Considering the Alternative

Landfills can enhance life expectancy and financial outlook with alternative daily cover.

James Loneman

The economic side of landfill management isn’t easy. Essentially there is a “product” being sold—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.

The problem is that space is not renewable. More airspace can be “manufactured” by building more cells or new locations, but these options aren’t always viable due to expense, regulations or other factors. Even with new areas, every cell and landfill will fill up eventually.

The only solution is making 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.

In many cases, landfills lose airspace by using dirt as daily cover, as opposed to employing alternative daily cover (ADC) options that take up much less space than the soil layer required to cap a landfill’s daily refuse intake. ADC not only preserves valuable airspace, but brings financial benefits through lower operating costs. The economic impact of ADC is a big reason why companies have invested in producing ADC materials, and why its use is gaining momentum.

The Dirt on Dirt

Another way to look at a landfill’s basic economic situation is as a balancing act that can’t really be balanced. Even if a landfill implemented guidelines to curb its intake to extend its life expectancy, this would subsequently diminish income. Landfills will never be able to have it both ways. But where landfills can achieve more balance and space efficiency is in the application of daily cover.

Federal and state regulations require that landfills cover their solid waste at the end of each day with six inches of dirt, if that’s what is being used as cover material. Four inches isn’t enough. Two inches? Not even close. A half-foot thick layer of soil is required to provide enough of a seal to hold trash in place and contain noxious odors.

This six-inch thickness represents a gross imbalance in the way space is being used on the landfill, particularly since many landfills will actually wind up spreading more tons of dirt per day than they will bring in trash. So why would a landfill continue to use up so much valuable space—in some cases more than 50-percent—on capping material alone? Even if the discrepancy is less drastic, say 80 percent trash and 20 percent dirt, there are more efficient ADC alternatives that can further optimize airspace usage.

One popular type of ADC is a mulch slurry product, which is typically applied through a spray-on process using a HydroSeeder, a machine that mixes slurries and applies them over broad areas, or a similar machine. The primary reason this method has taken off is that it is capable of achieving adequate daily cover with a layer of material only a quarter-inch thick, consuming only a fraction of the airspace occupied by a six-inch layer of topsoil. A few quick example calculations demonstrate just how valuable this space savings can be. An example landfill airspace analysis is:

Waste Intake Rate

300 tons per day

Tipping Fee

$40.00 per ton

Compact Density (on average)

1,200 pounds per cubic yard

Dirt used for Daily Cover

400 cubic yards per day

Days of Operation

5 days per week / 250 days per year

This data can be used to calculate the dollar value per cubic yard of airspace.

  • Calculate daily revenue. 300 tons x $40 = $12,000 per day.

  • Calculate the intake rate in pounds per day. 300 tons x 2,000 pounds = 600,000 pounds per day.

  • Use 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.

  • Next, find the actual dollar value of landfill space. $12,000 divided by 500 cubic yards per day = $24 per cubic yard.

Now that the value of landfill space is known, one can apply this dollar amount to determine how much potential revenue-earning space is being filled by nothing more than dirt.

  • Calculate daily lost revenue using the amount of dirt for daily cover and the value of the space that dirt occupies. 400 cubic yards per day x $24.00 = $9,600.

  • Calculate annual lost revenue. $9,600 x 250 days per year = $2,400,000.

Naturally, a small portion of the $2.4 million that would be lost under a six-inch dirt layer scenario would still be lost even if ADC were used. But considering a 24:1 soil to ADC space consumption ratio, millions of dollars could still be saved each year with ADC.

Granted, the dollar value assigned to space savings doesn’t literally translate into dollars in a landfill’s pocket right away. But it does increase the number of years the site will remain open by approximately 25-percent on average. This effectively allows profit to be made for a longer period on the same site while other landfills find themselves investing in new cell construction or preparation of new locations.

Many municipal landfills may be more focused on remaining open longer and even long-term employee job security than they are on profit gains, but the same principles apply. Public landfill or private, wasted space is wasted space—regardless of whether that space is viewed as lost money, lost years on a site or a combination of both.

