bioEnergy

Digestate, the material remaining after the anaerobic digestion of a biodegradable feedstock, is excellent fertilizer replacement. It can be used on-site immediately or upgraded to more easilty packaged and/or transportable form. 

The first step in upgrading is usually dewatering of the digestate using a screw press or decanting centrifuge. This yields:

• a solid fraction, containing most of the phosphates and organic dry matter (ODM); and
• a liquid fraction containing most of the nitrogen and potassium.

The solid fraction can be pelletized directly, or mixed with sawdust and turned into energy pellets. These can then be sold to energy companies or used on site in a biomass combustion system. These options usually increases the economic prospects of a project.

There are several options for the liquid fraction:

a) discharge to the sewer;

b) purification and discharge to sewer or open water;

c) use direcly as liquid fertilizer;

d) concentrate using ultrafiltration and reverse osmosis, use as concentrated liquid fertilizer;

e) evaporate (part of) the water;

f) use natural evaporation to dispose of liquid fraction.

Each option has advantages and drawbacks. For each situation a unique upgrading concept is developed since usually no two situations are alike. Sometimes reduction of volume is of overriding concern, sometimes the production of organic fertilizer is the most important.

Contact us in case you require assistance.