Compost is a huge subject, and there are constant debates about what is the best way to make compost. Although there may be many different methods to make compost, they all rely on starting with a good set of initial materials. Composting is the process of breaking down organic matter in a controlled way.
There are two main goals of compost. Firstly, to create a high quality volume of decomposed organic matter which is a healthy source of nutrients for the plant, water holding capacity and a way to add structure to the soil. Secondly we are aiming to increase the diversity and quality of soil biology by encouraging health biology to proliferate in the compost, and then to continue in the garden soils.
In this article, we will explore an excellent starting material that is able to increase the quality of your compost and result in healthier plants. I will describe what chitin is, how it helps your garden, what it does in your compost, and where you can find sources of chitin.
What is Chitin?
After cellulose, chitin is the second most abundant polysaccharide in nature. Similar to cellulose it is made of long chains of simpler molecules. Unlike cellulose, chitin is not produced by plants, instead it is produced by all fungi, crustaceans like lobsters and crabs, and insects. Animals use the strength of chitin as their exoskeletons.
Chitin is a valuable material because of its strength, and its ability to chemically attach to other minerals and elements in its structure. Chitin is stronger than cellulose which is drawing attention to it as a possible building material. Chitin is also important since it forms the cell walls of all fungi (including molds), and most pest insect exoskeletons.
Chitin can be broken down to form chitosan, by the action of an enzyme called chitinase. All three of these molecules are known to have different beneficial effects on plants. Below is a picture showing the similarities between Cellulose, Chitin and Chitosan. All three are beneficial to produce a healthy level of organic matter in your garden.
Why is Chitin good for your garden?
The main method that chitin related molecules help is in its ability to trigger the immune system of the plant. This can be done by applying chitinous materials directly onto the plant, or by supplementing your compost and soils with this material.
In plants we always notice better health and more yield when the immune system is activated. An activated immune system is also better able to fight against stress like pests, disease, and pathogens. Most of the benefits are noticed with the application of chitosan or chitinase to the plant and soil. This is because these are more chemically active than pure Chitin. Here is an excellent article that summarizes many of the plant benefits that have been studied.
In your soil chitin adds other benefits that go beyond just the plants you are trying to grow. Your soil will increase its ability to fight against pests with high chitin in their bodies. By adding a regular source of chitin or chitosan to your soil, it will be feeding more beneficial organisms that are able to digest this chitin. These microbes will produce high levels of chitinase and other powerful digesting enzymes. The benefit of this is two-fold. Firstly, your solid will be able to naturally fight off disease causing fungi that would normally attack your plants. This is summarized in this article about fungal relations with chitinous materials. Secondly, your soil will become inhospitable to insects that have part of their life cycle in the soil. This includes insects like Cutworms, Moths, Grasshoppers, Ants, Borers, and Beetles which lay eggs within the top few inches of soil.
A lot of the same results can be noticed whether you add the chitin to the soil, compost, or foliar applied to the plant.
What does it do in a compost pile?
Similar to the soil, compost will proliferate the organisms that best digest the material that is available to decompose. Adding chitin to your compost pile will give similar effects to the use of chitin in your soil. The added benefit is that a good compost pile will increase the speed of decomposition and abundance of chitin digesting microbes. In a short time you can have a lot of beneficial organisms and enzymes that you can spread into your garden. There are two main results of starting a compost pile with high chitin content. Your pile will have more fungi than other piles, there will be high amounts of chitinase and related chitinous molecules.
Fungi are organisms with incredible abilities to digest organic matter. Lignin (woody material) and chitin are especially hard for bacteria to digest, which means that fungi are the primary digesters of these materials. Most compost piles have high levels of cellulose and lignin in the form of woody plant materials, paper, cardboard, and sawdust. Adding high levels of chitin as well as lignin, will result in more diversity of fungi in your compost. This will result in a more complete compost, with a greater diversity of microbes and plant stimulant molecules.
The other benefits of starting compost with more chitin is that you will end with higher amounts of chitinous materials. Chitin that is present will mostly be broken down into smaller molecule sizes which means that the plants will be able to take it up more easily. Some of the chitin that is digested will be transformed into chitosan which is even more plant available. Chitosan is also an excellent plant stimulant that will boost your plant’s immunity. The final molecule that is beneficial for your garden is Chitinase. This is the molecule that is able to help suppress pathogens and insects in the soil and on the crops.
What are some sources of chitin?
Now you are probably asking yourself what you can use as good sources of chitin for your compost pile. Although all the sources have different characteristics all these sources are great for your compost. Mushrooms and depleted mushroom fruiting blocks, Insects and their frass, and the shells of sea-food like lobsters, crabs and crayfish are the main available sources of compostable chitin materials.
Fungal sources are generally more locally available since most larger communities have local mushroom farms. You can get finished mushroom blocks from these producers and crush them up before adding them to your compost. You can also collect wild mushrooms that grow around your place and add them into your piles. A benefit of these fungal sources is that they almost all contain high levels of other digestive enzymes that will help your compost pile break down more completely.
Insects are more difficult to collect yourself, and although they are becoming more common as a feed source for animals, they are generally not available as a waste product. The frass (poop) of insects is where the opportunity comes for a compost input. Mealworms, Black Soldier Flies, and Crickets all produce high amounts of this Frass and it is usually high in Chitin as a result of these insects molting regularly. Something unique about frass is that it contains the biology of the insect guts, as well as organisms that are able to digest chitin since most insects will consume their own molted exoskeletons.
The final and most pure form of Chitin is from crustaceans harvested for human consumption. This material is widely available, and it is majorly under utilized in composting. Most of these shells will end up in the landfills. Crustaceans shells are available as a pure product in a ground form online, but they can also be collected from local restaurants if they are willing. If you can make a deal with a local restaurant you can get the chitin sources as well as the other vegetable waste from their kitchen. Both of these will improve your compost.
All of these sources are good to add to your compost, but there are differences. Frass, and depleted mushroom fruiting blocks are sources that can be applied directly to your garden. The other sources of chitin will be mostly unavailable to the plants until they have gone through a good compost pile. There are many reasons to add chitin into your garden compost. At our farm we produce plenty of mealworm frass which we sell for other gardeners. We also add high levels of this material into all of our compost.
In 2023 we used frass and dried mealworms in a specialized compost that was able to control our grasshoppers. We used only a small amount for our acreage in the form of an extract sprayed at night. We are working on making this compost more repeatable so that we can share it with others. Grasshoppers were a huge problem for us, and now that we have a solution it is very exciting.
I welcome you to join the exciting benefits of chitinous products by adding it into all your compost. This will allow you to garden with better results, and fewer worries.