TRJ What about bugs? Compost piles are somewhat famous for housing insects. LF We do also have microarthropods, which are insects. Even though they’re larger than these other microbes, some of them are hard to see with the naked eye, like mites and springtails. These guys are kind of chomping down on some of the organic material in the pile, helping to break apart those materials, so it’s easier for things like bacteria to colonize them and break them down further. They’re kind of our little chipper-and-grinder mechanisms. They also help to aerate on a micro level, moving things around. TRJ How do all these microbes make their way into a compost pile? LF We live in a microbial world. They’re all around us. They’re in our bodies and in the air. They already exist on your food scraps. They’re in the wood chips you build your pile with. All the ingredients we use to build the compost pile, they already have existing microbial communities on them. One thing I love about manure is that it has a more unique, enriched microbial community in it because of the animal it came from. Animals are culturing vessels for specific types of microbial communities. That’s why manure is known as an “activator” in a compost pile, because of the microbes it imparts. You’re supposed to layer your greens to browns, your carbon to nitrogen, in a specific ratio, which really allows the most amount of microbes to be introduced. This is an engineered process, based on the natural process of decomposition. But we’re tweaking the variables. On a forest floor, you have leaf litter and some animal droppings, but it’s a much slower decomposition process. With compost, we engineer it to go faster. We activate more microbes. More of them can consume these materials at the ratio we provide.
TRJ How does something so small, like aerobic bacteria, begin to break down something so big, like a piece of food? LF We zoom in, onto the food. Food is made with cellular structures. Generally, actinobacteria and fungi can help to break through the kind of tough cell wall layer. Then you have different compounds inside your cellular organelles, like proteins and fatty acids. You have different cytoplasmic nutrients and DNA structures — energetic molecules are in there. Once those are released, the bacteria can access all of those things. We see this, on the macro level, as decomposition. But really, these bacteria are just accessing those organic materials on a much smaller, molecular level.
THE ROOTED JOURNAL How would you explain what compost is to a beginner? LYNN FANG Compost is the process of decomposition, where your food scraps and organic materials are transformed, by microbes, into soil organic matter, or humus. Compost is a nice soil amendment that can activate the biology in your soil, support nutrient cycling, provide disease suppression, and provide all these other benefits to the soil. TRJ There are so many outwardly invisible processes involved in compost, which can make it all seem quite mysterious. What do you see under your microscope? What are these microbes at work? LF Yes, all these invisible creatures! The smallest organism that we think of with compost is bacteria, a single-celled organism and primary decomposer that feeds directly on carbohydrates and compounds in organic waste material. Fungi are another primary decomposer. They can also feed on food waste, but they’re specialized a little more in woody materials, like wood chips or plants. Fungi are known to be more efficient at incorporating those compounds into what is known as “soil organic matter.” Bacteria primarily release secondary nutrients, like carbon dioxide.
TRJ The microbes of the compost pile are so abundant and complex. What else do you see in there? The stuff people have maybe never heard of. LF Those are our secondary decomposers. We have protozoa, like amoebas; flagellates, which have a long tail; and ciliates, which have tiny hairs around their bodies. Flagellates and ciliates can move very quickly, because they have these hairs and tails to propel them. Some of them can swim. The more amorphously structured ones can extend these little pseudo-feet from their bodies in order to move better. These guys feed primarily on bacteria. Bacteria have more nitrogen than they need, though, so the protozoa, for example, don’t utilize it all. Instead, they poop it out in plant- available form, like ammonia or nitrate. We also have actinobacteria, which are a kind of hybrid between bacteria and fungi. They’re tiny bacterial cells that link up to form a filament. They’re super common in soil and compost — ubiquitous, even. You’ll see them when you open up your pile. They look like white, ashy stuff. They are working on some of the tougher, more woody plant fibers.
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ISSUE 02
THE MICROSCOPIC LIFE OF COMPOST
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