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Design Optimization of Low-Solids Anaerobic Digestion: Increasing Solids Retention Time through Effluent Recirculation

Abstract

Low-solids anaerobic digestion (LS AD) is extensively applied for biogas production, but its limited solids retention time (SRT) restricts methane yields and economic viability, highlighting the need for process intensification. This study integrates innovative process design, numerical simulation, and systematic optimization to enhance LS AD performance by incorporating effluent recirculation and separation technologies. Seven novel configurations were evaluated using a single-stage mesophilic digestion model (ADM1-R3) adapted for high-protein substrates, such as fish silage with sulfur components. Results demonstrated that segregated flow patterns and effective component separation significantly increased methane yields and profitability, driven by enhanced methanogen growth and organic matter conversion. The optimal configuration employing a hydro-cyclone and water-oil centrifuge achieved a remarkable 57.00 USD·d/kgVS and a 180% increase in gross profit, along with 0.283 kg/kgVS and a 39% increase in methane yield compared to conventional systems. This scalable and cost-effective approach provides substantial practical benefits, promoting sustainable and profitable implementation of LS AD in industrial biogas operations.

Category

Academic article

Client

  • Research Council of Norway (RCN) / 309558

Language

English

Author(s)

Affiliation

  • Norwegian University of Science and Technology
  • SINTEF Industry / Biotechnology and Nanomedicine

Year

2025

Published in

Bioresource Technology Reports

ISSN

2589-014X

Publisher

Elsevier

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