Talk about a mouse taking down a lion!  When it comes to square footage, it takes only an area of 4 to 6 square centimeters to take down acres of landfill, especially when that small area is in someone’s nose.

By Diane Gow McDilda

Each human nostril is lined with olfactory membranes, the first step in odor identification. Once an odor has been detected by your nose, it’s off to be identified through a series of membranes and receptors that ultimately send a message to your brain. With the nose’s potential for identifying over 5,000 smells, it’s doubtful that any odor emanating from your landfill will go unrecognized.

So what’s the stink and where is it coming from? Odors are produced during bacterial decomposition of waste. The higher the organic content of your wastestream, the more likely odors will be an issue. This is of particular concern at landfills where sludge or foodwaste makes up a considerable component of the wastestream. The majority of gas produced during decomposition is composed of methane and CO₂, both of which are odorless. Unfortunately, there are a few other components, such as ammonia, sulfides, and some nonmethane organic compounds that even in small amounts can trigger a negative reaction, like a phone call or complaint, by neighbors or passersby.

In the case of construction-and-demolition debris, the amount of hydrogen sulfide produced by decomposing gypsum in drywall is significant. The rotten-egg smell irritates neighbors so much that regulators are looking at drywall disposal practices more closely.

Before smells like these bring on a stressful regulatory inspection, costly violation, or—even worse—a facility shutdown, owners and operators need to evaluate their operations. For the most part, odor can be controlled through proper application of cover material, and that’s no secret to the regulators.

It’s in the Rule
To protect not only human health but also the environment, federal regulators aim to promote a sense of stewardship of solid waste facilities. Landfills already get enough of a bad rap, and causing a neighborhood stink isn’t going to win them any friends. The best practice for controlling odor at a solid waste facility is to keep a lid on it and make sure that appropriate cover is applied as often as needed. That’s why federal regulations require owners or operators of Class I, or municipal-waste, landfills to cover the working face at the end of each day, or more frequently if need be, with 6 inches of compacted soil. Class III waste requires weekly cover, but construction-and-demolition debris has historically, for right or wrong, been considered less of a concern, thereby eliminating the need to cover it at all.

Central Fiber Corp.'s Topcoat is applied using a hydroseeder, the same equipment commonly used to spray mixtures of seed, water, and fertilizer.

Using dirt for cover seemed like a good idea. Dirt provides a good barrier, entombing the waste and the odors it produces. Because dirt was routinely excavated as part of landfill construction, it was usually stockpiled and easily accessible onsite. But dirt has become a more costly cover material in more ways than one. These days it’s not always so accessible, it’s expensive to move, and it takes up a lot of valuable space. It’s estimated that 6 inches of daily cover can use up to 20% of the total landfill volume. That’s dirt that was most likely costly to obtain and move around—dirt that didn’t earn a tipping fee. Apart from the immediate cost, using dirt as cover material has more long-range impacts. Since dirt takes up space, it eats into the life of the landfill, reducing the lifespan by years over the long haul. Real estate is expensive, and with the complications in siting a new landfill, owners are aggressively looking to maximize the volume of waste placed within the landfill footprint.

Soil may have its advantages, but it isn’t the only option when it comes to cover material. Federal regulations allow for alternative daily covers, or ADCs, as long as they meet the same criteria, such as keeping blown litter at a minimum, reducing the potential for fires, making the landfill less welcoming to scavenging birds and such disease vectors as rodents and flies, and, of course, eliminating odor. As part of the approval process, permittees are required to submit a collection of information including material safety data sheets and flammability characteristics. And analyses, such as the toxicity leaching procedure or the synthetic leaching procedure, may be necessary to ensure that the proposed ADC doesn’t adversely impact the environment. When it comes to regulatory approval, ADCs have a lot to prove.

Beyond the generic criteria that must be met, there are site-specific criteria too. Landfill slope, wind velocity, and waste type must be taken into account when determining the most effective ADC. After an ADC is found that looks to meet the expectations of landfill operation, it’s up to the landfill owners to gain approval from state and local regulators. Some ADCs have a general acceptance in most, if not all, of the states, but other materials deserve a look.

