Co-composting poultry carcasses with wood-based, distillers' grain and cow manure biochar to increase core compost temperatures and reduce leachate's COD.

Composting has been recognized as a viable method to dispose of animal carcasses. Common concerns related to the composting process include low core temperatures, leachate generation, and ammonia emissions. This study tested co-composting full-size poultry carcasses with commercially available biochars at an aeration rate of 0.8 L∙min-1. Biochars prepared by gasifying wood pallets, distillers' grains, and cow manure were added to the composting bins at the 13% rate (by volume). Results showed that poultry carcasses with wood-based and cow manure biochar increased temperatures by 2.0 to 3.3 °C. All biochar-amended bins met the time-temperature criteria to eliminate avian influenza (H7N1) viruses, which could not be achieved without biochar addition. Wood-based biochar amendment lowered the cumulative chemical oxygen demand of the leachate samples by 87% (P = 0.02). At the rate studied, the biochar amendment did not significantly affect ammonia emissions (P = 0.56). BET surface area of wood-based biochar was 1.4 and 28 times greater than that of cow manure and distillers' grain biochar, respectively. Compared to no biochar addition, wood-based biochar resulted in significantly higher compost temperatures (P = 0.02), lower leachate COD values (P = 0.02), and a higher total nitrogen content (P = 0.01) while it did not cause an increase in sodium content (P = 0.94) of the finished compost. In conclusion, amending the poultry carcass composting process with wood-based biochar (13% by volume) is recommended, especially to eliminate disease-causing agents.

Quantification of pathogens and antibiotic resistance genes in backyard and commercial composts.

Compost is widely used for gardening. Growers can choose to buy compost from markets or make compost at home. Potential exposure of users to pathogens through composting includes ingesting foodborne pathogens and inhaling airborne pathogens. This study compared the abundances of the genetic markers of five opportunistic foodborne and airborne pathogens in the backyard and commercial composts, as well as an immature swine mortality compost. We found that ttrC of Salmonella enterica and ftsZ of Escherichia coli were absent from all ready-to-use compost samples. In contrast, the genes of airborne pathogens such as groEL2 of Mycobacterium spp., mip of Legionella pneumophila, and gyrB of Pseudomonas aeruginosa were detected in the backyard and commercial composts. The groEL2 gene of Mycobacterium spp. was detected in all samples, including the control soil. The abundance of gyrB of P. aeruginosa was high in the two backyard composts, and it was higher than those in any other compost samples. The relative abundances of ARGs were significantly lower in backyard composts than commercial composts. We found that ftsZ of E. coli co-existed with multiple single-drug resistant ARGs in the immature swine mortality compost. We also found that mip of L. pneumophila and gyrB of P. aeruginosa co-existed with aminoglycoside resistance genes. Our findings suggest that inhaling airborne pathogens may carry more risk than ingesting foodborne pathogens when applying composts.

Testing the plastic-wrapped composting system to dispose of swine mortalities during an animal disease outbreak.

Composting has been used to dispose of animal mortalities and infected materials, such as manure and feed, during major animal disease outbreaks. In this study, we adapted the plastic-wrapped mortality composting system developed by the Canadian Food Inspection Agency during the 2004 highly pathogenic avian influenza outbreak to compost swine mortalities. The goals of the study were to evaluate the performance of the plastic-wrapped composting system to dispose of swine mortalities and to field test its ability to eliminate the spread of airborne pathogens through the aeration ducts. Two cover materials, ground cornstalks and woodchips, were tested using passively and actively aerated composting sheds. The mortalities were inoculated with Salmonella spp. and vaccine strains of Bovine herpesvirus-1 and Bovine viral diarrhea virus. Air samples collected from the upper aeration duct (air outlet) during the first 10 d of composting were negative for Salmonella and the viruses tested, which indicated that aerosol transmission of the pathogens was limited. The aeration plenum placed under the mortalities helped to keep conditions aerobic, as O2 concentrations of both passively and actively aerated test units were above 11%. Actively aerated cornstalks had the highest degree-hours (1,462 °C h d-1 ), which was followed by passively aerated cornstalks (1,312 °C h d-1 ), actively aerated woodchips (1,303 °C h d-1 ), and passively aerated woodchips (1,062 °C h d-1 ). After a 7-wk composting period, all three pathogens were inactivated based on quantitative polymerase chain reaction test results. The mortalities were not inoculated with the African swine fever virus, but temperature data showed that if they were, the system had the potential to eliminate this virus.

