Daily cover, although it is necessary, is not an exciting issue, says Milton Knight, president and CEO of New Waste Concepts Inc. Alternative Daily Cover plays a critical role at MSW landfills, helping to prevent fire, escaping odor, blowing litter, scavenging, and vectors. Additionally, ADC saves space; he calculates between 17% and 20% of the volume created, which equates to significant savings as high as $300,000–600,000 in air space annually for sites that take in 600 tons a day.
Historically, daily covering involved a dozer or crawler placing a thin layer of compressed soil on top of the exposed waste, explains Brian Fraser, vice president of Layfield Geosynthetics, a geomembrane manufacturer and fabricator. While soil covers are still used, they can reduce the capacity and operating life of the landfill over time.
Over recent decades, ADCs began replacing soil, often prompted by spatial or economic concerns. For example, the cost of application, wear and tear on the application equipment, fuel, maintenance, labor, and associated costs of a tow vehicle are roughly one-third when an ADC replaces soil.
History by legislation
The impetus to add some form of ADC came in 1993 when the Environmental Protection Agency issued federal regulations and published a document outlining the use of appropriate ADCs for landfills. However, Knight says, the Superfund Act (Comprehensive Environmental Response, Compensation and Liability Act of 1980), which focused on investigation and cleanup of sites contaminated with hazardous substances, and the Resource Conservation and Recovery Act of 1976, with amendments in 1984 focusing on waste minimization and phasing out land disposal of hazardous waste, provided the “backbone” to force the states to adopt legislation mirroring the federal mandate. Congress also gave the EPA power to develop regulations and rules for the disposal of hazardous and solid waste in these acts.
“Effectively,” Knight explains, “the federal government established a timeline for the states to adopt mirror legislation to accomplish the same tasks and to make sure counties, municipalities, and private industry were all focused on accomplishing the same tasks. Remember, at the time of adoption of this legislation by Congress, the USA had nearly10,000 landfills—some of which would have been known as dumps. Dumps were often a ditch excavated and covered over with dirt. Contaminants reached groundwater, and gas collection systems were non-existent.”
EPA’s authority, and the states’ agency authority provided cradle-to-grave jurisdiction over hazardous waste, Knight continues, with enforcement through criminal judicial actions. “The EPA made provisions to help lower the cost of disposal and encapsulation, which were aimed at being a way to counteract the rising cost of building a cubic yard of space in a landfill.” One of those cost-reduction provisions the states could adopt were alternatives to 6 inches of daily soil cover.
Joel Lanz, president of LSC Environmental Products, LLC, says that as the implementation of the new RCRA Subtitle D Regulations began to pick up steam, daily sanitary landfill operations changed dramatically—and “clearly for the better.” Small mom-and-pop open “dumps” were quickly closed, he says, as secure engineered landfills became the norm, primarily driven by larger, well-funded waste companies that were singularly committed to protecting the environment for the long term.
Another factor that played an important role in the development of ADCs is that the more populated states had to close or develop quick closure plans for landfills that no longer complied with the state-adopted regulation. There was panic that there would be no space to deposit waste due to the accelerated closure of landfills and the inability of new landfills to meet state and federal standards and get permitted. “The landfills that were given a limited life and any new landfills did not want to fill up the space they built with soil,” Knight says.
Thanks to the new Subtitle D Regulations, daily and intermediate cover standards were implemented to protect the public and the environment from wind-blown litter, odors, fire, vectors, and scavenging. “While the cover regulations, which require 6 to 18 inches of soil, did a good job addressing these concerns, it became clear fairly quickly that perfectly clean cover soil was consuming a valuable environmental resource,” namely, landfill airspace, Lanz says.
This realization was the genesis of the development of zero-volume cover products. A handful of early innovators began to drive change in the regulations one landfill at a time by bringing ADCs to the market. Lanz says, “ADCs can easily extend a landfill’s life by 15-20% and result in millions of dollars of additional tipping fees for landfill operators.”
“Soil used as daily cover gave them no return on their initial investment in the hole in the ground that was to be filled up with either hazardous waste or household solid waste. The benefits of saving 20% of the space in the landfill used up for daily cover was ‘clear,’” Knight concludes.
