Composting is a proven technique to process organic wastes into a more stable and valuable form. On-site composting of dairy manure allows a dairy to recycle manure solids into a safe bedding material and sell finished product. Recycling to create bedding reduces the expense of importing straw or other materials, and exporting compost creates a means to manage excess nutrients. However, increasingly stringent air emissions regulations have made open windrow composting less tenable.
One of the key goals of this research has been to quantify the ability of the ACC to capture and control air emissions. During the composting trials air emissions samples were collected by a CSUF team under the direction of Dr. Charles Krauter. Samples were taken from the exhaust duct, the surface of the biofilter, and the surface of the covered piles. Samples were analyzed using a real-time photoacoustic gas analyzer (LumaSense INNOVA 1314). Sampling from a tap in the exhaust, along with flow measurements at the same point, were used to determine the actual air emissions flux in the duct. Samples at the biofilter and pile surfaces were taken using Surface Isolation Flux Chambers. These chambers are placed over the surface to be measured and charged with clean air at a known rate to measure gas emissions flux emanating from the enclosed surface (Radian, 1986).
Initial data for air emissions from the system are summarized in Tables 1 and 2. The data shows that the capture rate for the ACC is 100%. It also shows that the biofilter control rates are significantly higher than BACT. The high control rate is largely due to the low loading rate of the biofilter (i.e. a longer retention time). Because the ACC makes low aeration rates feasible, it becomes cost-effective to have a biofilter with a low loading rate.
ECS has applied for a Phase II USDA CSREES SBIR grant to continue this research and collect more comprehensive emissions data from a larger prototype system operating at a large commercial dairy. Phase II research is scheduled to begin in September of 2008. For more information on the AC Composter™ system, please contact ECS or go to www.compostsystems.com.
ND represents a measured concentration below the detection limit of the INNOVA device for a given species. For methane, the detection limit is 0.3ppm.
References
Hao, X., C. Chang, F.J. Larney, and G.R. Travis. 2001. Greenhouse gas emissions during
cattle feedlot manure composting. J. Environ. Qual. 30: 376-386.
Radian Corporation. 1986. Measurement of Gaseous Emission Rates from Land Surfaces
Using an Emission Isolation Flux Chamber, Users Guide, EPA /600/8-86/008, February
1986.
San Joaquin Valley Air Pollution Control District (SJVAPCD). 2007. Rule 4565 -
Biosolids, Animal Manure, and Poultry Litter Operations
Inventive minds have come up with an amazing number of variations to channel air through a floor and into, or out of, a compost pile. Designs that have been based on sound engineering calculations and experience have generally worked. However, since all aeration floors are constrained by physics and Murphy, the floors that were less rigorously designed have not faired well.
The characteristics by which compost aeration floors should be evaluated are:
• Uniformity of air distribution
• Capital cost
• Durability
• Operational Cost
• Safety
• Functionality as a floor drain
The Physics
Some mal-distribution of air flow in aeration floors is guaranteed since air flowing through any confined space loses pressure due to frictional losses. It turns out that the mechanisms of this frictional loss are non-linear, somewhat counter-intuitive, and, on close inspection, complicated; some very smart engineers with crew-cuts and slide rules have spent careers characterizing the physics of channeled air-flow. At the simplest level we can say that as air flows down a pipe it looses pressure. If that pipe is perforated, we can be assured that the pressure forcing the air through those orifices will vary along that length, and therefore the flow through the orifices will vary as well. The extent of the flow variations amongst the orifices is the mal-distribution.
Broadly speaking, the only method the aeration floor designer has to minimize mal-distribution is to make the distribution frictional losses “small” in relationship to the combined frictional losses at the orifices and through the compost pile (compost pile frictional losses are notoriously overestimated). This means that a suspended aeration floor with tiny high speed orifices over a huge plenum volume of slow moving air would be great; except when it came time to pay for it. In the spectrum of aeration floors designed from basic principles we see at one end the “sparger” type design that relies on very high orifice pressure (few holes spread far apart), and on the other end designs with very low speed air flows through the distribution channels and low orifice pressure loss. There are also designs that try to balance these two effects and operate at medium pressures. These designs can be classified as High, Medium, and Low Pressure; examples of each are shown below.
