Next Article in Journal
A High-Efficiency Bi-Directional CLLLC Converter with Auxiliary LC Network for Fixed-Frequency Operation in V2G Systems
Previous Article in Journal
Vertical-Axis Wind Turbines in Emerging Energy Applications (1979–2025): Global Trends and Technological Gaps Revealed by a Bibliometric Analysis and Review
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Anaerobic Co-Digestion of Sewage Sludge and Organic Solid By-Products from Table Olive Processing: Influence of Substrate Mixtures on Overall Process Performance

by
Encarnación Díaz-Domínguez
1,
José Ángel Rubio
1,
James Lyng
2,
Enrique Toro
3,
Fernando Estévez
3 and
José L. García-Morales
1,*
1
Department of Environmental Technologies, Faculty of Marine and Environmental Sciences, IVAGRO-Wine and Agrifood Research Institute, University of Cadiz, 11510 Cadiz, Spain
2
School of Agriculture and Food Science, University College Dublin, D04 C1P1 Dublin, Ireland
3
Empresa Metropolitana de Abastecimiento y Saneamiento de Aguas de Sevilla S.A. (EMASESA), C/Escuelas Pías, 41003 Sevilla, Spain
*
Author to whom correspondence should be addressed.
Energies 2025, 18(14), 3812; https://doi.org/10.3390/en18143812 (registering DOI)
Submission received: 6 June 2025 / Revised: 9 July 2025 / Accepted: 14 July 2025 / Published: 17 July 2025
(This article belongs to the Special Issue Zero Waste Technology from Biofuel Development)

Abstract

Sewage sludge, characterized by its high organic matter and nutrient content, as well as the presence of microbial pathogens and other contaminants, requires proper management due to its significant generation rate. The table olive sector, which is highly significant in Spain as a global leader in production and export, generates various waste streams such the Organic Solid By-Products from Table Olive Processing (OSBTOP), which are mainly derived from the olive pit after the pitting process. The main aim of this study was to enhance the methane production performance of sewage sludge through co-digestion with OSBTOP as a co-substrate. Batch assays demonstrated that employing OSBTOP as a co-substrate increased methane content by 35–41% across all tested mixtures. While the highest methane yield was produced at a 40:60 (sludge:OSBTOP) ratio, a 60:40 mixture proved to be a more advantageous option for scale-up and practical application. This is attributed to factors such as the higher availability of sludge and its inherent buffering capacity, which counteracts the accumulation of volatile fatty acids and promotes process stability, thereby contributing to the study’s objective of significantly enhancing methane production from sewage sludge through co-digestion. In semi-continuous operation, methane yields in the co-digestion scenario exceeded those of mixed sludge digestion, showing a yield of 180 versus 120 LCH4−1 · kgVSadded−1, representing a 50% improvement. This study highlights the potential of anaerobic digestion as a strategy for valorizing OSBTOP, a by-product with no prior studies, while demonstrating that its co-digestion with sewage sludge enhances methane generation, offering a sustainable approach to organic waste treatment.
Keywords: biosolids; co-substrates; mesophilic digestion and biogas biosolids; co-substrates; mesophilic digestion and biogas

Share and Cite

MDPI and ACS Style

Díaz-Domínguez, E.; Rubio, J.Á.; Lyng, J.; Toro, E.; Estévez, F.; García-Morales, J.L. Anaerobic Co-Digestion of Sewage Sludge and Organic Solid By-Products from Table Olive Processing: Influence of Substrate Mixtures on Overall Process Performance. Energies 2025, 18, 3812. https://doi.org/10.3390/en18143812

AMA Style

Díaz-Domínguez E, Rubio JÁ, Lyng J, Toro E, Estévez F, García-Morales JL. Anaerobic Co-Digestion of Sewage Sludge and Organic Solid By-Products from Table Olive Processing: Influence of Substrate Mixtures on Overall Process Performance. Energies. 2025; 18(14):3812. https://doi.org/10.3390/en18143812

Chicago/Turabian Style

Díaz-Domínguez, Encarnación, José Ángel Rubio, James Lyng, Enrique Toro, Fernando Estévez, and José L. García-Morales. 2025. "Anaerobic Co-Digestion of Sewage Sludge and Organic Solid By-Products from Table Olive Processing: Influence of Substrate Mixtures on Overall Process Performance" Energies 18, no. 14: 3812. https://doi.org/10.3390/en18143812

APA Style

Díaz-Domínguez, E., Rubio, J. Á., Lyng, J., Toro, E., Estévez, F., & García-Morales, J. L. (2025). Anaerobic Co-Digestion of Sewage Sludge and Organic Solid By-Products from Table Olive Processing: Influence of Substrate Mixtures on Overall Process Performance. Energies, 18(14), 3812. https://doi.org/10.3390/en18143812

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Article metric data becomes available approximately 24 hours after publication online.
Back to TopTop