Benchmarking environmental and economic indicators of sludge management alternatives aimed at enhanced energy efficiency and nutrient recovery

• Published in: Journal of environmental management 2021-02, Vol.279, p.111594, Article 111594
• Main Authors: Arias, A., Feijoo, G., Moreira, M.T.
• Format: Article
• Language: English
• Subjects: Benchmarking; Biogas production; Chemical pre-treatment; Economic analysis (EA); Life cycle assessment (LCA); Nutrients; Sewage; Thermal hydrolysis (TH) process; Waste Disposal, Fluid; Waste Water
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2020.111594

Wastewater treatment plants (WWTPs) have been developed as multifunctional systems that aim to eliminate pollutants present in wastewater, manage the sludge produced and improve energy efficiency. Specifically, sludge management accounts for the largest share in operational costs. Considering the relevant role of sludge treatment within the overall management scheme, this study aims to evaluate different alternatives and strategies for sludge management and treatment from the perspective of life cycle analysis, with special emphasis on those options that reduce environmental impacts and economic costs. Two pre-treatments (chemical or thermal) and two post-treatments (composting unit followed by land application or incineration) were evaluated to improve the eco-balance of the anaerobic digestion (AD) process in terms of operational (biogas production and digested sludge), environmental and economic indicators. According to the results obtained, both sludge pre-treatment alternatives proved to be an adequate alternative to improve biogas production without negatively affecting environmental and economic impacts. Finally, if the final disposal of the digestate is analysed, its application to the soil as a biofertiliser is recommended, since it presents a better environmental profile than incineration. •Sludge pre-treatments present a good environmental profile when are included in a sludge line.•The incorporation of sludge pre-treatments does not increase significantly operational costs.•Pre-treatments increase biogas production which implies more eco-efficient wastewater systems.•Payback time is reduced in the plants that incorporate a sludge pre-treatment.