A quantitative understanding of the role of co-composted biochar in plant growth using meta-analysis.

The combined use of biochar and compost as a soil amendment presents benefits to crops and nutrient cycling. Although there are literature reviews regarding biochar and biochar-compost mixtures, a quantitative literature review on the role of co-composted biochar (hereby called COMBI) in plant productivity is currently missing. The goal of this review paper is to find evidence-based measures of the effects of application rates, soil pH, plant types, biochar feedstock, and compost materials, on plant productivity. Plant productivity covers a variety of measurements but mostly refers to grain yield and above-ground biomass. Response ratio was selected as the effect size. Funnel plot showed that the studies were reasonably symmetrically distributed around the mean effect size. Results showed that application rates of <20 t/ha and >30 t/ha significantly increased plant productivity by 48.3 and 15.7%, respectively, while no significant yield increases were found for the application rates between 20 and 30 t/ha. When data was grouped based on the soil pH, the greatest increase in plant productivity was found to be at acidic soil pH values (pH 4-5), which was expected because the liming effect of biochar is often reported as one of the main mechanisms behind the increased crop yields. When different plant species were compared, cereal grasses grown with COMBI yielded significantly higher grain yields (39.7%). Rice husk biochar yielded the highest increase in productivity but this result was based on only one study. The second highest increase was obtained with wood-based biochars (29.4%) based on ten studies. The effect sizes found with our meta-analyses are based on 14 research works worldwide and represent the most updated information regarding the effects of COMBI on plant production. As more data on COMBI become available, data analyses can be updated to make more robust comparisons.

A systematic review of biochar use in animal waste composting.

The animal production industry in the United States is currently undergoing a phase of growth; however, such growth brings certain challenges. One of the most prominent concerns in this regard is the increasing amounts of animal waste produced as a natural consequence of stock population growth. For decades, composting, including that of manure and animal mortalities, has been utilized to manage animal waste. Recently, in an effort to enhance the composting process, biochar has been proposed for use as a compost amendment, and over the last few years, an increasing number of papers on composting with biochar have been published. However, although there have been a few review papers that have summarized the literature regarding biochar use in composting, none of these has focused on animal waste composting. Accordingly, the purpose of this review is to critically analyze the role of biochar in livestock and poultry waste composting, identify gaps in our current knowledge, and propose future research directions. On the basis of the studies analyzed, biochar has the potential to improve animal waste composting processes at application rates of 5-10%. Biochar can extend the thermophilic phase of the composting process, lower the pH of compost material, prevent leachate formation, and reduce ammonia, methane, and nitrous oxide emissions. Given that the feedstock used to produce biochar and the pyrolysis conditions employed in its production affect the performance of biochar, it is important to report the physicochemical properties of the biochars used to enable comparison of the results of different studies. Moreover, there is a need for further research to gain a better understanding of the impact of biochar regarding the elimination of antibiotic-resistant genes and animal mortality composting.

A review of the animal disease outbreaks and biosecure animal mortality composting systems.

Despite the development of new vaccines and the application of rigorous biosecurity measures, animal diseases pose a continuing threat to animal health, food safety, national economy, and the environment. Intense livestock production, increased travel, and changing climate have increased the risk of catastrophic animal losses due to infectious diseases. In the event of an outbreak, it is essential to properly manage the infected animals to prevent the spread of diseases. The most common disposal methods used during a disease outbreak include burial, landfilling, incineration and composting. Biosecurity, transportation logistics, public perception, and environmental concerns limit the use of some of these methods. During a disease outbreak, the large number of mortalities often exceeds the capacity of local rendering plants and landfills. Transporting mortalities to disposal and incineration facilities outside the production operation introduces biosecurity risks. Burying mortalities is limited by the size and availability of suitable sites and it has the risk of pathogen survival and contamination of groundwater and soil. Portable incinerators are expensive and have the potential to aerosolize infectious particles. Composting, on the other hand, has been recognized as a biosecure disposal method. Research showed that it eliminates bacterial pathogens such as Escherichia coli O157: H7, Salmonella spp., as well as viruses including highly pathogenic avian influenza, foot-and-mouth disease, Newcastle disease, and porcine epidemic diarrhea. This paper summarizes the lessons learned during the major animal disease outbreaks including the 2010 foot-and-mouth disease, 2016 highly pathogenic avian influenza, and recent African swine fever outbreaks. The purpose of this review is to critically discuss the biosecurity of composting as a mortality disposal method during the outbreaks of infectious animal diseases.

