Analysis of the extrusion as a pretreatment for the anaerobic digestion process

In the last year anaerobic digestion have become widespread throughout Europe, since anaerobic digestion provides the possibility to recover energy from the produced biogas from different natural materials. Among the factor that are influencing on the mass transfer in each biological step of anaerobic digestion, both the composition and the quality of the substrate play a fundamental role. According to this, the schemes of substrate pretreatments can be used in order to optimize biological process yield. In this work the application of an extruder to increase the methane yield, and so the electric energy that can be produced, are examined. An extruder was tested on nine samples of maize silage and on one sample constituted by a mix of silage maize and manure. The biogas and methane yield after 1, 6, 16, 24 and 33 days of batch tests were measured. By analyzing the obtained values it can be observed an improvement, deriving from the extruder utilization, that can lead to values from 0 to 15% and so an improvement of the electric energy that can lead to values from 0 to 6.5% (the lower increase of electricity is due to the extruder self-consumption).