Co-Composting of Biowaste and Poultry Waste

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1 Co-Composting of Biowaste and Poultry Waste Ana P. Gomes, Maria I. Nunes, Cândida C. Vitoriano and Elisabete Pedrosa Department of Environment and Planning, University of Aveiro, Portugal CONTACT Ana Paula Gomes Department of Environment and Planning, University of Aveiro Aveiro - Portugal Telephone: Facsimile: pgomes@ua.pt EXECUTIVE SUMMARY The increasing environmental awareness of today s society turned the issue of waste management a major problem leading to improved efforts on waste reduction. The implementation of large-scale composting brings greater economic benefits. However, the centralization leads to economic costs and environmental impacts resulting from transport of waste and these may well exceed the benefits turning the management unsustainable. Co-composting of more than one type of waste can, in many cases, be the answer to such situations when the availability of just one type of waste is not enough to feed a big system. The main objective of this study was to assess the outcome of the co-composting of biowaste with a residue from the activity of farming - poultry waste, with or without the incorporating a bulking agent waste resulting from the processing of forest biomass. The work presents the results of four co-composting experiments of biowaste produced from a canteen and poultry waste. These residues are abundant in some communities and whose physicochemical characteristics are complementary in several parameters. Forest biomass was used as bulking agent in two experiments. In order to evaluate the waste stabilisation and the final product quality the composting experiments were carried out in small-scale system (3 L). These experiments took place in the external outdoor with two aeration systems: forced and passive. The evolution of the process was followed by monitoring the parameters: gaseous composition, temperature, moisture, ph and volatile solids. The resulting compost was characterized in its total content of organic matter, cellulose components, lipids and organic nitrogen. The agronomic value of the matured compost was evaluated based on the content of nitrogen, phosphorus, potassium, sodium and heavy metals as well as through biological tests of relative production of biomass and germination assays. In the co-composing of biowaste and poultry waste experiments it was reached average values around 7% of volatile solids degradation and 85% of reduction in the volume, in a time processing of five weeks. The pilot scale process was carried out with a high level of biological activity, ensuring the thermophilic temperature range during a week. The two systems of ventilation produced no significant differences in the performance of the process.

2 The presence of biomass shown to be important once it allowed the conservation of the nitrogen in the compost as result of the reducing ammonia emissions during the process and of the detectable odour. Regarding the quality of the compost, it was found that a month after the end of degradation phase, the compost was maturated according to phytotoxicity assays. and the chemical parameters fulfilled most of the recommended values by the Decision of the Commission nº 26/799/CE, relative to attribution of eco-label for soil improvement and growing media, except for copper element (in all composts) and for zinc element (in one case). The high level of these metals may conditioning the application of this type of compound in the soil before the source is identified and remedied the situation. The experiments reveal that biowaste and poultry waste are compatible in the composting process and by this way they can be managed in an integrated way. INTRODUCTION The issue of waste management is increasingly important in today's society, because of the difficulty in reducing their generation and due to increased environmental awareness that led to the need to properly manage waste, including some types of waste long ago of free discarding in the environment, nominated in the soil. One example is the case of waste from the agro-livestock activity that often is deposited in the soil without prior stabilization and is responsible for cases of soil pollution and of surface and groundwater contamination. Regarding the disposal of waste in landfills, the European Directive 1999/31/EC establishes criteria and procedures for waste admission in landfills aiming to minimize the negative environmental impacts of such practices. As the disposal of biodegradable waste in landfill becomes more restricted more important is the development of alternative processes of waste management. One of these alternative processes is the treatment of waste using composting techniques leading to the organic recovery of the biodegradable waste. Integrating different types of waste in the composting process allows diverting from the landfills the biodegradable organic fraction of the municipal solid waste as well as other types of waste, e.g. the agricultural. Composting is an easy to implement technology with several technical options available ranging from small domestic systems up to centralized composting plants. More, this recovery operation can be performed either at the municipal or inter-municipal scale. In terms of population acceptance, this type of waste treatment when compared with others, such as incineration or landfill, is usually well accepted. Composting also has the added advantage to produce a final product - compost - with high agronomic value which can be sold to be applied in the soil with subsequent economic and environmental benefits. As in the most production processes, the implementation of large-scale composting brings greater economic benefits. However, the centralization leads to economic costs and environmental impacts resulting from transport of waste and these may well exceed the benefits turning the management unsustainable. Co-composting of more than one type of waste can, in many cases, be the answer to such situations. The agronomic value of the compost depends on the characteristics of the waste namely, the nutrients balance and the physical structure. These characteristics can be attained and/or improved through the co-composting of different types of waste.

