U.S. EPA PROJECT XL: YOLO COUNTY’S ACCELERATED ANAEROBIC AND AEROBIC COMPOSTING (FULL-SCALE CONTROLLED LANDFILL BIOREACTOR) PROJECT Ramin Yazdani Yolo County Planning and Public Works Department 292 West Beamer Street Woodland, California Don Augenstein IEM 4277 Pomona Avenue Palo Alto, California ABSTRACT million tons of waste annually (U.S. EPA, 1997). The The County of Yolo Planning and Public Works annual production of municipal solid waste in the United Department (Yolo County), will operate its next 20-acre States has more than doubled since 1960. In spite of landfill module near Davis, California as a controlled increasing rates of reuse and recycling, population and bioreactor landfill to attain and demonstrate a number of economic growth will continue to render landfilling as an environmental and cost savings benefits in a full-scale important and necessary component of solid waste landfill operation. As part of this project, Yolo County is management. requesting that the EPA grant regulatory flexibility from the Resource Conservation Recovery Act (RCRA) In a Bioreactor Landfill, controlled quantities of liquid are prohibition in 40 CFR 258.28 regarding Liquid added, and circulated through waste as appropriate. The Restrictions, which may preclude addition of useful bulk purpose is to accelerate the natural biodegradation and or non-containerized liquid amendments. Yolo County is composting of solid waste. This process significantly also requesting flexibility in state regulatory requirements increases the biodegradation rate of waste and thus for bottom linings based on project performance, available decreases the waste stabilization and composting time (5 to controls, and environmental safeguards which have been 10 years) relative to what would occur within a demonstrated in their smaller-scale 9000-ton test program conventional landfill (30 to 50 years, or more). If the waste at the Yolo County Central Landfill. In the first phase of decomposes (i. e., is composted) in the absence of oxygen this 20-acre project, a 12-acre module has been (anaerobically), it produces landfill gas (biogas). Biogas is constructed. This 12-acre module contains one 9.5-acre primarily a mixture of methane, a potent greenhouse gas, cell, which will be operated anaerobically and a 2.5-acre cell aerobically. carbon dioxide, and VOC's, that are local air pollutants. Methane is also a fuel. This by-product of anaerobic Co-sponsors of the project with Yolo County are the Solid landfill waste composting can be a substantial renewable Waste Association of North America (SWANA) and energy resource that can be recovered for electricity or Institute for Environmental Management (IEM, Inc.). The other uses. Other benefits of a bioreactor landfill County is proposing to supplement the liquid addition with composting operation include increased landfill waste groundwater and leachate, but would like to obtain the settlement and therefore increase in landfill capacity and flexibility to possibly utilize other liquids such as gray- life, improved opportunities for treatment of leachate that water from a waste water treatment plant, septic waste and may drain from fractions of the waste, possible reduction food-processing wastes that are currently land applied. of landfill post-closure efforts, landfill mining, and Liquid wastes such as these, that normally have no abatement of greenhouse gases through highly efficient beneficial use, may instead beneficially enhance the methane capture over a much shorter period of time than is biodegradation of solid waste in a landfill for this project. typical of waste management through conventional landfilling. INTRODUCTION DESCRIPTION OF THE FACILITY Sanitary landfilling is the dominant method of solid waste The Yolo County Central Landfill (YCCL) is an existing disposal in the United States, accounting for about 217 Class III non-hazardous municipal landfill with two Class II surface impoundments for disposal of selected non- 1994, the Yolo County Planning and Public Works hazardous liquid wastes. This site encompasses 722 acres Department initiated a bioreactor landfill demonstration and is owned and operated by Yolo County. The YCCL project to evaluate the Bioreactor Landfill concept for its was opened in 1975 for the disposal of non-hazardous Central Landfill near Davis, California. The construction solid waste, construction debris, and non-hazardous liquid phase of the project was funded by Yolo and Sacramento waste. Existing on-site operations include an eleven-year Counties ($125,000 each), the California Energy old landfill methane gas recovery and energy generation Commission ($250,000), and the California Integrated facility, a drop-off area for recyclables, a metal recovery Waste Management