BioCycle May 2009, Vol. 50, No. 5, p. 35
Research trials assessing use of immature biosolids-derived compost to manage poultry mortalities found it to be a suitable tool, achieving temperatures necessary to inactivate the Avian Influenza Virus.
Mark A. King, Bill Seekins, Mark Hutchinson and George MacDonald
POULTRY farmers nationwide face disposal challenges resulting from routine and catastrophic mortalities. Many states,including Maine, have flocks of birds numbering in the millions, housed in a few concentrated areas. In the event of a catastrophic epizootic disease outbreak, such as Highly Pathogenic Avian Influenza (H5N1), mortalities could easily exceed several hundred thousand birds, undoubtedly exhausting normal local response capabilities. Traditional disposal methods, including rendering, burial and incineration, have proven to be dependable and cost-effective options. However, tightening of rendering regulations in response to livestock disease outbreaks of Borine Spongiform Encephalopathy (BSE) in Europe and Canda, coupled with a general decline in the demand for rendered products, has resulted in a disappearance of rendering facilities. Threats to groundwater from burial practices, especially in areas with shallow waters tables, along with allegations of declining air quality and public health risks from incinerator emissions, have forced the animal-rearing industry to seek suitable alternatives elsewhere.
The ultimate goal of any disposal scenario must include a plan that is cost-effective, environmentally sound and, ultimately, protective of public health. Composting offers such a solution. In general, poultry composting as a carcass management tool has been well studied and documented. The carcasses are well suited for composting, as the mass provides the bulk of the nitrogen component necessary for the compost mix. Sustained periods of high temperatures (in excess of 55°C) achieved during the active compost phase help to destroy pathogenic organisms that may persist in the poultry carcass. Research by H. Lu et al., reported in a 2003 paper, “Survival of Avian Influenza Virus H7N2 in SPF Chickens and Their Environments” (published in Avian Diseases), found that H5N1 is inactivated at sustained temperatures of 37°C for 24 to 36 hours.
To date, most composting methodologies have relied upon amending the poultry carcasses with existing litter and available (on site) carbon sources. Recent studies in Maine, however, have focused on the use of immature biosolids-derived compost as a poultry carcass management tool. For example, during February 2002, a small central Maine game bird-rearing farm experienced an outbreak of a low pathogenic strain of Avian Influenza (H7N2). To address this outbreak, the Maine Department of Agriculture employed a disposal method consisting of burying approximately 3,500 bird carcasses (averaging 1.5 to 3 lbs each) into a pile of active biosolids-derived compost. After only three weeks of treatment with the compost, swabs were taken from the interior of the pile and tested for Avian Influenza; results were negative. Only a small amount of the feathers and leg bones were noted when exploratory excavations were done following a month of composting.
During the late summer and fall of 2006, a series of poultry composting trials using active, immature municipal biosolids-derived compost were conducted at Highmoor Farm, a University of Maine Experimental Research Farm in Monmouth. The biosolids compost was obtained from the Hawk Ridge Compost Facility in Unity Plantation, Maine. The material met US Environmental Protection Agency (USEPA) approved Pathogen Reduction (55°C for three consecutive days) and Vector Attraction Reduction standards (14 consecutive days or longer at higher than 40°C with an average temperature of 45°C), but had not yet completed the full, active composting or curing phase. Temperatures of the compost were between 55 and 65°C.
Compost piles were formed using a front-end loader to establish the base layer and to complete carcass covering. A total of three piles (Pile #1, #2 and #3), measuring 10 feet wide by 5.5 feet high by 16 feet long (approximately 25 cubic yards of compost), were formed and observed over a five-week compost period. For each trial, an initial base layer of compost, measuring 18 inches in depth, was placed on the ground prior to off-loading the poultry mortalities. Piles were comprised of two separate layers of birds, measuring 12 to 15 inches in depth, and separated by a 6-inch layer of compost. Compost was placed between the layers of birds to absorb potential leachate generated from decomposition of the birds, while also providing additional texture and “bulkiness” to enhance even airflow through the pile. A final cover of biosolids-derived compost, measuring 2 feet to 3 feet in depth, was placed over each pile.