Tarps—They’re Not Just For Camping
Tarps come in a variety of materials and thicknesses. Lighter in weight than the canvas tarps of yesteryear, polyethylene tarps have shown themselves to be more durable and longer lasting. Often tarps are coated with both water- and fire-resistant sealants, a must when being used at a landfill.

The automatic tarp machine (ATM) by Tarpomatic is available also with an odor-control unit attached.

While tarps can be deployed and retrieved manually, it’s not a job willingly tackled. Not only is it backbreaking on the person providing the manual labor, it’s hard on the tarp since manual deployment and retrieval causes life-shortening wear and tear on the tarp. It’s much more practical to use an automatic deployment system, such as the Automatic Tarping Machine (ATM) manufactured by the Canton, OH-based Tarpomatic Inc. The ATM attaches to heavy equipment routinely used at landfills, typically fitted to the blade of a dozer. Operators simply drive up and connect to it. The ATM can be used to unroll and retrieve different kinds of tarps of varying lengths. Bill Glick, western regional sales representative with Tarpomatic, explains that the ATM allows tarps to be applied and retrieved via a wireless remote control with one operator and a single piece of equipment.

And when it comes to odor control, Tarpomatic has you covered. Besides the ATM, the company also offers the ATM with odor control, or ATM/OC. Tarpomatic introduced the product at the WASTECON show in 2005 but still considers it relatively new.

“Regarding the odor-control application, we’ve simply added a 55-gallon tank to the ATM, and, via our wireless remote control, odor-control solution is applied from a series of spray nozzles located on the bottom of the ATM frame during the deployment and retrieval processes,” says Glick.

Randall Kippenbrock, executive director of the Santa Fe Solid Waste Management Facility, has used both the ATM and the ATM/OC deployment and retrieval systems. He was happy with both systems but admittedly doesn’t use the odor-control system anymore. Not because he wasn’t satisfied, but because odor at the facility was minimal and the standard ATM system was sufficient. During the time they used the ATM/OC, employees benefited when retrieving the tarps every morning, because they weren’t greeted by that routine garbage smell.

“It had a certain smell; I think it was cherry,” recalls Kippenbrock. “The guys could smell it every morning when they picked up the tarp.”

While odor may not have been a concern for Kippenbrock, birds were. With the tarp system in place, it’s been bye-bye birdie.

The effort needed to lay out the tarp is minimal. Kippenbrock says that one operator can deploy the tarp within 15 minutes at the end of the day. The tarps are kept in place with cables and chains lining the hems, which Kippenbrock says keeps the tarps down even in winds close to 40 mph.

Tarpomatic's ATMs may be attached to heavy equipment routinely sed at landfills, typically to a dozer blade.

Another manufacturer of tarp deployment systems is Mercer Motor Works, of Mercer, ME. Owner Terry Pitcher explains that the company’s tarp deployment system can be used with just about any kind of tarp, from very lightweight, high-density polyethylene to thicker tarps treated with fire retardant and water repellant. It takes just one operator and one radio-controlled machine to deploy or roll up the tarp. Tarps can be manufactured with pockets so chains can be pulled through to serve as ballast, but a number of Pitcher’s clients use tires to weigh down the cover.

While the benefits of tarps are relatively well-known, one important aspect is the proper application. By using a deployment system that rolls the tarp rather than dragging it, users can avoid punctures and tears, increasing the lifespan of the tarp and making it a cost-effective ADC.

Scott Mangle is administrative supervisor for the Southeastern Chester County Refuse Authority in Pennsylvania. The 80-acre landfill receives approximately 450 tpd and uses a Caterpillar 826 Compactor with the Mercer system to deploy and retrieve the tarps. Mangle is pleased with the ease of use of the system and appreciates that one piece of equipment is not designated solely for hauling dirt around.