Board ($63,000). More recent grant facility, a wood and yard waste recovery and processing funding for the monitoring phase of the project has been area, and a concrete recycling area. received from the U. S. Department of Energy through the Urban Consortium Energy Task Force ($110,000), and the PURPOSE OF THE U.S. EPA XL PROJECT Western Regional Biomass Energy Program ($50,000). A national pilot program called Project XL, which stands Greenhouse gas and emission abatement cost-effectiveness for "eXcellence and Leadership", allows state and local studies have recently been completed with $48,000 in governments, businesses and federal facilities to develop support from the National Energy Technology Laboratory with EPA an innovative strategies to test better or more (NETL). Further support, $462,000 recently committed by cost-effective ways of achieving environmental and public NETL, is enabling operation of the test cells for health protection. approximately 2 more years as well as helping prepare for larger module operation. Through the EPA Project XL the data will enable EPA and State of California regulatory agencies to develop or In addition, on January 26, 2000 the California Integrated modify regulatory requirements for such projects and Waste Management Board committed Yolo County therefore lead to commercialization of this technology. $400,000 for the construction and testing of the full-scale Yolo County is in the process of obtaining regulatory bioreactor demonstration project. flexibility from the federal and state regulatory agencies. This approval is based on project performance, available controls, and environmental safeguards which have already Concerning local support for this XL project, Yolo County been demonstrated in Yolo County’s smaller-scale has held several public meetings for the full-scale demonstration project at the Yolo County Central Landfill demonstration project. These meeting have been held during the regular Waste Advisory Committee meetings to This project will demonstrate three main objectives: locate potential members of the local stakeholder group in a) Acceleration of waste decomposition and leachate addition to special stakeholders meeting. The County will treatment, via liquid amendments and recirculation through convene periodic meetings of the stakeholder group to pipe network serving the waste mass and demonstrate that obtain comments on this proposal, as well as to brief the this could be accomplished without excessive leachate group on their progress during the duration of the XL head build up over the base liner. The goal is to agreement. accomplish rapid completion of composting, stabilization and generation of methane to the maximum practical yield. DESIGN AND OPERATIONS OF THE MODULE D FULL-SCALE LANDFILL BIOREACTOR b) Efficient capture of nearly all generated methane, Yolo County proposes to operate its next full-scale 20-acre withdrawn at slight vacuum from a freely gas-permeable landfill module (Module D) with both anaerobic and shredded tire collection layer beneath low-permeability aerobic bioreactor areas (also termed modules below). In cover, without impacting local air quality. Near-complete the first phase of this 20-acre project, a 12-acre module has extraction with this approach has already been been constructed. One 9.5-acre cell will be operated demonstrated in the 9,000-ton small-scale demonstration anaerobically and the other 2.5-acre cell aerobically. The cell at the Yolo County demonstration project. anaerobic and aerobic design and operations are summarized below: c) Document the capital and operations cost of a full-scale bioreactor and determine the economic viability of its Under current plans, the first phase of Module D will be commercialization. further subdivided into the two independent bioreactor systems, the aerobic system and the anaerobic system. STALKEHOLDER INVOLVEMENT AND SUPPORT Module D was designed and constructed in a ridge and Stakeholder involvement and support for this concept has swale configuration to optimize landfill space and to already been demonstrated by previous federal, state, and maintain good drainage for the collection system. The local support of this bioreactor concept. For example, in blanket drainage layer slopes at 2% inward to two central collection v-notch trenches. Each of the trenches drain at LCRS and Liner Performance 1% to their prospective leachate collection sumps located As described above, the more rigorous Module D LCRS at the south side of the module. Phase 2 of Module D will and liner system is intended to outperform the California also be constructed in a similar manner as Phase 1 of regulations, Title 27 and Subtitle D prescriptive liner. The Module D. leachate collection and recovery system