Commercial-Scale Pyrolysis Demonstration for PFAS Destruction, Syngas Recovery, and Biochar Production at the Synagro Drying Facility, City of Baltimore Back River WWTP

Introduction A commercial-scale short-term demonstration of biosolids pyrolysis will be conducted at the Synagro Drying Facility at the City of Baltimore Back River WWTP i, Maryland. The pyrolysis process is designed and supplied by CHAR Technologies, of Toronto, CA. This project aligns with current environmental priorities, particularly the need for PFAS (per- and polyfluoroalkyl substances) mitigation in waste streams. The proposed objectives for this temporary pyrolysis demonstration unit will be: a. Verify the PFAS (synthetic, per- and polyfluoroalkyl substances) characteristics of the biosolids, the Syngas and the Biochar confirming the anticipated PFAS destruction in the pyrolysis process. b. Demonstrate the viability of converting biosolids pellets into valuable by-products: syngas for potential energy recovery and biochar for agricultural or environmental applications.. c. Verify the performance of the pyrolysis process on biosolids continuously for at least six months. d. Verify the resultant Syngas characteristics, and the opportunities and requirements for reusing within the dryer system or upgrading to renewable energy. e. Verify the resultant Biochar characteristics, and suitability for its use as a soil amendment. This six-month demonstration, scheduled from January 2025 to July 2025, aims to provide valuable insights into the operational sustainability and environmental benefits of pyrolysis in biosolids management. Process Description The Pyrolysis Demonstration Unit from Char Technologies uses a pyrolysis process to thermally decompose biosolids pellets in the absence of oxygen; the absence of oxygen prevents incineration from occurring. This pyrolysis process occurs within a rotary kiln chamber with an external burner that after starting-up with propane, burns the Syngas generated during the pyrolysis process. The Char Technologies pyrolysis demonstration unit will process over 8 tons per day of dried biosolids pellets and is projected to produce approximately 143 standard cubic feet per minute of high heating value Syngas containing dust, steam, hydrogen, carbon monoxide, carbon dioxide and methane. The Pyrolysis Demonstration Unit includes Syngas scrubbers that convert the Syngas for internal use in the pyrolysis unit. The excess Syngas that is not used in the pyrolysis process will be combusted, in a thermal oxidizer unit before being discharged at the Demonstration Unit Stack. An isometric of the facility being constructed is presented in Figure 1. A photo of the pyrolysis kiln is provided in Figure 2. A process flow diagram is presented in Figure 3. Sampling and Analytical Methodology Comprehensive sampling and analysis will be performed throughout the six-month demonstration period, with multiple data points collected from key stages of the process. These sampling points are presented in red in Figure 3. Parameters measured include: - Feedstock and Biochar: Elemental and proximate analysis, metals, nutrients, PFAS - Wastewater Analysis: BOD/COD, nutrients, pH - Raw pyrogas, clean syngas, and exhaust gas analysis: hydrocarbons and VOCs, particulates and metals, acid gas, NOx and Sox, PFAS US EPA Method 1633 will be followed to test for all PFAS compounds. Sampling will be conducted at regular intervals to capture variability in process performance. Quality assurance measures, including duplicate and blank samples, will be implemented for data validation. The test methods used for analysis are outlined in Table 1. Results and Discussion We expect to have interim analytical results available by April 2025 for presentation at RBC. Primary discussion will include fate and transformation of PFAS compounds, but will also discuss biochar characteristics, syngas quality and lessons learned in operating and maintaining the pyrolysis unit.