Envron Ozone Odor Control Systems

Traditional odor control "scrubbers" are expensive to set up and operate. As urban sprawl continues, there are inevitable conflicts between agriculture and residential concerns. And a lot of the issues revolve around odors. To some people it’s the "smell of money". But to the neighbors, odors can spoil a family barbecue or force people indoors on a sunny day. Envron has successfully used Ozone in large scale mushroom composting, hog barns, poultry barns, vehicle and home odor remediation and disinfection applications with excellent results.

Ozone has been used for over a century for odor control. One of the first applications for Ozone was to control odors from a slaughterhouse in Nice, France in the 1890s. Since then, Ozone has been primarily used in Europe both in water and air pollution control. Its use in North America has grown dramatically in the last 10 years, largely through the development of micro-electronics, smaller generators and advanced Ozone engineering.

Ozone is generated through the use of Ozone Generators. These machines strip Oxygen out of the air and pass it through an electrical discharge (corona). This converts Oxygen (O₂) into Ozone (O₃). As such, there are no on-going input costs for chemicals or other consumables. As well, if the system is properly set up maintenance is nominal. Generators are designed to run continuously or on intermittent schedules.

Test Site

The British Columbia Ministry of Agriculture hired Envron to demonstrate the use of Ozone for controlling odors from a mushroom composting facility. A number of complaints had been made and the facility was in danger of being shut down.

The Ministry of Agriculture evaluation of the technology can be summed up quite succinctly: when properly applied, Ozone kills odors from mushroom composting facilities. A commercial scale installation that also had an independent study further confirmed this finding.  In order to understand how Ozone does this, a look at the properties of Ozone is in order.

Ozone is in a class of chemicals called oxidants. Oxidants are substances such as chlorine, fluorine, hydrogen peroxide and others. This group breaks down organic substances into base compounds. Ozone is one of the fastest acting Oxidants known and very quickly converts organics into inert substances. Odors in the air are simply organic compounds that are "tasted" by the nose. Break those compounds down into something else and the odors disappear.

So what exactly causes the "bad" odors in a composting facility? Envron’s research into hog barn odors shows that the really penetrating odors are only a very small portion of the total gases being released by the barns.

These "worst offender" odors are typically sulphur-based and produced in an anaerobic process. However many of these sulphurous substances by themselves are not offensive. That’s right. They don’t stink by themselves. They need some of the others to form that truly unforgettable bouquet. So if you can disrupt the sulphur-based compounds, most of the smell will be killed immediately.

So how do hog barns compare to mushroom composting facilities? Quite simply, the hog barns and mushroom composters all produce some gases through anaerobic processes. And it is these sulphur-based gases that are truly offensive. Ideally, in an odor control application you destroy the anaerobic gases and also decrease the rest of the "non-problem" gases for good measure. As it turns out, Ozone is well suited to this task.
 

Ozone breaks down sulphur-based gases in a one-step process. That is, it takes one gram of Ozone to break down one gram of Hydrogen Sulphide. Conversely, it takes Ozone four steps to break down Amines such as Ammonia. That is, it takes four grams of Ozone to break down one gram of ammonia. So if we know that Ozone is reducing amines we also know that Ozone has already reduced the sulphur.

Which is exactly what happens in hog barns. Using Ozone in a hog barn, the first thing to go is the "typical" or penetrating smells associated with the barns. The question in B.C. was, would this also hold true for mushroom composting facilities? Envron determined that by seeing a reduction in Amines, it would also be evident that the sulphur-based compounds were being eliminated as well (it is very hard to detect trace amounts of sulphur compounds).

In order to determine if this would happen, a "destruct stack" was set up at the composting facility. This stack was used to draw air from a tent built over the compost heap and push it down a 110-ft section of 8 inch ductwork.

As well, an odor panel was set up by Monty Bruce, an Environmental Engineer from the University of British Columbia to see if the results could pass a rigorous odor panel test.

The odor panel tests are double-blind experiments in which people are given measured odorous gases or non-odorous gases to sniff through a machine. As the human nose is very sensitive (and also the ultimate test in odor control) the panel indicates whether people would find the odors offensive or not. The odors are then diluted by the machine to see at what levels it becomes non-offensive.

After running the tests using the destruct stack, Envron found an average decrease in total Amines after 48 seconds contact time of 21%. After 303 seconds an average decrease in total Amines of 59% was found. Everyone at the test site sniffed the gases coming out of the stack with Ozone applied and without Ozone applied. Without Ozone everyone agreed that the gases were odorous. With Ozone everyone agreed that the smell was gone.

The reductions in Amines indicated that within a number of seconds, there should have been a very high reduction in sulphur compounds as well. With the sulphurs gone, the odors should be killed as well. But would the odor panel agree?

After the tests came back from the UBC, the odor panel had indeed confirmed the on-site "sniff" tests. The untreated samples required dilution rates of between 1701-3043, which is typical of odorous substances.

 The Ozone treated samples were between 209-264, which is typical of non-odorous substances. As well, the treated samples actually smelled like Ozone which has an almost antiseptic or sanitary smell.

These results are consistent with other commercial uses for Ozone. One of the major markets for Ozone generators in North America is sewage lift stations. Odors at lift stations result from anaerobic processes and Ozone kills these odors quite readily. From work in hog and poultry barns, Envron had already seen Ozone’s ability to quickly kill even very penetrating odors.

The big trick in applying Ozone is to get the Ozone and the odorous gases mixed. This can be accomplished in an open air facility through the use of a ventilation system that pushes Ozonated air across the tops of the compost. Or if the composting facility is enclosed, Ozone can be added to the ventilation system at the exhaust. A "destruct stack" can also be added to ensure adequate mixing of the air and the ozone.