Biogas production from wet olive mill wastes pretreated with hydrogen peroxide in alkaline conditions

Olive mill residues, due to their low biodegradability and high amounts of phytotoxic compounds, aredifficult to treat by means of conventional biological processes. In recent years several pretreatments ofthese by-products have been developed to increase their anaerobic biodegradability and to exploit themfor biogas production. However, these processes are often expensive and hard to carry out. In this paper aneffective and easy-to-manage pretreatment, based on the use of hydrogen peroxide under alkaline conditionswithout the addition of catalysts, is proposed. Many experiments were carried out onwet olive millwastes in order to evaluate the influence of pH and peroxide dosage on process performance. Polyphenolsabatements of about 72% were observed. The kinetic analysis of experimental results allowed us toinvestigate the reaction mechanisms and to optimize the operating procedures. This permitted to reducethe peroxide dosage without the occurrence of a remarkable performance reduction. By means of batchdigestion tests, conducted in a pilot scale plant without co-substrates addition, it was verified a negligiblebiogas production detectable on raw olive mill waste, while a COD reduction about of 77% and a highmethane yield of approximately 0.328 LCH4 /gCODremoved were obtained on pretreated waste