The aim of this study was to assess the outcome of the co-composting of biowaste with a residue from agro-livestock activity - poultry waste, with or without the incorporating a bulking agent waste

This strategy had the objective to assess how the model of home composter used can be improved to increase the aeration of the material in composting.

The last one was sealed and had air pumped in at a known flow rate at the base and exits through the top. The passive aeration was implemented using four vertical perforated pipes (see Sylla et al.

3 The aim of this study was to assess the outcome of the co-composting of biowaste with a residue from agro-livestock activity - poultry waste, with or without the incorporating a bulking agent waste resulting from the processing of forest biomass. The experiments were carried out in smallscale systems (3 L) adapting home composters commonly found on the market. This strategy had the objective to assess how the model of home composter used can be improved to increase the aeration of the material in composting. EXPERIMENTAL SET-UP Apparatus Using typical home composting bins (3 L) two types of aeration systems were run: a passive and a forced as shown in Figure 1a and 1b, respectively. The last one was sealed and had air pumped in at a known flow rate at the base and exits through the top. The passive aeration was implemented using four vertical perforated pipes (see Sylla et al., 26) and the composter was supported by a wood perforated device as shown in Figure 1c. a b c Figure 1 Composter photographs: (a) passive aeration, (b) forced aeration, (c) filled composter on support device. Waste Inputs Biowaste produced from a canteen, poultry waste and residues from the processing of forest biomass were used as feed materials. The biowaste was composed of residues from potato, orange, vegetables and coffee grounds. The poultry waste was constituted of sawdust, bird droppings and ration remains. The residues from the processing of forest biomass (from now on called biomass) were predominantly composed by eucalyptus bark. Methodology Two set of experiments (A and B) were performed in order to evaluate the influence of bulking agent - biomass. In each set a passive and forced aeration was tested, totalizing four runs. Table 1 summarizes the composition of the initial mixtures to be composted in each experiment. Table 1 Composition of the initial mixtures. Residue, kg arb¹ Set A Set B Biowaste Poultry waste Biomass 7.6 TOTAL ¹ arb as received base

4 The temperature and exit gases (CO 2, O 2 ) were monitored during the degradation phase. The solid mixtures were characterized at the beginning and at the end of this phase by determining the parameters: moisture, ashes, organic nitrogen, ph, lipids and fiber (hemicelluloses, cellulose, lignin). The characterization of the compost quality parameters was done through the determination of nutrients (P, K and Na) and heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and assays of phytotoxicity (vase test and germination index) were also carried out. Methods, equipments and norms used in those determinations are listed in Table 2. All composting mixtures were manually turned over once per week, specifically at 2, 4, 6 and 8 hours of reaction time. In those moments samples were collected for ph monitoring and for moisture control. Table 2 - Methods, equipments and norms used in parameters determinations. Parameter Method Equipment/Norms Temperature Thermocouple NiCr/NiAl Testo 175 data logger CO 2, O 2 Automatic sampling (1h period) and IR detection Manual sampling (1 day period) and paramagnetic detection Suction pump and MI7 VAISALA data logger SIGNAL mod. 8, range a 25% ph Dissolution of solid in CaCl (1g/L) Potentiometer and ph electrode Moisture Drying oven at 15ºC ASTM D Ashes Muffle furnace incineration at 6ºC ASTM D Organic nitrogen Kjeldhal Kjeltec Tecator Application Note, AN 16/79 Fiber Neutral Detergent Fiber (NDF) Tecator Application Note, AN 6/78 according to van Soest Method Hemicelluloses Acid Detergent Fiber (ADF) according Tecator Application Note, AN 3/78 to van Soest Method Lipids Soxhlet Extraction Soxtec Tecator Application Note, AN 23/8 Phosphorus Acid ascorbic Standard Methods 45-P E. Ascorbic Acid Method Potassium an sodium Acid digestion followed by EEA Standard Methods 33 G. Nitric Acid- Sulfuric Acid Digestion Heavy metals Acid digestion followed by EAA Standard Methods 33 G. Nitric Acid- Sulfuric Acid Digestion Relative biomass production (RBP) Vase test with Lollium multifolium Dry biomass after 15 days for 25% and 5% of compost with peat Germination index (GI) Germination of Lepidium sativum Incubation at 27ºC during 24 h for 25% and 5% extract dilution Note: The analyzed samples were air dried and shredded up to 1mm except for moisture and organic nitrogen determinations. RESULTS AND DISCUSSION In order to attain the proposed objectives it was necessary to characterize the solid matter before composting, after the degradation phase and at the end of maturation period. It was also important

