Aerobic digestion is neither a new technology nor a laboratory gimmick: it is what has always been happening in the soil. What a biodigester does is replicate that process within a controlled chamber and speed it up so that it can be completed within a working day.
It is the microorganisms that do the work
Microorganisms are microscopic, living, single-celled organisms: bacteria. Most of them are hugely beneficial. They are, in fact, the guardians of the planet: they remove toxins from water and soil and break down the organic matter from dead plants and animals. Without them, life would be impossible.
Their tools are enzymes. And here’s the interesting bit: microorganisms are quite clever. They detect which organic compounds are present in the waste and produce only the enzymes needed to break them down. They do not waste energy producing what is not needed.
There are thousands of strains of microorganisms, each with its own characteristics that make it more or less suitable for digesting a specific type of material. That is why a digester does not contain just one strain, but a combination selected to cover the widest possible range of waste profiles.
What the machine offers
If the microorganisms do the work, what is the digester for? To create the optimal environment in which they can do so quickly:
- A constant supply of oxygen. The agitator and the paddle arms continuously aerate the mixture. «Aerobic» means precisely that: with oxygen. This is what distinguishes it from anaerobic digestion, which produces methane and unpleasant odours.
- Stable temperature. The process involves a mesophilic stage, a thermophilic stage and a maturation stage, each of which requires its own specific conditions.
- A place to live. Microbes need a surface to attach themselves to and congregate on.
From coarse particles to greywater
The process is gradual. Enzymes produced by the microorganisms break down food particles and, as digestion progresses, these particles become smaller and smaller. When they are small enough, the microorganisms consume the remains and convert them into organic effluent, which flows from the digester into the sewerage system.
The result is water with a very low organic content, free from suspended solids and contaminants. Up to 99.9 % of food waste is removed in this way.
There’s no need to blend
A practical detail that surprises many people: there is no need to grind or pre-process food before putting it in. The natural process of aerobic digestion breaks them down just the same. It is, however, advisable to prevent hard or metallic objects – particularly cutlery – from entering the machine, which is why the machines are fitted with foreign object detection.
Why the sewer is the logical destination
The idea of pouring something that was once food down the drain may seem shocking. But if the digested waste has turned into greywater, the natural thing to do is to use the municipal sewerage system to carry that water to the treatment plant, where it is recovered. This infrastructure already exists and is designed precisely for that purpose.
Furthermore, this water is not simply harmless: it contains dissolved nutrients such as nitrogen and phosphorus, which make it a natural fertiliser. It is often used safely for watering green spaces, trees, shrubs or industrial crops such as fibres or biomass. However, each local authority has its own regulations on this matter, and these must be checked before using it for this purpose.
If you’d like to see the specific technical specifications for the device — capacity, power consumption, dimensions — they’re in the Technical specifications of the Biorgmax DR300.