Cost, Durability, and Operational Considerations
Below is a table that attempts to evaluate and compare different aeration floor designs that are assumed to be competently designed to minimize mal-distribution. This analysis is by necessity generalized, but some helpful definitions and ranges can be given. For example: High pressure systems generally operate between 10-30 static inches; Low pressure systems often run between 1-4 static inches; Medium generally operate between those ranges. Energy costs follow pressure ranges. The O&M costs for above grade perforated pipe is considered high because it generally has to be handled each time a pile is built. High pressure aeration floors generally work well only in positive aeration since the orifices tend to plug in suction (negative); this also means they are not suitable for reversing aeration.
The right choice of aeration floor design will depend on your cost structure and your facility needs.
Increasingly stringent air-emission regulations and demands to better control odors has put an economic strain on industries that recycle large amounts of organic materials, such as compost facilities, dairies, and feedlots. ECS has recently introduced an affordable composting technology to greatly improve facility compliance and odor control. This technology is the AC Composter™.
Air Quality Issues
National and state air quality standards are bringing increased scrutiny on composting facilities (see Appendix I for a more complete discussion). While this is especially true in so-called “nonattainment” areas where Federal clean-air standards are frequently not met, it also holds for areas with more pro-active regulations as well. These regulations are already quite restrictive in some places, and the trend is toward increasing emission control requirements nationwide.
Odor Issues
Compost facilities across North America have been closed due to nuisance odors crossing property lines and beyond. Many of these facilities operated for years before their rural buffer zones were replaced by housing developments, hobby farms, or commercial enterprises. Most of these facilities were open air type (windrow, giant piles or ASP) with little or no odor control technology. The threat of closure has forced permitting agencies, banks, and facility owners to put odor control at the top of the facility design requirements. The traditional methods used to contain (enclose) and control odors universally pushed up the costs of facilities. So much so, that numerous planned facilities “didn’t pencil” and were never been built.
Traditional Approach for Controlling Odors & Air Emissions
Controlling compost emissions is done by enclosing process and/or capturing air. Enclosing the process is done with buildings and/or with in-vessel technology. ECS and others have successfully implemented these methods at numerous facilities feedstocks such as biosolids and source separated organics. However the precludes them from being widely adapted. The open-pile in-building approach, capital cost advantages over in-vessel methods, has other draw backs. These building ventilation rates required to meet health and safety requirements unusual); in-building facilities need large air handling systems, water hungry biofilters with comparable footprints to the compost piles themselves.
AC Composter™
For years ECS has designed and built traditional in-vessel and ASP systems. But as the concern for emissions has grown, we have received more inquiries from compost facility designers and operators whose business model would not support traditional enclosed approaches. With this incentive ECS set out to develop a technology with in-vessel like emission capture efficiencies, but at a greatly reduced system cost. In the spring of 2007 ECS introduced the AC Composter™ (patent pending), a covered ASP system that has achieved these design goals.
The AC Composter™ (shown in detail in Appendix II) is designed to control both the VOC’s and the NH3 emissions from the compost pile and captured in the process exhaust gas stream. It has four major components:
The cover is made of a fabric that is impermeable to both VOCs and NH3. This fabric is medium weight, highly UV resistant, and readily repaired in the field. The cover has single-direction air ports that allow continuous aeration of the biomass under negative aeration. The result is an enclosed compost pile with near zero fugitive emissions from the surface, and relatively small volume of process exhaust air that can be effectively scrubbed.
The AC Composter™ has the added advantages (over an open and standard ASP) of significantly reducing O&M costs; and, facility footprint. In traditional aeration system design large air flow volumes are used to control pile temperatures and maintain Oxygen levels at or above 16%. This approach minimizes odor generation within the pile, but requires a large mechanical system with significant energy costs and a commensurately sized biofilter. The high capture efficiency of the AC Composter means that these traditional design constraints don’t apply to odor control. Our results show that slightly slower biodegradation rates (due to higher temperatures and lower Oxygen levels) are easily outweighed by vastly improved moisture control, lower energy costs, and a much smaller biofilter.
AC Composter™ Installations
The AC Composter was put into large scale operation in Washington State in April of 2007, and is currently in pilot scale operation in Wyoming, Texas, and California. In Washington State, regulators with the Olympic Region Clean Air Agency (ORCAA) granted the AC Composter™ an emission capture rate of 100% (based on SCAQMD data – Appendix I), along with the BACT standards of 80% control efficiency for biofilters.