Performance of a plastic-wrapped composting system for biosecure emergency disposal of disease-related swine mortalities.

A passively-ventilated plastic-wrapped composting system initially developed for biosecure disposal of poultry mortalities caused by avian influenza was adapted and tested to assess its potential as an emergency disposal option for disease-related swine mortalities. Fresh air was supplied through perforated plastic tubing routed through the base of the compost pile. The combined air inlet and top vent area is ⩽∼1% of the gas exchange surface of a conventional uncovered windrow. Parameters evaluated included: (1) spatial and temporal variations in matrix moisture content (m.c.), leachate production, and matrix O2 concentrations; (2) extent of soft tissue decomposition; and (3) internal temperature and the success rate in achieving USEPA time/temperature (T) criteria for pathogen reduction. Six envelope materials (wood shavings, corn silage, ground cornstalks, ground oat straw, ground soybean straw, or ground alfalfa hay) and two initial m.c.'s (15-30% w.b. for materials stored indoors, and 45-65% w.b. to simulate materials exposed to precipitation) were tested to determine their effect on performance parameters (1-3). Results of triple-replicated field trials showed that the composting system did not accumulate moisture despite the 150kg carcass water load (65% of 225kg total carcass mass) released during decomposition. Mean compost m.c. in the carcass layer declined by ∼7 percentage points during 8-week trials, and a leachate accumulation was rare. Matrix O2 concentrations for all materials other than silage were ⩾10% using the equivalent of 2m inlet/vent spacing. In silage O2 dropped below 5% in some cases even when 0.5m inlet/vent spacing was used. Eight week soft tissue decomposition ranged from 87% in cornstalks to 72% in silage. Success rates for achievement of USEPA Class B time/temperature criteria ranged from 91% for silage to 33-57% for other materials. Companion laboratory biodegradation studies suggest that Class B success rates can be improved by slightly increasing envelope material m.c. Moistening initially dry (15% m.c.) envelope materials to 35% m.c. nearly doubled their heat production potential, boosting it to levels ⩾silage. The 'contradictory' silage test results showing high temperatures paired with slow soft tissue degradation are likely due to this material's high density, low gas permeability and low water vapor loss. While slow decomposition typically suggests low microbial activity and heat production, it does not rule out high internal temperatures if the heat produced is conserved. Occasional short-term odor releases during the first 2weeks of composting were associated with top-to-bottom gas flow which is contrary to the typical bottom-to-top flow typically observed in conventional compost piles. In cases where biosecurity concerns are paramount, results of this study show the plastic-wrapped passively-ventilated composting method to have good potential for above-ground swine mortality disposal.

Health risk assessment of occupational exposure to hazardous volatile organic compounds in swine gestation, farrowing and nursery barns.