5 to evaluate the performance of the composting process, through the increasing of temperature and the biological gases production. The analysis of the solid samples collected at the turning moments revealed no need of moisture correction. The monitoring of ph showed that this parameter increased from 6 to 8 in the first seven days of reaction, remaining between 8 and 8.5 until the end of the degradation phase. Initial Solid Mixtures Characterization For both mixtures presented in Table 3, the C/N ratios are suitable for composting process and the moisture belongs to the recommendable range of 55-65% (Hang, 199). The biowaste is a major component as received base (arb). However, considering the dry base composition, the poultry waste is present in.52 and.62 kg per kg dry mixture for set A and B, respectively. The bulking agent was used in 18% (db) to provide structural support to the composting mixture, since the biowaste and poultry waste per si tend to compact during the degradation phase. Moreover, this agent has the capability to absorb the excess of water generated during the microbiological reactions. In both sets of experiments, half of the dry matter is composed by fiber. Nevertheless, part of this fiber was accounted as hemicelulloses which in turn is easily biodegradable. Table 3 Physical and chemical characterization of the components and initial mixtures. Mass fraction Biowaste Poultry Mixture of Mixture of Biomass waste set A set B Moisture, arb.79.24, ¹ Ash, db² Volatile solids, db N-Kjeldhal, db Proteins³, db Lipids, db Fiber, db Hemicelluloses, db C/N ¹ Quantified water was added to reach 6% of moisture content. ² db dry basis. ³ Proteins was estimated multiplying organic nitrogen by the coefficient 6.25 of the bibliography. 4 Carbon was estimated dividing volatile solids by the coefficient 1.8 of the bibliography. Final Solid Mixtures Characterization - Compost After five weeks of degradation, the material moisture is still ranging 5-6%. Comparing sets A and B (see Table 4) in terms of this parameter, it can be seen that the bulking agent promoted the release of water vapour. More, the composts from processes using the biomass have lower C/N ratios. In the set A experiments the C/N ratio is approximately the same in the initial mixtures and in the composts. Figures 2 and Figure 3 show the volatilization of organic matter and the maintenance of ash between the beginning and the end of the biological process. Theoretically, the ash mass should be kept constant in each run. The observed differences are due to some experimental mass loss, resulting in an average 1% error.

6 Table 4 Composts characterization Set A Set B Passive aeration Forced aeration Passive aeration Forced aeration Degradation time, week Final mass, kg arb Mass fraction: Moisture, arb Ash, db Volatile solids, db N-Kjeldhal, db Proteins, db Lipids, db Fiber, db Hemicelluloses, db C/N Comparing those figures, it can be seen that higher lost of mass was registered in set A, corresponding to the volatilization of fiber and other carbohydrates, lipids and protein. Mass [kg] 45, 3, 15, Other carbohyd. Lipids Proteins Fiber Ash Mass [kg] 45, 3, 15, Other carbohyd. Lipids Proteins Fiber Ash, Initial Final Initial Final, Initial Final Initial Final Passive aeration / Forced aeration Figure 2 - Initial and final mass of the dry components of set A in the passive and aerated systems Passive aeration / Forced aeration Figure 3 - Initial and final mass of the dry components of set B in the passive and aerated systems The relative conversion of organic matter (volatile solids) was around 6% in passive run of set B and 7% for the remaining three runs. The lipids and hemicelluloses were the most biodegraded compounds (see Figures 4 and 5). In all experiments the fiber degradation ranged between 63 and 7%. The presence of biomass allowed the conservation of the nitrogen in the compost by reducing the ammonia emissions during the process and the detectable odour (Silva, 29). This aspect is more evident in the passive aeration system (see Figure 5). The registered temperature profiles for all runs are shown in Figures 6 and 7. Despite the mass of waste used in each run has been small, corresponding to 3 L pilot system, it was attained the recommendable values for sanitation reported in the Working Document for Biological Treatment of Biowaste (second draft) (ECC 21), i.e. T > 6ºC during a week. After each turning a peak of temperature was observed. The influence of the aeration system on the temperature profile is not evident. The presence of bulking agent created a higher temperature peak at the beginning and an earlier cooling of the process.

