Effect of particle size and organic co-substrates on the anaerobic digestion performances

Anaerobic digestion for treating organic solids results economically and environmentally convenient if compared with other treatment methodologies. As the performance of this process strongly depends on several operational factors, an opportune choice of them can vary significantly the outcome of the process. The present paper is therefore focused on the study of the effects of two of these factors, i.e. the size of organic solids constituting the substrate and the simultaneous digestion of more substrates. Ten bio-methane potential tests have been carried out to assess the effectiveness of shredding and mixing substrates and the results have showed that the process performance can be improved when the particle size is made smaller as well as when complementary substrates are mixed together. However, BMP tests have highlighted the need to plan carefully the operation of both shredding and mixing because an improvement in process performance is not always guaranteed. Therefore a mathematical model capable to simulate the anaerobic digestion process, as the one recently proposed by the author, represents an useful tool to set up easily, correctly and successfully the operational conditions of the anaerobic digestion and improve its performance. The potential of this model is presented in the paper.