Technology development
The cost of constructing landfills, the difficulty of permitting new sites, and increased regulatory scrutiny make landfill airspace more valuable. This prompted landfill operators to look for ways to conserve space and improve efficiency without compromising public health.
Since ADCs were developed, they have been grouped in one of three basic categories: tarps, spray-applied, or revenue-generating materials. From Lanz’s perspective, most of them haven’t changed much over the years, although he has witnessed greater application and formulation flexibility.
Early products consisted of materials such as ash, shredded automobile components, sludge, shredded tires, construction/demolition waste, and green waste, lists J.D. Mohr, business development executive for Enviro Cover System. Many of these generated revenues for the landfill; however, not all sites had access to these inbound waste streams.
Mohr says ADC technology has been developed with the following in mind:
- The effect of ADC on landfill capacity
- Soil requirements
- Application and performance considerations
- Climatic conditions
- Leachate migration (rainwater infiltration)
- Gas movement and containment (odor)
- Operational costs
Membrane technology
Each of the various methods and products has also developed along the way. Numerous geosynthetic materials have been used for daily cover over the past 30 years, including both woven and non-woven geotextile materials, tarpaulin-grade products, and thinner gauge reinforced and non-reinforced geomembranes. Applied films are generally deployed by a machine that unrolls them like plastic wrap.
Geomembrane has typically offered long-term odor control for areas that won't receive waste for several years. Knight says that while effective, this interim method is expensive and requires the removal of material that is going to be added to the face.
“There is often some confusion between the use and application of an interim landfill cover and an alternative daily landfill cover,” Fraser points out. “Interim covers are typically produced from lightweight, high-strength reinforced polyethylene geomembrane materials.” Fabricated in large custom panels, they are normally installed over the exposed waste until the landfill operator is ready to place a permanent cap to close a section. Interim covers are normally designed to be in place for 1–3 years and help prevent leaching from rain, control odors, and prevent blowing litter.
Membranes are used for daily cover today, Fraser says, thanks to improved polymeric resins, processing additives, and manufacturing capabilities that create better products. “These include materials with stronger mechanical strength and endurance properties.” Some of this newer generation of reinforced polyethylene geomembranes feature improved UV properties.
Similarly, the Enviro Cover System, which consists of Enviro Cover film and deployer marketed by EPI Environmental Products, Inc., is a non-reusable geosynthetic film that has been engineered with good tear strength, puncture resistance, and elongation characteristics enabling it to stretch over uneven surfaces. Mohr points out its impermeable nature, which effectively controls vapors, gases, and odor emissions, sheds rainwater and minimizes water infiltration. It can be deployed rapidly, even in adverse weather, and does not require removal.
Tarps
Tarps are still used extensively, perhaps because of the low cost (less than a penny per square foot). Improvements over the years include providing fire retardancy in the fabric, sewing steel cables along the edges to eliminate the need for putting weights on the tarps, and the introduction of specialized machines to apply them. In the early days, dozers had to drag them on and off, Knight recalls.
There remain some downsides, Knight continues: difficulty in applying and removing them in inclement weather, added labor to remove and replace daily, sizes that don’t match the space and require “tucking in” at the sides, the capture of rain in pockets on top, difficulty working with frozen tarps or tarps on steep slopes, and trapping odors and gases.
Tarpomatic Inc. has addressed many of these issues. They originally operated using a PTO from the host machine—typically a dozer—because they didn’t have their own engine, explains Marlon Yarborough, sales and marketing manager. Today, they are self-contained units with a 26.5 hp Cat diesel Tier IV engine that provides power to spool up the tarp. “The weight of the tarp with hardware for wind can reach 3,300 pounds,” he acknowledges. “The larger engine gives it the torque it needs to wrap traps quickly and safely. It’s easier to maneuver around the face, Yarborough continues.
They went through variations of polyethylene fabric to find one that is strong, withstands pulling, and is water- and flame-resistant to suppress fire underneath by keeping oxygen out. Other advantages include air space savings and speed, which reduces man-hours, machine hours, and fuel usage.
