Optimal use of the Hosoya system in composting poultry manure

Transcription

1 Bioresource Technology 72 (2000) 227±233 Optimal use of the Hosoya system in composting poultry manure D. Georgakakis *, Th. Krintas Department of Agricultural Engineering, Agricultural University of Athens, Iera Odos 75, Athens, Greece Received 17 September 1998; received in revised form 26 July 1999; accepted 9 August 1999 Abstract A study was undertaken to optimize the use of the Hosoya system in composting poultry manure in a typical layer poultry farm in Greece. The farm is located about 50 km north of Athens with a Hosoya system installed which has been in operation for more than 4 years. During the study the performance of the system was investigated and samples of the material under process were taken for moisture determination and total and volatile solids analyses. The temperature of the material, as well as the temperature and the relative humidity of the surrounding air, were also monitored. The results showed that the composting process could not be completed in the oval Hosoya installation. This could be attributed to the required intensive daily turning and pushing of the manure in the installation, in order to reach the exit at the desired rate. As a result, an early drastic temperature drop of the material occurred. A further step is then necessary for e cient completion of the composting process of this type of manure. In such a case, the Hosoya system can be considered as the necessary mechanical precomposting step required for the high moisture and muddytextured layer poultry manure prior to its being fully composted in piles or windrows. Ó 1999 Elsevier Science Ltd. All rights reserved. Keywords: Composting systems; Poultry manure; Compost piles; Mechanical turning; Odour control 1. Introduction Poultry manures are mostly uniform in physical appearance and rich in bre, ammonia nitrogen and moisture. These factors do not favor their composting alone and so they are not mentioned in the literature. Only one citation was found for poultry manures (Edwards and Daniel, 1992). The implementation of a coste ective poultry-waste treatment and utilization system, such as the composting process, would reduce the environmental impact and also probably allow for a cash return to the farmers through the sale of a usable, recycled end product. Mixing of these wastes with other raw materials is one way to e ectively compost such wastes (Georgakakis et al., 1995). However, the lack of availability or the cost of transportation of such raw materials makes the mixing a rather expensive and not practical procedure. It becomes more applicable for centralized composting stations which can more e ectively produce and market composts from raw materials of di erent origins. * Corresponding author. On-site composting in the production farm is the way required for the poultry manure to be managed in Greece. Two main treatment systems have been applied for the treatment of these wastes: The Okada and the Hosoya systems, both of Japanese origin. A common feature of these systems is that both are based on the operation of a specially designed manure turning and chopping mechanical system (MTCM). The system consists of a series of rotating metallic knives or forks with which the manure is completely turned, aerated and gradually pushed to the exit of the installation. The installation consists of an open shallow, oval shaped, concrete channel about 80±100 m long and 4±6 m wide, as shown in Fig. 1. It can serve about ± layers. The channel is placed under a closed greenhouse-type shelter, of a metallic skeleton covered by hard plastic sheets of milky color. The purpose of this type of covering is the sun warming of the inside air during the sunny days of winter and early spring. The rest of the year, mainly during summer and fall, the excess solar heat loads are removed by opening large doors and windows on the side walls of the shelter. This type of construction is mostly suggested for countries with mild and dry climates /00/$ - see front matter Ó 1999 Elsevier Science Ltd. All rights reserved. PII: S ( 9 9 )

