Environmental Engineering and Management Journal November 2013, Vol.12, No. S11 Supplement, 93-96 http://omicron.ch.tuiasi.ro/EEMJ/ “Gheorghe Asachi” Technical University of Iasi, Romania ANAEROBIC DIGESTION OF POTATO INDUSTRY BY-PRODUCTS ON A PILOT-SCALE PLANT UNDER THERMOPHILIC CONDITIONS Extended abstract Agata Pistis 1 , Carla Asquer 1 , Efisio Antonio Scano 1,2 1 Biofuels and Biomass Laboratory, Sardegna Ricerche, Z.I. Macchiareddu 09010 Uta (CA), Italy. 2 University of Cagliari, Department of Mechanical, Chemical and Materials Engineering, Via Marengo, 2 09123 Cagliari, Italy Background Potato industry by-products are typically produced in industrial processing such as freezing, drying, canning and frying. This kind of waste includes, for instance, skins and tubers with defects and mechanical damages that are rejected in the process of potato chips production. These residues have a high perishability and their quick removal and disposal is therefore mandatory, with consequent high costs for the food companies. Since these materials have a high moisture content, they are an eligible feedstock for anaerobic digestion (AD). Nevertheless, because of their high soluble organic compounds content, the anaerobic digestion of potato by-products as a single substrate is considered very critical. Scientific literature contains some studies on anaerobic digestion of potato tuber and its industrial by-products (Kaparaju et al., 2005; Parawira et al., 2004, 2005). Many authors have reported unstable process conditions when treating this kind of substrate in mesophilic conditions. In fact potato industrial by-products contain high amounts of soluble substances that can be easily degraded to volatile fatty acid and inhibit the methanogenic microorganisms in single stage anaerobic digesters, as shown by Kaparaju et al., 2005. To overcome this problem, these authors used pig manure as co-substrate. Another study reports the results of the batch anaerobic digestion of potato waste alone and in combination with sugar beet leaves (Parawira et al., 2004). In this case the authors obtained an improved methane yield when applying the co- digestion compared to the digestion of the single substrates. They studied the anaerobic digestion of solid potato waste in two double-stage mesophilic anaerobic digestion systems. The first consisted of a solid-bed reactor connected to an upflow anaerobic sludge blanket reactor (UASB), while the second was a solid-bed reactor connected to a methanogenic reactor packed with a wheat straw biofilm. The configuration with the packed straw bed had a greater speed of degradation compared to an UASB system. The methane yield was the same for both systems (Parawira et al., 2005). The anaerobic treatment of potato processing solid waste was also studied in completely stirred tank reactors (CSTR) under thermophilic conditions (55°C) and on lab-scale equipments. In particular a kinetic study to find simple model equations for the design of completely stirred tank reactors (CSTR) was carried out (Linke, 2006). The study shows that an increase in the organic loading rate (OLR) causes a decrease in both biogas yield and CH 4 content. To the authors’ knowledge, all the experiments described were performed on laboratory scale reactors, while experiments at large scale have not been performed yet. Actually, anaerobic digestion of potato industrial by-products as a single substrate is a challenging process due to the high biodegradability of this material which can lead to the rapid and strong acidification inside the reactor with a consequent inhibition of the methanogenic bacteria activity. In this paper an experimental assessment of biogas production from potato industrial wastes at thermophilic conditions is presented.  Author to whom all correspondence should be addressed: e-mail: pistis@sardegnaricerche.it