Livestock producers are exposed to a high number of airborne pollutants during their daily duties of cleaning, feeding and maintenance activities. Hazardous air pollutants (HAPs) are a major group of pollutants that may cause cancer or other serious health effects including neurological, respiratory, reproductive and developmental disorders. In this study, health risks of occupational exposure to eight hazardous VOCs (phenol, p-cresol, o/m-cresol, benzene, toluene, ethylbenzene, o-xylene, and m/pxylene) that are most likely to be emitted from swine buildings were assessed using Monte Carlo simulation. The purpose of the study was to calculate emission rates and to quantify cancer and hazard risks of the target VOCs. Cancer and hazard risks were calculated for workers A, B, and C, who spent six hours in the gestation, farrowing and nursery barns, respectively, and one hour in the office space every day. Concentrations of the target VOCs did not exceed their recommended exposure limits (RELs). But, concentrations of p-cresol and benzene exceeded their preliminary remediation goals (PRGs). The highest emission rates in mg s(-1) were measured from the gestation rooms while the highest emission rates in mg per s per head were measured from the farrowing rooms. Cancer risks of ethylbenzene, benzene and p-cresol were higher than EPA's benchmark of one per million. Hazard risks of benzene, toluene, p-cresol, and o/m-cresol were higher than the maximum acceptable risk threshold (10(-4)). Worker B (farrowing) had the highest cumulative cancer (16.6 in one million) and hazard (11 342 in one million) risks. It was followed by workers A (gestation) and C (nursery). Sensitivity analysis showed that inhalation unit risk (IUR) had the highest impact on cancer risk assessment while recommended exposure limit (REL) had the highest impact on hazard risk assessment.

Full-scale biofilter reduction efficiencies assessed using portable 24-hour sampling units.

Portable 24-hr sampling units were used to collect air samples from eight biofilters on four animal feeding operations. The biofilters were located on a dairy, a swine nursery, and two swine finishing farms. Biofilter media characteristics (age, porosity, density, particle size, water absorption capacity, pressure drop) and ammonia (NH3), hydrogen sulfide (H2S), sulfur dioxide (SO2), methane (CH4), and nitrous oxide (N2O) reduction efficiencies of the biofilters were assessed. The deep bed biofilters at the dairy farm, which were in use for a few months, had the most porous media and lowest unit pressure drops. The average media porosity and density were 75% and 180 kg/m3, respectively. Reduction efficiencies of H2S and NH3 (biofilter 1: 64% NH3, 76% H2S; biofilter 2: 53% NH3, 85% H2S) were close to those reported for pilot-scale biofilters. No N2O production was measured at the dairy farm. The highest H2S, SO2, NH3, and CH4 reduction efficiencies were measured from a flat-bed biofilter at the swine nursery farm. However, the highest N2O generation (29.2%) was also measured from this biofilter. This flat-bed biofilter media was dense and had the lowest porosity. A garden sprinkler was used to add water to this biofilter, which may have filled media pores and caused N2O production under anaerobic conditions. Concentrations of H2S and NH3 were determined using the portable 24-hr sampling units and compared to ones measured with a semicontinuous gas sampling system at one farm. Flat-bed biofilters at the swine finishing farms also produced low amounts of N2O. The N2O production rate of the newer media (2 years old) with higher porosity was lower than that of older media (3 years old) (P = 0.042).

Biofilter performance of pine nuggets and lava rock as media.

Wood chips and bark mulch are commonly used biofilter media because they are generally locally available and inexpensive. Nevertheless, these organic materials degrade and require replacement every 2-5 years. In this study, airflow characteristics and gas reduction efficiencies of two alternative biofilter media (pine nuggets and lava rock) with high porosity and potentially longer service lives were evaluated at three empty bed contact times (1, 3, and 5s) and two moisture levels (82% and 90% relative humidity). The lava rock had a lower pressure drop across the media and maintained higher media depth. Gas reduction efficiencies were highest for lava rock at 5s empty bed contact time and 90% humidity. The reduction efficiencies at these conditions were 56%, 88%, 87%, 25%, and 0.7% for ammonia, hydrogen sulfide, total reduced sulfur, methane and nitrous oxide, respectively. Odor reduction up to 48% was observed but was not consistent.

Air sampling methods for VOCs related to field-scale biosecure swine mortality composting.

Monitoring specific volatile organic compounds (VOCs) as markers of biosecure carcass degradation is a promising method to test progress and completion of the composting process. The objective of this study was to test the feasibility of using existing aeration ducts in composting units as practical sampling locations. The secondary objective was to test the feasibility of using marker VOC concentrations in aeration ducts to elucidate information about airflow patterns inside composting units. Marker VOC concentrations were significantly higher in the upper aeration duct and this duct can typically be used to collect air samples instead of placing special air sampling probes inside the composting units. Occasionally, the airflow direction inside composting units can change. Marker VOC concentrations can be used to decide the airflow direction inside the composting units. In this study, higher VOC concentrations were measured from the upper aeration duct, and this duct was shown to be an outlet.