ADC Efficiency

So just how does ADC accomplish with a quarter-inch of material what it takes dirt six inches to do? The biggest factor is how the two materials are actually applied. Moving dirt with trucks and bulldozers is an inexact science to say the least, so more material is understandably required to ensure adequate coverage. Applying spray-on mulch could almost be described as “painting” the working face of a landfill. Every nook and cranny can be covered with a precise layer of mulch with no need to over-apply. The material then sets and cures, sealing in refuse and providing the necessary daily cover on the landfill to prevent erosion, control disease vectors and reduce fire hazards.

Once on the ground, the basic properties of the material make it effective from an environmental standpoint as well. Some ADC contains microbes that help break down organic matter. Landfills can also introduce a variety of additives to the mulch slurry as it’s mixed, such as odor control products or repellants to keep birds and other landfill pests away from the surface. Another common “green-friendly” component of ADC material is newspaper waste and recycled magazine print, meaning some of what’s being used to cover the trash has been repurposed so as not to wind up as general landfill waste in the first place. Using ADC, a landfill can essentially get much more with much less.

Lowered Operating Costs

The dirt versus ADC comparison isn’t all about space. Other considerations involve the labor and machinery needed to apply daily cover. In the case of dirt, the process takes all day and requires a lot of equipment. Excavators dig up the dirt. Articulating dump trucks spend several hours hauling a sufficient amount of soil to the landfill’s working face. Finally, bulldozers spread the dirt at the end of the day. Compare this lengthy procedure to a spray-on mulch ADC application where a HydroSeeder is the only piece of equipment needed to apply daily cover. Fewer personnel are needed to do the job. Instead of an all-day affair, the process takes just an hour to an hour-and-a-half to complete.

Landfills using ADC will still have a need for excavators, trucks and dozers, but by eliminating the everyday dirt-moving project, landfills can reduce the required number of these machines. The smaller capital investment for heavy equipment saves money up front, while additional savings come in the form of reduced equipment maintenance costs. By running fewer machines, these landfills subsequently burn far fewer gallons of diesel fuel per day. Even with a modest decrease of 20 gallons per day over 250 days a year with a diesel price of $4 per gallon, a landfill could save $20,000 in fuel each year.

Added cost can also be incurred by landfills that must buy and ship in dirt from outside their premises. ADC does present a similar scenario, as landfills will have to pay for the material itself. Generally a spray-on mulch product costs a few cents per square foot of coverage. However, this cost is quickly minimized by fuel savings alone, which is usually more than enough to offset the cost of ADC material. Again, this doesn’t even take into account the far more substantial savings in added airspace.

When using ADC, landfills that no longer require as many heavy equipment operators can choose to reduce their workforce as another cost-cutting measure. But because landfills must comply with so many government regulations, many landfills that switch to ADC will instead repurpose employees for other necessary daily tasks rather than letting workers go. In either case, the result is greater operating efficiency.

Doing A Little Of Everything

Some may look at ADC and only see yet another machine they must purchase to apply it—a HydroSeeder. Many landfills find it difficult to justify another capital investment on a site already loaded with machinery that has seemingly gotten the job done for years. This view clearly is missing the potential for space savings and reduced operating costs, but furthermore, it looks past a HydroSeeder’s versatility and wide range of capabilities on the landfill.

Rather than only using a HydroSeeder for application of ADC at the end of the day, a landfill can keep a tank of material mixed up throughout particularly windy days and spray it on as needed to prevent litter from blowing across the site. Composting facilities can make use of the HydroSeeder for odor control during the funky breakdown stages of green waste decomposition. The machine even simply can be used as a truck for carrying water around a site and putting out small fires.

The HydroSeeder can also make use of a landfill’s daily collection of leachate. Rather than going through a special storage process or paying to have this contaminated water shipped elsewhere, landfills can re-use hundreds or even thousands of gallons of wastewater per day as a carrier for the spray-on mulch cover. Even latex paint can be recycled in a HydroSeeder, as this paint can be added to the mix as a tacking agent for ADC as it is applied.

Another use for the HydroSeeder is obvious—hydroseeding. An average landfill must re-vegetate 8 to 12 acres a year. This job is often subbed out, but can be performed in-house with a HydroSeeder during operating hours before it’s time to tend to daily cover at day’s end.

Gaining Acceptance

Ultimately, 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 won’t be long before ADC is no longer regarded as an “alternative,” but simply the most cost-effective daily cover method in the landfill business.

James Loneman is territory manager for FINN Corporation (Fairfield, OH). He can be reached at (800) 543-7166 or via e-mail at [email protected]