EFFECT OF CARBON TO NITROGEN RATIO ON THE COMPOSTING OF CASSAVA PULP WITH SWINE MANURE

This research investigated the composting process of cassava pulp and swine manure at various initial C/N ratios of 20/1, 30/1, and 40/1 and the effect of microbial activator, p.d.1, on composting process. Compost with an initial C/N ratio of 30/1 seeded with p.d.1 showed the highest maximum temperature (63.5°C), the lowest number of faecal coliform (2.87 Log10 MPN g-1), and the shortest time (around day 42) to reach maturity, suggesting a suitable initial C/N ratio

Journal of Water and Environment Technology, Vol.4, No.1, 2006 EFFECT OF CARBON TO NITROGEN RATIO ON THE COMPOSTING OF CASSAVA PULP WITH SWINE MANURE Nattipong Kamolmanit*, and Alissara Reungsang** *Department of Biotechnology, Graduate School, Khon Kaen University A.Muang, Khon Kaen 40002 THAILAND E-mail: kamolmanit@yahoo.com **Research Centre for Environmental and Hazardous Substance Management and Department of Biotechnology, Faculty of Technology, Khon Kaen University, A.Muang, Khon Kaen 40002 THAILAND E-mail: alissara@kku.ac.th; Correspondence author ABSTRACT This research investigated the composting process of cassava pulp and swine manure at various initial C/N ratios of 20/1, 30/1, and 40/1 and the effect of microbial activator, p.d.1, on composting process Compost with an initial C/N ratio of 30/1 seeded with p.d.1 showed the highest maximum temperature (63.5°C), the lowest number of faecal coliform (2.87 Log10 MPN g-1), and the shortest time (around day 42) to reach maturity, suggesting a suitable initial C/N ratio KEYWORDS: Cassava pulp, C/N ratio, Compost, Swine Manure INTRODUCTION Cassava (Manihot esculenta Crantz) is one of the most important crops in Thailand Approximately 40 percent of the cassava produced in Thailand is converted into starch Domestic demand for cassava starch is as high as 1.3-1.7 million tons per year (Thai Tapioca starch Association, 2005) The cassava processing industry produces solid residues known as “pulp” Cassava pulp contains a large amount of carbohydrate (up to 50-60% dry weight basis), fiber and minerals such as Cu, Zn, Mn, Fe and Mg (Penuliar, 1940) and has a moisture content of about 60-70 % (Sriroth et al, 2000) Cassava pulp is commonly used as organic soil amendment and bulking agent for composting Some researches focused on the utilization of cassava pulp as a single cell protein and as a raw material for ethanol production (Boonyakamol, 2003; Potisung, 2003) However, since cassava pulp has high carbon content, its value can be enhanced if mixed with other organic waste of high nitrogen content and used as soil amendment Composting is a biological decomposition process, wherein organic matter is degraded to achieve inorganic nutrients and stable organic material (compost) at the end Composting - 33 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 is generally used for the treatment of organic wastes such as sewage sludge and animal manure It is also used in agro-industrial process to obtain products which can be applied to soil to increase soil organic matter content as well as enhance soil structure and cation exchange capacity (Contreras-Ramos et al, 2004) During the decomposition process, initial carbon to nitrogen ratio (C/N) in compost material is the major controllable factor indicating the digestion process which include enzymatic activity by microorganisms (Bertoldi et al, 1983) The C/N ratio can be used as an indicator for compost maturity The initial C/N ratio in compost affects the quality of mature products (Heerden et al, 2002; Huang et al, 2004) It is reported that an initial C/N ratio of 25-30 is suitable for microbial activities during the nitrification process (Alexander, 1961) Animal manure such as pig manure, spent pig manure, cow manure, and solid poultry manure had been used for adjusting C/N levels in composting pile (Tiquia et al, 1996; Guerra-Rodriguez et al., 2001; Contreras-Ramos, 2004; Huang et al, 2004) Swine manure is one promising N-source because it contains 70 % water, 36.6 % total organic carbon, 3.24 % total nitrogen and 1.72 % total phosphorus (Tiquia and Tam, 1998; Huang et al, 2004) Furthermore, the pH and C/N ratio of