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Effects of bioadditive with yeast and zeolite on the performance and odor emission from poultry manure… Wen, Zhiping (Simon) 2006

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EFFECTS OF BIO ADDITIVE WITH YEAST AND ZEOLITE ON THE PERFORMANCE AND ODOR EMISSION FROM POULTRY MANURE COMPOSTING PROCESS by ZHIPLNG (SIMON) WEN M.Sc, South China Agricultural University, P.R. China, 1987 B.Sc, South China Agricultural University, P.R. China, 1984 A THESIS SUBMITTED IN PARTIAL FULLMENT OF THE REQURIEMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Bioresource Engineering) The University of British Columbia August 2006 © Zhi Ping (Simon) Wen, 2006 ABSTRACT Objectives of this thesis research are to determine the effectiveness of the bioadditive in reducing odor emissions, to delineate the circumstances or operating conditions under which the bioadditive would be effective, and to determine how the use of the bioadditive would affect the thermal performance of the composting process and the finished compost product. In tests performed using small bioreactors, the high dosage of the bioadditive at 10% w/w resulted in consistently greater odor removal efficiency, when compared to the low dosage at 1% w/w. However, for larger enclosed bioreactors, the bioadditive did not significantly reduce the odor levels in comparison with the control treatment. With pre-drying of the poultry manure, the bioadditive led to greater odor removal versus the control treatment on Day 2, but the reverse trend was observed and odor levels became significantly higher on Days 4 and 8 for the bioadditive treatment. Hence, pre-drying of poultry manure was not effective in eliminating the odorous volatile organic compounds from the manure, thus resulting in an increase in odor emission after the initial two days of composting. Inocula in the form of recycled compost, with previous bioadditive enhancement during the curing phase of the composting process, induced greater odor removal efficiencies, but again only up to Day 2 relative to the control treatment, which used the inocula but without previous bioadditive enhancement. Nevertheless, both experimental treatments demonstrated a significant reduction of odors, versus the treatment without using recycled compost at all as inocula, thus reaffirming the fact that recycled compost could be very effective in odor control for composting. The bioadditive had similar effects on odor removal efficiencies when poultry manure was co-composted with biosolids, versus using manure alone as the composting substrate. The thermal performance of the composting process was improved with the application of the bioadditive. The treatment with higher dosage reached thermophilic temperatures sooner than the other treatments and the high temperatures stayed for a longer time period. Similarly, treatments with bioadditive-enhanced inocula had consistently better thermal performance. Composting without pre-drying of manure was also observed to perform better than that with the manure undergoing a pre-drying process. ii Higher seed germination index was observed for the compost product with the application of the bioadditive, implying that it is beneficial for compost maturation. TABLE OF CONTENTS Abstract ii Table of Contents iv Lists of Figures vi Acknowledgement viii CHAPTER 1 General Introduction 1 1.1 Introduction 1 1.2 Aim and scope of the study 2 1.3 Organization of this work 3 CHAPTER 2 Literature Review 4 2.1 Odor Generation 4 2.1.1 Characteristics of odorous compounds from composting 4 2.1.2 Mechanism of odor generation and emission 6 2.1.3 Factors affecting odor emissions during composting 7 2.2 Principles of odor control 9 2.2.1 Inhibition of anaerobic condition 9 2.2.2 Biological or chemical transformation 9 2.3 Odor measurement 12 2.3.1 Analytical methods 12 2.3.2 Sensory methods 13 2.4 The role and application of yeast in waste treatment 14 CHAPTER 3 Materials and Methods 3.1 Experimental lab set up and configuration 17 3.2 Sampling and analytical measurements 17 3.2.1 Sampling 18 3.2.2 Olfactometry analysis 18 3.3 Composting feedstock characterization 20 3.4 Composting recipe formulation and preparation 20 3.5 Compost quality 21 3.6 Experimental design 22 3.7 Details of experimental treatments 23 3.7.1 Experimental set #1 23 3.7.2 Experimental set #2 23 3.7.3 Experimental set #3 24 3.7.4 Experimental set #4 24 3.7.5 Experimental set #5 26 iv CHAPTER 4 Results and Discussion 29 CHAPTER 5 Conclusions 59 CHAPTER 6 Recommendations 62 Reference 63 Appendices 69 Appendices A. Specifications of the Dynamic Olfactometer 70 Appendices B. Experimental Odor Concentration and Temperature Data for All Test Series 73 Appendices C. Total Nitrogen Contents of Compost at the Active Phase of Compost 79 v LIST OF FIGURES Figure 3.1. Dewar flask and cork lid details 27 Figure 3.2. Adiabatic box details 27 Figure 3.3. Experimental lab configuration and airflow direction 28 Figure 4.1. Temperature profiles during active phase of broiler litter composting with Bioadditive WT dosage (Run 1) 35 Figure 4.1 a. Temperature profiles for broiler liter composting with high dosage of Bioadditive WT (100 g/kg compost) 36 Figure 4.2. Temperature profiles during active phase of broiler litter composting with WT dosage (Run 2) .37 Figure 4.3. Temperature profiles after active phase of broiler litter composting with Re-dosing of bioadditive WT 38 Figure 4.4. Temperature profiles during active phase of broiler litter composting in Exposed bioreactors 39 Figure 4.5. Temperature profiles during phase of broiler litter composting in Enclosed bioreactors 40 Figure 4.6. Temperature profiles during active phase of broiler litter composting with Pre-dried manure 41 Figure 4.7. Temperature profiles during active phase of broiler litter composting, Without pre-drying manure .42 Figure 4.8. Temperature profiles for broiler litter composting, with and without WT- enhanced recycled compost (Run 1) 43 Figure 4.9. Temperature profiles for broiler litter composting, with and without WT - enhanced recycled compost as inocula (Run 2) 44 Figure 4.10. Odor concentrations associated with two dosages of bioaddtitive WT application during the active phase of broiler litter composting 45 Figure 4.11. Odor concentrations from enclosed (upper) and exposed (lower) Bioreactors during the active phase of broiler littler composting, With bioadditive application 46 vi Figure 4.12. Odor concentrations associated with bioadditive application during the active phase of broiler litter composting, with (upper) and without (lower) pre-drying of manure 48 Figure 4.13. Effectiveness of recycled compost as inocula in odor removal, with and without enhancement by the bioadditive WT, during the active phase of broiler litter composting (upper: run 1; lower: run 2) 50 Figure 4.14. Effectiveness of recycled compost and bioadditive in odor removal during the active phase of the co-composting of broiler litter and biosolids 52 Figure 4.15. Total nitrogen content of compost during the active phase of Composting (Run 1) 54 Figure 4.16. Total nitrogen content of compost during the active phase of Composting (Run 2) 56 Figure 4.17a. Seed germination index after 30 days of composting 57 Figure 4.17b. Seed germination index after 30 days of composting 58 vii ACKNOWLEDGEMENTS I would like to acknowledge, my supervisor, Dr. Anthony Lau, for his whole-hearted encouragement, support, and guidance. I am thankful to my committee members, Dr. Victor Lo and Dr. Kim Cheng, for their valuable advice and suggestions. I wish to extend my thanks to Dr. Ping Liao, for his technical support and all "olfactometer panelists": Gladis Lemus, Weigang Yi, and particularly Wenxiu Zhang, who also endured countless hours of my frustration. viii CHAPTER 1 GENERAL INTRODUCTION 1.1 INTRODUCTION Animal manure management is one of the most important environmental issues confronting the world today. Canadian livestock produce an estimated 0.36 million tonnes of manure daily; this translated to over 132 million tonnes of manure a year (Statistics Canada, 2001). In British Columbia, the poultry industry sector is the largest producer of surplus nitrogen in the Fraser Valley and this trend will continue towards 2010 (Timmenga and Associates Inc., 2003), when there will be close to 320,000 tonnes of poultry manure produced annually. As the population increases and livestock industries expands to meet the demand, the huge amount of manure together with other organic waste materials such as municipal biosolids, yard waste, food waste and wood waste has imposed a significant challenge to environmental protection and sustainable development. Airborne odor and dust emissions which originate from manure and feed constitute a significant environmental sustainability issue facing the poultry industry. While land application of poultry manure is a common practice in the Fraser Valley, provincial regulations require that manure be stored rather than spreaded from October to April (wet seasons) in the Lower Mainland and Fraser Valley of B.C. in order to avoid contamination of receiving water (surface runoff or groundwater). Concerns about pathogen contamination will likely put more constraints on land application of manure, and some kind of treatment is required for the manure. Composting is being perceived as an essential element of the holistic approach in solving the environmental challenges via converting organic wastes into a value-added product. Nevertheless, composting being an aerobic biological oxidation process of organic matter involves the undesirable emission of gaseous products, particulate matters (dust and bioaerosols), and leachate. So far, odor control is the most difficult problem to solve in 1 today's composting practices (Feinbaum 2000, Gage 2000). Failure to adequately control odors has led to numerous neighbor complaints causing the closure of many large-scale facilities. Traditionally, odor has been regarded primarily as a nuisance issue, but the health effects of odors are now receiving rigorous scientific study (Schiffman and Williams, 2005). Odor emission is now considered to be a high priority air quality issue because of its immediate impact on the population (GVRD, 2005). Traditional means used by the majority of operators for odor control involve collection and treatment using absorption (such as chemical scrubbers), adsorption (such as activated carbon) or thermal oxidation. In recent years, the use of biofiltration is becoming widespread (Goldstein, 1998; Sironi and Botta, 2001). These solutions to the odor challenge require additional equipment and/or space, which could be costly, and do not address the source of the problem. Moreover, the scrubbing solution must be utilized or disposed of in some way. Prevention, a strategy that reduces odor and ammonia emission potential from its generating sources, could be a viable alternative. 