Seeking a Solid Landing

• Mar 01, 2001

Current regulation of municipal solid waste (MSW) landfills is based upon two principles: MSW is less threatening than hazardous waste, and federally mandated containment systems will protect the environment as long as the waste remains a threat. Neither of these principles appears to be true. The U.S. Environmental Protection Agency (EPA) may be about to compound the problem by allowing the intentional introduction of liquids into existing and future landfills, thereby creating more dangerous and difficult-to-control leachate. EPA should examine alternatives, such as composting of the organics that are the source of the problem. Such alternatives may prove far preferable to both conventional landfills and the new variants, known as "bioreactors."

Adopted in 1991 following the 1984 amendments to the Resource Conservation and Recovery Act of 1976 (RCRA)¹, EPA's Subtitle D regulations² closed down nearly 5,000 unengineered open dumps across the country. The RCRA amendments decreed that the new generation of engineered landfills under Subtitle D would handle "sanitary," as opposed to "hazardous," waste.³ EPA's rules embodied a "dry tomb" approach to landfilling sanitary (i.e., municipal) waste. They relied upon a single composite liner and cover as barriers, combined with leachate collection, gas extraction and monitoring systems, in an attempt to keep moisture out of the landfill and isolate the leachable constituents in the municipal waste load from the environment for the time that they posed a threat.⁴ For hazardous waste, in its Subtitle C regulations, EPA concluded that double the protection was necessary - two sets of composite liners and leachate collection systems, among other extra measures.⁵

As adopted, the Subtitle D regulations set a post-closure period of 30 years (with undefined extensions) as the length of time the waste needs to be isolated.⁶ Preliminary efforts to recognize a more long-term problem were deleted from the final rules, with perhaps - in hindsight - imprudent recourse to the provision in Subtitle D permitting the agency to "take into consideration the practicable capabilities of such facilities."⁷

However, the constituents of what is legally defined to be "sanitary" waste have been documented to be essentially indistinguishable from hazardous waste.⁸ Also, it has become increasingly apparent in recent years that the time for a MSW landfill to reach the point which the load becomes benign extends for hundreds of years, depending upon site-specific local conditions - not 30 years.⁹ Moreover, EPA has repeatedly acknowledged that the containment systems prescribed in the landfill rules will fail over time:

Thus leachate generation and escape are a danger at existing dry tomb landfills, and should cause us to question their viability. Given this fact, is it not strange that EPA should consider allowing even more moisture to be introduced into landfills intentionally? That appears to be exactly what is happening. By notice dated April 6, 2000, EPA requested comments concerning the design and performance of so-called "bioreactor landfills." ¹¹ EPA's April 6 Notice stated:

Left unstated here is what appears to be a major factor motivating bioreactor proponents: cost savings due to reductions in the landfill space required for a given amount of waste from accelerated decomposition of organic material.

Proponents of bioreactor systems rarely explicitly concede the inherent inadequacies of the current entombment standards. But they do express the hope that, as stated in EPA's April 6 Notice, recirculation will "transform and more quickly stabilize the readily and moderately decompostable organic constituents of the waste stream"¹³ and thereby reduce the leachate and gas formation that occur after closure. Proponents add that the cost of the basic piping and pumps for recirculating leachate and accelerated gas extraction will be offset by recirculating instead of treating leachate and by recovering 50 percent of the airspace through higher final densities so that "operating a bioreactor landfill saves money in the long-term."¹⁴

However, bioreactors suffer from a number of major problems:

• Because much municipal waste is encased in plastic bags, and only some may be breached when the loads are compacted, a significant fraction of the waste will remain isolated from recirculating liquids and not be decomposed prior to landfill closure, absent pre-shredding.
• Installing effective gas extraction systems as soon as recirculation begins in order to capture the greenhouse and volatile gases that recirculation encourages - all while rapid settlement due to recirculation is occurring - may be exceedingly difficult.¹⁵
• Maintaining even wetting to avoid destabilizing differential settlement may be difficult.
• Avoiding excessive wetting near sidewalls, where breakouts might occur following
  saturation of the waste load, may also prove difficult.
• Providing a liner/leachate collection system that will work properly with the
  far greater hydraulic loadings involved in bioreactors is not likely to be achieved absent (at a minimum) two composite liners and leachate collection systems.¹⁶

