Keeping a Lid on Odor

Lynn Merrill

For most people, the smell of baking bread is pleasant. Conversely, the smell of that bread decaying in a landfill is not. Because solid waste facilities typically handle foul-smelling, putrid materials, odor control is critical.

Collection-related odors typically are a minor concern - they are temporary and lift soon after trash bins are serviced. On the other hand, transfer, processing and disposal facilities are more susceptible to angry neighbors and face stricter regulations to keep odors in check.

"People who design, construct and operate these facilities tend to put odor at the bottom of the priority list," says Ralph Landano, president of Maspeth, N.Y.-based Aireactor, which provides odor control products. "But it's probably one of the first things that will precipitate closure."

Environmental conditions - temperature, moisture and air flow - can minimize or maximize odors. For example, as the temperature rises, so does the odor. Transfer station odors may be minimal in the winter, but in the summer, the smell at that same facility may linger. Likewise, moisture accelerates decomposition, increasing odor. Consequently, a wet organics processing plant that handles restaurant waste may have more odor than a recycling facility that handles paper.

The adage, "the solution to pollution is dilution" holds true. Circulating air helps to reduce odor by diluting its intensity. However, air can be a double-edged sword. It can carry odors off-site, increasing the chance that the neighbors will be exposed to them.

From the Ground Up Before constructing a facility that may generate odors, consider how neighbors will be affected. A facility's design can reduce off-site odor migration, Landano says. Enclosing the facility and installing a ventilation system that uses negative air pressure to draw outside air into the facility will help contain odors. Similarly, a filtration ventilation system using a large fan to pull odorladen air through activated charcoal or screened compost will freshen the air before it is discharged out-side. This is called bio-filtration. Constructing vehicle entry doors away from the path of prevailing winds also will prevent smells from being carried on the breeze.

Odor problems are not restricted to enclosed buildings, but they often are more concentrated there. Consequently, facility managers should consider installing an odor management system.

One option is a spray distribution system that ejects a neutralizing or deodorizing agent into the building automatically at regular intervals. The American Re-Fuel transfer station, Braintree, Mass., has had success with such a system, which has been in place for approximately two years. Made by Global Odor Control Technologies, New Bedford, Mass., it consists of 31/48 -inch plastic tubing installed on the ceiling of the transfer station along the perimeter of the tipping floor. Sixty nozzles are located every 8 to 10 feet and above the load out bays.

A pump with an automatic timer provides constant pressure at 50 pounds per square inch (PSI). It boosts pressure to approximately 125 PSI, which opens the nozzles to discharge a liquid odor neutralizer. A metering system mixes the odor control product, which comes in 55-gallon drums, with the appropriate amount of water.

The system's timing can be set to meet the facility's needs, says Douglas Cote, operations supervisor for American Re-Fuel. "We set the [spray] interval anywhere from every 2 minutes to every 20 minutes," he says. "The discharge interval can be set from 5 seconds to 20 seconds." The spray interval is the length of time between releases of the neutralizer, and the discharge interval determines how long the spray operates.

According to Cote, the system requires little maintenance. It also works well during the winter. However, during that season, a glycol-alcohol mix is used instead of water so the tubes don't freeze.

Previously, the company used pelletized odor products, Cote says, but the manpower required to distribute the pellets made this option less economical, particularly when the facility processed highly rancid organics from commercial customers, such as restaurants and supermarkets.

"When the load would hit the floor, we would pelletize it," he says. "We found this caused a lot of operational overtime because we had to have a man do it. It [the spray system] certainly is cheaper than having someone out there sprinkling pellets, and it seems to be more effective."

Venturing Outdoors While filtration and spray systems can manage odors inside, some outdoor facilities, such as compost operations and landfills, may need to consider other approaches.

The Collier County landfill, Naples, Fla., is fighting for its life, battling severe odor problems and complaints from the nearby densely populated residential development. The directive? Solve the odor problems or re-site the landfill.

"Siting a new landfill isn't easy in this environmentally sensitive area of Florida," says Ed Ilschner, public works administrator for Collier County. "We've already spent $1 million researching a new site."

Collier's odor problems stem from using ground construction and demolition waste, particularly gypsum board, as a daily and intermediate cover on approximately one quarter of the landfill. When this porous material mixes with moisture, it emits hydrogen sulfide, a pungent gas.

Collier County, which accepts 1,200 tons per day, will take several steps to solve the odor problem. First, operators will close and seal the portion of the landfill covered by the gypsum, and implement a gas collection system. Second, a standard soil cover will be used on the remaining active area instead of the gypsum.

Finally, Ilschner says the county will lease an air circulation system by Eric'sons Odor Answers, Dallas, Ga., with the option to buy if the system works.

The system consists of large fans placed in a circle around the odiferous area blowing fresh air from around the landfill inward. An 18-foot diameter vertical fan, which can move 850,000 cubic feet of air per minute, sits in the circle's center and mixes fresh air with the pungent air before propelling it up 500 feet.

The system blows the smelly air on top of the atmospheric layers that hold odors close to the ground when there is little wind. The next day, the sun oxidizes the old odor molecules as it normally would during the day. An on-site weather station monitors wind speeds, automatically turning on the fans when the wind dips below 5 mph.

The Collier County landfill has 20 more years of life, says Ilschner, with the potential for 50 years "if we can make more room with height adjustments."

Staying put will save the landfill $1.75 million per year over a 50 year period, determined by the annual $1.8 million cost of moving minus the $55,000 per year cost to buy and operate the fan system, he says.

"We have to address the reputation and the smell if we hope to stay where we are," Ilschner says. "There always will be the chance for odor if we are not careful."

Out of Site ... While your odor control system may be operating efficiently, ironically, sight can play a major role in odor intensity. If neighbors see a dirty or cluttered facility with unkempt equipment leaking trails of garbage juice on the street, odor will be magnified in their minds. Good housekeeping practices go far toward mitigating concerns and generating a "neighborly" reputation for the facility. Attractive landscaping to conceal the site also can reduce complaints.

But closing the door on the trash doesn't make it go away, so keep an open communications policy within the community.

When Aireactor's Landano receives an odor complaint, he identifies exactly who has been affected. At some sites, he canvasses the neighborhoods and talks to residents.

"We literally will do a walk-through of the whole facility and the surrounding area," he says. "We'll even ring doorbells and talk to people to explain how the facility serves them."

Failing to solve an odor problem adequately can lead to investigation and demands from politicians and regulators to take action.

To avoid conflict, put odor control at the top of your priority list, Landano says.

He suggests training one employee as an "odor semi-specialist" to control smells.

"There have been facilities closed down coast to coast because of odor problems," Landano warns. "If you're the unlucky operator who thinks odor control is not relevant, you probably won't have the last laugh."