1.2 AIM AND S C O P E OF THE STUDY Some research studies have been done on additives that can enhance the performance of composting and reduce odors at the source of generation since the 1970's, but the results have been mixed. A more comprehensive evaluation is desirable. The goal of this thesis research is to investigate the use of bioadditive in the form of yeast in combination with zeolite to reduce odor generation during the active phase of poultry manure composting. Specific objectives are: 1. To determine the effectiveness of a bioadditive in reducing odor emissions from poultry manure composting process; 2. To delineate the circumstances or operating conditions under which the bioadditive would be effective; and 2 3. To determine how the use of the bioadditive affects the thermal performance of the composting process and the finished compost product. 1.3 ORGANIZATION OF THIS WORK The thesis is comprised of 5 chapters. Chapter 1 is a general introduction to the problems associated with poultry manure disposal and composting as an alternative means of treatment. The general aim of the study and the organization of the work are also presented in this chapter. Chapter 2 provides an in-depth literature review of previous works on poultry manure composting, with emphasis on odor emissions, as well as the effects of additives on odor control. Chapter 3 concerns to the methodology used in the actual experiments, with lab scale in-vessel composting technology. The results pertinent to odor emissions are presented in Chapter 4 along with discussion of thermal performance, odor emissions and compost quality in terms of nitrogen content and seed germination index. Finally, Chapter 5 summarizes the main findings of this research, and recommendations for future studies are found in Chapter 6 of the thesis. 3 CHAPTER 2 LITERATURE REVIEW 2.1 ODOR GENERATION 2.1.1 Characteristics of Odorous Compounds from Composting Odors are defined as sensations resulting from the reception of a stimulus by the olfactory sensory system, which consists of two separate subsystems: the olfactory epithelium and the trigeminal nerve. Substances that stimulate the human olfactory sensory system are known as odorants. Odors may come from the raw materials or the products of biochemical metabolism. Usually organic wastes such as manure, sludge, fish waste and grass clippings will tend to have significant odor potentials due to their composition (high in sulfur and/or nitrogen contents), and their tendency to compact; thus becoming anaerobic. Manure composting also has a high potential for ammonia emission. In the high-rate phase of composting, nitrogen-rich materials are transformed by biochemical reactions. This decomposition is accompanied by a high rate of ammonification (Bishop and Godfrey 1983). Studies showed that as much as 33 to 62% of the initial nitrogen may be volatilized as ammonia gas emission (Morand et al. 1999, Sommer and Dahl 1999, Mahimairaja et al. 1994, Martins and Dewes 1992, Witter and Lopez-Real 1988, Hansen et al., 1989, Kithome et al. 1999). Ammonia is toxic, reactive, and corrosive with sharp odor. The substantial loss of ammonia not only leads to severe odor and health nuisance on site at composting facilities, but also reduces the agronomic and market values of the compost product. Most odors discharged to atmosphere from agricultural sources consist of complex mixtures of many odorants (Haug 1993, Day et al. 1999, Goldstein 2002), in the form of gases and vapors; odorants are also carried on dust particles. More than 150 odorous 4 compounds were identified in manure odors (Sweeten et al 1994, O'Neill and Phillips. 1992). Sulfur Compounds Total reduced sulfurs are identified as major malodorous compounds in composting. Under anaerobic conditions, reduction of the sulfur takes place, leading to the production of hydrogen sulfide. Mercaptans can be formed under both aerobic and anaerobic conditions. If more oxygen is available, mercaptan can be oxidized to dimethyl sulfide and dimethyl disulfide. Reduced sulfur gases have highly offensive smells and can be detected at very low concentrations. Nitrogen Compounds Ammonia is produced from either aerobic or anaerobic decomposition of proteins and amino acids. It has a sharp and irritating characteristic smell. However ammonia has relative high threshold odor concentration, and can be diluted rapidly to below detection. It is a major odor on site, but is usually a minor odorant away from the composting facility. Amines, which are produced during anaerobic decomposition of proteins and amino acids, are also nitrogen-based compounds with bad smelling, and can also have high toxicity (Busca and Pistarino 2003). Trimeththyl amine is difficult to biodegrade because microbes cannot easily break apart its molecules (Goldstein, 2002). Indole and skatole, as well as phenolics are produced during anaerobic decomposition of protein matter and have a very offensive nauseating odor with low human detection limits. Volatile Fatty Acids Volatile fatty acids (VFAs) are the most significant odorous compounds in manures. VFAs are by-products of anaerobic decomposition. They decompose rapidly when air passed through them (Cooper et al., 1978). Rapid, early composting removes most of the VFAs through bacterial consumption, and this could substantially reduce the potential for later release (Elwell et al., 2001). Other odorous compounds found in composting facilities include ketones, aldehydes, alcohols and terpenes. These odorous compounds could be contained in feedstock or 5 formed as intermediates during composting. The odor strength of these compounds are relatively insignificant compared to the other major types of odors. 2.1.2 M e c h a n i s m o f O d o r G e n e r a t i o n a n d E m i s s i o n Biochemical metabolism in composting process produces many intermediate compounds that are odorous. Offensive odors generally result from anaerobic metabolism. However, odors may also be generated by aerobic decomposition although aerobic intermediates may sometimes be less obnoxious. Some malodorous compounds naturally present in the plant and animal materials may also be objectionable regardless of whether or not they become anaerobic. Odor generation from composting process involve quite complicated mechanisms, and are generally believe to be a combined result of microbial activity and contribution of environmental factors. During composting, odorous compounds with high volatility and low molecular weight typically 17-152 g/mole (Yuwono et al., 2004) are generated as intermediate or end products by either aerobic or anaerobic bacteria. The low molecular weight compounds generally have high vapor pressure and potential for emission to atmosphere. However, the volatility of molecules is not solely determined by their molecular weight; the strength of the interactions between the molecules also plays an important role, with non-polar molecules being more volatile than polar ones. Odor emission, then, is primarily dependent on the type and age/state of feedstock (Elwell et al., 2001). High odor emissions normally occur during the active phase of composting (Bidlingmaier, 1993; Benedict et al., 1988; Day et al., 1998). As the process progresses, some odorous compounds such as amines and VFAs decrease (Goldstein, 2002). 6 2.1.3 Factors Affecting Odor Emissions during Composting The major factors affecting odor emissions generated during composting are: substrate characteristics (carbon-to-nitrogen C/N ratio, bioavailability, particle size and pH), environmental conditions (temperature, moisture, partial pressure of oxygen), and operational parameters (aeration, agitation). The key factors that can be readily controlled to promote aerobic conditions are aeration, moisture content, temperature, C/N ratio and particle size distribution (Richard and Trautmann, 1995, Day et al., 1999, Ohio EPA, 1999). Aeration is probably the most influential factor to odor emissions. Aeration promotes aerobic conditions and reduces the more offensive anaerobic odors. Air emissions from composting are directly related to the aeration rate, with increased volumes of air emissions for larger aeration rates. On the other hand, aeration also serves as driving force for volatilization of odorous compounds. The effectiveness of aeration is dependent not only upon the flowrate in the case of forced air used, but also the particle sizes, moisture and density of the compost mix. Small particles, excess moisture and overly dense material will reduce free air space, impede aeration and increase the potential for odor generation (Ohio EPA, 1999). Moisture content is a crucial factor as it affects many aspects including free air space, microbial activity, and heat and mass transports. Because oxygen diffusion is some 10,000 times greater in air than in water, when excess moisture fills the pore space creating larger water filled zones between particles and reducing free air space, oxygen diffusion is slowed down, resulting in anaerobic clumps. With most composting materials, as moisture content increases beyond 65-70%, anaerobic conditions can be developed. Small particles can also interact with high moisture levels to reduce oxygen transport and generate anaerobic odors, since they reduce the number of large pores and increase the likelihood that oxygen will need to diffuse a long way through small pores. (Richard and Trautmann 1995). Moisture content in the composting mix also has an effect on the amount of ions that can be kept in solution. In the case of ammonia, a higher 7 moisture content would keep more ammonia in solution, thus decreasing its volatilization, and increasing immobilization (Liang 2000). Temperature is important to odor emissions. The concentration of a particular odorous chemical in air emission is dependent upon its vapor pressure; the increase in vapor pressure of chemical compounds with temperature is well known. For forced aeration system odor emission is a function of both odor concentration and airflow rate. Since more air has to be used to lower the compost temperature, a higher volume of exhaust air will be generated. However, government regulations (BCMWLAP 2004) require active compost temperatures greater than 55°C for pathogen elimination, hence, it is not practical to reduce air emissions via lowering the composting temperature. Nevertheless, odor emission rate, which is a product of odor concentration and aeration rate, could be curtailed if a high aeration rate was not needed for temperature control (removal of excessive heat) of the composting process. Whereas the overall effect of high temperatures on odor emission is indefinite, ammonia volatilization increases with temperature, since higher temperatures increase the relative proportion of NH3 versus NHV" (especially under high pH conditions), decrease the solubility of NH3 in water, and increase NH3 diffusion in the composting mass (Liang 2000). Such positive correlation of ammonia emission with temperature and pH has also been reported by Jakobsen (1994). C/N ratio determines nutrient balance. A lower ratio can result in higher ammonia emission. Excess nitrogen can also cause accelerated microbial growth, which will rapidly use up the available oxygen, resulting in anaerobic conditions. A higher C/N ratio, however, may result in insufficient nitrogen for optimum growth of microorganisms and slowing down the composting. 