Tarpomatic updated its Gen 4 in 2020 for increased safety. Interchangeable tarp spools are controlled hydraulically by remote control. “We added a camera to assist in aligning the tarp,” Yarborough adds. Additional labor savings come from making the job a one-person task. “No one is needed on the ground; it’s all controlled in the cab of the host machine.”
Spray-On
Following tarps, Knight says, came a film system. Creating a film over the soil minimizes the escape of VOCs. When the City of New York sanitation division was being sued because it was thought that barges moving garbage from Manhattan to Freshkills landfill in New Jersey were the cause of blown litter on the New Jersey public beaches, New Waste Concepts offered a formulation of chemicals that would adhere to plastic, which they had developed for a hazardous landfill in Michigan and a landfill in Ohio. ConCover concentrates fiber and polymers in a mix that temporarily hardens on the surface but creates a film, helping minimize escaping odors, blowing litter, and the intrusion of bugs and birds. It was also recognized as an important way to fight fires.
Posi-shell was another pioneer in landfill cover materials. The product initially used the combination of CKD, a cement manufacturing byproduct, along with a minimal amount of fiber to create a cementitious material that hardened like cement. “Our earliest manifestation of Posi-Shell established the standard of one-pass complete coverage, but was admittedly limited in its formulation or application flexibility,” Lanz confesses.
LSC uses environmentally friendly natural materials and recycled products. “Some of our latest innovations include bulk delivery formats, equipment upgrades, pelletized products, and products targeting natural soil amendments,” Lanz lists. He says the most recent changes from LSC have been to create both short-term and long-term versions of their landfill cover products. Their line now includes waste cover products (daily and intermediate); remediation cover solutions; odor, erosion, and dust control products; and hydroseeding/revegetation products, all of which can be applied with the same piece of equipment.
Cost-saving measures: Better than dirt
Knight considers cost savings the biggest challenge for the future of the industry. “For non-municipal or county landfills that are sales- and contract-driven, controlling costs and keeping the daily cover cost at the landfill as low as possible is of greater focus.”
Some ADC methods and products can help cut expenses at the landfill. Revenue Generating Cover materials bring in a lower than normal daily tipping fee but can save the landfill money on using other forms of cover.
Hydroseeding typically costs less than other forms of ADC, but Knight attributes that to the limited polymer content as well as the quality of the polymer used. However, he admits, application of hydroseeding material and grass seed can be done in half the time and reduces labor needs. Furthermore, “if you can use the same machine you have for daily cover, you have reduced the capital cost of the equipment.”
Today’s ADCs are often more economical than soil. “The ADC can typically be deployed much faster and performs better,” Fraser observes, adding that they also require less carbon footprint. “Many of these lightweight, high-strength daily covers can be cleaned and recycled at the end of their use.”
Mohr concurs, pointing out that “Enviro Cover is less expensive to procure and place than six inches of soil. When airspace savings is part of the equation, the cost savings are even more dramatic.” His product can be applied with one machine, compared with soil’s need for equipment to load it, trucks to transport it, and equipment to spread it.
Soil can also generate issues in the landfill by creating impermeable layers that prevent leachate and landfill gas from flowing effectively to their respective collection systems, Lanz points out. “When this happens, the leachate travels horizontally, causing ‘breakouts’ on side slopes of the landfill, which allows leachate to comingle with clean stormwater, resulting in violations. Posi-Shell does not have this issue because it easily crumbles with the placement of the next day’s trash.”
The dirt on dirt
However, Knight says, ADCs have not been as widely adopted as he’d like, often because of price and sometimes due to quality. “Landfills in the states of Washington, Tennessee, and Kentucky have made decisions to go back to a soil cover because they feel the quality of the coverage of the material they purchased did not do the job.”
For some, the benefits of ADCs are too far in the future to envision. There may be more immediate needs to address. “The value of space savings is not realized in lower cost, but in the life of the existing cell. Instead of needing to build and capitalize new cells in five years, you might delay the construction for six or seven years,” Knight explains.
There is no perfect daily cover, Knight realizes. Weather takes a toll on all coverings, blowing litter can occur during dumping and spreading, odor and leachate are ongoing battles. But, he maintains, using ADCs will save 17–20% in volume compared with soil.
