What is the Wave-Box?

The Wave-Box is a new PRE development for the high-power digestion of fibrous substrates. Using a reversible pump, the digester substrate or digestate is continuously and optimally brought through a cleverly designed system of pipes into the effective range of ultrasound-emitting "sonotrodes". The control unit allows the user to adjust the flow rate, pressure, flushing cycles etc. The Wave-Box operates in a bypass circuit and can be integrated into the PRE high performance digester and the PRE Kombi Hydrolysis unit or can be retrofitted to biogas systems.

What does the Wave-Box consist of?

The main component is the newly developed high-power ultrasound system. Other components include a volumetric flow meter, pressure and volume controlled pumps, sensors, flushing pipes as well as a self-optimising and self-monitoring control unit.

How does the Wave-Box work?

Ultrasound is sound at frequencies beyond the range of the human ear: from 20 kHz up into the megahertz range. In aqueous media, ultrasound waves produce a periodic compression (positive pressure) and extension (tension, negative pressure) of the medium subjected to the sound. In the negative pressure phase, high-intensity ultrasound leads to the disintegration of the water phase, which in turn leads to the creation of microscopically small voids in the liquid. The small bubbles fill with water vapour or gas. They grow in the tension phases and shrink in the compression phases until they implode.

The implosion of these bubbles is called cavitation. On the micro scale, the pressures involved can be as high as 500 bar. The forces created by ultrasound are capable of destroying even the most robust surfaces.

The Wave-Box is a patented high-power ultrasound system designed to be very effective at disintegrating biomass. The ultrasound reactors in the Wave-Box work as a continuous system at a high intensity and amplitude in the lower frequency range (20 and 35 kHz).

When biomass comes into the effective range of the sound waves, the organic agglomerate is first destroyed and the total surface area of the biomass suspension increased. Further sonification opens plant and bacteria cells, tearing apart fibres and allowing the contents of the cells to escape. In this way, enzymes, nutrients and micro-nutrients are released and additional substrates made available. The sonified biomass is not only a superb substrate for active microorganisms, it also supports the overall digestion process through the actions of enzymes and nutrients.

What benefits does the Wave-Box offer?

The PRE Wave-Box ensures that fibre-rich constituents of the substrate are degraded, which means that the biochemical hydrolysis is more efficient. More methane (10-20%) is formed from the organic content. The increased yield exceeds the energy input by a factor of 12-15.