Hydrothermal-based Wastewater Solids Management for Targeted Resource Recovery and Decarbonization in the Contiguous...

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Sustainable Energy

Background:

• Wastewater solids management significantly impacts operational costs and greenhouse gas (GHG) emissions in water resource recovery facilities (WRRFs).
• Conventional practices are energy- and emission-intensive, necessitating sustainable alternatives.

Purpose of the Study:

• To evaluate a hydrothermal liquefaction (HTL)-based 'waste-to-energy' strategy for managing wastewater solids.
• To assess the financial viability, cost savings, GHG reduction, and resource recovery potential of HTL systems in the contiguous U.S. (CONUS).

Main Methods:

• An independent facility analysis was conducted for 576 WRRFs in the CONUS.
• A hub analysis examined shared processing at HTL-based treatment centers for WRRF networks.

Main Results:

• Deploying HTL-based systems could yield cost savings of $4.81 million per day and reduce GHG emissions by 1,300 tonnes CO2 eq per day across 576 WRRFs.
• The system can offset approximately 1-2% of synthetic fertilizers, recovering nitrogen and phosphorus.
• Hub analysis indicated expanded opportunities for WRRF networks with specific solids mass flow rates and transportation distances.

Conclusions:

• HTL-based systems present a financially viable strategy for wastewater solids management, offering significant cost savings and GHG emission reductions in the CONUS.
• Biochemical composition of solids and internal rate of return are key sustainability drivers.
• Shared processing via HTL treatment centers enhances decarbonization potential for interconnected WRRFs.