8 2.2 PRINCIPLES OF ODOR CONTROL A wide variety of measures for composting odor control have been investigated and some of them are used in practice. Two main principles relevant to this thesis are summarized in this section. 2.2.1 Inhibition of Anaerobic Condition Inhibiting anaerobic condition and minimizing the opportunity for odorant volatilization can reduce the odor emission potential. Oxygen availability is the key to prevent anaerobic conditions. It was found that anaerobic pockets start forming, which then leads to formation of odorous compounds if oxygen content drops below 17 percent (Goldstein, 2002). Forced aeration is probably the most viable choice to prevent anaerobic odors technically as well as economically. Some studies suggested that increased aeration generally results in decreased concentration but an increase in total emission of odorous compounds (Walker, 1993, Fraser et al. 2000). In contrast, a study conducted by Elwell et al. (2001) gave mixed results. Their data showed that a 76% reduction in airflow resulted in a substantial reductions in acetic, propionic and butyric acids release, but isobutyric, isovaleric and valeric acid emissions increased. While it has been well known that aeration strongly affects odor concentration, its net effects on odor production are still not clear. 2.2.2 Biological or Chemical Transformation Chemicals can bind odorants by adsorption, absorption, or chelation. The effectiveness of the commercial products varies widely, with many of the products untested in a controlled, unbiased setting (Powers, 2004). Bioadditives purport to degrade odorous compounds via biologically generated enzymes. Each enzyme can act on many molecules of an odorous compound before it is eventually degraded (Richard and Trautmann 1995). 9 With respect to odor emission in the form of ammonia (NIB), various additives have been studied to adsorb N H 3 and N H 4 + or chemically transform them before releasing. Alum and phosphoric acid have both been shown very effective in reducing NH3 volatilization from animal manures. Alum produces H + when it dissolves, which reacts with NH3 to form N H 4 + . , which can in turn react with the sulfate to form ammonium sulfate. Phosphoric acid can directly react with NH3 and form ammonium phosphates. DeLaune et al. (2004) reported that Alum and phosphoric acid could reduce N H 3 volatilization from composting poultry litter by as much as 76% and 54% respectively. Witter and Kirchmann (1989) used peat, zeolite and basalt to reduce NH3 emission. All these adsorbents were proved to be effective in adsorbing ammonia in gases, but less effective when mixed with manure. Kithome et al. (1999) also investigated reducing N H 3 losses during composting of poultry manure with various amendments, including zeolite, clay, coir, chloride and sulfate salts of calcium and magnesium, and alum. They found that 38% zeolite and 33% coir amendments were the most suitable of treatments out of those tested for reducing ammonia losses. The advantages of using either zeolite or peat are that they are non-hazardous and can act as good soil conditioners. In the late 1970s, more than 20 commercially available manure additives were tested at the University of Illinois for their ability to control odor and reduce solids in stored manure slurry. The overall performance of these products was reported to be disappointing, and there was little difference between treated and untreated manure. In the past decade, some more commercial products and organic material (Examples: Agri-Scents, Biosurge, Micro-Aid, Natural Odor Catalyst, and sphagnum peat) have been suggested to farmers for addition to manure to obtain beneficial effects. Claims of such beneficial effects include: reduction in odor and ammonia losses, stimulation of bacterial activity, improvement in solids handling, increased manure decomposition and composting rates, and so forth. However, very little information about the test results was reported in scientific publications. 10 Among other studies, controlled tests were performed on these products at the Research Branch of Agriculture Canada in Ottawa in the early 1990s (for instance, Patni and Jui 1993). No significant effects were observed on volatile fatty acids (VFA) production, leading to the conclusion that these additives could not control the offensive nature of manure odor. Apparently, these studies did not provide a full assessment of odor emission, for two reasons: a) only the concentration of VFAs was measured, but total odor level was not quantified via olfactometry; and, b) even if individual odor-causing substances such as VFAs were used as indicators of product effectiveness, other major odors present in poultry manure, such as sulfur-compounds, amines, skatole and indole were not measured. Starbuck and Wesley (1998) were among those who insisted that commercial additives such as microorganisms, mineral nutrients, vitamins, enzymes or readily available forms of carbon do not do much and that the most important additive is still good composting pile management. Kdrner et al (2003) observed from lab-scale experiments that odor reducing additives might limit microbial degradation under aerobic conditions; if a higher concentration of the additive was used, oxygen consumption rate would be lowered and the period of microbial inhibition lengthened. Nevertheless, they also found microbial adaptation to the additive at a later part of the trial, resulting in effective biodegradation. Yulipriyanto et al. (2002) used three different additives (lingo-cellulosic waste, microbial additive or Yucca juice) to assess their effects on the nitrification-denitrification activities during composting of chicken manure piles. In particular, the microbial additive had modified the composting conditions and microbial environment, thus conserving more nitrogen; lingo-cellulose waste had increased the C:N ratio (hence less ammonia volatilization), and Yucca juice was effective in regulating the ammonia emission via promoting denitrification activities. 11 2.3 ODOR MEASUREMENTS Odor measurement is a complicated task due to the complex composition of odors, environmental factors, and varying human perceptions of offensive smells (Chapin et al., 1998). Generally, the measurement of odors can be classified as either analytical or sensory methods. Conventional measurement of odors involves two techniques: (1) measurement of the concentrations of individual odor-causing chemical compounds, and (2) measurement of total odor level via olfactometry using the human sense of smell. Physical and chemical detection methods include gas chromatography and mass spectroscopy (GC/MS). Olfactometry, which is directly related to receptors, is still a widely used method of measuring odors (Feddes et al. 2001, Chen et al. 1999, Bruce 1998, Krzymien and Day 1997, Callan 1993, Berglund et al. 1987). 2.3.1 Analytical Methods Analytical method does not rely on human sensory perception but instead aims at identifying surrogate compounds that are major contributors to the perceived odor. From the standpoint of odor control, it might be useful to identify these compounds, so that they can be targeted with control strategies (Powers, 2004). The analysis of chemical odorants can be accomplished using a variety of analytical methods ranging from wet chemical methods, colorimetric detector tubes to GC/MC techniques. Wet chemical method involves several absorption techniques. This method is frequently used for measuring hydrogen sulfide and ammonia. Wet chemical method is also capable of measuring other odorous compounds such as methyl mercaptan, dimethyl sulfide, dimethyl disulfide, aldehydes, and amines (WEF and ASCE, 1995). Colorimetric detector tubes can provide useful information by identifying specific gaseous compounds that emit odors instantly. However, this method usually has a large error range and can only be used for discrete sampling purposes. 12 Odor often consists of a complex mixture of numerous odorous compounds. In order to identify and quantify the constituents of odor, gas chromatography coupled with mass spectrometry (GC/MS) technique is most frequently used, where chemical compounds are separated based on their volatility. However, the interpretation of results in this method is complicated because odors that are equal in concentration may not be equal in offensiveness or intensity. Furthermore, two odors of equal concentrations may not be perceived as having different intensities (Powers, 2004). 