Integrating anaerobic digestion and pyrolysis for treating digestates derived from sewage sludge and fat wastes

• Published in: Environmental science and pollution research international 2020-09, Vol.27 (26), p.32603-32614
• Main Authors: González-Arias, Judith, Gil, María Victoria, Fernández, Ramón Ángel, Martínez, Elia Judith, Fernández, Camino, Papaharalabos, George, Gómez, Xiomar
• Format: Article
• Language: English
• Subjects: Activation energy; Anaerobic digestion; Anaerobic treatment; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Biogas; Charcoal; Cogeneration; Drying; Earth and Environmental Science; Ecotoxicology; Electric power generation; Electricity; Environment; Environmental Chemistry; Environmental Health; Environmental science; Grease; Integrated approach; Pyrolysis; Research Article; Sewage disposal; Sewage sludge; Sludge; Sludge digestion; Sludge disposal; Substrates; Thermogravimetric analysis; Waste disposal; Waste Water Technology; Wastewater treatment; Wastewater treatment plants; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-020-09461-1

The coupling of biological and thermal technologies allows for the complete conversion of wastes into energy and biochar eliminating the problem of sludge disposal. The valorisation of fatty residues as co-substrate in a mesophilic digester of a wastewater treatment plant was studied considering an integrated approach of co-digestion and pyrolysis. Four digested samples obtained from co-digestion of sewage sludge and butcher’s fat waste were studied by thermogravimetric analysis. The activation energy corresponding to the sludge pyrolysis was calculated by a non-isothermal kinetic. Arrhenius activation energy was lower for the pyrolysis of a digested grease sample (92 kJ mol −1 obtained by OFW and 86 kJ mol −1 obtained by Vyazovkin) than for the pyrolysis of sewage sludge and its blends (164–190 kJ mol −1 obtained by OFW and 162–190 kJ mol −1 obtained by Vyazovkin). The analysis of the integrated approach of anaerobic co-digestion and pyrolysis of digestates demonstrated that the addition of 3% (w/v) of fat to the feeding sludge results in a 25% increase in the electricity obtained from biogas (if a combined heat and power unit is considered for biogas valorisation) and increasing the fat content to 15% allows for covering all thermal needs for drying of digestate and more than doubles (2.4 times) the electricity production when the scenario of digestion and pyrolysis is contemplated.