The economic side of landfill management isn't easy. Essentially, the product being sold is airspace. Revenue is generated through tipping fees charged per ton. The more garbage taken in, the more income earned. From that perspective, selling space is good. However, as more garbage is taken in, less space remains, and the landfill's lifespan decreases.
That space is not renewable. More airspace can be “manufactured” by building more cells or adding locations, but these options aren't always viable due to expense, regulations or other factors. And no matter how much land is added, every landfill will fill up eventually.
Thus, landfills must make the most of available airspace to stay open as long as possible. But while most landfill operators realize the importance of common space-saving measures, such as compaction, many fail to recognize that trash isn't the only thing filling up landfills.
Landfills commonly sacrifice airspace by using dirt as daily cover. Alternative daily cover (ADC) options take up much less space than the soil layer required to cap a landfill's daily refuse intake. ADC solutions include tarps, foams and certain types of repurposed waste material such as shredded tires or construction and demolition debris. ADC not only preserves valuable airspace, but also can lower operating costs.
The Dirt on Dirt
Federal and state regulations require that landfills cover waste daily with six inches of dirt — if that's the cover material of choice — to hold trash and contain noxious odors. This thickness represents a gross imbalance in space utilization, particularly in landfills that spread more tons of dirt than they bring in trash. Why use up valuable space — in some cases more than 50 percent — on capping material? Even if the discrepancy is less drastic (80 percent trash to 20 percent dirt), more efficient ADC alternatives can optimize airspace usage.
One ADC is a mulch slurry product, applied through a spray-on process using a HydroSeeder or similar machine. This method can achieve adequate daily cover with a quarter-inch-thick material layer, consuming only a fraction of the airspace occupied by a six-inch layer of topsoil. A few example calculations demonstrate the value of this space savings.
Example Landfill Airspace Analysis
- Waste Intake Rate — 300 tons/day
- Tipping Fee — $40.00/ton
- Compact Density (on average) — 1,200 pounds/cubic yard
- Dirt used for Daily Cover — 400 cubic yards/day
- Days of Operation — 5 days/week, 250 days/year
This data is used to calculate the dollar value per cubic yard of airspace.
Calculate daily revenue. 300 tons × $40.00 = $12,000 per day.
Calculate the intake rate per day. 300 tons × 2,000 pounds = 600,000 pounds per day.
Use the intake rate and compact density to determine the daily, in-place compacted volume. 600,000 pounds divided by 1,200 pounds/cubic yard = 500 cubic yards per day.
Find the dollar value of landfill space. $12,000 divided by 500 cubic yards per day = $24.00 per cubic yard.
One can apply the value to determine how much potential revenue-earning space is filled by dirt.
Calculate daily lost revenue using the amount of dirt and the value of the space it occupies. 400 cubic yards per day × $24.00 = $9,600.
Calculate annual lost revenue. $9,600 × 250 days per year = $2,400,000.
A fraction of the $2.4 million lost with dirt would still be lost using ADC. But considering a 24:1 soil to ADC space consumption ratio, millions of dollars could still be saved each year. Granted, the value assigned to space savings doesn't translate into immediate dollars, but it does increase landfill lifespan by 25 percent on average. This allows profit to be made for a longer period on the same site while other landfills must invest in new cells or locations.
Municipal landfills may be more focused on staying open longer and employee job security than on profit gains, but the same principles apply. Be it a public landfill or private, wasted space is wasted space, regardless of whether it means lost money, lost years or a combination of both.
How do ADCs accomplish with a quarter-inch of material what it takes dirt six inches to do? The biggest factor is material application. Moving dirt with bulldozers is an inexact science, so more material is required to ensure adequate coverage.
Applying spray-on mulch is like painting the working face of a landfill. Every nook and cranny can be covered with a precise layer of mulch without over-applying. The material sets and cures, sealing in refuse and providing the necessary daily cover to prevent erosion, control disease vectors and reduce fire hazards.
The material's properties also make it environmentally effective. Some ADCs contain microbes that help break down organic matter. Landfills can also introduce additives to the mulch slurry, such as odor control products or pest repellants.
Lowered Operating Costs
The dirt versus ADC comparison isn't all about space. Labor and machinery are additional considerations. Using dirt takes all day and requires a lot of equipment. Excavators dig up dirt, dump trucks spend hours hauling it to the landfill's working face, and bulldozers spread the soil at day's end. Compare this to a spray-on mulch ADC application that only requires a HydroSeeder. Fewer personnel are needed. And instead of an all-day affair, the process takes just an hour to an hour-and-a-half.
Landfills using ADC will still need excavators, trucks and dozers, but by eliminating the daily earthworks, less equipment is needed overall. The smaller heavy equipment investment saves money up front, while additional savings come from reduced equipment maintenance costs. By running fewer machines, these landfills burn less fuel. Even a modest decrease of 20 gallons per day over 250 days a year with a diesel price of $3.00 per gallon could save $15,000 annually.
Added cost is incurred by landfills that buy and ship in dirt from outside their premises. Spray-on mulch ADC products also cost money — a few cents per square foot. However, this cost is quickly offset by fuel savings. And there's the more substantial savings gleaned from added airspace.
Using ADC can also reduce the need for heavy equipment operators, cutting labor costs. But because landfills must comply with many government regulations, many landfills that switch to ADC will instead repurpose employees for other tasks. Either way, the result is greater operating efficiency.
Economics provide the most compelling argument for ADC. More airspace. Lower costs. Higher profits. Increased landfill life. Given appropriate education and more first-hand experience with its benefits, it may not be long before alternative daily cover is no longer regarded as an “alternative,” but simply the most cost-effective daily cover method in the landfill business.