A Public-Private Success Story for Biosolids Management in Northern California

A Public-Private Success Story for Biosolids Management in Northern California James Dunbar, PE, General Manager, Lystek International Limited Jordan Damerel, PE, Director of Engineering, Fairfield-Suisun Sewer District The Fairfield-Suisun Sewer District (FSSD) and Lystek International Limited (Lystek) have built a progressive public-private partnership (P3) to provide solutions to the biosolids management challenges faced by Northern California wastewater agencies. FSSD is a special district (located 45 miles northeast of San Francisco) and has a history of looking for progressive approaches to wastewater treatment technologies. Lystek is a Canadian-based private company with a patented biosolids treatment technology, a thermal-chemical hydrolysis process employing high-speed shearing, alkali pH, and low-pressure steam injection (Lystek THP). The Lystek THP process hydrolyzes biosolids and residuals to produce a concentrated liquid that has multiple applications in resource recovery, including as a Class A biosolids fertilizer (LysteGro), and a digester enhancement (LysteMize). This paper will present the background of biosolids issues in Northern California and the steps taken by FSSD and Lystek to be leaders in overall biosolids solutions, resource recovery, and high-value beneficial uses. The San Francisco Bay Area relies on a diverse portfolio of biosolids outlets. More than 1,500,000 wet tons of biosolids are generated each year from almost 40 wastewater treatment plants. The solids treatment processes employed by the various plants include digestion, lime-stabilization, mechanical drying and solar/wind drying. The management outlets include incineration, landfills (both for disposal and alternate cover material), composting, and agricultural land application. For many years, there were economical outlets for the seasonal volume fluctuations and land application requirements of regional governments. About 15 years ago, it became clear that alternative solutions needed to be explored due to increasing volumes and a desire to capture the value inherent in biosolids. Individual agencies and sub-regional groups started to investigate potential solutions and spent considerable time, effort, and money in this area, however, a lack of financial commitments by both the private sector and public entities prevented any real progress in finding a proven solution. In 2016, Lystek and FSSD entered into a +20-year partnership to develop an onsite solution for biosolids management and resource recovery. The partnership agreement allowed the development of the Fairfield Organic Material Recovery Center (OMRC) as a regional biosolids and organics management facility, owned and operated by Lystek, leveraging under-utilized infrastructure and assets at the FSSD plant. The Fairfield OMRC location is ideally situated to provide a regional solution, straddling the edge of urban density which provides biosolids quantities, and an established agricultural community seeking soil amendments. The partnership between FSSD and Lystek has successfully created a complete solution for utilities in the Bay Area through Lystek's efficient process, on-site storage solution, and development of a strong market for the Class A biosolids fertilizer. The OMRC accepts residuals year round, is able to store the fertilizer during inclement weather periods, and land applies fertilizer throughout the year as field conditions allow. The material is classified as a Class A biosolids by USEPA (Part 503 standards), and has received a bulk fertilizer registration by the California Department of Food and Agriculture (CDFA). This dual-designation material has allowed LysteGro to be widely used and accepted by area farmers and ranchers as a fertilizer (Figure 1) to avoid the use of chemical and synthetic fertilizers. The use of Class A LysteGro is now accepted in multiple counties which have historically been restrictive to traditional Class B biosolids and its land application practices. The other major component of the FSSD-Lystek partnership involves enhanced digestion and biogas generation. FSSD operates anaerobic digesters to treat wastewater solids and utilize the biogas for onsite co-generation (electricity plus heat for the digesters). This reduces the overall plant energy dependence on fossil-fuels sources. Through the LysteMize process, a portion of the Lystek THP treated biosolids can be re-fed to anaerobic digesters to increase volatile solids destruction and boost biogas yields. The LysteMize process was initiated at FSSD in 2018, refeeding 10% - 30% of processed biosolids from FSSD and third party generators to the digesters. Due to new California legislation related to organics diversion from landfills, generators of undigested biosolids who send their material to the OMRC are able to obtain diversion and recycling credits for the volumes processed with this enhanced digestion. The LysteMize process has measurably increased biogas quantities generated compared to historically generated volumes. At the greater than 30% refeed rate, gas levels have increased by approximately 17% compared to pre-feeding quantities. There is also a noticeable increase in biogas yield (the cubic feet of methane per lb of influent VS) as a result of the increased digestibility of the hydrolyzed material. Since Lystek became operational, there have been additional regulatory and market changes in options for biosolids management. Private companies, primarily landfills, have banned or limited the amount of biosolids they are willing to accept, stressing winter outlets for biosolids. In addition, regulatory requirements have been established, mandating organic material diversion and increased recycling goals, further limiting landfills' ability to offer beneficial uses on a year-round basis. These changes have resulted in a growing customer list of utilities utilizing the Fairfield OMRC as a secure, sustainable biosolids management option (Figure 2). This successful P3 partnership between FSSD and Lystek has offered regional agencies a reliable, sustainable and cost-controlled biosolids management solution. Generators now have a local management facility which produces and manages a Class A biosolids fertilizer, and reduces GHG emissions through additional biogas recovery in the FSSD digesters. The successful LysteGro management program has sold and applied more than 250,000 tons of CDFA registered fertilizer (Figure 3), and substantially grown the market and demand for the product. Increasing fertilizer value has provided the opportunity for revenue sharing opportunities with generators who send their biosolids to the FSSD OMRC. This paper will present a case study of this regional processing facility and discuss the successes and challenges experienced over this time.