In California ECS has teamed with Cal State University in Fresno, through a USDA SBIR grant, to study the efficacy of the AC Composter™ at controlling emissions while stabilizing manure for use as bedding and compost. The trials are taking place at CSUF’s research dairy facility. Air emissions from the system are being measured by the experts from the College of Agricultural Sciences and Technology, Air Quality Lab. This data will be used to determine compliance visà- vis BACT. The Phase I research is scheduled to be completed by January 2008. Initial data has demonstrated a high capture rate and good process outcomes.
Appendix I - Air Quality Issues and Their Impact on Compost Facilities
Nationwide, regional air control districts have enacted tighter air-emission regulations to respond to the federal Clean Air Act and to improve ozone standards. The Environmental Protection Agency has identified the counties that are not attaining air-quality standards for Ozone and fine particulates (PM). Many of these counties center on large urban areas with impacted zones that stretch into surrounding countryside.
California
California seems to be the leader in setting and implementing air quality standards. The San Joaquin Valley (SJV) is one region whose air quality meets neither federal nor state standards for ozone emission control. Composting operations in the San Joaquin Valley Air Basin emit an annual estimated 511 tons of volatile organic compounds (VOC) which are an Ozone precursor (Source: San Joaquin Valley Unified Air Pollution Control District, 2005). The San Joaquin Valley Air Basin has been charged under the federal Clean Air Act to attain new 8-hour standards for ozone by 2013. (This date subject to an on-going debate).
New compost facilities in the SJV are now required to reduce projected criteria pollutants (including VOCs) emissions, and existing facilities will likely need to be in compliance in the near future. The SJVAPCD boards use the anticipated criteria pollutants emitted as the basis of their permitting process. In cases where the proposed facility is not an accessory to agricultural operations, it is subject to offset requirements according to the New Source Review Rule. Offset thresholds are currently set at 10 tons of emissions per year. Compost facilities whose annual emissions exceed this limit may be required to pay for proportional “pollution offsets”. A relatively modest sized open-air compost facility (approximately 11,250 tons per year) would exceed this limit. There is a clear incentive to implement improved control and capture
technologies.
If a proposed composting project is subject to the California Environmental Quality Act (CEQA) process then ideally a facility it could be granted a finding of “No-Significance” if calculations show a discharge of less than 10 tons per year of non-methane VOCs. (Note: each air district can have different standards for significance - for example, L.A. is a 55 pounds per day.) With such a finding a facility is not required to produce a costly and time consuming Environmental Impact Report (EIR) and submit to a relatively complicated public review process.
The emission volumes are calculated using factors and capture and control efficiencies established by the South Coast Air Quality Management District (SCAQMD) Rule 1133 for co-composting facilities. The emission factors baselines are 1.78 pounds of VOC and 2.93 poundsof ammonia per each ton of waste accepted by the facility. The baseline capture and control efficiencies are based on BACT (best available control technologies), and BACT varies with the composting and air-scrubbing technologies employed. For open aerated static piles (ASP’s) the capture rates are 25% and 33% for positive and negative aeration, respectively. In-vessel systems are credited with 90-100% capture rates. The BACT standards grant 80% control efficiency for biofilters used to scrub the captured air-stream.
These regulations have serious implications for compost operators and large-scale farmers that want to recycle the nutrients produced on their farms.
After evaluating the cost of regulatory upgrades against revenue models, many planned facilities never leave the drawing board. Some facilities that have been in the planning for years—such as L.A. County Sanitation’s Westlake Farms—continue to watch costs go up, in part due to the evolution of regulations that require higher levels of capture and control, and the purchase of pollution offsets. There is clearly a need for a cost effective means of meeting these regulations.
Washington
In Washington the Department of Ecology and the Regional Air-Pollution Control Districts have regulations for limiting emissions; and, new compost facility permit applicants are required to calculate total VOC and NH3 discharge levels based on SCAQMD BACT standards.
If the discharge levels of the proposed facility exceed the high limits, regulations can restrict the facility throughput, with the possibility of making it not viable economically.
For example, recently ECS was asked to calculate discharge levels for a Client facility located in Washington, based on SCAQMD standards. The BACT were based on several existing compost facilities, all with different feedstocks and processes. In performing the calculations, ECS notes choosing BACT standards for facilities with similar feedstocks and process is essential.
