It was about a decade ago that the Environmental Protection Agency (EPA) published Subtitle D of the Resource Conservation and Recovery Act, which established current regulations for the disposal of municipal solid waste (MSW.) Since this time, a lot of work has been done creating landfill facilities with the new regulations in mind, much of it under the philosophy of "pile it higher and deeper." Recently, however, observers within the MSW industry have questioned this line of thinking and are offering an alternative view.

The decade-old MSW regulations were patterned after similar regulations governing hazardous waste sites. As a result, industry insiders charge, the MSW regulations are somewhat short sighted in terms of future closure and stabilization. Like their hazardous waste counterparts, the current MSW regulations have put a high premium on "airspace," the three-dimensional space that the landfills occupy, due to the expensive cost of their liner systems. An example of the "pile it higher and deeper" philosophy in the hazardous waste industry would be the trend of using drainage materials to replace soil in the landfills. After all, with "airspace" being so expensive, why use 30 cm of sand when a mere 0.3 cm of a geotextile composite would suffice? This philosophy has lead to permits for landfills being repeatedly amended and has encouraged the creation of mountains of waste. The owners and operators of MSW sites feel obliged to please taxpayers and stockholders by maximizing the use of airspace. Thus, pile it higher and deeper is the guiding mode of thought.

The downside to all of this is that recent studies have shown that higher and deeper landfills will require several centuries of post-closure care before stabilization can occur. This timeframe is significantly longer than what is accepted as a maximum governmental attention span –a period generally defined as less than two hundred years. Bioreactor technology can shorten this period to as brief as 12 to 30 years, yet current waste acceptance and screening practices make this option difficult to employ. Piling waste higher and deeper is also likely to result in serious permeability problems i.e. the tightly layered waste will not be porous enough for water to pass through, thus inhibiting the degradation process. The increased disposal of biosolids in the landfill only worsens this trend. Landfill owners and operators may eventually need to construct costly vertical drainage systems to rectify the situation.

To address these issues, some industry insiders maintain that the present state of post-closure planning and prevailing definitions of sustainability need to be re-assessed. The regulations, as they currently stand, don't require for the landfill owner to define the post-closure use of the landfill cell and since most landfills were created with the "selling airspace" philosophy, the steepest side-slopes and shallowest top deck that the regulations permit typifies their dimensions. This configuration severely limits options for future land use.

It should also be noted that nearly every municipal waste landfill is in an area that is already surrounded by human habitation or that will be in the near future. Having accepted this inevitability, many in the MSW industry have mentioned working with urban planning professionals in designing the landfill sites. To the urban planner, the areas we inhabit are comprised of four interlocking elements: the natural environment, the human environment, the built environment and the financial environment. Any proposed urban development, landfill or otherwise, must consider each of these four elements if it is to be successful over a long period time. With this updated outlook, MSW industry insiders have criticized the prevalence of short-time thinking in landfill development. They maintain that developers must look beyond considerations of initial cost and plan for the eventuality of how future generations will deal with the areas.

In an article on long-term landfill planning on the MSW Management web site, authors Richard T. Sprague and Gregory N. Richardson suggest an alternative to the "pile it deeper and higher" method of landfill development. Their alternative model envisions the landfill as an "anaerobic digester vessel" similar to those constructed by industrial waste treatment plants. With this model in mind, the most cost-effective operation is the one that "allows the fastest passive degradation of the waste and least expensive recharge of the vessel." This sort of sped-up degradation will require adding a greater amount of moisture to the waste, however, and rainfall alone will not do the trick. Since landfills with inordinately high elevations and compressed strata will have a tougher time getting the water they need so, the authors recommend that landfill cells be of a moderate size to facilitate the addition of water. Their suggestion is that the landfill be kept at less than 150' tall and only hold five to eight years' worth of waste. This estimate is based on the expectation that the landfill cell could be "constructed, filled, allowed to stabilize, and then mined to reclaim the airspace at a cost less than that of the one-time use mandated by piling it higher and deeper." The authors contend that the time frame needed for this model to stabilize is well within the attention span of our government to oversee.

In order for an alternative landfill model to be adopted, the authors believe landfill planning needs to shift its focus to the long-term. More specifically, they suggest that the landfill operation be able to mine and process its stabilized waste for less money than the cost of a new liner, a scenario that may require solid waste professionals to encourage developing markets for the compost-like stabilized waste. Finally, they suggest modifying the regulations of Subtitle D regarding landfill's post-closure use, which means that the municipal solid waste industry will need to grow beyond the current "pile it higher and deeper" philosophy.

Source: Is Piling It Higher and Deeper the Only Answer?
Richard T. Sprague & Gregory N. Richardson
MSW Management,
http://www.forester.net/mw_0109_piling.html