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

P. 32603-32614The 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.S

High Temperature conversion of fats: Cracking, gasification, esterification and transesterification

Burning fossil fuels increases the concentration of carbon dioxide in the atmosphere. Alternative sources of energy are necessary to control global warming. Diverse synthetic methods transform vegetable oils and animal fats, inexpensive carbon sources to biofuels. This chapter reviews the main chemical and thermal processes that transform triglycerides into fuels. We collected the most cited and recent scientific publications about transesterification, thermal and catalytic cracking, and gasification reactions and their respective technologies