Biodrying – Stabilizing and Processing Wet Organic Waste

There is a lot of wet organic waste produced in our society, including food and food processing waste, biosolids and animal manures. Moisture contents of these materials are often 75-80% or higher. There are at least three potential challenges with these materials including:

1. High odor potential – many of the wet organic wastes do not have a pleasant odour, or are
2. Material handling – many of the wet organic wastes are wet and sticky, and can be challenging to manage as it neither flows nor pours very well.
3. Transportation – many of these organic wastes have excellent nutrient value, but must be processed before beneficial reuse. Transporting 80% water is not efficient.

Drying these materials for more efficient management is not economically viable in most cases.

There is a concept called biodrying that has been used successfully to dry and stabilize wet organic waste. Biodrying uses the potential energy in the organic waste to allow the moisture to evaporate. Let’s look at one recent example from our own work.

Temperature and airflow during biodrying of wet organic waste starting at 77% moisture and ending at 26% after two weeks.

We evaporated 80% of the water contained in the wet organic waste in two weeks, with 80% of it evaporating in the first week. The other interesting observation was that the organic waste, which started out as a highly malodorous material, had almost an earthy smell after biodrying.

In these experiments, there was no energy input of any kind, other than the energy in the waste. Incoming air was provided only by the vacuum caused by the self-heating of the organic waste – there were no air blowers.

Its a fun process utilizing principles of microbiology and physics!