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Aerobic Composting vs Anaerobic Composting

HotRot units use continuous aerobic composting technology to turn putrescible organic wastes into compost, a renewable resource. So what do we mean by aerobic composting and why do we prefer this over anaerobic composting technology?

Aerobic composting

Aerobic composting is decomposition of organic matter using microorganisms that require oxygen.  The microbes responsible for composting are naturally occurring and live in the moisture surrounding organic matter. Oxygen from the air diffuses in to the moisture and is taken up by the microbes. As aerobic digestion takes place the by-products are heat, water and carbon dioxide (CO2). While CO2 can be classified as a greenhouse gas it’s evolution from the composting process is not counted in emissions. Additionally, CO2 is only 1/20th as harmful to the environment as methane (the main by-product of anaerobic degradation).

The heat produced in aerobic composting is sufficient to kill harmful bacteria and pathogens as these organisms are not adapted to these environmental conditions. It also helps support the growth of beneficial bacteria species including psychrophilic, mesophilic, and thermophilic bacteria which thrive at the higher temperature levels.

From start to finish, the HotRot in-vessel aerobic composting process takes only 8-10 days. No leachate is produced as any surplus moisture is extracted as water vapour which can be condensed and used for watering nearby vegetation.

Anaerobic Composting

Anaerobic composting is decomposition that occurs using microorganisms that no not require oxygen to survive. In an anaerobic system the majority of the chemical energy contained within the starting material is released as methane. The process is characterised by very strong odours and only a small amount of heat is generated meaning decomposition takes much longer and doesn’t reach sufficient temperatures to safely kill plant pathogens, weed and seeds. To overcome these limitations external (artificial) heat is normally added.

As the material is broken down by anaerobic digestion, it creates a sludge-like material that is even more difficult to break down. This material, digestate, typically requires aerobic composting to complete the stabilisation process.