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TO-SYN-FUEL Project to Convert Sewage Sludge in Value-Added Products: A Comparative Life Cycle Assessment

Author

Listed:
  • Serena Righi

    (Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
    Interdepartmental Centre for Research in Environmental Sciences, University of Bologna, Via S. Alberto 163, 48123 Ravenna, Italy)

  • Filippo Baioli

    (Interdepartmental Centre for Research in Environmental Sciences, University of Bologna, Via S. Alberto 163, 48123 Ravenna, Italy)

  • Andrea Contin

    (Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy)

  • Diego Marazza

    (Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
    Interdepartmental Centre for Research in Environmental Sciences, University of Bologna, Via S. Alberto 163, 48123 Ravenna, Italy)

Abstract

Second-, third-, and fourth-generation biofuels represent an important response to the challenges of clean energy supply and climate change. In this context, the Horizon 2020 “TO-SYN-FUEL” project aimed to produce advanced biofuels together with phosphorus from municipal wastewater sludge through a combination of technologies including a Thermo-Catalytic Reforming system, Pressure Swing Adsorption for hydrogen separation, Hydrodeoxygenation, and biochar gasification for phosphorous recovery. This article presents the environmental performance results of the demonstrator installed in Hohenberg (Germany), with a capacity of 500 kg per hour of dried sewage sludge. In addition, four alternative scenarios are assessed, differing in the source of additional thermal energy used for sludge drying: natural gas, biogas, heat pump, and a hybrid solar greenhouse. The environmental performance of these scenarios is then compared with that of conventional fuel. The comparative study of these scenarios demonstrates that the biofuel obtained through wood gasification complies with the Renewable Energy Directive, while natural gas remains the least sustainable option. Heat pumps, biogas, and greenhouse drying emerge as promising alternatives to align biofuel production with EU sustainability targets. Phosphorus recovery from sewage sludge ash proves essential for compliance, offering clear environmental benefits. Although sewage sludge is challenging due to its high water content, it represents a valuable feedstock whose sustainable management can enhance both energy recovery and nutrient recycling.

Suggested Citation

  • Serena Righi & Filippo Baioli & Andrea Contin & Diego Marazza, 2025. "TO-SYN-FUEL Project to Convert Sewage Sludge in Value-Added Products: A Comparative Life Cycle Assessment," Energies, MDPI, vol. 18(19), pages 1-22, October.
    • Handle: RePEc:gam:jeners:v:18:y:2025:i:19:p:5283-:d:1765406
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    References listed on IDEAS

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    1. Jolanta Latosińska & Przemysław Czapik, 2020. "The Ecological Risk Assessment and the Chemical Speciation of Heavy Metals in Ash after the Incineration of Municipal Sewage Sludge," Sustainability, MDPI, vol. 12(16), pages 1-14, August.
    2. Alice Sorrenti & Santo Fabio Corsino & Francesco Traina & Gaspare Viviani & Michele Torregrossa, 2022. "Enhanced Sewage Sludge Drying with a Modified Solar Greenhouse," Clean Technol., MDPI, vol. 4(2), pages 1-13, May.
    3. Castello, Daniele & Haider, Muhammad Salman & Rosendahl, Lasse Aistrup, 2019. "Catalytic upgrading of hydrothermal liquefaction biocrudes: Different challenges for different feedstocks," Renewable Energy, Elsevier, vol. 141(C), pages 420-430.
    4. Katarzyna Śpiewak, 2024. "Gasification of Sewage Sludge—A Review," Energies, MDPI, vol. 17(17), pages 1-31, September.
    5. Augusto Bianchini & Jessica Rossi, 2020. "An Integrated Industry-Based Methodology to Unlock Full-Scale Implementation of Phosphorus Recovery Technology," Sustainability, MDPI, vol. 12(24), pages 1-17, December.
    6. EGLE Lukas & MARSCHINSKI Robert & JONES Arwyn & YUNTA MEZQUITA Felipe & SCHILLACI Calogero & HUYGENS Dries, 2023. "Feasibility study in support of future policy developments of the Sewage Sludge Directive (86/278/EEC)," JRC Research Reports JRC134591, Joint Research Centre.
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