The Italian tannery industry produces 9% of the global and 73% of the European bovine leader. One of the most important districts is located in the area surrounding Florence and Pisa, in Tuscany. From 1kg of raw hide, the tanning process generates 0.7-0.6kg of solid waste (fleshing) and 25-45L of wastewater. Fleshing and tannery sludge are typically treated separately and sent to land application. Before final disposal, fleshing undergoes alkaline hydrolysis and biosolids are thermally dewatered. Recent research focused on the benefits of anaerobic co-digestion of tannery sludge and fleshing, due to their potential for biogas production and concurrently to the need for alternative solutions for fleshing treatment. This study aimed at investigating the technical and economic feasibility of anaerobic co-digestion of tannery sludge and fleshing. Two reactors (150L each) were maintained at mesophilic conditions, with a retention time (SRT) of 25d for approximately 1y. After the start-up phase (t=115d) when both reactors were fed only tannery sludge, the first reactor (R1) was fed with fleshing plus tannery sludge, while the second (R2) was kept as control (i.e., tannery sludge only). Two sludge/fleshing mass ratios were evaluated, 8:1 (t=116-230d) and 3:1 (t=231-302d). Our results showed a solids (VS) reduction and load (COD) conversion of 50% and 30% for R1 and R2, respectively. The biogas production was 0.94±0.06 and 0.98±0.07Nm3kg-1VS removed, for R1 and R2, respectively, with methane percentage of 79% and 69%, respectively. No inhibition was recorded in the reactors, despite ammonium values in the digested sludge of 959±155 and 762±69mgN_NH4L-1 for R1 and R2, respectively. In proportion, were fleshing the only substrate applied to R1, 2300 mgN_NH4L-1 would be released, assuming a biodegradable fraction of 82%. Our research can be applied to all co-digestion of industrial organic waste and addresses the technological challenges of process inhibition.
ANAEROBIC CO-DIGESTION OF FLESHING AND TANNERY SLUDGE: LABORATORY SCALE TESTS / Francesca, Giaccherini; Cecilia, Polizzi; Andrea, Ricotti; Gualtiero, Mori; Alberto, Mannucci; Claudio, Lubello; Felipe, Alatriste-Mondragón; Diego, Rosso; Giulio, Munz;. - CD-ROM. - (2015), pp. 8-10. (Intervento presentato al convegno Ecomondo 2015 tenutosi a Rimini nel 3-6 Novembre 2015).
ANAEROBIC CO-DIGESTION OF FLESHING AND TANNERY SLUDGE: LABORATORY SCALE TESTS
Cecilia, Polizzi;MANNUCCI, ALBERTO;LUBELLO, CLAUDIO;MUNZ, GIULIO
2015
Abstract
The Italian tannery industry produces 9% of the global and 73% of the European bovine leader. One of the most important districts is located in the area surrounding Florence and Pisa, in Tuscany. From 1kg of raw hide, the tanning process generates 0.7-0.6kg of solid waste (fleshing) and 25-45L of wastewater. Fleshing and tannery sludge are typically treated separately and sent to land application. Before final disposal, fleshing undergoes alkaline hydrolysis and biosolids are thermally dewatered. Recent research focused on the benefits of anaerobic co-digestion of tannery sludge and fleshing, due to their potential for biogas production and concurrently to the need for alternative solutions for fleshing treatment. This study aimed at investigating the technical and economic feasibility of anaerobic co-digestion of tannery sludge and fleshing. Two reactors (150L each) were maintained at mesophilic conditions, with a retention time (SRT) of 25d for approximately 1y. After the start-up phase (t=115d) when both reactors were fed only tannery sludge, the first reactor (R1) was fed with fleshing plus tannery sludge, while the second (R2) was kept as control (i.e., tannery sludge only). Two sludge/fleshing mass ratios were evaluated, 8:1 (t=116-230d) and 3:1 (t=231-302d). Our results showed a solids (VS) reduction and load (COD) conversion of 50% and 30% for R1 and R2, respectively. The biogas production was 0.94±0.06 and 0.98±0.07Nm3kg-1VS removed, for R1 and R2, respectively, with methane percentage of 79% and 69%, respectively. No inhibition was recorded in the reactors, despite ammonium values in the digested sludge of 959±155 and 762±69mgN_NH4L-1 for R1 and R2, respectively. In proportion, were fleshing the only substrate applied to R1, 2300 mgN_NH4L-1 would be released, assuming a biodegradable fraction of 82%. Our research can be applied to all co-digestion of industrial organic waste and addresses the technological challenges of process inhibition.
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