From Paper Waste to Landscape: Designing Smarter Landfill Covers
Several years ago, a client approached our team to assess the feasibility of using an alternative cover system instead of the traditional clay cap they were considering for a paper waste landfill in Mississippi. This initial inquiry led to a broader collaboration as part of a facility closure project, with goals of achieving long-term stabilization, meeting regulatory requirements, and reducing capital costs. While the starting point was an evaluation of an alternative cover, our expertise ultimately guided us toward a slightly different solution—one that is explained in more detail later in this blog post. By applying innovative design principles and leveraging locally available materials, we delivered a Mississippi Department of Environmental Quality (MDEQ)-approved approach that saved the client several million dollars in closure costs compared to conventional landfill capping methods.
Background
Challenges of Paper Waste Landfills
Paper waste landfills can present unique challenges due to the nature of the material they contain. Unlike municipal solid waste, paper waste has a relatively high pH, decomposes at a slower rate, can retain significant moisture, and often generates leachate with high organic content. However, the hydraulic conductivity of the waste is very low and is comparable to that of a compacted clay.
Clay Caps vs Alternative Covers
Clay caps are a traditional component for landfill closure, intended to stabilize the waste and to block rainfall from percolating into the waste, thereby reducing the production of leachate. Regulatory standards require these covers to limit infiltration to protect groundwater and surface water, however, clay caps often degrade over time allowing water to percolate into the waste. They are also costly to build because of material, transportation, and other construction costs.
Our client wanted to evaluate the feasibility of constructing an Alternative Landfill Cover. Alternative Landfill Covers (alternative to compacted clay) typically use uncompacted soil and cover vegetation to manage water flux through evapotranspiration (they are also called Evapotranspiration or ET Covers). Acting like a sponge, the monolithic soil cover stores percolating rainfall where it can then be consumed by vegetation before it percolates beyond the reach of the cover vegetation root system. The net water flux is upward, preventing water from reaching the waste. Success depends on proper soil thickness and plant selection to match seasonal moisture patterns and vegetation dormancy. The physical properties of the waste at this site made the water flux component of the cover less important than stabilization and sediment control.
The Mississippi Paper Waste Project
Feasibility Assessment and Agronomic Field Study
Our involvement in the project began with a client request to evaluate how an evapotranspiration (ET) or another alternative cover system might be implemented for the closure of a paper waste landfill in Mississippi. Specifically, they were interested in a concept aligned with ET cover principles. However, as we began our research and field assessments, a different picture emerged.
Through site observations, it became clear that the paper waste itself was already exhibiting early signs of natural volunteer revegetation. Grasses were volunteering in several areas of the uncapped landfill, triggering natural pH buffering and initiating soil formation. Our focus shifted from evaluation of an ET cover feasibility to the possibility of establishing vegetation directly into the paper waste to promote gradual transformation of the waste material into viable soil. The new objective became an assessment of the feasibility of a biologically driven revegetation strategy.
To evaluate the feasibility of this approach, we conducted a comprehensive agronomic study. We established a structured grid of test plots to assess the performance of various treatment combinations. Initial trials were designed to identify grass species capable of thriving in the site’s high-pH environment, using both broadcast seeding and targeted planting. Once the most suitable species were identified, the study expanded to include larger test plots with different cover configurations: seeding directly into untreated waste, applying 6 or 12 inches of topsoil, and using targeted combinations of organic and chemical amendments.
The resulting data allowed us to make a science-based recommendation that was both practical and cost-effective. We advised the client to till gypsum, sulfate of potash, and elemental sulfur into the surface of the waste, followed by the placement of 6 to 12 inches of uncompacted topsoil and hydroseeding with a mix of selected grasses. This approach not only stabilized the landfill surface but also aligned with the natural processes already underway, eliminating the need for a more complex and costly ET cover system.
The Economic and Environmental Impact
With our client’s commitment to implement an unconventional yet evidence-based approach, the project delivered substantial financial and environmental benefits:
Significant Cost Savings: Avoiding importation and compaction of clay led to dramatic reductions in capital expenses.
MDEQ Approval: The solution was fully approved by the Mississippi Department of Environmental Quality, confirming its regulatory compliance and environmental performance.
Long-Term Sustainability: The vegetative cover and amended waste surface proved resilient to weathering and erosion.
Transformation of Waste into Soil: The presence of active vegetation and associated micro-organisms, arthropods, and natural soil-forming processes, will gradually transform the shallow waste into viable soil.
Enhanced Site Aesthetics and Function: The site transitioned from a barren, high-pH waste surface to a vegetated landscape, improving both ecological function and visual appearance.
A Model for Future Landfill Closures
This project in Mississippi exemplifies how flexibility, professional integrity, and risk-informed design can lead to superior economic and environmental outcomes. Initially tasked with evaluating the feasibility of an evapotranspiration (ET) cover system, our team remained open to where the science would lead us and recognized that percolation was not a significant concern. This allowed us to pivot from the original scope and recommend a more effective, lower-cost solution.
By embracing a site-specific, nature-based approach, we eliminated the need for a traditional clay cap and delivered a Mississippi Department of Environmental Quality (MDEQ)-approved closure strategy that met regulatory goals while substantially reducing costs. The project underscores our commitment to adaptive, sustainable design in landfill management—prioritizing practical outcomes over prescriptive solutions.
