Work

A comparative assessment of sewage sludge valorization via anaerobic digestion and supercritical water gasification: A techno-economic case study in Norway

Year: 2024

Type: article

Abstract: This study compared the performance of supercritical water gasification (SCWG) to conventional anaerobic digestion (AD) for treating sewage sludge from a wastewater treatment plant (WWTP). Based on plant data from a WWTP in Norway, kinetic-based process models have been created in Aspen Plus® to investigate the energy and economic feasibility of AD and SCWG for sewage sludge treatment. The findings showed that low ambient temperatures significantly reduced the energy efficiency of the AD, while their effect on the SCWG process was negligible. At the average ambient temperature of 7°C and sludge concentration of 7 wt.%, AD and SCWG achieved thermal energy self-sufficiency (TES) of 0.76 and 0.63, respectively. Under these conditions, the AD and SCWG had energy conversion efficiencies (η) of 25.8% and 46.6%, respectively. However, increasing the sludge content in the SCWG to 15 wt% improved the TES to 1.22 and η to 73.2%, making it a more attractive alternative to the AD. At 7 wt% sludge concentration, the AD and SCWG processes required an investment cost of 4.08 M$ and 6.83 M$, respectively. Under the study assumptions, neither AD nor SCWG proved profitable, revealing negative NPVs and operating costs of $0.96 M$ and $0.92 M$, respectively.

Source: Journal of Water Process Engineering

DOI: 10.1016/j.jwpe.2024.106016

Authors: R. Ochieng, A. Gebremedhin, S. Sarker

Institution: Norwegian University of Science and Technology

Language: English

Topic: Anaerobic Digestion and Biogas Production

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

SDGs: Responsible consumption and production, Affordable and clean energy, Clean water and sanitation, Climate action, Industry, innovation and infrastructure

Open Access status: hybrid

Estimated APC paid: $3,420