2.3.2 Sensory Methods Sensory evaluation of smells is accomplished by using a variety of devices: scentometers, odor observation rooms, static olfactometers, butanol olfactometers, and dynamic olfactometers (Watts 1999). Perception of a mixture of odorants is usually very different from how each chemical would be perceived individually. Moreover, total odor strength which is required for regulatory purposes cannot be directly quantified using GC/MS. Electronic nose analysis with a sensor array is an emerging new tool for odor evaluation. The electronic noses have been developed in attempt to mimic the human response to odor. Olfactometry analyzes the complete gas mixture so that contribution of each compound in the odor is included in the analysis. The main challenges of this method are variation in the performance of panelists and odor fatigue. Proper procedural protocol is therefore very important. The most recent advance is the development of the "European Standard". The use of this standard has substantially improved the reliability of odor concentration analysis and reduce the degree of subjectiveness of the human perception of odors, over a number of years (CEN 2002, C E N 1995, A S T M 1991). While electronic nose technology has aroused a lot of interest lately (Nicolas et al. 2000, Krzymien and Day 1997), and is potentially useful in providing an objective non-sensory method, it is currently providing little practice use (Power, 2001). For odor measurements, methods to apply electronic nose devices in a practical way still need further research and development. Olfactometry remains a widely used and most valid method for odor evaluation at present (Zhang et al. 2002, Feddes et al. 2001, Chen et al. 13 1999, Bruce 1998, Callan 1993, and Berglund et al. 1987); (Sweeten et al., 1994, WEF & ASCE, 1995, Chapin et al., 1998, Power, 2004). A typical olfactometer (dynamic dilution device to measure odor units, or 'ou') is a forced choice, dynamic triangle olfactometer having 3 sniffing ports per panelist station. In this device the diluted sample is flushed into one sniffing port, whereas filtered and odorless air is flushed into the other two ports. The panelist needs to differentiate which port has the odorous sample (a 'yes/no' type of question). Usually, 6 to 8 panelists participate in the test. These persons need to be screened to ensure a "normal" sense of smell. The number of times a given amount or volume of sample needs to be diluted with odorless air to reach an odor threshold level is called the Threshold Odor Number (TON). Different names have been used for the TON: Odor unit (ou), effective dose at 50% level (ED50), dilution-to-threshold value (D/T), dilution ratio Z, and dilution ratio K (or K50). Usually the terms 'ou' and 'D/T' are preferred. It is important to note that this 'ou' term refers to the number of volumes (i.e. m3) that a sample will occupy when diluted to the odor threshold. Thus, odor units (ou) are volume of sample diluted to threshold volume of original sample. In other words, 'ou' is a dimensionless value. However, most of the times the odor concentration is equivocally expressed as ou/m3 (Haug 1993). Typical composting odor concentration values, in odor units [ou], (values of odor concentrations of exhaust gas samples from typical composting operations) found in the literature are summarized below: received materials (800 - 7500); in-vessel pile (380 -3400); curing pile (540 - 3200); windrow composting (5000 - 25000); rotating drum MSW composting (25000 - 50000); and biofilter outlet (45 - 510) (Lau et al. 1996, Giggey et al. 1995, Haug 1993). 2.4 THE ROLE AND APPLICATION OF YEAST IN WASTE TREATMENT biotechnology has received increasing attention in recent years for waste treatment and waste conversion to resources. It includes a wide variety of applications of biotechnology 14 to natural, agricultural and man-made environments, though it is generally perceived as bioremediation, i.e. the use of living organisms to help clean up the environment. Microorganisms Environmental dominate environmental biotechnology; the main groups of organisms which environmental biotechnologists employ are algae, bacteria and fungi (including the non-filamentous yeasts). Research studies have indicated the use of yeasts in the treatment of wastes is technically feasible and may have economic significance. In the early 1970's, a food yeast, Candida utilis NRRL Y-900 was found to be able to rapidly convert the soluble and suspended solids (as measured by BOD) from sauerkraut waste into yeast cell. The yeast completely neutralized the waste acid and removed approximately 70-90% of the waste BOD, T K N and TP (Haug, 1973). In another study, Candida utilis helped to reduce the COD of confectionery wastewater by 65%, making it weak enough for direct discharge to the sewer system. A strain of Candida utilis isolated from silage effluent in pure culture could remove the COD and TOC of the silage effluents (Arnold et al, 2000). For different concentrations of the silage effluent, 75-95% of COD removal efficiencies were obtained; high reductions of phosphate and some removal of ammonia were also observed. Choi and Park (1998) observed an early increase in the growth of yeast followed by the growth of thermophilic bacteria due to the removal of organic acids (but with a subsequent rapid decline in yeast population) during composting of food waste at 50oC using a lab-scale composter. Enzymes that contain P-glucan and P-glucosidase (cellulase) are present in certain yeasts, which can readily degrade cellulose, a major component of plant and animal wastes. A number of studies have shown yeasts can be successfully used in wastewater treatment. 'Lactic yeasts' could produce some extracellular metabolites, as well as biomass, when cultivated in whey (Cristiani-Urbina et al. 2000). Yeast might be working at the biochemical level, shifting microbial population. Tequia et al. (2002) found that the population of fungi and actinomycetes were most positively correlated with the activities of the a-galactosidase and P-glucosidase enzymes. Kim et 15 al. (2002) isolated and identified yeasts from soil and compost sources; both yeasts identified as Candida rugosa and Candida maris were found to be effective in reducing NH4-N, soluble-N and BOD of pig feces. The former was highly effective to reduce propionic acid, butyric acid and iso-valeric acid; therefore, it had beneficiary effect on the deodorization of VFAs in pig feces. In a study of grass composting with olive mill wastewater added, a high correlation was observed between phenol degradation and 0-glucosidase activity (Grego et al., 2002). In an earlier study, Vuorinen (2000) monitored the effect of the bulking agent on P-D-glucosidase activity during the composting of cattle and pig manure; the choice of bulking agent was found to strongly affect the potential capacity and property for mineralization of organic phosphorus in manure composts, but did not affect glucosidase activity, although this is one of the key enzymes in the decomposition of cellulosic plant materials like straw. 16 CHAPTER 3 MATERIALS AND METHODS The bench-scale composting trial reported in this study was completed at the University of British Columbia, Waste Management Pilot Plant of the Chemical and Biological Engineering Department. The details on composting reactors configuration, analytical procedures, as well as feedstock preparation and recipe formulation are described in the following sections. 3.1 Experimental Lab Set Up and Configuration Composting bioreactors were double-walled stainless steel Dewar flasks with vacuum in between, that gives them thermos-like characteristics (Cole Parmer Instruments Company, Vernon Hills, IL, USA) of 6 litres working volume. The composting vessel was positioned inside an insulated (adiabatic) box in order to simulate typical in-vessel composting process, or the core part of a compost pile. Temperatures inside the composter and ambient temperature were monitored hourly using copper-constantan thermocouples. The temperature data were collected using a data acquisition board and a PC. Fulfillment of the pasteurization requirement was determined from the composting temperature profiles. Figures 3.1 shows the schematics of the experimental lab set up and composting process configuration. Composting process temperature control was attained by using Labtech Control™ Software. The strategy used was the industrial standard (Rutger's Method), where aeration is intermittent (33% duty cycle) below the temperature set point, and continuous above the temperature set point. Aeration was provided to the bioreactors using a series of pumps. Airflow was according to the standard rate of 0.72 L/min.kg dry matter as suggested by Rynk (1992). Air entered the composting vessel from the bottom and was exhausted from the top area. A metallic mesh at the bottom of the reactor provided support for the composting mass, and an 17 aquarium air diffuser located below the mesh distributed the incoming air. Temperature data were collected for the first 7-14 days during the active phase of composting. 3.2 Sampling and Analytical Measurements 3.2.1 Sampling Samples from the exhaust gases were collected manually using the bag-and-vacuum technique. During sampling, a Tedlar bag, with a volume of 5-L or 10-L and fitted with one plastic valve (Safety Instruments Inc., Edmonton, AB), was filled with exhaust gas by activating the vacuum-inducing pump. The sampling period lasted 2 minutes whereby the aeration pump was 'on' for 1 min, and then "off for 1 min. In each sampling event, approximately 2-3 L of exhaust gas sample was collected for further analysis. Odor sampling took place on Day 1 (prior to start of experiment), Day 2, Day 4 and Day 6 or 8. Sample bags were reused until they cannot be totally refreshed. In order to reuse the bags, a 'bag-cleaning system' was set up by using 2 peristaltic pumps (one for filling the bags, and one for emptying them, Cole Parmer, Model No. 7553-70), an activated carbon filter, an automatic chronometer (Chrontrol Model CD-4, Lindburg Enterprises Inc., San Diego, CA) and Tygon R-1000, NSF 51 tubings. The bags were 'flushed' with filtered air for a number of 10-minutes fill-empty cycles, and then stored for 30 hours. Regular odour measurement via the odor panel and dynamic olfactometer was performed on each bag; a bag material shall be considered odourless if no threshold can be measured for the bag. 3.2.2 Olfactometry analysis A full evaluation of odor involves five parameters: (1) threshold odor concentration, which refers to the minimum concentration of an odor-causing compound or odorant that will arouse a sensation; (2) odor intensity, a measure of odor