David Elwell

Bacterial inoculum enhances keratin degradation and biofilm formation in poultry compost

Native microbial populations can degrade poultry waste, but the process can be hastened by using feather-degrading bacteria. Strains of Bacillus licheniformis and a Streptomyces sp. isolated from the plumage of wild birds were grown in a liquid basal medium and used to inoculate feathers in compost bioreaction vessels. Control vessels had only basal medium added to the feathers, litter and straw. Temperature, ammonia, carbon and nitrogen were monitored for 4 weeks. Scanning electron microscopy of the feather samples showed more complete keratin-degradation, more structural damage, and earlier microbial biofilm formation on inoculated feathers than on uninoculated feathers. A diverse community of aerobic bacteria and fungi were cultured early, but declined rapidly. Thermophilic B. licheniformis and Streptomyces spp. were abundant throughout. Enteric gram-negative bacteria, (e.g., Salmonella, E. coli) originally found on waste feathers were not recovered after day 4. Vessel temperatures reached 64-71 degrees C within 36 h and stabilized at 50 degrees C. When tumble-mixed at day 14, renewed activity peaked at 59 degrees C and quickly dropped as available carbon was used. Feathers soaked in an inoculum of B. licheniformis and Streptomyces degraded more quickly and more completely than feathers that were not presoaked. Inoculation of feather waste could improve composting of the large volume of feather waste generated every year by poultry farms and processing plants.

Preliminary Study of the Effect of Continuous and Intermittent Aeration on Composting Hog Manure Amended With Sawdust

The effects of using intermittent aeration during composting on ammonia emissions and dry matter loss were determined during composting of hog manure amended with sawdust. Composting trials lasted three weeks and used pilot-scale 200 liter vessels (four). The experimental design used replication of two treatments, continuous aeration (CA) and intermittent aeration (IA), in two series of experiments (total of eight tests). In the CA sequence, compost temperatures were controlled at 60°C using feedback control on high and low air flow fans while the IA sequence consisted of five minutes of air flow followed by 55 minutes of rest. Mixing ratios of hog manure to sawdust were 1:l.l and 1:1.7 dry weight basis with resulting C:N ratios of 18.2 5 1.2 and 23.7 2 2.2 for the twoseries of tests. Airflow reduction was 63 percent for 1A compared to CA. Percent nitrogen loss between treatments were moderately statistically different (a = 0.14) with average percent nitrogen loss at 29.7 percent for CA and 23.0 percent for IA. Nitrogen loss as ammonia-N was higher for CA than IA (25.9 versus 14.3) but was not statistically different. No significant differences existed in dry solids loss between treatments and the physical and chemical properties of the compost produced from IA were similar to that from CA for each series. Results showed that IA compared to CA may be a practical way to reduce nitrogen loss and ammonia emissions during composting of swine manure with sawdust.

Controlled, High Rate Composting of Mixtures of Food Residuals, Yard Trimmings and Chicken Manure

Three mixtures of ground yard trimmings (50 percent by volume in each mix), chicken manure (50, 27 and 40 percent) and potato processing, gelatin and bakery wastes were composted in four pilot-scale, 208 liter, insulated vessels (the first mixture was replicated). The mixes were obtained from a commercial composter and were studied both to obtain kinetic parameters for materials of this type and to help solve a problem of inconsistent maturity of product at the commercial operation. A 65°C set point controlled a high/low fan aeration system for each vessel. Temperature (at several points), air flow, oxygen consumption, carbon dioxide evolution and ammonia production were monitored. The vessels were weighed and materials were remixed twice each week during a four week composting period. At each remix, water was added to maintain a 50 percent by weight moisture content, and samples were taken for moisture content, volatile solids, chemical composition (including C:N ratio), pH and compost stability determin...

Composting Hog Manure/Sawdust Mixtures Using Intermittent and Continuous Aeration: Ammonia Emissions

Odorous emissions from manures have become a significant problem. Preliminary work on composting hog manure with sawdust had indicated that intermittent aeration could reduce ammonia emissions during this process. This paper presents results from four additional runs with a total of 22 pilot-scale vessels that have confirmed that ammonia emissions are affected by aeration. The pilot-scale vessels consisted of insulated, stainless steel, 205 L drums that either received continuous (high/low rate, thermostatically controlled blowers) or intermittent (5 min on high rate, 55 min off) aeration. Ammonia emissions, air flow rates, carbon dioxide production, oxygen utilization, and temperatures at four locations in each vessel were monitored. Ammonia emissions under intermittent aeration were roughly 50% less than those from the continuously aerated vessels. However, this appeared to result more from total air flow than from the aeration technique used. A linear regression of emissions versus total air flow data for all vessels yielded a fit of y = 0.1309x + 29.385 (y being total ammonia emitted [in g of N] and x being total air flow [in kg]) with an R2 = 0.6808. Since air flow termination was relatively arbitrary, this only means basically, that ammonia emissions were doubled for a quadrupling of air flow. Under intermittent aeration, the minimum oxygen level in the exhaust air occasionally dropped to as low as 1%. So the aeration pattern used probably represents the lowest one suitable for maintaining aerobic conditions. Within this constraint, however, lower air flow appears to be suitable for reducing odorous ammonia emissions.