2 228 D. Georgakakis, Th. Krintas / Bioresource Technology 72 (2000) 227±233 Fig. 1. The Hosoya oval concrete channel with the di erent sampling sites. The manure lls the channel up to a total depth of 1.0±1.2 m. In both systems the MTCM rolls along metallic rails placed on the top of the channel side walls. A striking di erence between the two systems is that with the Okada the channel is straight while the Hosoya is oval shaped. As a result, in the Okada the manure is pushed straightforward by the MTCM from the entrance at the one end of the channel to the exit at the other end. In the Hosoya, the manure is continuously kept turning around in the oval channel and only a part of it, equivalent to that entered the channel, is regularly taken out from the exit hole. The MTCM in the Hosoya system completes a full run along the oval channel in about 2.0 h, including a rest period of about 15±20 min for maintenance or rest. On a daily basis, a maximum of 12 full runs can then be completed. One complete run results in a manure displacement by 1.5 m along the channel or a maximum of 18 m after a 12 full runs completion in 24 h. Thus the minimum travelling time for the fresh manure to reach the exit of the 80 m long channel is 4.44 days. Fresh manure is batch fed daily to the oval channel and an equivalent quantity of nal material is removed from the exit, in order to keep the total quantity in the channel at the desired depth. During turning and pushing of the manure in the channel by the MTCM, surrounding air is incorporated and moisture is lost by evaporation. Moisture and C/N ratio are considered as the keyfactors for a successful composting process. For layer poultry manure, the low C/N ratio is the factor resulting in large ammonia losses (Gray et al., 1971). The excess of moisture, more than 75% (MWPS-1, 1983) is considered as the most adverse factor for a quick start of the composting process. The moisture content or the degree of material drying is indicative of the decomposition rate and the tendency to stabilize, since the metabolic heat generation during decomposition drives evaporation. Factors that contribute to moisture loss include evaporation, leaching and aeration, natural or forced. A moisture content between 40% and 60% (wb) should be maintained during the composting process (Rynk et al., 1991), although it is mentioned (Fernandes et al., 1994) that successful composting of poultry manure mixed with peat or chopped straw has been obtained in a passive static pile at high initial moisture levels (73± 80%). The Hosoya system controls the initial moisture content of the material in the oval channel and helps to start the composting process, by proper mixing the incoming fresh and muddy-textured manure with the recirculated dry old material in the channel. Moisture control of the material in the oval channel is necessary to avoid blockages of the MTCM operation (Hosoya & Co., 1996). With the Hosoya system, particles of di erent size, less than about 12 mm, are readily formed from the initially muddy-textured raw material due to the turning e ect of the MTCM on the material in the oval channel. Particles formation is bene cial for degradation, because of the greater surface area available to microbes and void space for oxygen, especially during the thermophilic stage of composting, where oxygen demand is greatest. Such a compost, with particles size less than 12 mm in diameter, a ph between 6.0 and 7.8, a soluble salt level less than 2500 lmhos/cm and few contaminants will have almost unlimited use (Rynk et al., 1991). The initial increase of the material temperature, usually observed in the Hosoya oval channels, followed by a signi cant decline as the material approaches the exit, raises questions of whether is this a result of process completion or simply a direct e ect of manure overturning and over-aerating by the MTCM. In this work, the Hosoya system e ciency in manure composting was studied and optimized in situ, in a typical Greek poultry farm of about layers, for process economy and environmental protection. 2. Methods 2.1. Materials This study was nanced by a consortium of four industrial type layer poultry farms, operating at di erent locations in Greece. It actually took place in one of them, named ÔPapayannis Poultry Farms Co.Õ, located about 50 km north of Athens. The layer poultry manure used in this study can be considered as that typically produced in Greek mediumto-large size, industrial type, layer poultry farms. The manure in the farm under study is mechanically transported from the collecting plastic belts placed under each row of cages in the rearing buildings to the Hosoya

3 D. Georgakakis, Th. Krintas / Bioresource Technology 72 (2000) 227± installation site. Every day, about 12±14 m 3 manure are normally transported to the Hosoya operation site for composting. It is a soft creamy material, muddy in appearance, a mixture of high moisture content wastes and powdered poultry feed losses. During the dry and warm periods of the year it becomes slightly drier in appearance and texture. The almost daily removal of the manure from each rearing building does not allow production of a high degree of dryness of the material, prior to its transportation to the Hosoya oval basin Methods The Hosoya system of the Papayannis Farms Co. was studied in this work for a period of 282 consecutive days, from 4 July 1997 until 13 April The manure was put in the channel, on a regular daily basis, through the entrance opening A, as shown in Fig. 1. Then gradually was pushed to the exit by the MTCM. Based on the working status of the poultry farm under investigation, the MTCM had been adjusted to perform from three to more than six complete runs every day, depending on the season of the year. The colder the weather the fewer complete runs were performed during the day, in order to keep the MTCM working e ciently in the manure mass, without blockages. The variation in the daily number of the MTCM complete runs, during the year, a ected in turn the manure quantity fed daily to the system, in order to keep its moisture content under control and MTCM in e cient operation. In Table 1 the number of complete runs and the corresponding quantity of manure fed daily in the channel, according to the season, are shown. To adjust the moisture content of the incoming fresh manure, the depth of the recirculated dry old manure at the entrance port was adjusted to 0.40±0.50 m during the ``warm'' and to 0.60±0.80 m during the ``cold'' period of the year. The rest of the channel depth, up to 1.0±1.2 m, was left for the fresh manure. All sampling and measurements during the study were done on speci c sites along the oval channel, characterized by the letters A, B, C, D, E, as shown in Fig. 1. The site A corresponded to the entrance and the site E to the exit hole. The proper mixture of the incoming fresh manure and the recirculated dry old one, reached the exit hole E by passing successively through the sites B, C and D of Fig. 1. All material samples were taken from the middle of the oval channel at a 0.4 m depth in the manure mass. The high degree of material homogenization resulting from the MTCM operation assured that all samples taken were representative of the manure status at each sampling site along the channel Chemical analysis Moisture content, total solids and volatile solids of the manure at the di erent sampling sites along the channel were determined as described in Standard Methods (American Public Health Association, 1985). In addition, the instant temperature of the manure at all sampling sites was measured by inserting a metallic thermometer to a depth of 0.4m in the manure mass. The surrounding air relative humidity and temperature were simultaneously measured by a small portable digital dual electronic meter. 3. Results and discussion A direct output of the Hosoya system operation is that aeration of the material in the oval channel takes place actually only during turning and pushing of the manure by the MTCM. Thus aeration is strictly related to the daily operation schedule of the MTCM and not to the composting process requirements, as it normally should have to be. As a result, excess aeration of the material was actually expected in order for the system to keep up with the manure quantities fed in daily. The e ect of excess turning and aeration on the temperature pro le was studied during this investigation. In Table 2, instant temperature values measured at the di erent sampling sites along the oval channel, marked by the letters A, B, C, D, E in Fig. 1, are listed. The corresponding instant values of the surrounding air are also included. The values in Table 2 were divided into four groups, each group representing one typical season of the year. The average of the temperatures for each season was considered as the seasonal temperature representative value of the material at each sampling site. A graphical presentation of all seasonal temperature representative values is shown in Fig. 2. From these graphs it is clear that all temperature pro les of the manure in the oval Table 1 Seasonal MTCM complete runs and raw manure input and travelling in the channel for optimum system performance Season Complete runs of MTCM/day Manure quantity (m 3 /day) Manure travelling time in the channel (days) Winter (D, J, F) 3±4 5.5±7.0 18±13 Spring (M, A, M) 4±5 7.0±9.0 13±11 Fall (S, O, N) 5±6 9.0± ±9 Summer (J, J, A) >6 >11.0 <9

