Microscale investigation of anaerobic biogas production under various hydrodynamic conditions

This work presents an investigation at microscale of various mechanisms affecting anaerobic reactions within the microdevices. In particular, the effect of different hydrodynamic conditions associated with the granular particles' size and density on the biogas production was studied in order to intensify the performance of the anaerobic reactor. The image analysis techniques offer an opportunity to observe and quantify the nucleation and growth of biogas bubble at microscale on a single granule. In addition, the flow conditions were perfectly controlled in the microdevice, and the liquid flow fields were measured by a microparticle image velocimetry (micro-PIV) system. The effect of real hydrodynamic conditions exerted directly on granules onto the maximum biogas production rate was described for the first time. Finally, the role of hydrodynamic conditions on the biogas production at microscale is discussed through a straightforward relationship between the shear rates exerted on the granule and the optimal biogas production rate. The investigation reveals that big granules could have satisfactory biogas production ability under relatively weak hydrodynamic conditions. Thus they would be priority selection for industrial reactors.