Retrofitting Municipal Wastewater Treatment Facilities toward a Greener and Circular Economy by Virtue of Resource Recovery: Techno-Economic Analysis and Life Cycle Assessment

Abstract

A promising route to transition wastewater treatment facilities (WWTFs) from energy-consuming to net energypositive is to retrofit existing facilities with process modifications, residual biosolid upcycling, and effluent thermal energy recovery. This study assesses the economics and life cycle environmental impacts of three proposed retrofits of WWTFs that consider thermochemical conversion technologies, namely, hydrothermal liquefaction, slow pyrolysis, and fast pyrolysis, along with advanced bioreactors. The results are in turn compared to the reference design, showing the retrofitting design with hydrothermal liquefaction, and an up-flow anaerobic sludge blanket has the highest net present value (NPV) of $177.36MM over a 20-year plant lifetime despite 15% higher annual production costs than the reference design. According to the ReCiPe method, chlorination is identified as the major contributor for most impact categories in all cases. There are several uncertainties embedded in the techno-economic analysis and life cycle assessment, including the discount rate, capital investment, sewer rate, and prices of main products; among which, the price of biochar presents the widest variation from $50 to $1900/t. Sensitivity analyses reveal that the variation of discount rates causes the most significant changes in NPVs. The impact of the biochar price is more pronounced in the slow pyrolysis-based pathway compared to the fast pyrolysis since biochar is the main product of slow pyrolysis.

Can decontamination and reuse of N95 respirators during COVID-19 pandemic provide energy, environmental, and economic benefits?

“… Unit Base case Lower extreme Higher extreme Total cost for the base case Total cost for lower extreme Total cost for higher extreme Price of N95 masks [57] , [58] $ 1.27 0.5 4.92 306.5 152.5 1036.5 Discount rate [44] % 10 5 15 306.5 304.6 308.5 Transportation distance km 80.5 0 434.5 306.5 305.3 312.2 Plant life year 3 - 20 306.5 - 291.1 Capital cost [65] % 100 80 120 306.5 301.2 311.9 Electricity price [54] $/kWh 0.055 0.050 0.067 306.5 306.4 307.0 Disposal fee [55] , [66] $/ton 76.82 62 790 306.5 306.3 318.0 Labor cost [53] , [67] $/person-hour 16.71 12.50 21.18 306.5 301.2 312.2 Number of FFR uses [15] - 5 2 11 306.5 668.2 175.0 ...…”

Quantitative Sustainable Design (QSD) for the Prioritization of Research, Development, and Deployment of Technologies: A Tutorial and Review

“…254,255 The analysis of other systems has followed a similar workflow, transferring data among multiple tools used for different steps of QSD. 107,227,[256][257][258][259][260][261][262] Although programming languages can be used to facilitate data formatting and transfer, this nonetheless presents challenges in QSD execution when system simulation and sustainability characterization need to be repeated thousands of times or more to consider uncertainty (Section 5.2). Alternatively, there are ongoing efforts in tool development to integrate system simulation and sustainability characterization on a single, opensource platform (e.g., for sanitation and resource recovery systems, 230 biorefineries 215 ).…”

Green Transition: The Frontier of the Digicircular Economy Evidenced from a Systematic Literature Review

“…Many studies highlight the importance for decision makers to define specific national and regional policies in order to promptly promote the principles of the circular economy [11,104]. Specific actions are essential to foster sustainable production, consumption, and the use of essential raw materials, a fact made clear by Tian et al [105] and by Micari et al [106], respectively. In their studies, a technical environmental assessment of wastewater treatment facilities and water softening treatment is provided.…”