strength; (3) hedonic tone, which is a measure of odor acceptability; (4) pervasiveness, which concerns the difficulty 18 of eliminating an odor by dispersion; and (5) character or odor quality, which describes what the odor smells like (Feddes 2001, Haug 1993). In this thesis research, odor will be primarily characterized via odor concentration. A dynamic dilution olfactometer previously designed, assembled, and calibrated by Bruce (1998) in accordance with the A S T M E-679 Standard (1991) was available for olfactometry measurements. It was upgraded in 2003 to comply with some of the recommendations by the European standard prEN13725 (CEN, 2002). Figure A l in Appendix A shows this instrument for odor analysis. Its dilution capability ranges from 25 to 2 1 8. The panelists who participated in the odor panel tests need to be screened by n-butanol vapor at 40-80 ppb to ensure a "normal" sense of smell. Each test sample was presented to the panelist in ascending order of sample concentrations. A series of dilution ratios with a factor of 2 was used in order to avoid olfactory fatigue (odor habituation and loss of sensitivity). A forced-choice triangular test protocol was used, via three sniffing ports associated with each of the two panelist stations. The airflow rate through each port was controlled at 20 L/min. The diluted sample air is flushed into one sniffing port, whereas odor-free air is flushed into the other two ports at the same time. Compressed air from the building air supply system is filtered with activated carbon to generate odor-free air. The panelist must select one of the three ports to be associated with the diluted but odorous sample. The automated system used has six electrical switches arranged in two sets - one set for port selection, and the other set for certainty of choice ("positive, inkling or negative" perception of the presence of odors). The electrical switches are connected to a computer, which processes the results with the aid of a software program. Olfactometry analysis gives the total odor concentration of the sample, expressed in [odor units, ou, or traditionally known as dilution-to-threshold, D/T\. The European standard defines an odor unit, O U E , as the amount of odorants that, when evaporated into 1 m of neutral gas (air or nitrogen) at standard conditions, elicits a physiological response from an odor panel equivalent to that elicited by one European Reference odor mass (with 40 19 ppb n-butanol) under the same conditions. The odor threshold value, then, is the dilution at which 50% of the panel members could just detect an odor. The value of odor units represents the pervasiveness of the odor, which concerns the difficulty of diluting and eliminating an odor. The statistical analysis of the panelists' responses produces a number called 'Best Estimated Threshold Concentration (BET)' of the panelist. The 'BET' numerically corresponds to the geometric mean of the last missed and the first correctly identified concentration. The "OU" number was then calculated as the statistical combination of these responses for a given sample. 3.3 Composting Feedstock Characterization Total composting mass was measured gravimetrically (Balance OHAUS I-10, Ohaus Corporation, Florham Park, NJ) before and after composting. Moisture content was measured by gravimetric analysis and oven drying (at 101°C) for 18-24 hours. The amount of volatile solids was measured by gravimetric analysis and ash content (ignition at 550°C for 2 hours, APHA 1995). Carbon content and nitrogen content were determined by using a Carlo Erba NA-1500 C N Analyzer at the Earth and Ocean Sciences Lab at UBC. Bulk density of the composting mixes was measured by the mass-per-volume technique, where a container of known volume is filled up with the composting mix, special care was taken to not over-compact the mixture. 3.4 Composting Recipe Formulation and Preparation Literature review indicated that the use of manure additives, in the form of biological or chemical products, is not a new concept. Nevertheless, products continue to evolve in recent years. The bioadditive used is "WT", a product patented by C K Life Sciences International Inc., Hong Kong. "WT" is 85% zeolite, 10% starch, and 5% yeast by mass. The product contains common powdered-form yeast strains, primarily Saccharomyces 20 cerevisiae (baker's yeast) and Saccharomyces carlsbergensis (brewer's yeast), with no genetic modification. The production of yeast is via selection, activation and acclimatization by proprietary biochemical and biophysical methods to improve the expression of enzymes responsible for the biodegradation, transformation and sequestration of pollutants in situ. The major substrate used in the laboratory-scale composting experiments was poultry manure in the form of broiler litter or layer litter, which comprised mainly of manure and wood shavings, and with different moisture contents. In order to have an effective composting process it is necessary to set the key process parameters (moisture content, carbon-to-nitrogen ratio C:N and bulk density of the composting mix) to the optimum ranges (Richard et al. 2002) using a composting recipe formulation. The proportions of each feedstock were changed manually until the achieved the target or desirable range of values. The initial composting mixture was targeted to have a C:N ratio of 30-40, moisture content of 50-55%, and bulk density of 350-450 kg/m3. In actual operation then, water was added to the mixture when it is too dry, whereas extra bulking agents (bark) were added to improve the porosity. 3.5 Compost Quality Compost quality was determined via its nitrogen content and seed germination index. The nitrogen content is a major indicator of the fertilizer value of compost. It has been observed that when fresh or immature compost is applied to soil, plant growth may be irregular and even inhibited owing to the toxic substances evolved from the decomposing organic matter. The effects may become lethal when unstabilized organic matter is placed in direct contact with an existing root system. The phytotoxicity of compost may be determined using the seed germination test, which was conducted as follows: Water extracts (4:1, distilled water to compost) were mixed for 1 hour at 180 rpm in an orbital shaker, and centrifuged at 13000 rpm for 20 minutes and 21 then filtered using Whatman No.l filter paper. Two ml of at least 10% dilution of the water extracts was poured into Petri dishes (10 cm O) lined with filter paper. Ten seeds of radish (West Coast Seeds Ltd., Delta, BC) were placed in the Petri dishes (7 replicates per sample). The samples were incubated for 48 hours in the dark at 27 ± 2°C. After that period 1 ml of a 50% v/v ethanol solution was added to halt germination. The status of seed germination (yes or no), and root length, in [mm] were measured and compared to blank samples that had only distilled water added to the seeds, without any compost sample. The germination index, Gl in [%], was calculated using the following formulae: G l = (SGSample X R L s a m p i e ) / (SGblank X RLblank) where SG is the average number of germinated seeds and RL is the average root length. A germination index (Gl) of 50% or less would indicate a potential phytotoxicity (Zucconi et al. 1981). 3.6 Experimental Design The experimental treatments were divided into 5 experimental sets. Each set of experiment lasted for 7 days when the composting process is going through the active phase; odor emission was measured and analyzed mostly over this 7-day period. If the curing phase is involved, odor sampling will take place during the first two weeks of curing. The high-rate phase of composting was deemed to be finished whenever the composting mix temperature had dropped back to ambient level. For most of the experimental treatments this occurred within 168 hours (7 days). Thus the duration of the high-rate phase for all treatments was chosen to be 168 hours, and data were collected during this period. 22 All experimental sets used broiler litter as the feedstock, with initial moisture contents of 15-25%, and C:N ratio of 35-40. Water was added to the composting materials to achieve a final moisture content of 65%. Experiments were conducted during the period January to December 2003. The experimental series were repeated where necessary. 3.7 Details of Experimental Treatments This section describes the objective and the particulars of each experimental set. 3.7.1 Experimental Set #1 The aim of experimental set #1 was to find out whether the bioadditive WT has a significant advantage over composting in reducing the odor release from poultry manure. The various treatments involve the control without any bioadditive, and two dosages of the bioadditive, 10 g/kg compost (or 1% w/w) and 100 g/kg compost (or 10% w/w). The effectiveness of WT was determined via comparison with the control treatment. However, in some of the tests, the treatment "No WT, No aeration" was included in the study to reflect current practice in poultry farms, i.e. manure stored in pits, untreated, and without the supply of forced aeration. Another objective of these treatments is to test the effect of adding WT after the temperature-ascending (active) phase of composting 3.7.2 Experimental Set #2 The objective is to compare between exposed (open-top),and enclosed bioreactors during the active phase of composting. Exposed bioreactors are meant to represent aerated static 23 pile composting, whereas enclosed bioreactors represent in-vessel composting or the core part of windrow or aerated static composting piles. 3.7.3 Experimental Set #3 The aim of experimental set #3 was to determine whether the effectiveness of the manure additive in reducing odor release from manure might be enhanced, if there is no competition from other indigenous bacteria and there is a relatively low content of volatile solids in manure. The experimental design therefore involved pre-treatment of poultry manure via drying. In other words, it is to test the hypothesis that drying the manure in an ordinary manner will remove some odor so that during subsequent aerobic treatment, odor release form the manure will be reduced Manure was placed in the 104oC oven for at least 8 hours. After a composting mixture with the proper initial moisture content, pH and C:N was established, experiment started and run for 7 days. Air samples were collected for odor analysis on Days 2, 4 and 8. Compost samples were collected and measured for C and N again on day 8. Control treatment is one without pre-drying the manure. 