Paul Stamets, a renown fungi expert, calls decomposer or saprobic fungi the grand molecular disassemblers of nature. It's a perfect description. These organisms take large, complex organic molecules, like the fats, carbs and proteins, found in dead plants and animals, and disassemble them into the simple inorganic compounds such as water, nitrates and CO2 that plants use as nutrients.
The average compost pile has a huge variety of material in it. Each material has a set of molecules - some simple and some complex.
Each decomposer fungi produces a limited number of enzymes. Each enzyme decomposes a limited number of complex compounds. To fully breakdown the complex plant and animal bodies that are present in your compost, you need many different members of the soil community. Here we'll focus on the waves of fungi that colonize your compost.
You might find some delicious looking mushrooms growing in your compost or mulch. Heed this first.
WARNING: While many saprobic mushrooms are edible, most aren't. There are around 1.5 million types of fungi. We've only described and named about 75,000 or 5% of these. Of these about 250 are good to eat and at least 200 will make you very sick or kill you. It's often hard to tell the difference between the delicious and the killers so don't eat what you don't know for sure is edible.
That said - many of the delicious cultivated mushrooms are decomposers. In other words they feed on dead material like mulch, compost and stumps. One way to classify them is by what they like to eat. Two common groups are:
Fungi are a vital part of healthy fertile soil. We already know their role as decomposers, recycling nutrients back to plants. They infuse the soil with a mat of hyphae that serve to hold the soil in place. Paul Stamets says they can absorb and hold up to 30,000 times their mass and are in large part the generators of humus soils throughout the world.
But most of us are a little nervous around fungus. Seeing a mushroom sprout in your lawn, or your wood chip mulch sporting a white fuzzy fungal coat, isn't usually a cause for celebration. More often we'll search for fungicides.
In truth we'd be farther ahead encouraging them and making conditions better for fungi to establish themselves.
These two things are a good start -
There are other players in the decomposition story. Bacteria, like fungi are primary decomposers. Other major players,like earthworms, ants, flies and termites, are often classed as shredders. They breakdown materials into smaller pieces making it easier for fungi and bacteria to do their job.