Biovalorization of Red Radicchio (Treviso Variety) Byproducts by a Two-Stage Anaerobic Digestion

Italian horticulture is characterized by a large number of vegetables. Such products comprise red or variegated chicories, called “radicchio” which are cultivated mainly in northeastern Italy. The increased consumers’ demand for these products has led to an increased production which reaches approximately 250000 t/y. A major problem though is the by-products produced from their elaboration in the farm, reaching approximately 10 t/ha. Therefore the bio-valorization of these by-products may be a useful tool to give an additional value to a product otherwise deemed to be wasted. In this work the bio-valorization of red radicchio (Treviso variety) waste was evaluated in a two-stage anaerobic digestion (AD) laboratory-scale apparatus. The tests were made also by mixing this waste with maize to check the possible bio-valorization of the mixture. Two coupled 5 L batch-fed completely stirred reactors, one for the hydrolytic-acidogenic step and one for the acetogenic-methanogenic step, kept at mesophilic temperature, were adopted. All runs were performed without the addition of chemicals. After the evaluation of the retention time of each stage, samples of hydrolized substrates from the first hydrolytic bioreactor were sent to the second methanogenic bioreactor to assess the specific gas production, the methane yield in the biogas produced and the specific methanogenic activity.