3.7.4 Experimental Set #4 The objective of experimental set #4 was to test the influence of the dosage of inoculum on the composting process - thermal performance and odor emission. For the bioadditive WT to be effective in treating manure composting odors, the cell counts must be substantially increased. Ideally, this can be done via acclimatizing and activating the yeasts in WT during the active phase of composting, when odor removal is of primary concern (as compared to the curing phase when some pervasive odors have already volatilized). However, yeast cannot survive the high temperatures. 24 The alternative method is to apply WT during the curing phase of composting. Mature compost has a rich diversity of bacteria, actinomycetes and fungi that make it an excellent biofilter media for odor treatment. In some aerated static pile composting systems, a layer of mature compost is placed on the pile surface for odor control. Hence, raw composting materials inoculated with mature/recycled compost might emit less odors. In this aspect, Ohta and flceda, (1978) suggested that, besides bacteria and fungi, actinomycetes are also effective in reducing malodors, for instance Streptomyces spp. and Actinomycetes spp. Tanaka et al. (1995) also found Streptomyces sp. No. 101, Thermoactinomyces sp. No. 64 and Micromonospora sp. No. 604 to be effective in deodorizing VFAs. Broiler manure and wood shavings, supplemented with wood chips were placed in large bioreactors having a working volume of 120 L. The compost mixture was allowed to go through the active phase of composting whereby thermophilic temperatures are expected to kill the pathogens as required. When compost temperature had reached the peak, and as the temperature descends to below 30°C, WT was applied to the curing materials (immature compost) in one bioreactor at a dosage of 10% w/w. The other bioreactor did not receive WT. Forced aeration was stopped, but the compost was exposed to air and turned every other day. This helped to maintain suitable moisture content around 40-45% for proper curing. After 4 weeks of curing, the compost had an earthy smell typical of cured compost, and this relatively mature compost was used as inoculum in the form of "recycled compost" for poultry manure composting in the 6L Dewar bioreactors, with and without pre-enhancement by WT during the previous, active phase of composting. The mixing ratio is 20% (v/v), i.e. 4 parts of raw poultry manure to 1 part of inoculum by volume. The control treatment did not receive any inoculum. 25 3.7.5 Experimental Set #5 This series of experiment concerns the co-composting of biosolids and poultry manure in 6L Dewar bioreactors, and having the same objective as experimental set #4. The mixing ratio is 1 part biosolids, 0.5 part poultry manure and 2 parts hog fuel (i.e. bark and wood chips) by volume. The biosolids were obtained from the Kent District wastewater treatment plant at Agassiz, B.C., which has a secondary treatment process with nutrients removal, using the sequencing batch reactor technology. Field scale tests were conducted using the aerated static pile composting method, and processing 6 tonnes of biosolids per week in 2003. The lab-scale experiments are meant to test the effects of varying the composting recipe on thermal performance and odor emission characteristics. 26 DEWAR FLASK DETAIL PROFILE VIEW Figure 3.1. Dewar flask and cork lid details INSULATION BOX DETAIL 20" PROFILE VIEW A-A VIEW Figure 3.2. Adiabatic box details 27 EXPERIMENTAL L A B SET UP THERMOCOUPLE PC WITH CONTROL SOFTWARE DATA ACQUISITION BOARD RELAY BOX EXHAUST GASES -TO FUME HOOD INSULATION BOX WITH DEWAR FLASK CONDENSATE TRAP EXHAUST GAS SAMPLING POINT Figure 3.3. Experimental lab configuration and airflow direction 28 CHAPTER 4 RESULTS AND DISCUSSION The results and discussion for all the experimental treatments are discussed in terms of thermal performance and odor emission. Some results on compost quality are then presented at the end of this chapter. Experimental Set #1 Fig. 4.1 indicates that, although broiler litter has a good balance of carbon and nitrogen materials, the control treatment (without WT application) did not attain high enough temperatures for pathogen destruction. In fact, the temperature stayed below 55°C during the active phase of composting, and its thermal behavior may be attributed to insufficient porosity of the composting medium. For the low dosage application of the bioadditive WT (1% or 10 g/kg), peak temperature was 59°C and was reached at 96 hours; the high dosage treatment (10% or 100 g/kg) attained a peak temperature of 63°C sooner (around 36 hours) after start-up. Nevertheless, all three treatments could not meet the pathogen destruction criteria, which requires the composting temperature to be greater than 55°C for at least 72 consecutive hours (BCWLAP 2004). Temperature profiles of the high dosage treatment in replicate are shown in Fig. 4.1a. In a subsequent composting run involving the same three treatments, more wood chips were added to the bioreactor. The temperature profiles are plotted in Fig. 4.2. Although all three treatments, including the control, exhibited similar temperature patterns, the treatment with high dosage of WT reached thermophilic temperatures sooner than the other two treatments and the high temperatures stayed for a longer time period. Such thermal performance is in line with the findings by Choi and Park (1998). The duration of temperature exceeding 55°C was between 75-80 hours for all treatments, thus fulfilling the pathogen destruction criteria for manure composting. Microbial analysis of samples collected on day 7 revealed that the yeast counts in WT (12000 CFU/g) were reduced or largely eliminated after the temperature-ascending (active) phase of composting (4100 CFU/g for the WT 10% treatment; < 10 CFU/g 29 for the WT 1% treatment). This confirms that yeast will not be able to withstand thermophilic temperatures. Fig. 4.10 shows comparative values of odor concentration between the two dosages of WT. The high dosage of WT results in consistently greater odor removal efficiency during the first 15 days of composting, when compared to the low dosage. The percent odor removal, in comparison with the control treatment, varied from 18% on day 2 to 40% on day 4, whereas the low dosage treatment had a 11% odor removal efficiency only on day 2, and no further odor removal was observed thereafter. More detailed data may be found in Appendix B. Upon cooling down to 25-30°C, the compost materials were transferred to another set of bioreactors for curing purposes. The bioadditive WT was re-applied to determine its effects on the curing process. For the control treatment, the compost was re-heated to 42°C within one day, so as the treatment with low WT dosage; whereas the high WT dosage treatment was re-heated to 48°C. All three treatments exhibit a gradual descend back to near-ambient temperature after 7 days, suggesting that WT might not have any significant effect on the curing process in terms of temperature profiles. Experimental Set #2 This set of experiment was conducted using large bioreactors having a working volume of 120 L for the composting materials. For the exposed (open-top) bioreactor, the composting materials were turned daily during the first 5 days. As illustrated in Fig. 4.4, all three treatments reached 67-68°C in a short time period of 16 hours. The high temperature attained by the control treatment without forced aeration may be attributed to natural aeration, whereby turning helps the diffusion of oxygen into the composting mass. The sharp rise in temperatures beyond 55°C was followed by a rapid decline in temperature for all treatments after the first day and could not stay for a longer period beyond 30 hours. It is very probable that heat loss to the surroundings occurred at a faster rate than the microbial heat production rate, thus heat could not be adequately retained in the composting mass. 30 Fig. 4.5 shows the temperature profiles associated with the enclosed and well-insulated bioreactors. The low WT dosage was able to induce a larger rise in temperature and satisfy the pathogen destruction criteria, when compared to the control treatment without WT (but with forced aeration). However, the control treatment without WT and without aeration had the worst thermal performance, with a maximum temperature of only 43°C. Odor concentrations were depicted in Fig. 4.11. Prior to the start-up of composting, the measured odor levels were 175-210 OU (odor units) for the three treatments. For the enclosed bioreactors, the WT treatment did not significantly reduce the odor levels (odor removal efficiency < 10%) associated with the control treatment, as evidenced by results from the odor panel analysis up to day 8 of the experiment, although both treatments had 40% less total odor strength on day 2 (5450 OU versus 9320 OU), in comparison with the second control treatment without WT and without aeration. For the exposed bioreactors, the WT treatment was less odorous than the control until day 4. Moreover, all three treatments had similar odor concentrations; this provides further evidence that natural aeration helped to reduce the generation of odors in the treatment without forced aeration; its peak odor concentration was 4560 OU, or about 50% of that from a parallel enclosed bioreactor. After two series of tests, odor levels were not found to be substantially reduced with the application of the bioadditive WT. This might be explained as follows: Without an active yeast cell population, the odor removal capability of WT ought to come from its major ingredient, zeolite (80% by weight). While it is an established fact that zeolite is effective for ammonia removal, its ability of deodorization is uncertain. Zeolite can adsorb ammonium ion (NBV) in solution via the ion exchange process, and hence prevents its volatilization into ammonia gas. However, many odors in manure composting are organic compounds (e.g. mercaptans, skatole, butyric acid, amines), and the ion exchange process does not work for these odorants. Furthermore, ammonia is not a pervasive odor and it can be readily diluted by ambient air. Based on values of ammonia gas concentration (100-2000 ppmv) reported in the literature for manure composting and its detection threshold odor concentration of 17 ppmv, ammonia emission alone should produce 5-120 OU. Since the measured odor levels are much greater than 150 OU, successful treatment of ammonia emission does not mean successful treatment of odor emission. 