Tired of odor complaints? Landfill odor management that actually works

Odor issues are affecting many landfills across the country and around the world, and while the term “landfill odors” might seem straightforward, it is a complex issue.

Within any landfill operation, odors can originate from inbound waste, older decomposing waste, landfill gas emissions or leachate. Conversely, landfills could generate odors that arise from nondisposal activities such as organics processing, composting, land application of sludge or contaminated soil or a stagnant sedimentation pond.

The power of suggestion

In many cases, the suggestive power of simply knowing a landfill is in the vicinity will lead neighbors to believe it must automatically be the source of any odor. Sometimes it is, sometimes it’s not.

Through my work with Blue Ridge Services Montana, I’ve encountered landfills that operated for years with virtually no odor issue—until the operation became visible above a screening row of trees. As soon as the neighbors could see the landfill, odor complaints increased dramatically. This begs the question: Did it smell bad before it became visible, or did residents begin expecting odors because they could see a landfill?

But it’s not necessarily just not-in-my-backyard syndrome that has finally found a focal point. The power of suggestion has some science behind it. Psychologists call this a “response expectancy.” The idea is that when we are in a certain situation, we can anticipate a certain type of response.

For example, you could be strolling along with no springtime allergy symptoms until you notice a thin layer of yellow pollen on the sidewalk. Almost instantly, your eyes begin to water and your nose begins to itch.

Or you could be working in your yard, caught up in the excitement of finishing your new deck, when suddenly you smell your neighbor’s BBQ. You realize you skipped lunch, and then forget all about the deck because you’ve been reminded that you are starving.

That’s the power of suggestion. Sometimes a neighbor’s response expectancy is legitimate, and the landfill really does smell bad. But that’s not always the case.

Blue Ridge Services worked on one project where a landfill was being blamed for hundreds of nuisance odor complaints. It was about a mile away from a residential development, and the neighbors were smelling something bad.

As it turned out, a wastewater treatment plant nestled between the landfill and the development was the true source of odor. However, residents could see the landfill, so it got the blame.

If your landfill is the subject of odor complaints, you can do several things to either verify or disclaim the responsibility. There also are many ways to determine if the landfill is in fact the origin of the odor. We’ll look at some of the most basic solutions before shifting to more complex and analytical methods.

Identify the source

Before you get into a situation where you are forced to play defense against a wave of odor complaints, consider taking a more introspective approach. Look at your operation through the lens of a regulator or neighbor.

Are you doing things that could lead to odors and odor complaints? Sometimes, you can make voluntary changes to reduce some particularly odorous materials or activities.

Start by asking your crew. If certain loads smell especially bad, they will know. Ask them and then take the next step to adjust your process to self-mitigate odor-causing activities. The solution is not always a matter of simply eliminating a specific waste stream.

Check the wind direction

When faced with odor complaints, the first step always should be to verify what the wind direction was an hour or so before the odor complaint. Odor will always follow the prevailing wind. Sure, there could be some localized shifting related to topographic features, thermal patterns or other factors, but odors will not move upwind. Like a river, eddies, swirling or crosscurrents could be visible, but water always flows downstream.

In an effort to stick to the facts, installing a digital recording weather station at one or more locations around your landfill can provide valuable information. You might need to start with data from a nearby weather station, but if things get serious, you will want—and need—on-site data.

Wind speed also is an important factor in odor. Higher wind velocities will tend to increase mixing and dilution. Think about it: At any given time, odor is being emitted at a specific rate. Higher wind speed will naturally increase dilution, making odors less noticeable.

But there’s more to the equation. Higher wind speed generally means more turbulence. This tends to increase mixing. Many of the molecular compounds that create nuisance odors can be oxidized or otherwise broken down while mixing with air.

Sometimes, good results can be generated by setting up very large fans to artificially increase turbulence at or just downwind of the odor source.

Look for seasonal variations

As you evaluate wind direction and speed, don’t overlook how those factors might change seasonally or because of a localized storm event. You can’t change the weather, but you could be able to adjust when and where you place certain types of trash to help reduce the risk of nuisance odors.

Time of day is an important consideration, as well. Two factors are at play during the day that could impact the movement of odor and increase the likelihood of complaints.

First, wind patterns can change as areas around the landfill warm up during the day and cool down at night. Your on-site weather station can help you track and quantify those changes.

Second, for odor complaints to occur, someone must first be present to detect the odor. That’s often why we’ll see odor complaints clustered in the morning, when people are leaving their houses to go to work or school, or in the afternoon and evening, when they are outside taking a walk or relaxing in their backyards. Odors don’t automatically translate into odor complaints until someone smells the odor.

The day of the week also can be a consideration. Begin by evaluating your inbound waste stream. For example, your landfill could receive certain types of waste on specific days. You could get several loads of wastewater treatment sludge on Mondays and Fridays. Based on this sample chart to the right, a strong correlation appears between those days you receive loads of sludge and when you receive complaints.

By slicing and dicing data in many ways, you’ll often find these kinds of direct relationships that can help you connect the dots between cause and effect.

You can follow up by considering what is happening downwind. Office workers could be more likely to smell odors and generate complaints Monday through Friday because that’s when they are at work. Conversely, residents could be more likely to detect odors on holidays or weekends, when they tend to be at home and outside recreating.

It’s vital to correlate what’s happening at the landfill at or just prior to when complaints were logged. Remember to factor in the travel time for odors to leave the landfill and reach those downwind receptors.

This can help identify specific sources of odors and provide ideas of how specific operational changes can help reduce nuisance odors.

Wind flow modeling

From a more scientific perspective, sometimes it’s important to understand the details of how wind moves on the landfill and how that affects odor.

Wind flow modeling can run the gamut from simple to complex. A basic smoke test can show which way wind is moving from specific on-site sources.

On the other extreme, you could conduct a comprehensive wind flow analysis using computerized fluid dynamics (CFD) that can model many scenarios of wind speed, velocity and point source. In some cases, you might need to model hundreds of scenarios to finally identify those that are most applicable to a specific facility under specific conditions.

Smoke test

Wind flow patterns can be modeled in several ways, and the results can be helpful in mitigating odors. A simple smoke test can be done with commercial smoke bombs. These are available in various colors and sizes. Larger ones produce lots of smoke over a short time, maybe one to two minutes.

Other types of smoke generators can produce continuous smoke for a much longer duration. Some models can produce dense, nontoxic smoke, similar to what might be used in a theatrical performance, for 30 minutes or more.

CFD modeling

Powerful software programs are available that can model wind flow patterns accurately. Such an analysis can cost several thousand dollars because of the time to set up the parameters that include topography, wind direction, wind speed, rate of odor emissions and other factors.

The benefit of using CFD software is the ability to model many different scenarios quickly and consistently.

This kind of modeling often is completed as part of developing annual fill sequence plans to determine where to place active fill areas during potentially unfavorable wind patterns to help reduce odors and litter.

The more you know about what materials and activities can cause odors, the more success you’ll have in mitigating those odors in your operations. Being proactive when it comes to managing odors at your facility can help prevent problems down the road.

Neal Bolton is president of Blue Ridge Services Montana Inc., Hamilton, Montana. He can be reached via email at neal@blueridgeservices.com.