Composting organic wastes represents an important pathway for carbon flow and nutrient cycling in both developed and developing countries. Composting, often described as nature’s way of recycling, is a self-heating, aerobic, solid-phase process, during which organic waste materials are biologically degraded into an extremely useful humus-like substance. The product resulting from this process is called “compost” (from Latin compositum meaning consisting of more than one substance), which stabilizes biologically numerous types of organic waste by converting them into a final product containing a proportion of humus. The compost, which is rich in nutrients and hygienically safe, is created by reproducing processes that are found in nature that ensure the recycling of nutrients in a controlled and accelerated way. The main protagonists of this dynamic process are microorganisms (via the rapid growth of bacteria, fungi, and actinomycetes) and their enzymes [1]. Human control of the biological decomposition process is what differentiates composting from the natural decomposition of organic matter; in fact, regulating and optimizing the conditions ensures a faster process and the generation of quality end products.
The composting process is characterized by four phases:
(1) the initial mesophilic phase (10–42 °C), during which, the temperature rapidly rises and initiates organic matter decomposition;
(2) the thermophilic phase (45–70 °C), which is distinguished by prolonged high temperatures due to the extensive metabolic activities undertaken by endogenous microorganisms;
(3) the middle mesophilic phase (65–50 °C), during which, the temperature decreases, allowing for re-establishment of the heat-resistant microbes;
(4) the finishing phase (50–23 °C), during which, the organic matter and biological heat production stabilize [2].
Moreover, it is carried out by different classes of microbes, such as mesophiles and thermophiles. Generally, mesophilic microorganisms, which function best between 30 and 50 °C, initiate the composting process. As microbial activity increases soon after compost piles are formed, temperatures and density within the piles also increase and thermophilic microorganisms take over at temperatures above 50 °C. The temperature in the compost pile typically increases rapidly from 50 to 70 °C within 24 to 72 h of the pile formation and can stay there for several days depending on feedstock properties, pile size, and environmental conditions. This represents the “active phase” of composting, during which, decomposition is the most rapid. It continues until the materials containing nutrients and energy within the piles have been transformed. As the microbial activity decreases, the pile compost temperature gradually declines to approximately 37 °C. Mesophilic microorganisms recolonize the pile, and the compost enters the “curing phase.” The oxygen consumption during curing declines and organic materials continue to decompose and are converted to biologically stable humic substances that represent the mature or finished compost. Potentially toxic organic acids and resistant compounds are also stabilized during curing. A long curing phase is needed if the compost is unfinished or immature, which is possible if the compost pile contained too little oxygen or either too little or too much moisture [2]
Bugs, Critters, and Microorganisms
When you’re creating the perfect compost pile, what you’re really doing is providing a space for loads of organisms to live and thrive. These organisms help break down all the materials you throw into your heap and create that beautiful compost you can use in your garden. And while they may be creepy and crawly, they’re actually really helpful.
Here are some of the critters you can find in your compost.
Ants – You may find some ants bobbing about as they’re looking for food. While they burrow through the compost, they create passages which allow air to pass through. This helps the other organisms breathe and assists with the degrading process. They also help break down the material into smaller pieces.
Pill bug – These creatures do more than just roll up into a little ball. They help eat all the organic matter and are even able to digest the cellulose fibres of sticks and branches, making them a valuable addition to any compost.
Millipedes –Try not to be intimidated by all their legs – millipedes are very helpful compost critters. They love to eat dead plants, as well as decaying sticks, branches, and leaves.
Soldier Fly Larva – For such a small grub, they sure can eat! Their intense appetite means they can eat a lot of greens and household waste, making these materials easier for worms to then eat and digest.
Worms – They may be slimy, but worms are one of the most important creatures of the compost pile. As they wriggle through the heap, they create passageways for air, water, and other nutrients to fall through. They also enjoy a varied diet of kitchen scraps, newspaper, and garden waste, which they then turn into cast – a substance that’s worth more than gold to a gardener.
RISE Foundation (NGO) 