Technical fixes may be devised for these potential problems. However, such means as pre-shredding and double composite liners would dramatically increase disposal costs for bioreactors as compared to entombment landfills, thus limiting the economic incentive to develop them.¹⁷

There are alternative means to address the threat to the environment from discarding compostable material into the ground, avoiding both the new risks that bioreactors present and the present threat posed by Subtitle D dry tomb landfills. Foremost among these is the separation and separate collection of organic materials. Already common throughout the United States today are systems that collect yard trimmings (including grass clippings, leaves and prunings) separately for processing often in windrow composting facilities. Increasingly, many communities are studying or implementing new programs to collect residential and/or commercial/institutional food discards and food-contaminated paper. The latter programs have been demonstrated extensively in Europe, particularly the Netherlands, and are often combined with collections of yard trimmings for maximum collection efficiencies.¹⁸

Finally, some areas have begun to experiment with wet/dry systems for composting. While wet/dry systems are not yet commonplace, there are a number of programs, including a full-scale one in Guelph, Ontario,¹⁹ and a pilot in San Francisco, Calif.²⁰ These are sufficient to develop meaningful data that can be compared to the demonstration bioreactors and also to show, in response to RCRA § 4004(a), that wet/dry systems are a practical alternative.

In all of these organic recycling systems, the compostable fraction that is the source of the leachate and gas generation in landfills is never mixed with the hazardous constituents in municipal solid waste and discarded in the ground, threatening the environment. Instead, it becomes a valuable soil amendment.

Reducing landfilling of compostable material is already the policy in Europe. The European Community is requiring member states to adopt a "national strategy" to cut landfilling of "biodegradable municipal waste" by 25 percent within five years, 50 percent within eight years, and 65 percent within 15 years.²¹ Thus, separate collection and composting of organics is firmly grounded in professional solid waste practice today and cannot be seen as unrealistic or impractical.

The National Environmental Policy Act of 1969 (NEPA)²² provides a framework for EPA's analysis of both bioreactor and dry entombment landfill alternatives. Unfortunately, however, EPA's April 6 Notice fails to recognize EPA's duties under NEPA to "identify and assess the reasonable alternatives to proposed actions that will avoid or minimize adverse effects of these actions upon the quality of the human environment," and to "integrate the NEPA process with other planning at the earliest possible time."²³ Indeed, the only alternatives that appear to concern EPA are alternative landfill liner designs. While EPA requests information on such minutia as "relevant patent issues associated with anaerobic, aerobic, or other bioreactor landfills,"²⁴ it nowhere asks commenters for information on alternatives to bioreactors themselves. EPA may intend to consider bioreactor alternatives at a later date, but such delay is inconsistent with NEPA's mandate to weigh alternatives "at the ea rliest possible time."

EPA could ignore NEPA here only if its action in adopting rules for bioreactors were not a "major Federal action significantly affecting the human environment."²⁵ But given the impact bioreactor rules would have on thousands of major landfills across the country, and the "irreversible and irretrievable commitments of resources"²⁶ which would be involved in a national policy favoring bioreactors, a conclusion that such rules are anything other than "major Federal action" triggering NEPA seems inconceivable.

Advocates of recycling and composting are concerned about methods of dealing with solid waste that discourage alternatives to landfilling - whether of the dry tomb or bioreactor variety - because of regulatory inadequacies that allow landfilling to be priced below its true cost to the environment. EPA should revisit its present Subtitle D rules and re-assess its supposedly innovative bioreactor proposals. RCRA requires that EPA's regulations must "at a minimum" ensure that "there is no reasonable probability of adverse effects on health or the environment from disposal of solid waste."²⁷ This standard demands both a prompt revision of the existing Subtitle D rules and extreme care in adopting new rules authorizing bioreactors.