swine manure are 8.12 and 11.3, respectively, (Huang et al, 2004) which makes it suitable as supplement for C/N ratio adjustment in composting Composting process can be accelerated through the addition of microbial activators such as LD-1, F-60, Bionic, and p.d.1 (Subjarearn et al, 2002) A commercial microbial product is often added to the compost mixture to ensure the establishment of initial microbial population and enhance the composting process (Tiquia et al, 1997a; Subjarearn et al, 2002) The commercial bacterial product that has been used to enhance the composting process in Thailand is a microbial activator p.d.1 (Subjarearn et al, 2002) The p.d.1 consists of various degrading lignocellulolytic microorganisms such as bacteria, actinomycetes and fungi that can accelerate the decomposition rate when seeded to the compost (Land Development Department, 2003) Cassava pulp and swine manure composting processes with and without p.d.1 and the quality of the final compost products are worth investigated Several studies reported the use of animal manure compost for plant production in agricultural farm due to its low cost as compared to inorganic fertilisers (Stephanon et al., 1990; Gajalakshini and Abbasi, 2002; Ta-oun, 2003) However, there is a very limited information on the use of cassava pulp as raw material in composting process Thus, in this study, cassava pulp and swine manure were used as raw materials for compost production with and without microbial activator (p.d.1) - 34 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 MATERIALS AND METHODS Raw materials Cassava pulp Cassava pulp was collected from Takul Lek Tapioca Flour Factory Co., Ltd Mahasarakham, Thailand The pulp was air-dried for weeks prior to usage Swine manure Swine manure (a mixture of liquid and solid forms) was obtained from the pig farm located at the Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand Subsamples of swine manure were air dried at 80 °C for 24 h, ground and passed through a 2.0 mm sieve The samples were then stored in desiccator for further analysis and usage p.d Microbial activator (p.d.1) was obtained from the Land Development Department, Khon Kaen, Thailand The p.d.1 consists of strains of bacteria in Genus Bacillus sp., strains of Actinomyces in Genus Streptomyces sp., and strains of fungi that include Scopulariopsis sp., Helicomyces sp., Chaetomium sp., and Trichoderma sp (Sunanthapongsuk, 2001) These commercial microbial products are often added to the compost mixture to enhance the composting process in Thailand (Subjarearn et al, 2002;Land Development Department, 2003) Composting pile establishment The first set of composting piles was prepared as follows : Pile 1: Cassava pulp and swine manure at an initial C:N ratio of 20:1 (dw/dw) Pile 2: Cassava pulp and swine manure at an initial C:N ratio of 30:1 (dw/dw) Pile 3: Cassava pulp and swine manure at an initial C:N ratio of 40:1 (dw/dw) Each pile contained 20 kg of mixture The dimension of each pile was approximately 50 cm (width) X 50 cm (length) X 50 cm (height) Every seven days, the moisture content in each pile was adjusted to 60 % before and during the composting process until the temperature in compost reached the ambient temperature The second set of composting piles (pile 4, pile and pile 6) was prepared in a similar manner as the first set but the seeding microbial activator (p.d.1) was added to each pile in a p.d.1/composting pile ratio of 10 ml:500 g of compost Every seven days, the moisture content of the mixture was also adjusted to 60% through the addition of water before and during the composting process When the temperature in compost piles reached the ambient temperature, addition of water was stopped although the composting process - 35 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 continued Each compost pile was manually mixed with a shovel for about 10 minutes to turn the pile and provide aeration This was done every 3-4 days until the compost piles reached maturity The ambient temperature and the temperature within each pile at a depth of 15 cm from the surface of the piles were determined using a thermometer At days 14, 28, 42, 56, 70 and 84, after turning the compost