Odor is one of the most common challenges associated with composting operations. Organic materials are intentionally broken down through biological processes, and those processes can produce odorous compounds as materials are received, mixed, aerated, turned, cured, and stored.
So, what technology controls odor at a composting facility?
There is not one technology that is right for every composting operation. Biofilters, biotrickling filters, chemical scrubbers, activated carbon adsorption systems, covers, enclosures, and ventilation systems can all play a role in odor control. The appropriate technology depends on what is causing the odor, the concentration and characteristics of the contaminants, airflow requirements, facility design, and operating conditions.
At Webster Environmental Associates, Inc. (WEA), odor-control technology is selected based on the individual facility and its emissions rather than starting with a predetermined piece of equipment.
Biofilters for Compost Facility Odor Control
Biofiltration is one technology commonly associated with composting and other facilities that generate large volumes of odorous air.
A biofilter directs contaminated air through porous media containing microorganisms. As the air passes through the media, microorganisms biologically oxidize biodegradable odor compounds.
The effectiveness of a biofilter depends on maintaining appropriate conditions within the media. Moisture, pH, temperature, airflow, and contaminant loading can influence biological activity and system performance.
Biofilters can be an effective option when the characteristics of the air stream are appropriate for biological treatment. However, simply because a facility handles biological material does not automatically mean a biofilter is the best solution.
Biotrickling Filters
Biotrickling filters are another biological odor-control technology. Instead of relying on traditional biofilter media, these systems use structured media where microorganisms develop as a biofilm.
A liquid continuously or intermittently passes through the media while contaminated air moves through the system. Odorous compounds are transferred from the air into the liquid and biological film, where microorganisms can break them down.
Biotrickling filters can be useful for treating certain biodegradable contaminants, including hydrogen sulfide, when properly designed for the facility’s air stream and loading conditions.
Chemical Scrubbers
Chemical scrubbers use chemical reactions to remove contaminants from an air stream. Odorous air is brought into contact with a scrubbing solution, allowing targeted compounds to be transferred and chemically treated.
Scrubbers can provide effective treatment for certain contaminants and concentrations, but they also introduce chemical storage, feed, monitoring, and maintenance requirements.
The characteristics of the emissions need to be understood before selecting a scrubber because the chemistry must be appropriate for the compounds being treated.
Activated Carbon Adsorption
Activated carbon is another technology that can be used to remove odor compounds from contaminated air.
Rather than biologically or chemically destroying the contaminants, activated carbon captures compounds on the surface of the carbon media. Different carbon products can be selected depending on the contaminants present.
Carbon systems can be useful in odor-control applications, but media eventually becomes exhausted and must be replaced. Airflow, contaminant concentration, humidity, and the type of compounds present can all affect carbon life and operating costs.
For that reason, activated carbon should be evaluated based on both initial performance and the expected long-term requirements of the system.
Covers, Enclosures and Ventilation
Sometimes the first technology needed is not the equipment that treats the odor. It is the system that prevents odorous air from escaping uncontrolled.
Covers and enclosures can isolate odor-producing processes, while properly designed ventilation and ductwork collect contaminated air and transport it to treatment equipment.
At a composting facility, containment may be considered around particular handling or processing areas depending on where significant emissions are being generated.
Capturing too little air can allow odors to escape. Capturing more air than necessary can increase the size and cost of the downstream treatment equipment. Designing an effective air collection system therefore requires an understanding of both the odor source and the facility’s ventilation requirements.
More Than One Technology May Be Needed
Composting facilities can produce different types and concentrations of odors from different processes. The air collected from one area of a facility may have very different characteristics from air collected somewhere else.
That means the answer to what technology controls odor at a composting facility may involve more than one technology.
A facility could potentially use containment and ventilation to collect emissions, biological treatment for one air stream, and another treatment method for a different source. The final design should reflect what is actually happening at the facility rather than forcing every odor source through the same treatment approach.
Choosing Technology Starts with Understanding the Odor
Installing odor-control equipment before determining what needs to be treated can create an expensive problem.
An odor assessment can help identify and characterize emission sources before treatment alternatives are developed. Source sampling, odor testing, chemical analysis, and air dispersion modeling can provide information about which processes are contributing to odor and whether those emissions are likely to affect surrounding properties.
This allows treatment alternatives to be compared based on actual facility conditions.
WEA is independent of odor-control equipment manufacturers, which is important during this process. The goal is to determine which technology or combination of technologies is appropriate for the application rather than beginning with a particular manufacturer’s product and trying to make the facility fit the equipment.
Technology Is Only Part of the Solution
Effective compost facility odor control should also consider how the composting process itself affects odor generation.
Aeration, moisture, temperature, material handling, storage time, and the characteristics of incoming material can influence biological conditions and odor production. When operational changes can reduce odor at its source, the demand placed on downstream treatment equipment may also be reduced.
The strongest approach is often to prevent unnecessary odor generation first, capture emissions that cannot be avoided, and then treat that air with technology designed for its actual characteristics.
Finding the Right Odor Control Technology for Your Facility
There is no universal answer to odor control at a composting facility. Biofilters may be appropriate for one operation, while another may require a biotrickling filter, chemical scrubber, activated carbon system, improved containment, or a combination of approaches.
Webster Environmental Associates specializes in evaluating odor problems and developing control strategies around the specific needs of municipal and industrial facilities. From odor testing and evaluation through technology selection, design, construction support, and performance testing, WEA can help determine whether an existing system needs improvement or a different approach is required.
If you are evaluating odor-control technology for a new or existing composting facility, contact Webster Environmental Associates to discuss your facility, odor concerns, and the technologies that may be appropriate for your application.