The Opportunity for Water Resource and Recovery Facilities to Advance Regional GHG Reduction Goals

The need for a circular economy and organic waste diversion regulations aimed at reducing carbon footprint is driving cities and utilities to adopt a holistic resource recovery approach for organic waste streams typically disposed in landfills. These waste streams can range from organic fraction of the municipal solid waste (MSW), pre-consumer waste streams such as those produced by food processing facilities, packaged food and beverages, biosolids produced by water resource and recovery facilities (WRRFs), and organic wastes produced by other City public service departments. States and cities across North America are developing plans and strategies to reduce greenhouse gas (GHG) emissions for climate change adaption and develop a circular (green) economy. The plans typically identify WRRFs as a strategic solution provider for sustainable organic waste management and resource recovery, and to produce value added products such as biogas, renewable natural gas (RNG) and/or compost. WRRFs are typically located in urban environments, in proximity to pre-consumer and post-consumer food waste generation, fats, oil and grease (FOG) waste streams, and have the treatment infrastructure to efficiently process and manage these waste streams. A 2012 Water Research Foundation (WRF) Study concluded that hauling of food waste to municipal WRRFs and utilizing it beneficially for resource recovery through anaerobic digestion (AD) results in reduction of carbon footprint of food waste management, when compared with other commonly adopted industry practices such as landfills and composting. Although the benefits of co-processing of organics waste streams with wastewater solids are uncontested, the adoption of this approach by utilities has been slow. This is primarily due to limited understanding of managing this feedstock, especially pretreatment/conditioning required to make these feedstocks more amenable to process in anaerobic digestion, system design considerations, permitting requirements and plantwide operational impacts. Using case studies summarized below, the authors will share their experience and lessons learned assisting early North American adopters with planning, design, construction, commissioning, and operation of organic resource recovery and co-digestion facilities. 1)Case Study 1 - Oneida County WPCP Energy Independence, Utica, New York: Beginning January 1, 2022, the New York State Food Donation and Food Scraps Recycling Law went into effect. This law prohibits large generators of food waste that produce more than 2 tons per week from disposing of that food waste as solid waste. To help meet the requirements of the recycling law and reduce greenhouse gas emissions, the Onieda-Herkimer Solid Waste Authority partnered with the Oneida County WPCP to process source separated organic food waste slurry in the new anaerobic digesters at the Oneida County WPCP. The Oneida County Solid Waste Facility is located adjacent to the Oneida County WPCP. Under the County's Food2Energy Initiative, the Solid Waste Authority has been able to divert food waste, which makes up approximately 22 percent of the waste stream, away from the Regional Landfill. The co-digestion of food waste slurry with wastewater solids has allowed the WPCP to enhance biogas production and electricity generation onsite. To fully utilize the biogas and eliminate flaring, the County plans to expand its cogeneration facility by installing two new 200 kW microturbines, in addition to three (3) existing 200 kW microturbines. The case study will provide the attendees an understanding of the successful partnership between the Solid Waste Authority and the WPCP, and the benefits to the WPCP to advance its energy independence and reduce its GHG footprint. Exhibit 1 Process Flow Diagram for Oneida County's SSO Pre-treatment and Conveyance 2)Case Study 2 - Central Marin Sanitation Agency Organic Waste Acceptance and Power Generation Program, San Rafael, California The State of California has promulgated several regulations to reduce GHG emissions; most notably SB 1383 promulgated to achieve 75 percent reduction in landfilled organic waste by 2025 and reduce short-lived climate pollutants in California. Beginning 2014, the Central Marin Sanitation Agency (CMSA) entered into a public-private-partnership with Marin Sanitary Service (MSS), a private solid waste service provider, to accept pre-consumer food waste. The pre-consumer food waste is co-digested together with wastewater solids produced by CMSA's WWTP and fats, oil and grease (FOG) collected from the service area. Biogas produced by co-digestion is conditioned and used as fuel in an existing internal combustion engine based cogeneration system for electricity generation. The Organic Waste Receiving Facility (OWRF) has been successfully operational for many years now. Lessons learned through years of experience include high strength waste (HSW, a mixture of pre-processed food waste and FOG) storage limitation at the WWTP, pumping and handling challenges due to high solids content and corrosive nature of the HSW stream, and shredded inorganics in the HSW slurry resulting in operating and maintenance nuisances and high operating costs. The authors are in the process of making improvements to the OWSF to provide dedicated fine screening and storage for FOG to address storage and HSW slurry quality challenges. The case study will provide the attendees an understanding of lessons learned, operational and maintenance challenges, and improvements CMSA plans to make. The other purpose of the improvements is to enhance utilization of available anaerobic digestion capacity to increase biogas production and operate the cogeneration system 24 x 7. The most unpredictable failure has been with hose breakdown for the peristaltic hose pumps. CMSA has averaged approximately six (6) hose replacements per year for the pumps. The following graphic is a process flow diagram of the upgraded OWSF. Exhibit 2 Process Flow Diagram of CMSA's Organic Waste Receiving Facility after Improvements. 3)Case Study 3 - Rialto Bioenergy Facility, California, United States: The Rialto Bioenergy Facility (RBF) processes approximately 700 tons per day (tpd) of organics/food waste recovered from solid waste through anaerobic digestion and 300 tpd of biosolids from external WRRFs into renewable electricity, renewable natural gas (RNG), and fertilizer products. Dewatered cake from external WRRFs and anaerobically digested biosolids is dried in two belt dryer units. The dried biosolids will be processed in a pyrolysis system and converted into syngas, bio-oil and a nutrient-rich biochar. The pyrolysis process is expected to become operational by Q1 2023. The produced syngas would be used to run the dryers, along with the waste heat from the cogeneration system. The pyrolysis oil will be recirculated in the anaerobic digesters to enhance biogas production. This case study will provide the attendees an understanding of how various innovative technologies can be combined to enhance energy recovery and reduce GHG footprint, and preliminary operating data will be presented. The Facility initially became operational in 2020. Exhibit 3 Aerial Image of the Rialto Bioenergy Facility