4 230 D. Georgakakis, Th. Krintas / Bioresource Technology 72 (2000) 227±233 Table 2 Instant daily and seasonal average material temperature values obtained at the di erent sampling sites of the oval channel Season Date of sampling Sampling site a A B C D E Temperature ( C) Summer (J±J±A) 4/7/ /7/ /7/ /7/ /7/ /7/ /8/ /8/ Average Fall (S±O±N) 18/9/ /9/ /10/ /11/ Average Winter (D±J±F) 12/12/ /1/ /2/ Average Spring (M±A±M) 16/3/ /3/ /3/ ± 30/3/ /4/ /4/ /4/ /4/ ± Average Temperature of the surrounding air ( C) Overall av a For A, B, C etc., see Fig. 1. Fig. 2. Seasonal average temperature variation of the material along the Hosoya oval channel (for A, B, C etc., as shown in Fig. 1). channel follow the same path, an initial increase from the entrance site (A) up to a maximum at site (B) and then a gradual decline through sites (C) and (D) until the exit site (E), regardless of the season of the year. This is similar to the typical temperature time path during composting of organic materials (Gray et al., 1971), thus suggesting the conclusion that the process approaches its completion when the material reaches the exit of the channel. But more careful observations during this study have shown that this was not the case with the Hosoya system. Two small piles of about 1.5 m height each were formed from processed manure coming out from the oval channel exit. Pile I was installed under the shelter where the oval channel was operated and pile II outside the shelter in the open air. Both piles were mechanically turned by a small tractor from time to time. Wetting was performed only to pile II, but in a nonsystematic way. The temperature of the manure in both piles was instantly taken with the same thermometer used for obtaining manure temperatures in the oval channel. All

5 D. Georgakakis, Th. Krintas / Bioresource Technology 72 (2000) 227± Table 3 Instant daily temperature values of the experimental piles I and II formed from material coming out from the Hosoya oval channel exit hole Days Temperature ( C) Pile I Pile II Material Air Material Air > > ± ± ± ± ± ± 40 >60 38 ± ± ± ± values obtained are listed in 5-day intervals in Table 3. The data of Table 3, showed that the processed manure coming out from the oval channel had an increase in temperature, to levels well above 50 C, when left undisturbed in piles for over 24 h. This showed that the composting process was still going on very actively on the processed manure and that an extra time of more than 30 days was still required for the process to be completed. This agrees with the retention time of more than 25 days suggested in the literature for e cient composting of organic residues (Gray et al., 1971). The actual time taken by the mixture of fresh and old manure from the entrance site A to reach the exit E (see Fig. 1) ranged from less than 9 up to 18 days, depending on the season of the year, as shown in Table 1. Part of this manure was then taken out while the rest of it was gradually pushed back to the entrance, A, in order to be mixed with the incoming fresh manure. Based on these observations, it can be concluded that the composting process, which is shown to be well started immediately after the addition of fresh manure to the oval channel, is only partially completed because of excess heat losses, as shown by the material temperature drop in Fig. 2. The material temperature decline shown should then be attributed to the mechanical e ect of the daily over-turning and over-aerating of the material by the MTCM and not to the completion of the composting. A similar e ect of over-turning and overaeration on the composting process is also mentioned in the literature. In 1992, Edwards suggested that windrow turnings should be made every 2±3 days. In 1971, Gray mentioned that too much agitation can lead to excessive loss of heat and moisture, reducing the degradative ability of the microorganisms. From the data of Table 4, it can also be shown that the moisture content of the processed manure coming Table 4 Daily and seasonal average material moisture content values (%wb) determined at the di erent sampling sites of the oval channel Season Date of sampling Sampling site a A B C D E Moisture content (%wb) Summer (J±J±A) 8/7/ /7/ /7/ <30 18/7/ /7/ /7/ /8/ /8/ <30 Average Fall (S±O±N) 18/9/ /9/ /10/ /11/ Average Winter (D±J±F) 12/12/ /1/ /2/ Average Spring (M±A±M) 1/4/ /4/ Average Relative humidity of surrounding air (%) Overall av a For A, B, C etc., see Fig. 1.