Field scale evaluation of volatile organic compound production inside biosecure swine mortality composts.

Emergency mortality composting associated with a disease outbreak has special requirements to reduce the risks of pathogen survival and disease transmission. The most important requirements are to cover mortalities with biosecure barriers and avoid turning compost piles until the pathogens are inactivated. Temperature is the most commonly used parameter for assessing success of a biosecure composting process, but a decline in compost core temperature does not necessarily signify completion of the degradation process. In this study, gas concentrations of volatile organic compounds (VOCs) produced inside biosecure swine mortality composting units filled with six different cover/plant materials were monitored to test the state and completion of the process. Among the 55 compounds identified, dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be marker compounds of the process. Temperature at the end of eight weeks was not found as an indicator of swine carcass degradation. However, gas concentrations of the marker compounds at the end of eight weeks were found to be related to carcass degradation. The highest gas concentrations of the marker compounds were measured for the test units with the lowest degradation (highest respiration rates). Dimethyl disulfide was found to be the most robust marker compound as it was detected from all composting units in the eighth week of the trial. Concentration of dimethyl disulfide decreased from a range of 290-4340 ppmv to 6-160 ppbv. Dimethyl trisulfide concentrations decreased to a range of below detection limit to 430 ppbv while pyrimidine concentrations decreased to a range of below detection limit to 13 ppbv.

Laboratory scale evaluation of volatile organic compound emissions as indication of swine carcass degradation inside biosecure composting units.

Biosecure livestock mortality composting systems have been used to dispose of diseased livestock mortalities. In those types of system, visual inspection of carcass degradation is not possible and monitoring VOCs (volatile organic compounds) released by carcasses is a new approach to assess progress of the composting process. In this study, field-scale livestock mortality composting systems were simulated and a laboratory scale composting system with aerobic and anaerobic test units was designed to collect VOC samples from the headspace of decaying plant materials (70 g dry weight) and swine tissues (70 g dry weight) at controlled operating temperatures. Headspace samples were collected with SPME (solid phase microextraction) and analyzed by a GC-MS (gas chromatography-mass spectrometry) system. Among the 43 VOCs identified, dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be marker compounds of the mortality composting process. These compounds were only found to be produced by decaying swine tissues but not produced by decaying plant materials. The highest marker VOC emissions were measured during the first three weeks, and VOCs were not detected after the 6th week of the process, which indicates degradation processes were completed and compost materials microbially stabilized (no additional VOC production). Results of respiration tests also showed that compost materials were stabilized. Results of this study can be useful for field-scale composting operations but more studies are needed to show the effects of size and aeration rate of the composting units.

Air sampling and analysis method for volatile organic compounds (VOCs) related to field-scale mortality composting operations.

In biosecure composting, animal mortalities are so completely isolated during the degradation process that visual inspection cannot be used to monitor progress or the process status. One novel approach is to monitor the volatile organic compounds (VOCs) released by decaying mortalities and to use them as biomarkers of the process status. A new method was developed to quantitatively analyze potential biomarkers--dimethyl disulfide, dimethyl trisulfide, pyrimidine, acetic acid, propanoic acid, 3-methylbutanoic acid, pentanoic acid, and hexanoic acid--from field-scale biosecure mortality composting units. This method was based on collection of air samples from the inside of biosecure composting units using portable pumps and solid phase microextraction (SPME). Among four SPME fiber coatings, 85 microm CAR/PDMS was shown to extract the greatest amount of target analytes during a 1 h sampling time. The calibration curves had high correlation coefficients, ranging from 96 to 99%. Differences between the theoretical concentrations and those estimated from the calibration curves ranged from 1.47 to 20.96%. Method detection limits of the biomarkers were between 11 pptv and 572 ppbv. The applicability of the prepared calibration curves was tested for air samples drawn from field-scale swine mortality composting test units. Results show that the prepared calibration curves were applicable to the concentration ranges of potential biomaker compounds in a biosecure animal mortality composting unit.