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Fighting odors with Zeolite

Scrubbers containing the same material used in cat litter give hope to farms under pressure to control odor

October 11, 2016  by Tony Kryzanowski


If you raise or house livestock, you will have odor issues. How you control and minimize those odors to keep neighbors, employees, and livestock happy, while providing a safe and healthy work environment, is a constant challenge.

In some cases, odor and ammonia emissions threaten the future of dairy, hog, and poultry operations because of stricter regulatory standards or complaints from neighbors. Encroachment by residential development into traditional farming areas, and complaints about farm odors from barns and storage lagoons, is becoming a bigger and bigger challenge for farmers, especially in highly populated areas. Emission issues can also limit farm growth.

University of Idaho researcher Mario de Haro-Marti has achieved very promising results by scrubbing dairy farm emissions from a covered flush pit using a zeolite filter. Zeolites are the same minerals used to treat odor and ammonia in cat litter.


The zeolite filter research was conducted on the 4,000-head dairy owned by Dean and Deborah Swager, located about 15 miles from Twin Falls, Idaho. The dairy was established in 2000. Dean grew up on a dairy farm in California before moving to Idaho. The Swagers have collaborated with the university on several research projects. Dean says that he has a personal interest in research advances and understands the value of being among the first to hear about them.

The dairy consists of two, free stall milking barns and exterior pens to house the herd. Manure management within the barns consists of a flush flow system. Prior to the flush water arriving at a retention pit, it is processed through a DariTech manure separator, where the solids are accumulated and composted before being reused as bedding on mattresses in the barns. The liquids continue to the retention pit, and then eventually into a storage lagoon. Manure in the storage lagoon is land applied as fertilizer. What the separation system provides is a type of odor management, as it separates many of the gas-producing solids out of the manure stream before the retention pit.

De Haro-Marti works as the Gooding County extension dairy/livestock environmental educator and led the university’s experimental zeolite filter project at the dairy. The project was supported by a Conservation Innovation Grant from the U.S. Department of Agriculture’s Natural Resources Conservation Service.

Zeolite is a naturally occurring and commercially available mineral capable of absorbing ammonia and odor, marketed in consistency from powder to crushed rock. There are six large zeolite mines in Idaho alone. Its absorption properties are well known, since it is already used to remove ammonia in wastewater treatment, cat litter, and has also been tried on some hog farms.

“The idea was to test if the zeolites will retain odor and reduce ammonia emissions to serve as a tool in the future for a dairy that is, for example, being encroached upon by population,” says de Haro-Marti. “They can apply this technology to reduce odors, or if they are reaching the regulatory maximum on ammonia emissions, they can use this tool to reduce those emissions.”

While the research is still in its early stages, by blowing emissions from the dairy’s covered, 20-foot by 20-foot flush pit through a zeolite filter, they achieved more than 92 percent reduction in ammonia emissions running continuously over three days, and about 45 percent overall odor removal. This dropped to just more than 90 percent over six days, and just over 53 percent after 57 days. While the performance of the zeolites decreased over time, it still represented a reduction of ammonia emission of more than 50 percent, running continuously for two months.

“We were very surprised with the results,” says de Haro-Marti. “We were expecting that it would work, but we never expected 90 percent ammonia removal with dry zeolites.”

What’s also noteworthy is how these results were achieved.

“We were experimenting in real conditions, with a real pit, with real manure flushing every day, versus a lab setting,” he says.

Swager says he was ‘fairly confident’ that it would work well, being as zeolite is a compound similar to baking soda, which people commonly use to manage odors in refrigerators.

As a dairy farmer, he took a bit of a different view of how the zeolite filter might benefit a dairy operation. In addition to keeping neighbors and government regulators happy, he says better odor control on the farm could also have a positive impact on the herd in general. He says it has to be remembered that the cows are breathing in this air as well, and with a lot of ammonia and odor in the air, it could lead to respiratory and health issues, which could ultimately impact milk production. Healthier air translates into a healthier, happier herd.

“Cows can smell things a whole lot more acutely than we as humans can,” he says.

As demonstrated by the research, the zeolites’ absorption benefits are finite. Their effectiveness and the sizing of the filter depends on the concentration of ammonia and odor being absorbed. Eventually, they will become saturated and need to be replaced. De Haro-Marti says they installed their experimental zeolite filter to scrub emissions from the dairy’s flush pit because that is where emissions were most highly concentrated. The goal was to determine if a zeolite filter would work as a scrubbing agent and how effective it was, without factoring in the size of the filter at this point.

He expects that emissions concentration from a covered storage lagoon would be about one-third of those from a covered flush pit, so this will factor into the design and size of a zeolite filtration system in this application. The technology can be adjusted and scaled up, as needed. To maintain continuous emission treatment, he adds that it might be prudent to have more than one filter so that scrubbing continues when saturated zeolites are replaced.

To effectively use a zeolite filter, the flush pit or lagoon must be covered to capture the emissions. While this may represent a significant cost to a livestock operation, it’s something worth considering if the alternative is shutting down or limited growth potential.

De Haro-Marti’s experimental set up essentially consisted of a wooden structure to cover the flush pit, a blower attached to the side of the cover to suck out the emissions, and a four meter long and four-inch diameter PVC pipe to transport the emissions, which was connected to a custom-made, zeolite filter installed next to the flush pit. The filter itself consisted of a four foot by four foot by eight foot frame with racks of zeolite material inside.

“It’s basically a box with zeolites inside,” says de Haro-Marti. “This is an experimental design. Obviously, it is too small for the concentration of emissions that we had. I calculated that our filter would saturate in three to four months. To make it work at the farm level, you are going to need a much bigger filter.”

All of these components, including the zeolite minerals, are readily available. It is possible to custom design an emissions collection, transportation, and treatment system, however, it needs to match the concentration of emissions coming from the covered flush pit or lagoon to work effectively. Also, the zeolite material will need to be monitored regularly and replaced when saturated with ammonia.

To dispose of the ammonia-saturated zeolites, de Haro-Marti recommends crushing the mineral and land applying it. It has some nutrient value because plants have the ability to use the ammonia that is built up in the zeolites. Yet, it should not have an impact on the soil’s chemistry because the addition of the crushed zeolite material is negligible. In terms of potential re-use of the zeolites, he adds that current research shows that washing out the ammonia is ‘very difficult’, with researchers attempting to use an acid wash to remove it. But he continues to investigate various methods where the ammonia could be removed to avoid the expense of crushing and field application.

Installation of this emissions treatment system does not change the general flow-through, handling or storage of the dairy’s manure, and that was one of the goals of the research project – to provide a solution without disrupting a manure management system. The zeolite filter system is simply an add-on feature to treat the emissions.

De Haro-Marti says that there could be a business opportunity for someone who would be willing to educate themselves about what the research has discovered, and then developing an emissions scrubbing system using zeolites to match a livestock operation’s needs.

“It is just a question of sizing the filter and engineering the different coverings and connections, depending on the dairy,” he says. “It will change a lot from one dairy to another. But yes, it could be commercialized soon and I am working on it.”

Swager says he will continue to benefit from the zeolite filter already installed at the dairy, but he would have to conduct a very detailed cost-benefit analysis before he’d go any further. Where he views the greatest potential for this emission scrubbing technology is on farms under severe pressure from neighbors and government regulations, or where animal health is a concern, requiring immediate action to better control odors and emissions as a matter of survival or growth.

As to whether it will gain traction with other farms, he adds that it will depend on the overall installation cost, zeolite replacement costs, farm goals, and challenges that individual farms may be experiencing, but it is one option for odor control that is new and can be explored further.





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