The calculations began with determining the total pile surface area of the facility, including planned future expansions; and applying the NH3 emission rate for a static pile from the SCAQMD data. (NH3 was used as the most likely containment most likely to exceed threshold limits.) Since the Client facility used the ECS AC Composter™ with impermeable ASP covers and with continuous negative aeration, the collection (capture) of the NH3 was assumed to be effectively 100%. (Open positive and negative ASP are less than 33%.) Using the 78% NH3 destruction rate in the biofilter sited by the Regional Air District, the resulting estimate for annual pounds of NH3 emitted to the atmosphere was well under the limit of 17,500 pounds/year (SQER), and the facility was granted necessary permits to proceed.
Appendix 2: How the AC Composter™ works
A full sized AC Composter (patent pending) has been in operation since April of 2007 at the Silver Springs Organics (SSO) Facility in Tenino Washington (1.5 hour drive from Seattle). The Phase I installation has 24 separately aerated and controlled zones (piles) and processes about 7,000 tons of source separated organics per month.
One of the largest technical and cost hurdles, especially in a negatively aerated system, is the aeration floor. At SSO the AC Composter was implemented with the new patent-pending ECS pipe-less aerated floor technology—known as the CompDogTM. This design provides a well distributed air-flow under the pile, a clean surface for the front-end loaders when breaking down the piles, and does not require expensive below grade pipes or cast-in trenches; and, it works on any approved and flat surface. The CompDog avoids the limitations and risks found when using unwieldy above grade aeration pipes.
Building the Pile
In preparation for receiving raw compost, two CompDogs are placed stretched to full length in the zone, inflated, and connected to the aeration header. The wheel-loader then builds a pile over them. The pile is allowed to settle 12-24 hours. Then the CompDogs are deflated, and retrieved from under the pile using a powered spool. The pile retains the inflated vault shape of the CompDogs under its entire length.
The aeration vaults are connected to the negative aeration system through a push-wall located at the end of the zone. At the front end the vault is plugged with a small amount of material, the AC Cover is then placed over the entire pile. Two temperature probes are inserted through ports in the AC Cover to provide feedback for the automated aeration control and monitoring system.
Active Composting
During composting, fresh air is drawn through the air inlets in the AC Cover to provide oxygen to the biomass. The air is pulled through the biomass and into the vault,via a modulating damper, and into above-ground stainless steel aeration plenums. The aeration plenums deliver the process air to biofilters. When necessary, the control system automatically adds fresh air to cool process air and keep it below 40°C to prevent overheating the biofilters.
Damper position and fan output are automatically controlled by the ECS CompTroller™ system. The operator's software monitors the process, to record time/temperature data files for regulatory compliance, and to input process settings used by the automatic controls. Real-time technical support is available via Web access. CompTroller™systems are in operation at dozens of facilities in N. America.
Throughout the country, concern about air and water pollution from dairies is increasing. California is no exception to this, and regulation is putting more restrictions on how dairy operators can dispose of manure. These include restrictions on simple land application which can produce excessive odors and nutrient runoff into water systems. Using the AC Composter™, composting of manure solids can be done on-site with a minimum of cost, space, and odor emissions. It can also produce a final product that could be recycled for bedding, sold off-site, or applied to land with fewer restrictions.
Odor (incident) Logs
In January 2007 the Local Environmental Agency (LEA) provided “odor logs” to the county residents that were troubled by the compost facility’s odors. The odor logs were collected regularly and the recorded data (time, date, type of odor, etc) along with weather conditions were input into spreadsheets. These spreadsheets became the empirical measure of success for the process changes implemented at the facility.
Process Changes
ECS engineers visited the site in January 2007 and made the following process recommendations:
1. Lower the moisture content in the initial raw mix;
2. Remix the compost after an initial period of primary composting; and,
3. Increase the vessel aeration rates prior to vessel unloading.
4. Remove as much film and other plastics from the raw compost as possible;
5. Obtain wood chips for use as bulking agents; and,
6. Use AC Composter™ covers to contain odors during secondary composting
1. MSW feedstocks are typically rich in paper fiber. Lowering the moisture level was intended to reduce the forming of paper-wads (agglomerates). The agglomerates formed anoxic pockets that released odors when broken apart during loading and unloading the vessels. Lowering the raw compost moisture levels to approximately 60% did reduce the forming of agglomerates.
2. After several days in primary composting the degradable materials soften. Removing the compost from the vessels and running it through the heavy duty compost mixer breaks open the agglomerates that form even with reduced moisture. Remixing also exposes more degradable surfaces and further homogenizes the heterogeneous MSW mix.
