Introduction to Compost

If you are interested in becoming more self-sufficient, growing your own food, producing less waste, and lowering your carbon footprint, composting at home can help with all of those objectives. Compost is not a new idea. Beyond the fact that human cultures have been producing and using compost for centuries (if not millennia), Mother Nature has been composting for as long as organic matter has existed.

What is compost? It’s simply decomposed organic matter. All organic matter decomposes eventually, but composting generally involves techniques that harness natural processes to speed up decomposition. The final product is dark, crumbly, earthy-smelling, and full of nutrients and microorganisms that are beneficial to plants.

Finished compost is dark and crumbly.

Finished compost is dark and crumbly.

When many people think of compost, they think of worms. And while worms are certainly one decomposer—in fact, one method of composting relies exclusively on worms—they are a relatively minor part of the decomposition process. Worms and other creatures like snails, millipedes, sow bugs, and some types of nematodes, and fly larvae are all visible organisms that work on decomposing the organic material in your compost pile, but the powerhouses are all much smaller. Microorganisms such as fungi, bacteria, and actinomycetes (an unusual bacteria that forms colonies like a fungus) exist in such huge quantities that they are able to break down organic matter at a much faster rate than their larger counterparts, often without you ever seeing them.

Also surprising to most people are the extreme temperatures at which decomposers work. A class of bacteria known as psychrophiles are active at temperatures all the way down to 0°F, although they’re most effective around 55°F. As they oxidize organic material, they produce heat. If your compost pile is large enough to retain this heat, it becomes habitable by the mesophiles. These are your everyday bacteria that survive temperatures from about 40°F to 110°F, with the active range between 70°F to 90°F. Mesophiles are much more effective composters than psychrophiles, and they further warm up the pile to introduce yet another class of bacteria: the thermophiles.

Thermophilic bacteria are rapid decomposers that operate from 100°F up to as much as 200°F, though most home compost piles peak between 160°F and 180°F. These high temperatures will kill weed seeds and pathogens in the compost, which is especially important in commercial composting facilities. Temperatures will naturally drop again after 3-5 days as the bacteria use up their resources, but the process can be restarted by turning the compost pile to aerate and add necessary moisture. It takes a delicate balance of ingredients to reach the thermophilic stage, but mesophilic composting is still quite effective and much easier to accomplish.

Your finished compost will support a complex food web including many of the same macro and microorganisms that aided in the decomposition process. It will also be pH neutral, as the decomposition process buffers acidic or alkaline material. No matter what the original material, the compost will be dark and crumbly and smell like earth. There are often some materials, such as larger chunks of wood or fruit rinds, that don’t completely compost by the time the rest of the pile is finished; these can be screened out and added to the next compost pile. The finished compost can then be applied to your landscape plants and produce, adding vital nutrients to help you grow your next round of compost ingredients.