7 Mass reduction [%] Volatile solids Lipid Nitrogen Fiber Hemicellulose Mass reduction [%] Volatile solids Lipid Nitrogen Fiber Hemicellulose Passive aeration Forced aeration Passive aeration Forced aeration Figure 4 Mass reduction of the organic compounds, for co-composting of biowaste and poultry waste (set A). Figure 5 - Mass reduction of the organic compounds, for co-composting of biowaste, poultry waste and forest biomass residues (set B). Temperature ( o C) Passive aration Forced aeration T outdoor Reaction time (h) Figure 6 - Temperature profile for co-composting of biowaste and poultry waste (set A) and information of outdoor temperature. Temperature [ o C] Passive aeration Forced aeration T outdoor Reaction Time (h) Figure 7 - Temperature profile for co-composting of biowaste, poultry waste and forest biomass residues (set B) and information of outdoor temperature. The composition of the gas phase in contact with the solid mass was analysed in samples sucked from the interstices of the solid matrix. Both figures also illustrate the temperature of the outdoor environment at the time of experiments. Figure 8 shows the influence of the aeration system in CO 2 concentration. Thus, the passive aeration promotes a good exhaust of biological gases and a consequent fresh air entrance. The CO 2 volumetric concentration is always lower than 12%, except in peak situations, e.g. caused by turnings. In the forced aerated system is very important regulate the air flowrate for the requirements of biological reaction in order to prevent situations of CO 2 accumulation and lack of oxygen during the microbiological degradation. Figure 9 shows that the O 2 concentration was always nearby 21% in the passive aerated system, indicating that the phenomenon of convection is efficient to air circulation. However, in the forced aerated system it was necessary ventilate the composting mass since the beginning of the process, in order to meet the needs of microbiological oxygen and to maintain aerobic conditions.

8 CO2 (% v/v) Passive aeration Forced aeration 2,5 1,5 2 1, Nm 3 /h Fl ow aeration Reaction time (h) Reaction time (h) Figure 8 - CO 2 concentrations in gas phase samples of the co-composting of biowaste and poultry waste (set A). Information of the aeration flow rate of the forced aerated run. Passive aeration O2 (% v/v) Forced aeration Nm 3 /h Reaction time (h) Flow aeration 2,5 2 1,5 1,5 4 8 Reacti on ti me (h) Figure 9 - O 2 concentrations in gas phase samples of the co-composting of biowaste, poultry waste and biomass (set B). Information of the aeration flow rate of the forced aerated run. Quality Compost After a maturation period (4 weeks for the set A and a week for set B) the composts were evaluated as to its characteristics of phytotoxicity. Two different assays were done: (i) the bioassay of seeds germination (GI) and (ii) growing vase test (RBP). The germination assay has the advantage to be faster than vase test. However, the latter test is more sensitive to large number of toxic substances. The data stated in Table 5 show a good agreement between both assays for all experiments. It can be concluded that: The set A composts are maturated since RBP > 9% (Wallace, 25) and GI > 6% (Zucconi, 1981); The set B composts are not maturated since on average RBP < 8% (Wallace, 25) and GI < 5% (Zucconi, 1981). In short, it appears that the four-week maturity is sufficient to stabilize the compost. In contrast, a week is insufficient to attain it, since the compost still contains metabolites that are toxic to plants (phytotoxicity). It is observed that the aeration system has no influence on the maturity compost obtained. Notwithstanding, these experiments do not allow infer anything about the influence of biomass in the process of maturation of the compost. Table 5 Results of phytotoxicity assays: Relative Biomass Productions (RPB) and Germination Index (GI). Dilution Set A Set B (%) Passive aeration Forced aeration Passive aeration Forced aeration RBP, % GI, % The quality of a compound to be applied in a soil must meet the requirements stated in the Commission Decision 26/799/CE (CE, 26). This decision establishes ecological criteria and the related assessment and verification requirements for the awards community eco-label for soil improvement and growing media.

