Introduction:
Covering disposed waste in municipal solid waste (MSW) landfills is crucial to control odors, vectors, fires, litter, and scavenging. Traditionally, landfill operators have used a minimum of six inches of soil as daily cover. However, this method has drawbacks such as using up valuable airspace and impeding the movement of landfill gas and leachate. Fortunately, federal and state regulations allow for the use of alternative daily covers (ADCs) made of various materials. Let’s explore the benefits of using ADCs in landfills.
Waste-Derived ADCs
Waste-derived ADCs offer several advantages, including the potential to generate revenue for landfill facilities. These materials can be used as a substitute for soil cover, either on their own or blended with soil. Some common waste-derived ADCs include:
Ash: Obtained from the incineration of materials, like coal combustion. Ash can be used as-is or blended with soil or sludge.
Auto shredder fluff: Resulting from the shredding of automobiles, this material is less dense than soil and is typically blended with soil before use.
C&D waste fines: Leftover soil-like material after processing construction and demolition waste for recycling.
Composted materials: Consisting of decomposed wood, green waste, or other solid waste, these ADCs can be an attractive option if they don’t generate revenue otherwise.
Green waste: Readily available at most landfills, this material, ground or unground, can replace soil and even substitute gravel for maintaining roads and tipping pads.
Contaminated sediment and soil: This material can be an excellent ADC that allows landfill operators to receive payment for taking it. However, potential run-off concerns should be considered.
Sludges: Often having no other use, sludges can be used as ADCs. They can serve as a revenue source and increase waste density due to their high density and moisture content. Some sludges can also enhance soil nutrients and minimize erosion on landfill covers.
Shredded tires: Using shredded tires as ADCs allows for tire disposal without using additional airspace.
Non-Waste Derived ADCs
Non-waste derived ADCs have the advantage of using no airspace, but they can be more costly. They can be categorized as spray-ons and geosynthetic covers (tarps):
Spray-ons: Divided into foams and slurries, spray-on ADCs involve mixing substances like soap, starches, or resins with water. These materials form a thin layer over the waste and can include odor control agents. While spray-ons do not need to be removed, the additional cost of the material and specialized equipment is a disadvantage.
Geosynthetic covers (tarps): Large pieces of plastic or fabric material deployed over the landfill, tarps offer minimal cost, speed of deployment and removal, and reusability. However, they can be challenging to deploy, prone to tearing, and expose employees to waste.
Advantages of ADCs
The main advantage of ADCs is the conservation of valuable landfill airspace. By increasing the amount of waste that can be placed in a landfill, ADCs have a significant impact on the facility’s profitability. Additionally, using non-waste derived ADCs can improve landfill gas and leachate management by reducing soil barriers and allowing their free movement within the waste. This can lead to increased revenue from captured landfill gas and minimize leachate seeps.
ADCs can also serve as an additional source of revenue for landfills, reducing operating costs by replacing the need for hauling on-site soil or procuring soil from off-site. However, landfill managers should be cautious about prioritizing short-term cash flow over long-term profitability.
In conclusion, ADCs offer various benefits to landfill operators, including airspace conservation, improved waste management, and potential revenue generation. By exploring the options of waste-derived and non-waste derived ADCs, landfills can optimize their operations while meeting regulatory requirements.
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