The mortality count per pile was as follows: Pile #1 — 680 birds, Pile #2 — 517 birds and Pile #3 — 480 birds. The birds averaged about 3.5 to 4 lbs in size. The varying amount of mortalities per pile was due to the fluctuating number of daily mortalities available for delivery to the compost site. Pile #1 was constructed with dry sludge compost and the mortalities were not premixed with the compost upon their arrival. Subsequent piles (Pile #2 and Pile #3) were constructed with compost that had been exposed to precipitation; incoming mortalities for both piles were immediately blended with the biosolids compost upon receipt. This premix was utilized to help distribute moisture within the pile core, as well as ensure adequate contact with compost media.
Piles were monitored using a series of three dial type probe thermometers (Reotemp). At each sampling location, a 4-foot thermometer was inserted into the core of each pile to allow continual mortality temperature monitoring throughout the five-week composting period. Two additional thermometers were placed at each of four sampling locations at 1-foot and 3-foot depths to track the temperature profile of each pile. Also monitored were estimated pile volume losses over the compost period, extent of carcass deterioration on day 7, 14, 21, 28 and 32, and environmental concerns including odor, leachate and vector attraction issues.
As a subset of this study, Pile #1 was constructed over a fabricated PVC pipe leachate collection system, to better understand the effects of precipitation events and potential subsequent leachate losses. The pipes were placed on a plastic tarp to direct all leachate into the collection system. To maximize the potential for leachate collection, Pile #1 was deliberately constructed to intercept surface water (run-on) from an upslope drainage area. Leachate observations were made following each precipitation event.
RESULTS AND DISCUSSION
In each of the three trials, temperatures at the 1-foot, 3-foot and 4-foot levels remained in excess of 43°C for greater than two consecutive weeks, easily exceeding the published standard, necessary to inactivate the Avian Influenza Virus, of 37°C for 24 to 36 hours (Lu et al., 2003). This suggests that poultry growers could use this composting methodology for disposal of carcasses infected with Highly Pathogenic Avian Influenza (H5N1) without concern for transmission of the virus, as the high temperatures contained in this outermost layer would serve as a barrier to prevent virus escape. All three trials showed consistent temperature responses at the 1-foot level, however, both Pile #2 and Pile #3 showed consistently higher temperature performances, at both the 3-foot and 4-foot depths, than Pile #1. This is best explained by looking at the initial pile set-up. For both Pile #2 and Pile #3, birds were received on a bed of compost that had been exposed to precipitation. The premixing with moist sludge compost resulted in quicker onset and sustained temperature increases at both the 1-foot and 3-foot depths for Pile #2 and Pile #3 when compared to Pile #1.
Additionally, on Day 16, Pile #1 experienced a 10°C drop in temperature at both the 1-foot and 3-foot levels. The 1-foot reading shows the cooling effects of a precipitation event (measuring 2.8 inches in an 8 hour time span) as rain saturated the pile surface, whereas the 4-foot reading shows a similar temperature drop resulting from the absorption of surface water as it traveled underneath the pile. The 3-foot temperature remained unchanged, as moisture saturation did not reach this level.
Pile excavations and visual observations for all of the trials demonstrated that after two weeks of composting, approximately 50 to 70 percent of the soft tissue and feathers had been digested. Most of the bones had a gelatinous appearance and the only raw, soft tissue noted was a small amount of breast meat which constituted the bulk of the bird’s initial body mass. During the early phases of the study, it was noted that the extent of decomposition among all three piles appeared to be dependent on two factors: moisture content near the pile core and percentage of bird contact with compost. This was especially true for excavations conducted on Day 7 and Day 14, in which soft tissue and feathers showed more advanced breakdown and decomposition in areas where mortalities were in direct contact with moist compost.
Tissue decomposition also was more advanced in areas that appeared to be moist and slightly anaerobic, as evidenced by strong odors released during subsequent excavation attempts. Again, this suggests that moisture content may be a limiting factor to microbial activity, especially in areas of the pile where oxygen penetration is hindered. Additionally, as composting activity peaks in the pile core, oxygen demand often exceeds availability, thus creating a favorable environment for facultative anaerobes to take over and continue decomposition. The net result of anaerobic decomposition is the production of volatile organic acids (VOAs) which, when released into the air, release strong odors.
By day 21, approximately 90 percent of the soft tissue was gone, and remaining bones, now clean of soft tissue, were soft and gelatinous. Most of these bones could be teased apart easily using the blade of a shovel. Additionally, all of the remaining feathers had been digested down to the quills.