The benefits realized by implementing steps #1&2 included decreased the time to come up to PFRP temperature; and reduced odors. This was proven by decreasing entries in the odor logs.
3. The operators now manually select a high airflow setting on the ECS CompTroller™ aeration control software 24 to 48 hours prior to removing the compost from the vessel for any purpose (either to remix or move to secondary composting). This effectively saturates the compost with Oxygen, lowers the compost temperature, and scrubs compost odors from the biomass. Previously there was a clear association with removing compost from the vessels and the number of odor incidents recorded during loading and unloading. The reduction in odor incidents logged shows this high aeration technique is successful.
4. A huge amount of film plastic found in the Mariposa MSW. They have altered their pre-processing to manually pick more out by hand prior to the mechanical sorting process. It took the facility a while to fill the sorting positions (allocate funding and find staff) to bring the staff up to a full working compliment. Sorting staff are now directed to remove as much plastic as possible. Reducing the amount of film plastic improves the air flow through the feedstock, which we believe will further reduce odor generation.
Reducing the amount of plastic in the waste stream that reaches the Mariposa facility is an uphill battle. It will take years of infrastructure development (collection programs and opportunities to recycle) and education to significantly reduce the amount of plastic entering the facility. The aggressive sorting will need to continue until new programs are in place.
5. Last winter was wet and included a lot of snow. The loads of MSW that were placed on the tipping floor sloshed with free liquid and melting snow. Even without adding liquid from the storage tanks (to reduce moisture levels in the initial mix) the raw compost was just too wet. Staff has now found sources of wood waste and are stockpiling and drying it at the compost facility. The ground wood will be used to bulk the incoming feedstocks when the winter rain and snow again increase the moisture to unacceptable levels.
6. The original compost facility plan called for enclosing the Aerated Static Pile (ASP) area for secondary composting, however, in an effort to save capital costs, the building walls were omitted from the contractors scope of work. Since the time the facility was built, ECS has developed the AC Composter™, an ASP system using pile covers, negative aeration, and biofilter to contain and scrub odors. The AC Covers were added to the negative aeration system that was already in place and the combination has successfully controlled the odors associated with secondary composting. The same high aeration setting described in #3 above is used prior to removing the covers and moving the compost to the screening area.
Since these process changes have been made the number of odor incidents logged in the county odor logs have dropped dramatically. (From 18 complaint-days in March, to 3 complaint-days in June.) During this process the staff of the Mariposa County Compost facility has learned many valuable lessons. These lessons, and further updates of the continual improvements at Mariposa, will be the topic of a future Blog.
Facility Description
The facility is designed to receive about 60 tons of MSW per day on its tip floor. The material passes through a manual and mechanical preprocessing system where cardboard, large objects, ferrous materials, and a considerable amount of plastic are removed. The remaining materials, which are approximately 60% of the tip weight, are conveyed to the compost hall and deposited into a vertical mixer. The tip floor and pre-processing equipment are located in an openly ventilated building.
Water is added in the mixer which also affects some size reduction. The material is discharged into a pile and loaded into the adjacent compost vessels with a front-end loader. The material generally stays in the vessels 20+ days where Oxygen and temperature levels are kept within target ranges. The vessels are sealed. The compost hall contains the eight composting vessels and is maintained under negative pressure. The composting hall exhaust air is humidified and scrubbed in a biofilter. The process exhaust air from the vessels is also scrubbed in the biofilter.
After composting in the vessels, the material is transferred by front-end loader to an aerated curing floor that is under a roof but open on three sides. The curing area uses a negatively aerated static pile (ASP); the process air is pulled through the piles into an in-floor aeration system and again exhausted to the biofilter. After another 25+ days the material is taken from the static piles and passed through a trommel screen to remove oversized items (mostly plastic). The product is then taken to the land fill for use as cover material.
Odor Issues
During the spring and early summer of 2006 record rains overwhelmed the water re-use storage tank at the facility – it had to be pumped and hauled numerous times. One of the sources of water was the biofilter, both by direct precipitation and run-on from the large paved areas around it. To reduce the amount of water entering the plant, a roof was retrofitted over the biofilter. During this construction the profile of the biofilter media was changed. At the same time the exhaust air humidifier was turned off since it also caused more water to collect under the biofilter. Over the summer and into the fall, the media dried out. This, plus the change in profile provided major short-circuit paths; the media was no-longer doing its job.
