A very detailed study was carried out on separation of lipids from wet sewage scum taken from several wastewater treatment plants (WWTPs). A solvent-less separation of lipids was optimized by simply heating sewage scum at 353 K and centrifuging the heated mass at 4000 rpm per 1 min [1]. Recoverability of 93-99% of total oils was determined. Extracted lipids have a very similar composition in terms of free fatty acids (FFAs), calcium soaps (32-40%wt) and glycerides (mono-, di- and tri-glycerides were practically absents), as well as fatty acid profiles in all of samples studied. Since mainly composed of FFAs, once separated, lipids were converted into biodiesel through a direct esterification process. Reaction conditions were optimised using the desirability function applied on the response surface methodology analysis of a Box-Behnken factorial design of experiments. By carrying out the reaction at 72°C for 120 min and using AlCl3·6H2O as a catalyst (1.5% mol of Al respect to fatty acids), almost 94% of the starting acids were converted into methyl esters [2]. At the end of the reaction, a biphasic system was obtained in which the upper methanolic phase, which contained most of the starting catalyst, was separated from the heaviest phase, mainly composed of fatty acid methyl esters. Such a distribution not only allowed the biodiesel to be easily separated, but also catalysts were efficiently recovered and reused for at least four times, determining a total TON greater than 200,without revealing any loss of its activity [3]. This efficient separation between biofuel produced and unreacted methanol allow a three sequential batch reactors to be run, in which methanol and catalysts were charged in counter current respect to starting feedstock. In this way, the complete conversion (>99%) of starting FFAs into FAMEs was perfectly matched with using the minimum amount of reactants under very mild conditions (345 K, 2 h). The overall convenience of the process was completed by the anaerobic digestion of fibrous residues obtained from centrifugation of starting sewage scum: the final biogas resulted largely enough to sustain the overall heat of process [4].
BIOFUELS FROM URBAN SEWAGE SLUDGE: A NEW EFFICIENT AND SUSTAINABLE PROCESS TO TURN WASTE INTO A NEW FEEDSTOCK
Carlo Pastore;Luigi di Bitonto;Giuseppe Mascolo
2016
Abstract
A very detailed study was carried out on separation of lipids from wet sewage scum taken from several wastewater treatment plants (WWTPs). A solvent-less separation of lipids was optimized by simply heating sewage scum at 353 K and centrifuging the heated mass at 4000 rpm per 1 min [1]. Recoverability of 93-99% of total oils was determined. Extracted lipids have a very similar composition in terms of free fatty acids (FFAs), calcium soaps (32-40%wt) and glycerides (mono-, di- and tri-glycerides were practically absents), as well as fatty acid profiles in all of samples studied. Since mainly composed of FFAs, once separated, lipids were converted into biodiesel through a direct esterification process. Reaction conditions were optimised using the desirability function applied on the response surface methodology analysis of a Box-Behnken factorial design of experiments. By carrying out the reaction at 72°C for 120 min and using AlCl3·6H2O as a catalyst (1.5% mol of Al respect to fatty acids), almost 94% of the starting acids were converted into methyl esters [2]. At the end of the reaction, a biphasic system was obtained in which the upper methanolic phase, which contained most of the starting catalyst, was separated from the heaviest phase, mainly composed of fatty acid methyl esters. Such a distribution not only allowed the biodiesel to be easily separated, but also catalysts were efficiently recovered and reused for at least four times, determining a total TON greater than 200,without revealing any loss of its activity [3]. This efficient separation between biofuel produced and unreacted methanol allow a three sequential batch reactors to be run, in which methanol and catalysts were charged in counter current respect to starting feedstock. In this way, the complete conversion (>99%) of starting FFAs into FAMEs was perfectly matched with using the minimum amount of reactants under very mild conditions (345 K, 2 h). The overall convenience of the process was completed by the anaerobic digestion of fibrous residues obtained from centrifugation of starting sewage scum: the final biogas resulted largely enough to sustain the overall heat of process [4].I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