By day 32, the compost piles had visually decreased in size. The multiple bird layers formed during initial pile construction were reduced to a single layer. The compost surrounding this layer was noticeably dry. Pile excavations in this layer revealed clean, brittle bone fragments and some matted feathers that appeared to have been charred to a “leather-like” texture and consistency.
LEACHATE, ODORS, VECTORS
A total of 9.2 inches of rainfall was recorded for the 32-day study period. During this timeframe, 11 precipitation events and 5 subsequent leachate discharges were recorded for Pile #1. During the first two weeks of the trial period, there were several brief precipitation events of less than 3 hours in duration and less than one-quarter inch in accumulation each. This precipitation was readily absorbed by the compost piles and no leachate discharges were observed. However, following the storm mentioned above on Day 16 (2.8 inches of rain), the first leachate discharge was noted from Pile #1.
Excavations of the pile revealed that the precipitation had penetrated less than 1 foot into the pile surface, while the base was saturated. This would prove to be the case for each subsequent leachate event, suggesting that the leachate was not generated by moisture passing through the compost piles, but actually from surface water saturating the pile base (upslope side) and then flowing underneath the pile, into the leachate collection system. Throughout the study period, the slope and profile of Pile #1 changed noticeably, going from a steep slope at an initial height of 5.5 feet to a somewhat flatter slope at 3.5 feet in height at the study’s end. This profile change (flatter, wider top) obviously allowed the pile to absorb more water during precipitation events, but the major factor leading to leachate discharge was from upslope surface water saturating the base of the pile and, subsequently, flowing underneath it.
As an aside, the leachate pile demonstrated why it is so important to build windrows up and down the slope rather than across the slope, and the compost pad should be sited with as little upslope watershed as possible (i.e., minimize the area upslope from the pile where water could collect and run down hill through the compost site). Both of these best management practices were deliberately violated to generate the most leachate possible.
During the course of the study, neither odors nor vector activity played a prominent role. Once each pile was formed, the biosolids compost characteristically emitted a unique odor that was neither strong nor especially offensive in nature (except when piles were disturbed during excavations, and only for a brief duration). Compost odors were never observed outside of the study area, and did not noticeably change throughout the course of the study. No scavenging activity (pile disturbances) was observed throughout the study period. Similar results were observed in 2004 while conducting bovine and equine carcass composting trials comparing the use of biosolids-derived compost along with several other compost feedstocks. In all cases, piles formed with biosolids compost were never disturbed, whereas piles formed with wood chips and sawdust/ shavings were routinely visited by scavengers.
CONCLUSIONS, LESSONS LEARNED
This study demonstrated that active municipal sludge (biosolids) compost can be successfully used to dispose of poultry carcasses in a mass mortality situation. Even with adverse climatic conditions (9.7 inches of rain in a month!) the soft tissue can be completely degraded in four weeks leaving only some bones and feathers.
It also provided an opportunity for the researchers to develop some practical hands-on experience in managing poultry carcasses through this composting technique. Lessons learned include:
Receiving Area for Mortalities: Use Jersey barriers or other movable walls to create a receiving area for the dead birds. Also, lay out a bed of compost (or other bulking material) in the receiving area prior to receiving the birds. These two practices made it much easier to pick up the birds with a loader in order to build the piles. It also allowed more contact between the birds and the compost media.
Moisture Addition: Wet the compost or the birds prior to building the compost pile. The biosolids compost is usually very dry when delivered, therefore adding moisture greatly enhances the composting process. With the static pile or the “precondition and turn” methods, this is the only opportunity to adjust the moisture prior to the piles being broken down several weeks into the process.
Mark A. King is with the Maine Department of Environmental Protection. Bill Seekins is with the Maine Department of Agriculture. Mark Hutchinson is with University of Maine Cooperative Extension, Knox-Lincoln County Office, Waldoboro. George MacDonald is with the State Planning Office, Augusta, Maine. These members of the “Maine Compost Team” thank the leadership of their respective agencies for the continued support for undertaking this type of interagency collaborative work, as well as Highmoor Farm and its talented staff for their many contributions to the process.
May 27, 2009 | General
Active Biosolids Compost As Poultry Carcass Amendment
BioCycle May 2009, Vol. 50, No. 5, p. 35