9 Concerning the analyzed heavy metals (see Table 6), all composts fulfill the limits imposed by the cited document, except for copper element (in all composts) and for zinc element (in one case). This result suggests that the source of the high level of these metals could be poultry waste (Tiquia, 22). Future work should be done in order to clarify this subject. The composts contain the main nutrients needed for plant growth and do not exceed the value recommendable by the 26/799/EC document (CE, 26) for the total nitrogen, i.e. 3% (db). Table 6 Contents of heavy metals and nutrients in the compost. Pb Ni Cd Cr Cu Zn Na K P N Aeration mg/kg, db % w/w, db Passive nd 9 nd nd Set A Forced nd 11 nd Passive nd 6 nd nd Set B Forced nd 7 nd nd nd under detection limit CONCLUSION The main purpose of the present work was to contribute to the knowledge concerning the possibility of co-composting three organic wastes: biowaste, poultry waste and residues from forest biomass processing. The composting technique seems to be a good alternative for the valorisation of both the poultry waste and the forest wastes, as biodegradable wastes, thus contributing to the resolution of their environmental problems. The obtained results showed that the composting, being a way of treatment the biowaste and the poultry waste, becomes very efficient when it is performed by mixing them together. The main advantages of co-composting processes performed in this work are: i) balanced mixtures mainly in terms of moisture content and C/N ratio; ii) the process was carried out with a high level of biological activity ensuring the thermophilic temperature range during a week. The maximum conversion of organic matter is attained in five weeks; The two used systems of ventilation produced no significant differences in the performance of the process. It is suggested that the composters bin with passive ventilation has a performance equivalent to a forced ventilation system. Thus the performance of the common home composters can be improved through the use of vertical vents inside. After a period of maturation of four weeks the resulting compost is stabilized and without phytotoxicity. With respect to the heavy metal concentrations, Cu and Zn in compost was over limits proposed by the Commission Decision 26/799/CE (CE, 26). Future work should be done in order to identify the source of copper and zinc. ACKNOWLEDGMENTS This study was supported by the Department of Environment and Planning of the University of Aveiro. The authors gratefully acknowledge the availability of infrastructure and analytical equipment.

10 REFERENCES CE (26). Commission Decision 26/799/CE. Establishes ecological criteria revised and the related assessment and verification requirements for the awards community eco-label for soil improvement and growing media. ECC (21). Working Document on Biological Treatment of Biowaste (2 nd draft). Directorate General Environment (DG Env. A.2.) Brussels. HAUG, R.T. (1993). The practical handbook of compost engineering. Lewis. Silva, M.E., Lemos, L.T., Cunha-Queda, A.C. & Nunes, O.C. (29). Co-composting of poultry manure with low quantities of carbon-rich materials. Waste Management & Research, 27, Sylla, Y.B., Kuroda, M., Yamada, M., & Matsumoto, N. (26). Feasibility study of a passive aeration reactor equipped with vertical pipes for compost stabilization of cow manure. Waste Management & Research, 24, Tiquia, S.M. & Tam, N.F.Y. (22). Characterization and composting of poultry litter in forcedaeration piles. Process Biochemistry, 37, Wallace, P. Enviros Ltd., (25). Statistical Report on Test Methods (Section 9.7), ADAS consulting Limited, Published by: The Waste and Resources Action Programme, UK. Zucconi F., Forte M., Monaco A. & De Bertoldi M., (1981). Biological evaluation of compost maturity. Biocycle, 22,

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