31 Experimental Set #3 This experimental set is aimed at testing the hypothesis that oven-drying of the manure will remove some odors so that odor release from the manure will be reduced during subsequent aerobic treatment. Measured odor concentrations are shown in Fig. 4.12, for composting with and without pre-drying of poultry manure at 104°C. With pre-drying of the poultry manure, the bioadditive WT led to odor removal of 45-50% (2400 OU) versus the control treatment (4560 OU) on day 2, but the reverse trend was observed and the odor levels became significantly higher on days 4 and 8 (7430-10500 OU versus 4350 OU; and 1680-4350 OU versus 420 OU, respectively). Some strong odorous compounds could become more concentrated by drying at 104°C, which is yet below their boiling points and retained in the manure. As the composting mass heated up after 2 days, these odors were released along with the forced aeration. In terms of thermal performance, all three treatments reached thermophilic temperatures of 62-65°C, though lasting somewhat short of 72 hours (Fig. 4.6). The extra insulations placed around the Dewar bioreactors had probably resulted in high temperatures that stayed for a longer time period compared to previous runs. On the other hand, trials without pre-drying of manure had better thermal performance. Fig. 4.7 shows that the WT treatments peaked at 68-70°C and met the pathogen destruction criteria (T > 55°C for 81 hours). The control treatment also reached 65°C and (T > 55°C for 73 hours). Odor removal efficiency on day 2, as deduced from Fig. 4.10, was 23% and 57% respectively for the low and high WT dosage, versus the control treatment. Experimental Set #4 Two runs were conducted in experimental set #4. Results pertinent to Run 1 are illustrated in Fig. 4.8 for the temperature profiles of the composting materials, and Fig. 4.13 for odor concentrations and percent odor reduction. This trial used broiler litter from the UBC farm. Inocula (recycled compost) with previous WT enhancement had a significant odor reduction (4450 OU decreasing to 1680 OU) compared to the control treatment (10760 decreasing to 32 5320 OU) on all three days of sampling (Days 2, 4 and 8). For the treatment with inocula, but without previous WT enhancement, the odor reduction efficiency was not as well on Day 2; however, on Days 4 and 8, it had virtually the same performance as the treatment with WT-enhanced inocula. Run 2 used layer manure from an organic poultry farm located in Aldergrove, B.C. It had a higher moisture content of 60-65%, and hence requires no additional of water for proper composting. Fig. 4.9 demonstrates the temperature profiles whereas odor concentrations are also plotted in Fig. 4.13. The treatment with WT-enhanced inocula is again seen to have a significant odor reduction versus the control treatment (without recycled compost as inocula) on all three days of sampling (Days 2, 6 and 8). Furthermore, it has consistently better thermal performance (via maintaining thermophilic temperatures over a longer period) and greater odor removal efficiency compared to the treatment without WT-enhanced inocula throughout the active phase composting, thus demonstrating the effectiveness of WT. The control treatment could not attain thermophilic temperatures required for pathogen destruction. In theory, higher temperatures can lead to a faster biodegradation rate and hence less odor emissions, as the odorants become oxidized into carbon dioxide and water. However, it is possible that higher temperatures are not necessarily conducive to increased biodegradation; MacGregor had demonstrated in the 1980's that mesophilic temperatures can be better in this aspect. Experimental Set #5 Measured odor concentration and odor removal efficiencies are shown in Fig. 4.14. The control treatment had similar levels of odors (ranging from 8700 on Day 2 to 2090-2370 on Days 8/9) when compared to composting runs in experimental sets 1-4. Generally speaking, the treatment with previously WT-enhanced inocula had less odors from Day 2 to Day 8/Day 9 in comparison with the control, and it is also somewhat more efficient than the treatment without WT-enhanced inocula in terms of odor removal. These preliminary results suggest that the type of organic substrate might not be a major factor when recycled compost is used as inocula and pre-enhanced by the bioadditive WT. 33 Compost Quality Nitrogen contents of compost were measured during experimental sets #1 and #2 treatments with WT applied were found to have a significant increase in %TN at the end of the active phase composting (Figs. 4.15 and 4.16) and seed germination index after 30 days of composting (Figs. 4.17), suggesting a more mature compost product having higher agronomic value. Specifically, the average total nitrogen contents of compost were 3.44% (WT) vs 2.31% (Control) in Run 1 using the 6L Dewar bioreactors, whereas the respective values were 3.52% (WT) vs. 2.66% (Control) in Run 2 using the large 120 L bioreactors. This is in line with the reduction in peak ammonia levels: WT (< 60 ppmv) versus Control (120 ppmv) in Run 1, and WT (210 ppmv) versus Control (340 ppmv) in Run 2. It is probable that the zeolite in the bioadditive WT was effective in reducing the ammonia emission from the composting process, while retaining the nitrogen content of compost. The latter is evident even at the end of the active phase of composting and before curing. 34 Fig. 4.1 Temperature profiles during active phase of broiler litter composting with bioadditive WT dosage (Run 1) 80 -i 1 1 1 1 51 101 151 201 1 1— 251 301 Time, hrs WT Dosage #2 — - -WT Dosage* 1 -Control (No WT) -Ambient 35 Fig. 4.1a Temperature profiles for broiler litter composting with high dosage of the bioadditive WT (100 g/kg compost) • WT Dosage* 2 - - WT Dosage # 2 (replicate) - Control 2 (No WT, aeration) Ambient 36 Fig. 4.2 Temperature profiles during active phase of broiler litter composting with WT dosage (Run 2) 37 Fig. 4.3 Temperature profiles after active phase of broiler litter composting, with re-dosing of bioadditive WT 38 Fig. 4.4 Temperature profiles during active phase of broiler litter composting in exposed bioreactors 50 100 150 200 T i m e ( h r s ) WT Dosage* 1(1 Og/Kg) — -- Control 2 (No WT, aeration) Control 1 (No WT, no aeration) •Ambient 39 Fig. 4.5 Temperature profiles during active phase of broiler litter composting in enclosed bioreactors 80 0 4 - - r - - r - - n - -n 0 100 200 300 400 500 Time (hrs) WTDosage#1 (10g/Kg) No WT, aeration . .No WT, without aeration Ambient 40 Fig. 4.6 Temperature profiles during active phase of broiler litter composting with pre-dried manure 80 N 0 50 100 150 200 250 Time (hrs) W T dosage #2 — - - WT dosage # 1 Control (no WT) Ambient 41 Fig. 4.7 Temperature profiles during active phase of broiler litter composting, without pre-drying manure Fig. 4.8 Temperature profiles for broiler litter composting, with and without WT-enhanced recycled compost (Run 1) 43 Fig. 4.9 Temperature profiles for broiler litter composting, with and without WT-enhanced recycled compost as inocula (Run 2) 80 0 4- - r - -r- -r- _, 0 50 100 150 200 Time (hrs) Control — — — Without WT-enhanced inocula • - • Ambient 44 Fig. 4.10 Odor concentrations associated with two dosages of bioadditive WT application during the active phase of broiler litter composting 20000 •*>— bioadditive 1 % w/w » - bioadditive 10% w/w ± - control 6 8 10 Time (days) 12 14 16 45 Fig. 4.11 Odor concentrations from enclosed (upper) and exposed (lower) bioreactors during the active phase of broiler litter composting, with bioadditive application 46 10000 8000 •2 6000 4000 2000 ••—bioadditive 1% w/w «— no bioadditive, aeration •&T- no bioadditive, no aeration Time (days) 47 Fig. 4.12 Odor concentrations associated with bioadditive application during the active phase of broiler litter composting, with (upper) and without (lower) pre-drying of manure 48 12000 •-bioaddit ive 1% w/w •-bioaddit ive 10% w/w A — control 4 6 Time (days) 10 49 Fig. 4.13 Effectiveness of recycled compost as inocula in odor removal, with and without enhancement by the bioadditive WT, during the active phase of broiler litter composting (upper: run 1; lower: run 2) 50 Fig. 4.14 Effectiveness of recycled compost and bioadditive in odor removal during the active phase of the co-composting of broiler litter and biosolids •9y— r e cyc l ed c ompos t with bioaddit ive Time (days) 52 recycled compost with bioadditive 0 2 4 6 8 10 Time (days) 53 Fig. 4.15 Total nitrogen content of compost during the active phase of composting (Run 1) 4.0 4 3.0 Time (Days) H WT1 • WT2 • Control 1 I I Control 2 54 Nitrogen content of compost during active phase of composting (average of two replicates) 6 Time (Days) 10 • WT •; Control 55 Fig. 4.16 Total nitrogen content of compost during the active phase of composting (Run 2) 5.0 i 4.0 Time (Days) • WT1 S WT2 • Control 1 m Control 2 56 Fig. 4.17a Seed germination index after 30 days of composting Fig. 4.17b Seed germination index after 30 days of composting 58 CHAPTER 5 CONCLUSIONS Although yeast will not be able to withstand thermophilic temperatures during the composting process, the yeast and zeolite-based bioadditive WT was shown to have some benefits for composting. The following conclusions may be drawn from the results of this study. 1. Using the small (6L) Dewar bioreactors for the active phase of poultry manure composting, the high dosage of WT (10% w/w) resulted in consistently greater odor removal efficiency (varying from 18% to 40%), when compared to the low dosage (1% w/w) of WT, which had a maximum odor removal efficiency of 11%. However, for larger (120 L) enclosed bioreactors, the WT treatment did not significantly reduce the odor levels in comparison with the control treatment; differences between the two treatments were less than 10%. 2. With pre-drying of the poultry manure, the bioadditive WT led to greater odor removal (2400 ou) versus the control treatment (4560 ou) on day 2, but the reverse trend was observed and odor levels became significantly higher on Days 4 and 8 for the WT treatment. Hence, pre-drying of poultry manure was not effective in eliminating the odorous volatile organic compounds from the manure, thus resulting in an increase in odor emission after the initial two days of composting. 