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Alternative Landfill Technologies
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Alternative Landfill Technologies address regulatory and technical obstacles that inhibit the use of alternative landfill covers, bioreactor landfills, and a process to optimize post-closure care of landfills.
Design, Installation, and Monitoring of Alternative Final Landfill Covers (ALT-2, December 2003) is written for regulators, owners/operators, and consultants associated with the plan development, review, and implementation of alternative final covers (AFCs). This guidance facilitates the decision processes related to design, evaluation, construction, and post-closure care of AFCs through a decision tree provided at the end of the guidance. Alternative final landfill covers help DOD and DOE avoid the considerable expense of excavating old waste sites.
Bioreactor landfills increase the moisture content of waste to enhance the degradation and stabilization of the waste material. Characterization, Design, Construction and Monitoring of Bioreactor Landfills (ALT-3, February 2006) facilitates the decision processes necessary to create bioreactor landfills. Available research indicates that municipal solid waste degraded in a bioreactor landfill may reduce the long-term threat potential of “dry tomb” landfills resulting from breakdown of organics and sequestration of inorganics. Bioreactor landfills may accept nonhazardous liquids and sludges which provide nutrients, enzymes, moisture, and bacteria necessary to accelerate biodegradation of both municipal solid waste (MSW) and biosolids. Bioreactors can expedite beneficial reuse of landfill capacity, resources, and expedited reuse of the property.
While recirculating leachate from a landfill is fundamental to bioreactor operation, additional makeup liquids provide optimal moisture when not enough landfill leachate is generated. Liquids recirculation accelerates the decomposition of MSW by distributing moisture, nutrients, enzymes, and bacteria throughout the waste mass more efficiently than natural infiltration alone. A variety of reinjection systems provide a thorough and more homogeneous distribution of moisture throughout the waste material. Liquids recirculation may be accompanied by pressurized air to enhance the aerobic biodegradation process; however, with or without aeration, the anaerobic bioreactor process accelerates gas generation that can offer a revenue stream and decrease the contaminant load in the leachate. Ultimately, more land reuse options are available for closed landfills when using bioreactor landfills than could have been considered when using a dry tomb landfill design, and landfill capacity increases since waste degradation decreases volume.
Post-Closure Care (PCC) at an MSW landfill ensures that a solid waste facility is managed after final closure so that it does not pose a threat to human health and the environment (HH&E). ITRC’s Evaluating, Optimizing, or Ending Post-Closure Care at Municipal Solid Waste Landfills Using site Specific Data (ALT-4, September 2006) provides guidance to systematically evaluate the condition of the closed landfill, the waste it contains, the setting and make sound decisions to manage, reduce, or potentially end PCC while reducing threat to HH&E. Traditionally, 30 years has been considered the minimum period that PCC must be performed. However, previously there was no structure national or state-based process for evaluating, optimizing, or ending PCC. Many states are beginning to address PCC at landfill sites nationwide. This guidance eliminates the potential of having 50 different state approaches its evaluation. It makes far better sense to establish a standard, recommended process for the various states to use rather than have multiple independent approaches. Landfill performance data are used to extend or shorten the length of post-closure care.
Performance-based evaluations of PCC using this guidance align with existing regulatory structure of PCC. The guidance supports the concept of reducing or ending PCC based on the evaluation of four modules: leachate, gas, groundwater, and cap. Technical details and research supporting this modular approach is contained in A Performance-Based Approach for Ending Post-Closure Care at Municipal Solid Waste Landfills: A Procedure for Providing Long-Term Stewardship under RCRA Subtitle D ”.
Communities can realize significant benefit from the reuse of former landfill properties, such as brownfields-type redevelopment, by following the processes outlined in ALT-4. Even though the formal regulatory PCC ends, an obligation for continued management is required to maintain the property according to the potential threat at the point of exposure. This is referred to as “custodial care” (CC) of the facility and associated property. CC requires continued care to ensure that it does not pose a threat to HH&E. Institutional controls required by covenant, deed restriction, or other agency mechanisms continue to ensure the property is managed according to its planned end use and CC requirements.