Commissioning of the First Hydrothermal Carbonization Process in the United States at the Borough of Phoenixville Wastewater Treatment Plant

Prevalent biosolids management practices treat wastewater treatment facilities as cost sinks, leaving them to pay ever increasing disposal costs for biosolids. Utilizing hydrothermal carbonization (HTC) to convert wastewater solids and organic wastes into valuable products turns wastewater treatment plants into sustainable, revenue producing assets. Hydrothermal Carbonization, or HTC for short, is the cornerstone technology in SoMax BioEnergy's suite of solutions for organic wastes. SoMax BioEnergy's HTC process is a continuous thermochemical process that utilizes moderate temperatures and pressures of ~350F & 430F (180C & 220C) and less than 580 psi (40 bar). The HTC reaction has variable retention times based on the feedstock from as short as thirty (30) minutes and up to four (4) hours. When considering biosolids processing, HTC's greatest advantage is that the reaction takes place in an aqueous environment, eliminating the expensive process of drying biosolids prior to processing. The HTC process + drying of the BioCoal product, uses less energy than drying the equivalent biosolids alone. In fact, HTC uses the water present in the biosolids as the primary reactant to perform chemical reactions. The key reactions that occur during the HTC process are dehydration, hydrolysis, decarboxylation, and condensation, all of which result in a product with higher C:O ratio than original feedstock. Hydrothermal carbonization of biomass generates a biochar-like solid product, known as hydrochar, and a nutrient rich process water. Comparing hydrochar to the original feedstock, it is more easily dewatered, has greater fuel characteristics, sorption capacity, and has added benefits when used as a soil amendment, such as increased fixed carbon and carbon sequestration potential. Research institutes across the globe are creating value added bioproducts from hydrochar ranging from concrete additives, to battery electrodes and activated carbon. Considering alternative methods of biosolids processing (land application, compost, and anaerobic digestion), HTC is the most carbon efficient, creates the lowest greenhouse gas emissions, and utilizes a much smaller footprint. The hydrothermal carbonization thermochemical process is also more robust as it is not subject to the same sensitivity issues biological processes encounter. The Borough of Phoenixville Wastewater Treatment Plant, in Pennsylvania, has partnered with SoMax BioEnergy to build the first commercial scale hydrothermal carbonization facility in North America. While European and Asian countries already utilize HTC to treat organic wastes including woody biomass, sewage sludge, digestate, food waste, and even municipal solid waste, North America has yet to implement this technology. This changes with the Borough of Phoenixville project, which at the time of writing this abstract, has over $1,000,000 in project funding has come from county and state grants and is under construction with commissioning set for Q1 of 2022. At capacity the Phoenixville HTC project will process ~15,000 tons of prepared 15-20% solids feedstock, generating over 1,500 tons (d.b.) of BioCoal (hydrochar). SoMax BioEnergy and the Borough of Phoenixville are implementing a two-stage approach to maximize the benefits of the HTC facility to align with the Borough's sustainability goals. The first stage of the project is utilizing HTC for treatment of sewage sludge within the plant and surrounding wastewater treatment plants to process biosolids. The second stage will expand the HTC feedstock to include food waste from the Borough and surrounding businesses. Stage two includes introducing gasification technology that utilizes the hydrochar as a solid fuel to power the wastewater treatment plant and put electricity back on the grid. The Borough Council and Management team sees electricity generation from waste they would have paid to dispose of as a win-win situation and steps in the right direction to accomplishing their 2035 goal of 100% clean and renewable energy. The Borough of Phoenixville HTC project, when fully realized will generate over 150% of the electrical demand of the WWTP, covering all electrical and thermal demands of the HTC process, while utilizing the excess electricity for other borough owned properties. Over the 20-year project lifespan, it is expected to generate over $35,000,000 in savings with a capital equipment payback period of around 7 years. In Spring of 2020, SoMax BioEnergy's hydrothermal carbonization solution received recognition from the U.S. Department of Energy as a Phase One winner in the Water Resource Recovery Prize and this fall was 1 of 6 Phase Two submissions. Unfortunately, the Phase two winners are to be announced the second week of November, just missing the deadline of the abstract submittal. In this presentation, SoMax BioEnergy will: 1) Introduce the Hydrothermal Carbonization (HTC) technology 2) Compare HTC to the status quo WWTP technologies 3) Share research developments and HTC product applications 4) Use plant data to discuss the impacts of HTC on effluents and overall mass and energy balances of the plant 5) Talk about DEP permitting and pathways forward for beneficial use 6)Discuss the experience that is commissioning a new technology