3. Inocula in the form of recycled compost with previous WT enhancement (during the composting process) had greater odor removal efficiency up to Day 2 relative to the control treatment which used the inocula, but without previous WT enhancement. Nevertheless, this advantage could not be sustained for a longer time period. Both treatments demonstrated a significant odor reduction up to Day 59 8 of the composting process, versus the treatment without using recycled compost as inocula, thus reaffirming the fact that recycled compost could be very effective in odor control for composting. 4. WT had similar effects on odor removal efficiencies when poultry manure (broiler litter) was co-composted with biosolids, versus using broiler litter alone as the composting substrate. 5. The thermal performance of the composting process was improved with the application of WT. The treatment with higher dosage of WT reached thermophilic temperatures sooner than the other treatments and the high temperatures stayed for a longer time period. This enabled the composting process to satisfy the regulatory requirements of pathogen destruction (temperature greater than 55°C for 72 or more consecutive hours. Composting without pre-drying of manure also had better thermal performance than that with the manure undergoing a pre-drying process. Furthermore, treatments with WT-enhanced inocula had consistently better thermal performance, via maintaining thermophilic temperatures over a longer period compared to the treatment without WT-enhanced inocula. 6. Evidently, the application of WT could effectively reduce the loss of nitrogen during composting. The WT treatments had higher total nitrogen content (average T N of 3.48%) versus the control treatments (average T N of 2.48%), which would translate to better agronomic and fertilizer values. This is in line with the reduction in measured peak ammonia levels - average of 135 ppmv for the WT treatment versus average of 230 ppmv for the control treatment. This may be attributable to the zeolite in the bioadditive WT, which is known to be effective in reducing ammonia emission from the composting process, while retaining the nitrogen content of compost. 60 7. Higher seed germination index was observed for the compost product with the application of WT, meaning that WT is beneficial for compost maturation. 61 CHAPTER 6 RECOMMENDATIONS 1. It would be desirable to separately assess the effects of yeast and zeolite on odor and ammonia emissions during composting, and then determine the effects of the two components in combination. 2. More microbial yeast counts should be conducted and traced over the entire active phase of composting in future tests. The results can then be correlated with the measured odor concentrations. 3. Gas chromatography/mass spectrometry (GC/MS) analysis would be helpful towards identifying the odorous compounds that could be effectively treated during composting in the presence of the bioadditive WT. The analytical results can also be correlated with the olfactometer and odor panel analysis to provide a useful database for odor emission regulation purposes. 4. Further trials are needed under pilot-scale composting conditions to confirm the results derived from the lab-scale composting used in the thesis study. 5. 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Proceedings of the International Composting Research Symposium. 1992. Witter, E, and J. Lopez-Real. 1988. Nitrogen Losses during the Composting of Sewage Sludge, and the Effectiveness of Clay Soil, Zeolite, and Compost in Adsorbing the Volatile Ammonia. Biological Wastes. 23: 279-294. Yulipriyanto, H. , P. R. Philippe-Morand, G. Tricot and C. Aubert. 2002. Effect of additives on the nitrification-denitrification activities during composting of chicken manure. In: Microbiology of Composting, (eds. Insam, H. et al.), Springer. Yuwono, A.S. and P.S. Lammers, 2004. Odor Pollution in the Environment and the Detection Instrumentation. Agricultural Engineering International: the CIGR Journal of Science Research and Development. Vol. VI. pp.1-33. Zhang, Q., J.J.R. Feddes, I.K. Edeogu and X.J. Zhou. 2002. Correlation between odour intensity assessed by human assessors and odour concentration measured with olfactometers. Can. Biosystems Eng, 44: 6.27 -6.32. Zucconi F., M . Forte, A. Monac and M . de Beritodi. 1981. Biological evaluation of compost maturity, Biocycle 22: 27-29. 68 APPENDICES 69 Appendix A. Specifications of the Dynamic Olfactometer Figure A l . The home-built dynamic olfactometer 71 EU Standard D y n a m i c d i l u t i o n M o d e '3^ ;^.. - - * S t a t i o n N u m b e r o f s n i f f i n g p o r t s P a n e l s i z e P r e s e n t a t i o n o r d e r F a c e v e l o c i t y i n p o r t P r e s e n t a t i o n f l o w r a t e M a x i m u m ( l o w e r ) d i l u t i o n r a t i o M i n i m u m ( u p p e r ) d i l u t i o n r a t i o D i l u t i o n r a t i o r a n g e D i l u t i o n f a c t o r i n c r e a s e E v a l u a t i o n t i m e Yes Yes Forced-choice or Forced choice Yes/No Not required Minimum of 2 4 to 8 Ascending or random 0 . 2 - 0 . 5 20 L/min Less than 2 7 At least 2 1 4 At least 2 1 3 . 1.4 - 2.0 <15 seconds ' 2 3 4-8 . Ascending 0.2 20 L/min 2 5 2i8 2 1 3 : « - V 2.0 <15 seconds 72 Appendix B. Experimental Odor Concentration and Temperature Data for All Test Series 73 TABLE 1. Experimental Set 1 - Comparison between two dosages of WT application during the active phase of composting, in small (6L Dewar) bioreactors Run 1 Percent odor reduction vs. Control Thermal performance (temperature profiles) Day 1 Day 4 Day 7 Tp, °C tp, hrs t55, hrs WT@1% 11 0 0 52* 125* 0 W T @ 10% 36 40 0 63 36 43 Control 59 40 56 No WT, no aeration 35 50 0 Run 2 Percent odor reduction vs. Control Thermal performance (temperature profile) Day 2 Day 4 Day 7 Day 10 Day 15 T p , °C tp, hrs t55, hrs W T @ 1% 11 0 0 0 0 63* 37 40 W T @ 10% 18 40 0 21 0 63 37 23 Control 63 30 42 Control: No WT, but with Aeration T p: peak temperature tp: time required to reach the peak temperature t55: duration of temperature staying above 55°C (regulatory requirements: > 72 consecutive hours); note that this parameter only applies to the active or temperature-ascending phase 74 TABLE 2. Experimental Set #2 - Comparison between exposed and enclosed large (120 L) bioreactors during the active phase of composting Exposed (Open-top) bioreactor Percent odor reduction vs. Control Thermal performance (temperature profile) Day 1 Day 4 Day 7 TD, °C tp, hrs t55, hrs WT @ 1% 19 65 0 67 16 30 Control 67 16 27 No WT, no aeration 68 16 32 Enclosed bioreactor Percent odor reduction vs. Control Thermal performance (temperature profile) Day 2 Day 4 Day 8 Tp, °C tp, hrs T 5 5 , hrs W T @ 1% 8 10 3 65 88 76 Control 58 74 57 No WT, no aeration 43 12 0 TABLE 3. Experimental Set #3 - Comparison between two dosages of WT application during the active phase of composting, in small 6L Dewar bioreactors, with and without pre-drying of poultry manure at 104oC With pre-drying Percent odor reduction vs. Control Thermal performance (temperature profile) Day 2 Day 4 Day 8 TD, °C tp, hrs t55, hrs W T @ 1% 45 0 0 65 45 60 W T @ 10% 50 0 0 62 65 42 Control 62 38 62 * These two samples have characteristics smell of fermenting yeast (sour, alcoholic), whereas Other samples with high odor concentration all smell of mercaptan and/or skatole (fecal) at detection With pre-drying, repeated trial Percent odor reduction vs. Control Thermal performance (temperature profile) Day 3 Day 4 Day 7 Tp, °C tp, hrs t55, hrs W T @ 1% 50% 0% W T @ 10% 75% 64% Control * These two samples have characteristics smell of fermenting yeast f This sample also smells sweet to alcoholic, but not the same as the characteristics yeast smell Other samples have sulfur/fecal smell 75 Without pre-c rying Percent odor reduction vs. Control Thermal performance (temperature . profile) Day 2 Day 4 Day 8. TD, °C tp, hrs Us, hrs WT@1% 23 11 4 70 38 81 W T @ 10% 57 0 7 68 43 81 Control 65 43 73 * Only this sample has sour smell at detection; all other samples smell of sulfur/skatole 76 TABLE 4. Experimental Set #4 - Effectiveness of WT in odor removal during active phase composting of poultry manure Run 1 Percent odor reduction vs. Control Day 2 Day 4 Day 8 WT-enhanced inocula 59% 57% 68% Inocula without WT enhancement 19% 57% 64% Control Oc or concentration, ou Day 2 Day 4 Day 8 WT-enhanced inocula 4453 (64°C) 4453 (52°C) 1680 (28°C) Inocula without WT enhancement 8697 (65°C) 4453 (51°C) 1926 (28°C) Control 10756 (34°C) 10330 (38°C) 5318 (37°C) Run 2 Percent odor reduction vs. Control Day 2 Day 4 Day 8 WT-enhanced inocula 50% 38% 35% Inocula without WT enhancement 33% 38% 21% Control Odor concentration, ou Day 2 Day 6 Day 8 WT-enhanced inocula 3261 (64°C) 4723 (57°C) 3757 (45°C) Inocula without WT enhancement 4348 (58°C) 4723 (45°C) 4561 (36°C) Control 6522 (39°C) 7601 (33°C) 5798 (33°C) TABLE 5. Effectiveness of WT in odor removal during active phase composting of poultry manure and biosolids Runl Percent odor reduction vs. Control Day 2 Day 6 Day 8 WT-enhanced inocula 25% 50% TBA Inocula without WT enhancement 25% 33% TBA Control Odor concentration, ou Day 2 Day 6 Day 8 WT-enhanced inocula 6523 (57°C) 1632 (63°C) 2367 (52°C) Inocula without WT enhancement 6523 (51°C) 2175 (65°C) 3262 (51°C) Control 8697 (30°C) 3263 (39°C) 2367 (36°C) * Inocula: recycled compost from curing materials in the bioreactors * WT-enhanced inocula: WonderTreat added at the beginning of the curing process in the bioreactors * Control: no inocula * Temperatures of composting materials during gas sampling are indicated in brackets * n/m: Not measured 78 Appendix C. Total nitrogen contents of compost at the end of active phase of composting 79 Run 1 Day TN % Average 0 WT1 1.73 2.04 WT2 2.35 Control 1 3.17 3.05 Control2 2.92 6 WT1 1.03 1.84 WT2 2.64 Control 1 2.79 2.72 Control2 2.65 10 WT1 4.02 3.44 WT2 2.85 Control 1 3.06 2.31 Control2 1.56 Run 2 Day TN % Average 0 WT1 2.69 2.48 WT2 2.27 Control 1 3.14 3.08 Control2 3.02 6 WT1 2.15 2.24 WT2 2.33 Control 1 1.85 1.75 Control2 1.64 10 WT1 4.02 3.52 WT2 3.01 Control 1 3.07 2.66 Control2 2.24 


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