Micro-organisms in the compost heap, referred to as Aerobes need oxygen to assist them to grow, multiply and decompose the waste materials. However, there's insufficient oxygen offered inside the compost pile, these aerobic micro-organisms cannot survive and eventually die. As theses aerobes disappear, another kind of microorganism micro-organism referred to as Anaerobes takes over the duty of decomposition producing anaerobic compost.

Crawling Ladybugs
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Anaerobic organisms both live and thrive in an environment with little or no oxygen (oxygen-deprived). These anaerobic organisms work at a much slower rate than their air-breathing aerobic counterparts, creating the process of decomposition and therefore composting a much slower process.

Then the anaerobic composting process is the slow bioconversion of organic matter in the absence of oxygen using fermentation and is similar to the fermentation processes that occur naturally in bogs, swamps, marshes and other such wetlands that produce peat compost and moss.

Anaerobic bacterial Microbes

Anaerobic Composting works best with nitrogen-rich materials as they're principally wet, yet almost any organic material can be processed in an anaerobic composter like waste paper and cardboard, grass cuttings, leftover food, animal slurries, and manure, etc, or any other kind of feedstock that includes a particularly high water content.

Nevertheless, it's vital to avoid adding a lot of carbon-rich materials, for example, dry leaves, sawdust and woody garden waste. A high concentration of these kinds of dry materials will retard or even halt the anaerobic composting process either killing off the anaerobic microbes fully producing a smelly mess or turn it into an aerobic composting pile.

Unlike conventional aerobic composting, anaerobic composting is a low-temperature process that the compost pile won't heat up because of the high percentage of liquid. A lot of pathogens, diseases or weed seeds present within the mixture might not be killed in the fermentation process. However, the pathogens can gradually disappear over time because of the hostile atmosphere.

Since the biological process of anaerobic composting happens naturally in the absence of oxygen, it's effectively a controlled and sealed version of the anaerobic breakdown of organic waste that occurs naturally in landfill sites. The wet biomass feedstock is sealed in containers permitting the anaerobic bacterial microbes to thrive in an oxygen-free atmosphere as liquid composting.

The anaerobic digestion of the feedstock happens naturally over time, producing helpful biogas, usually methane, which will be collected and used to generate electricity or heat. However, over-exposure to oxygen impedes the anaerobic micro-organisms from multiplying and slows down efficient composting.