Abstract:
In this work, a novel industrial configuration for the lipid extraction from sewage sludge was proposed. In detail,
respect to conventional scheme based on direct extraction of lipids from wet sedimented sewage sludge using
hexane, a preliminary centrifugation of sewage sludge prior to the extraction process was introduced. Economic
and energetic balances for both configurations were evaluated using Aspen Plus simulator, including the posttreatment of exhausted sewage sludge obtained after the process. By centrifuging sewage sludge prior to the
extraction process, overall costs can be reduced (27 % less), while preserving the same extraction efficiency for
lipid recovery (80 %). Initial capital investments, amounts of reactants and total energy demand were sensibly
reduced to achieve BEP of extracted lipids of 784 € ton-1 (vs 1.291 € ton-1 for conventional route). Finally, the
economic feasibility of biodiesel production from lipids obtained from centrifuged sludge was evaluated by
applying direct esterification with methanol and AlCl3⋅6H2O BEP of biodiesel produced of 1.186 € ton-1 was
obtained with NPV of 27.5 M€ and DPP of 2.5 years. These values, show that biodiesel production from sewage
sludge could be profitable considering only the proposed approach, fully unlocking the potential of waste in
coherence with circular economy principles.