“You pull up, lift the blade, and it picks up the tarp machine,” says Mangle. “We’re a small site and don’t have a lot of redundancy in equipment.”

For the sideslopes, it’s a different story. Mangle uses a combination of soil on the sideslopes and tarps on the top of the landfill. Because the soil will eventually be part of the final cover system, it’s not wasted and serves as a barrier for odor. It’s a system that serves him well.

Film—It’s a Wrap
urrent technology allows film to cover waste daily without the effort of retrieval. Films are left in place and additional waste is placed directly on top. One example is Enviro Cover by EPI, which can also be used as bale wrap for packing solid waste into tidy bundles.

The polyethylene film is biodegradable, and degradation is activated as the film is subjected to heat, stress, or sunlight. It’s a given that this process will start when the film is in place as cover material, but the heat generated during waste decomposition is sufficient to keep the degradation going.

Kenneth Lee, waste management advisor for EPI, explains that the degradation rate depends on the site-specific conditions. “The hotter the landfill, the faster it will degrade.”

When it comes to state regulatory acceptance, Lee says that Enviro Cover has been approved in California, Arkansas, and many other states. Approval and use at one California landfill even led to blanket approval across the state.

Specifically designed for odor control, Posi-Shell, from Landfill Service Corp., is made from fiberized cement mortar that works by encasing a neutralizing odor.

Guy Enchelmayer is the executive director for the Craighead County Solid Waste Disposal Authority, in Arkansas, which began using the EPI cover system in 1997, not so much for odor control but for economic reasons. While it still does come down to costs, Enchelmayer is impressed with the performance of the material, especially when compared to soil.

“We can pull a 2-mil piece of plastic over the landfill in 15 minutes,” says Enchelmayer. “It used to take an hour and a half. That gives us an extra hour of operation.”

He explains that previously the landfill was using about 500 cubic yards of soil a day for cover. At a compaction rate of 1,000 pounds per yard and a tipping fee of $26 per ton, changing to Enviro Cover earns the county $6,500 per day in tipping fees. And this revenue doesn’t account for any cost to purchase dirt or the wear and tear to the equipment when hauling and placing.

The county uses a bulldozer already on hand to apply the film in 16-foot-wide rolls. Sand is dropped in 16-foot-wide lines across the film to serve as ballast. All of this is worked via remote controllers in the dozer’s cab, meaning there’s no need for the equipment operator to set foot on the waste, a factor important to Enchelmayer.

Enchelmayer rejects any thought that wind would be an issue in using this lightweight material. Winds at the Arkansas landfill have not impeded application of the cover system. The county does apply the lines of sand ballast more frequently when prompted by heavy winds.

Spray It On
Other players in the ADC arena are spray-on covers. Application usually requires dedicated equipment not part of the routine landfill operations. Generally, the covers go on wet, and then dry to encase the waste.

Rusmar Inc. manufacturers foam that can be sprayed on to blanket waste so that odors can't escape. The cover system consumes no discernible airspace.

Rusmar Inc., of West Chester, PA, manufactures foam that is sprayed on to blanket waste so odors can’t escape. The cover system consumes zero airspace because as waste is placed on top of the foam the air bubbles collapse, eliminating any discernible thickness. The foam can be applied to any type of waste regardless of uniformity and can be sprayed on vertically, even to sides of baled waste. And duration of the foam varies. The thicker the foam is applied, the longer it will last. The foam also comes cinnamon-scented, which helps mask any odors that might escape.

Debbie Perez, district manager for the Indian River Landfill in Vero Beach, FL, uses Rusmar foam for the county’s construction-and-demolition landfill. The landfill is located next to I-95, and the county received complaints from motorists as well as two nearby homeowner associations regarding the appearance and odor. The county is filling in the slopes of a closed, unlined Class-I landfill to provide a larger base for future Class-I waste, so operations are definitely atypical. Filling operations are taking place on 3:1 slopes and around gas vent wells, making cover application challenging.

But it is working. With the daily addition of 6–8 inches of Rusmar, the landfill has eliminated odor and, by using a soil alternative, provided additional volume for future municipal waste as well.