6 232 D. Georgakakis, Th. Krintas / Bioresource Technology 72 (2000) 227±233 out from the oval channel is not critical. The composting process is shown to go on at moisture contents close to the lower limits of 40% mentioned in the literature (Rynk et al., 1991). Table 4 shows the moisture content status of the manure during its processing in the oval channel. In this table, the actual moisture content values of the manure at the sampling sites A±E are listed. Moisture values were divided into four groups, one for each season, as it was done with the temperature values. The average of each season served as the seasonal representative value. In addition, the corresponding relative humidity values of the surrounding air were also determined. The data of Table 4 shows that the manure moisture content values remained mostly within the suggested range of 40±60% (wb), (Rynk et al., 1991). Only at the exit site E, and during summer and spring at the site D also, did the values fall below the lower limit of 40%, approaching 30%. Up to this level biological activity would still be going on actively, being greatly reduced only at lower values (Gray, 1971). In Fig. 3 the moisture content as well as the total and volatile solids values of the manure have been plotted. The values represent the seasonal averages of the manure samples taken at each sampling site, shown in Fig. 1, expressed as per cent of the corresponding values at site A. From the data of Fig. 3 it is shown that in addition to moisture content, the organic matter was also reduced during the processing of the manure in the oval channel, regardless of the season of the year. For such a result, a proper adjustment of the daily number of the MTCM complete runs, as suggested in Table 1, should rst be done. As previously mentioned, composting is not complete in the Hosoya channel, so an additional step is necessary, following the exit of the manure from this channel. This step could be the formation of piles or windrows which would then be turned according to the process needs for temperature and moisture content adjustment. In this case, the Hosoya system can be considered as a very useful ``tool'' in converting an initially creamy and muddy-textured raw material to a readily compostable and relatively dry end product, rich in discrete particles of 12 mm diameter and less. A direct practical consequence of this scheme is that the Hosoya channel can actually be shortened by about 20 m. This shortening of the channel can be justi ed by the fact that in the rst 60 m of the channel, the material temperature has already declined and the formation of the desired discrete particles of less than 12 mm diameter completed. So, any further increase in the Hosoya channel length does not actually add to the process ef- ciency. In contrast, shorter channels are less costly and better controlled, thus resulting in reduction of odors and minimal operation time and maintenance cost of the MTCM. References Fig. 3. Seasonal moisture, total solids and volatile solids content averages variation of the material along the oval channel (for A, B, C etc., as shown in Fig. 1). American Public Health Association, Standard Methods and Wastewater Analysis. APHA, Washington, DC, USA. Edwards, D.R., Daniel, T.C., Environmental impacts of on-farm poultry waste disposal-a review. Bioresource Technology 41, 9±33. Fernandes, L., Zhan, W., Patni, N.K., Yjui, P., Temperature distribution and variation in passively aerated static compost piles. Bioresource Technology 48, 257±263. Georgakakis, D., Tsavdaris, A., Bakouli, J., Symeonidis, S., Use of solid swine and poultry residues to produce high quality compost in mixture with lignite and other agricultural residues. A research report. European Union Research Program ``Brite'' Contract Bre-2-CT Proposal Fa Gray, K.R., Sherman, K., Biddlestone, A.J., A review of composting, Part 1 & Part 2. In: Process Biochemistry 6.

7 D. Georgakakis, Th. Krintas / Bioresource Technology 72 (2000) 227± Hosoya & Co., Hosoya Manure Fermentation System. Hosoya & Co., 412 Fukaya, Ayase-shi, Kanagawa-ken 252, Japan. MWPS-1, Structures and Environment Handbook. Midwest Plan Service, Iowa State University, Ames, Iowa 50011, USA. Rynk, R., Kamp, M.,Willson, G., Singley, M., Richard, T., Kolega, J., Gouin, F., On-Farm Composting Handbook. Northeast Regional Agricultural Engineering Service, 152 Riley-Robb Hall, Cooperative Extension, Ithaca, NY , USA, 174 p.