In the fall of 2006 nearby neighbors (as close as 400 ft from the curing area) began registering odor complaints. ECS was notified of these odor issues in December of 2006, and came on site in early January of 2007. The problem with the biofilter was immediately diagnosed and rectified within days. The media was rewetted and re-formed, additional media was added, and the humidifier was put back into service. Unfortunately by that time a number of neighbors had already been strongly impacted and were quite upset.
Once the biofilter was functioning per design, the odor emissions were significantly reduced both in frequency and severity. The compost related odors that have been reported since are the result of outdoor activities (there are other odors are associated with the tip floor and the landfill). The activities associated with odors have been identified as: 1) Transferring the material from the vessels to the outdoor curing piles; 2) Surface odor emanating from the curing piles: and 3) Screening the material coming out of the curing piles. The fundamental challenge is that composted MSW tends to form little agglomerates (0.2-2.0 cm) when wetted and mixed (see photo). Their principle constituents appear to be paper that is pulped by the mixer and film plastic. These agglomerates are relatively impermeable until they are mechanically broken up – which occurs when moving material with a front end loader and during screening device.
Remediative Steps
Adding AC Composter covers to the curing piles has stopped the fugitive emissions from the surfaces of the piles. But the ASP pile building and final product screening activities are still releasing odors. The approach we have recommended is first to break up the agglomerates so that more effective composting can be achieved in the vessels. The following recommendations have been made to achieve this:
• Add less water to the initial mix
• Pick more plastic during the sorting process
• Remove and remix the material mid-way through the in-vessel composting cycle
• Consider adding a bulking agent
• Improve the quality of the feedstock coming in through better diversion programs and education.
The operators are working on all of these fronts and have made progress over the past few months. Since it takes approximately 50 days for material to work its way from tip floor to final screening, improvements made on day 1 don’t show benefits for quite some time. One of the other challenges managers have had is finding, hiring, and training staff while starting up a new facility. Another challenge has been the waste stream itself, which has significantly more film plastic than was indicated in the waste audit from the late 1990’s.
If the remediation steps take longer than is politically palatable to address the problems, the other solution is enclosing the curing and screening area, and treating like the composting hall. It may come to this.
The RF TeleProbe™ offers the lowest operational costs, and the highest percentage “up-time” of any wireless compost temperature system on the market. It is a simple technology that doesn’t require mapping and sleep cycle coordination with a base controller. You simply turn it on and it runs.
In addition, the ECS RF TeleProbe™ is the only technology that offers a high enough data transmit frequency for operating an automated control of an aeration system while offering years of battery life.
Recently, there's been a buzz in the wireless industry about using mesh radio technology. Our radio technology can be implemented as a mesh radio system as well. But after reviewing the pros and cons, it is clear that a Spread Spectrum Direct (SSD) radio is a far better choice for compost applications. The reasons are simple:
Battery Life
The ECS Direct Radio technology is very well suited for small battery applications since the RF transceiver spends over 99.99% of the time off. One low cost non-rechargeable battery will power an RF TeleProbe for over three years. Mesh radios must always be on and ready to re-transmit data; rechargable batteries with a 5 week charge cycle are typical.
Suitability for Real-Time Control of Compost Aeration Systems
The ECS SSD radio makes an excellent device for real-time temperature control feedback in a composting application. Each probe can transmit temperature data frequently (a 3 minutes period is typical) without reducing the battery life. Mesh radios typically transmitt data much less frequently (60 minute period is common) in an effort to maintain their battery life. Effective real-time control of a composting aeration system require up-date rates range of 3-5 minutes. Also the ECS SSD radio is up and running within seconds of a power up. Mesh systems take 1-3 minutes per node to remap themselves after a re-boot.
Range and Susceptibility to Interference
The claim to faim for Mesh radio is overcoming interference. But both indoor and outdoor compost facilities tend be relatively open spaces where an antenna can be mounted with good vision of the compost piles; during ECS eight yeas of applying RF to compost facilities we've not found interference to be an issue with point-to-point radio. In addition the ECS SSD radio has superior range (line-of-sight 3,000 ft versus 600 ft for mesh radio). If inteference or additional range were an issue, the ECS SSD Radio technology can be implemented with low cost repeaters.
For more information, please contact ECS.