Along with the foam material, Rusmar provides the Pneumatic Foam Unit, specifically manufactured for mixing and applying the foam. When including the cost of the equipment with the costs of the foam, says Rebekah Gormish with Rusmar Inc., the cost is very comparable to that of other ADCs.

Another type of foam is Topcoat, produced by Central Fiber Corp. of Canton, OH. It is applied as slurry using a hydroseeder, the same equipment commonly used to spray seed, water, and fertilizer mixtures on areas needing grass coverage. Unlike Rusmar, the blanket dries to form a hard surface.

Dale Dearborff, sales representative for Central Fiber, says it’s been approved and is widely used in the Midwest and eastern US. The biodegradable material is made from a combination of recycled newspapers and chemical additives. The thickness of the sludge applied varies from site to site, so Central Fiber provides samples for landfill owners and operators to perform their own testing.

Director of solid waste for Larimer County, Co, Stephen Gillette has been using Topcoat since 2001. The change from soil to Topcoat as a cover system was more for savings in airspace than for addressing odor. As a bonus, the county has enjoyed a reduction in bugs and seagulls at the facility.

While wind may affect application of the foam, it doesn’t deter users. The wind blowing at your back allows for easy and even distribution. Wind frequently blows through the Larimer County facility at 30 mph or more, with gusts sometimes coming in at 80 mph. But Topcoat has fared just fine.

“I drive by the landfill every day coming in to work,” says Gillette. “There were mornings I knew we had winds of 70 mph the night before. I was afraid to look at the landfill, but everything was fine.”

While it dries hard, Posi-Shell breaks up under the weight of equipment, avoiding the creation of impermeable layers within the landfill.

Topcoat has worked well through the cold winters of Colorado, too. Because the slurry is water-based, it is stored in the hydroseeder and kept inside a building to keep from freezing. And with the slurry mixed it takes only 20 minutes to apply once the compactor makes its last pass. The slurry can be premixed, so come closing time all that’s needed is a drive over the waste. It’s just part of the routine the crew has worked into its daily operations at the facility.

Another spray that has been used specifically to reduce odors is Posi-Shell. Kippenbrock, of the Santa Fe facility, is a proponent of the Posi-Shell cover system for odor control. In his former position of landfill manager for the city of Laredo, TX, odor was the controlling factor in solid waste management. Kippenbrock explains that the landfill accepted quite a bit of sludge, which led to odor problems. While the mixing, application of the cover system, and cleaning of the equipment took time, Kippenbrock considers it time well spent.

“We sprayed the slurry on, and it hardened like an eggshell, consuming about one and a half hours at the end of the day,” says Kippenbrock. “It was great for odor control.”

Specifically designed for odor control, Posi-Shell is made from fiberized cement mortar that works by encasing and neutralizing the odor. While it dries hard, it breaks up under the weight of equipment, avoiding the creation of impermeable layers within the landfill.

Joel Lanz is the division vice president for the Apalachin, NY-based Landfill Service Corp., which makes Posi-Shell. He explains that while the gas will eventually diffuse, the material works to immediately reduce any odors and, along with that, odor complaints. One landfill used drywall as a component of its daily cover.

After it rained, the landfill began off-gassing hydrogen sulfide. As an immediate measure, Posi-Shell was applied. It was soon discovered that the gas discolored the ADC, and the landfill crew used this to its advantage. Knowing where the gas had migrated, the workers were able to install vents and flares in the most beneficial locations.

“Gas is going to migrate,” says Lanz. “It’s going to find its way out. Posi-Shell diffuses it and slows it down.”

When combating odor, time is often one of the most important factors.

Decisions, Decisions
Whatever your reason for switching from soil, there is a variety of ADCs to choose from. Site characteristics such as slope, weather, and material accepted, along with cost, would dictate the decisions owners and operators have to make in evaluating which ADC will work best at their sites. It only takes one nose on the right person to knock out a landfill.

MSW - September/October 2006