Modeling Composting Rate as a Function of Temperature and Initial Moisture Content

A 5×5×2 factorial design was used to determine the effects of temperature and initial moisture content on the decomposition rate of paper mill sludge with broiler litter composted in a laboratory-scale incubatorbioreactor system. The composting system included ten 4 L volume (filled to 2.76 L) small-scale bioreactors. A first order kinetic model based on CO2 captured using 200 ml of 3.0 N NaOH was used to calculate the decomposition rates. Data on monitored process variables showed that the composting process was not oxygen or moisture limited. Regression analysis applied on the decomposition as a function of temperature and moisture showed that the maximum decomposition occurred around 58°C and 44% w.b. (ash free moisture of 62% w.b.) using the 2-D Gaussian model (R2=0.96). The utilization of this result on operating cost of composting showed that operating the system at 60°C would require 31% of the energy cost of operating at 50°C.

Pilot and Full Scale Evaluations of Leaves as an Amendment in Sewage Sludge Composting

The use of leaf amendment in woodchips/sludge composting was studied in pilot-scale and full-scale operations. Use of leaves at a rate of 20 percent by volume was compatible with present practices and equipment at the Columbus Compost Facility, but higher rates caused materials handling and curing problems and would necessitate system modifications. Only very slight reduction in new woodchip usage was observed for the 20 percent leaf amendment, but output of sieved-finished compost was doubled. Leaf usage increased airflow requirement per unit dry matter during the initial stage of composting but decreased ammonia release throughout the composting process. On the other hand, use of recycled materials, compost and sieved woodchips, increased ammonia release. Adequate moisture and periodic turning in the pilot-scale studies enhanced composting for all treatments. Leaf usage may necessitate forced aeration during curing to keep full size piles aerobic. In addition, leaf usage increased the total materials ha...

AMMONIA EMISSIONS AND HYDROGEN SULFIDE LEVELS DURING HANDLING OF MANURE-LADEN DRYING BED MATERIAL IN A HIGH-RISE™ HOG FACILITY

Concentrations of ammonia and hydrogen sulfide within the exhaust air from a 960-head, High-Rise TM swine finishing facility were monitored during cleanout of the facility, and emission rates were calculated from these measurements. Ammonia concentrations of exhaust air from individual fans ranged from undetectable to 39 ppm during the June cleanout period. The average ammonia concentration of exhaust air from the fans did not increase as a result of handling manure in the building. As time went on and the cleanout progressed into quadrants with less-enriched material, ammonia concentrations subsided and distribution of ammonia within the building and exhaust air became more uniform. When the last set of readings were taken, the majority of fans were exhausting air with less than 5 ppm of ammonia. Relatively small concentrations of H2S (0.4 ppm and traces) were detected in the exhaust of a couple of fans during handling of material in June. In contrast to ammonia, hydrogen sulfide concentrations were higher in November than in June. Hydrogen sulfide was detected (> 0.2 ppm) in the exhaust of 10 of the 15 operating fans with a maximum reading of 3.6 ppm. Downwind ammonia concentrations were higher during cleanout of this facility than during the production phase, but the concentrations appeared likely to have subsided below detectable levels by the time the material in the last quadrant was moved. Ammonia could only be measured (³ 0.25 ppm) 30.5 m downwind of the building when the first quadrant was being cleaned out in June. Total unit emission rates of ammonia ranged from 21.0 to 37.0 mg/min/pig space or 23.8 to 41.8 mg/min/m 2 .

Evaluation Of Approaches For Composting Horse Manure And Commercial Cardboard Bedding

Studies on composting horse manure and a commercial cardboard bedding, based on full scale, pilot, and simulation experiments, are described. Chemical, physical, and kinetic data on composting materials that allows rational design and operation of composting systems are summarized. Results showed a compost mix of 45.1 lb horse manure and 9.5 lb bedding had desirable chemical and physical properties for composting. At the start of the full-scale composting process moisture contents were 56% and C/N ratios were about 33. On day 90, the end of windrow composting, moisture content had dropped to 48% and C/N ratio decreased to 17.3. From the full-scale studies with non-aerated windrows the compost mix was shown to compost significantly and without odor. Sizing of composting system for various horse stable sizes were done for both windrow and block composting systems using a computer simulation program that incorporated the pilot scale kinetic data. Results for a 1000 head horse stable were found to be 0.81 acres based on a composting time of 180 days, 28 days windrow composting and 152 days curing. Compost generated by the facility would be 5.5 ton per day @ 44% moisture. Mass reduction would be 80% base on wet weights. The finished compost looks to be favorable as an organic amendment for potting soils, topsoil manufacture, or direct land application.