Category: Technical Bulletin
In October 2007, ECS began conducting trials at California State University Fresno (CSUF) to explore using the new patent pending AC Composter™ (ACC) covered aerated static pile system to manage dairy manure solids and comply with airquality standards. A two-zone portable pilot system was delivered by ECS and installed at the CSUF research dairy. This research is being conducted under a Phase I USDA CSREES Small Business Innovative Research grant. The goal is to determine how well the ACC (Figure 1) can meet the operational and economic demands of manure management at a dairy and provide adequate capture and control to limit air emissions for compliance with California regulations.
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
Category: Technical Bulletin
In October, ECS began conducting trials at California State University Fresno to explore using the new patent pending AC Composter™ system to manage dairy manure solids and comply with air-quality standards. A two-zone portable pilot system was delivered by ECS and installed at the CSUF’s research dairy. This research is being conducted with funds from a USDA Small Business Innovative Research grant. The goal is to determine how well the AC Composter™ can meet both the demands of a dairy operation and the requirements for air emissions control in California.
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.
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.
Category: Technical Bulletin
Staring in the winter of 2006 the staff at the Mariposa Compost Facility worked quickly to make process changes to bring odor issues under control. Here is the latest chapter in their story.
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.
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.
Category: Technical Bulletin
The Mariposa County MSW composting facility was built at the county landfill to remove some dry recyclables from the waste stream and to produce compost for daily cover. One key motivation was to increase the lifespan of the landfill and to postpone a costly long-haul. The facility was permitted, designed and built by a team of engineers and vendors. It began operation in the summer of 2006. ECS supplied the in-vessel composting technology, the mixer, the curing system, and the biofilter and associated air handling equipment. Since November of 2006 the facility has been receiving odor complaints from neighbors.
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.
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.