. With this multiple bin setup, it also allows me to have multiple compost piles going at the same time by having a working pile in one bin while I start a new pile in a different bin. This system will allow me to always have compost working in various stages of decomposition and producing a continuous supply of finished compost material for my garden.
As I mentioned earlier, we need a certain sized pile to obtain the biomass necessary for hot-composting. This would be a pile that is at least three feet wide, by three feet deep, by three feet tall. A 3-foot cube of materials has enough biomass to generate the required 120 to 160 degrees Fahrenheit in its center for hot-composting. If the center does not rise above 120 degrees (technically it is 122 degrees) hot composting will not occur and you will have a slow cold-compost pile which we do not want, mainly because it takes way too long, and it stinks.
The larger the pile the higher the heat generated can become, which is also a bad thing because we do not want the heat to rise above 165 degrees because the high heat will start to kill off the beneficial bacteria that is necessary to break down the organic materials in your pile. We have to create a balanced pile that maintains a temperature between 120 and 160 degrees, preferably as close to the 140 degree middle-ground as we can. That way it is hot enough to compost the materials quickly, and not too hot that we are killing off beneficial bacteria.
A compost pile at 140 degrees in its center is a thriving and happy compost pile, full of bacterial life and microorganisms that are working away to create that wonderful dark rich compost for you, or, what gardeners refer to as "Black Gold".
This rich dark final compost is full of life and will give your garden what it needs for the plants to thrive.
Now that we have the location chosen to place our compost pile, and we have our compost cage set up it is time to start making our first compost pile.
The main question I often get about starting a compost pile is what can go into a compost pile. This is an easy answer, anything organic. Basically anything that was once alive. Grass cuttings, leaves, dead garden plants, food scraps, small dead animals, coffee grounds, shredded paper (without glossy coatings) & cardboard, toilet paper & paper towel cardboard rolls, etc.
Now there are a few rules that we want to try to adhere to, depending on the type of composting that we are doing. Since we will be doing hot-composting and the compost pile is located between my house and one of my neighbors houses, I only want to use organic materials that will be easy to decompose quickly and will not create any offensive odors. So for this reason I will not be adding any meat, dead animals, or dairy products to the compost pile.
Since I am in an urban setting in Hawaii, I will mainly be using grass cuttings for my compost pile. We do not have an abundance of deciduous trees here that shed their leaves in the fall like other areas have, so getting leaves for a compost pile is more difficult for me. We need to have both "green" products as well as "brown" products in the pile. No, green and brown doesn't necessarily have anything to do with what color the material currently is because grass will turn brown very soon as it does, but it is still considered a green product.
Green products contribute nitrogen to your compost while brown products contribute carbon. We need to take care when adding materials to our compost pile to make sure that we have a lot more brown materials than green materials. The perfect ratio would be about 3:1 or 3 parts brown to 1 part green. Now, it is not absolutely mandatory for you to have that exact ratio, but that is what works the best.
Here in Hawaii, I am limited to what materials are available for my compost. I will be using a lot more green materials in my compost than brown materials, simply because I have more green available to me. You can do a compost pile comprised only of grass cuttings, but I do not advise it if the pile will be close to your house as the more green you have in the compost, the more odors you will have from it as it breaks down. Adding brown materials in the pile helps to take care of those odors.
If you have a lot of green materials and need to add more brown materials one thing that you can use is shredded paper and cardboard, both of these items are considered brown and will add more carbon to your compost. I actually purchased a cross-cut shredder just for this purpose. Now I can put all of that junk mail they keep sending to me to good use in my compost.