piles, a 50 g sub-sample was randomly collected from the compost pile and analyzed using some physical and biological parameters (Table 1) Table Physicochemical and biological parameters used for analyses of samples Parameter pH Method pH meter Sampling date Every 3-4 day Temperature Thermometer Everyday Moisture content (%) Total organic carbon (%) Oven dry method Walkley and Black method Every day Every 14 day Total Nitrogen (%) Micro-kjeldahl method Every 14 day Reference Tiquia and Tam (1998) Tiquia and Tam (1998) Page et al (1982) Walkley and Black (1934) Black (1965) Total Phosphorus (%) Spectrophotometric method Every 14 day Black (1965) Total Potassium (%) Atomic absorption technique method Most Probable Number Every 14 day Black (1965) Every 14 day AOAC (2000) Faecal coliforms Statistical analysis Mean and standard deviation values were reported for all parameters measured Analysis of variance (ANOVA) and Duncan’ s multiple range test were performed using SPSS v 11 statistical software for windows One-way ANOVA was carried out to compare the means of different treatments where significant F-values at p≤ 0.05 were obtained Differences between individual means were tested using the least significant difference test - 36 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 RESULTS AND DISCUSSION Main characteristics of cassava pulp and swine manure Analysis of cassava pulp revealed that it had high carbon content but low nitrogen thus giving a high C/N ratio (Table 2) The pH of cassava pulp indicated that it was slightly acidic Although the carbon content of swine manure was twice as low as that of cassava pulp, its nitrogen content was about five times higher This caused the C/N ratio of the former to be 10 times higher than that of the latter (Table 2) indicating that swine manure was suitable for the adjustment of C/N ratio in composting Table Main characteristics of the raw materials Parameters pH Moisture content (%) Total organic carbon (%) Total Nitrogen (%) Total Phosphorus (%) Total Potassium (%) C/N ratio ‡ Cassava pulp 5.81 ± 0.05‡ 9.36 ± 0.11 51.51 ± 1.25 0.45 ± 0.09 0.011 ± 0.002 0.36 ± 0.01 118.34 ± 22.78 Swine manure 8.21 ± 0.02 16.89 ± 0.2 26.16 ± 0.09 2.47 ± 0.22 6.42 ± 0.06 1.42 ± 0.26 10.66 ± 0.89 Mean ± standard deviation Compost characteristics Temperature profile The initial mean temperature of all piles was approximately 25 °C A high temperature of 63.5°C was found in Pile at Day High temperature continued to be observed in this pile for about 24 days (Figure 1) and then gradually dropped to 30.5 °C at Day 40 After day 40, the temperature varied within a narrow range until day 84 (Figure 1) The other piles showed a similar pattern of temperature changes as in pile except that the maximum temperatures recorded in piles and were lower (≈59 °C) as shown in Figure The pattern of these temperatures i.e., increase to a certain temperature, remain constant at that temperature and then decrease was a typical temperature profile of composting process especially for cow manure and wheat straw composts (Tiquia and Tam, 1998), citrus wastes compost (Heerden et al, 2002), spent pig manure and sawdust litter composts (Huang et al, 2004) and filter cake and bagasse composts (Meunchang et al, 2005) The levels of temperature in the compost piles increased and reached 50-60°C due to the energy released from biochemical reaction of microorganisms in the compost piles while - 37 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 the temperature in compost piles tend to decrease after the thermophilic phase due to the loss of substrate and a decrease in microbial activity (Bertoldi et al., 1983) The level of temperature in compost piles can be used as an indicator of compost maturity (Tiquia et al, 1997a; Tiquia et al, 1997b) Tiquia et al (1997a, 1997b) reported that a compost material could be considered mature when the temperature in the compost reached the ambient temperature With this, the compost in pile was considered matured after day 40, which was the fastest among the piles C /N , C /N , C /N , C /N , C /N , C /N , Temperature (c) 60 /1 /1 /1 /1 /1 /1 n o s e e d in g ( p ile ) n o s e e d in g ( p ile ) n o s e e d in g ( p ile ) s e e d in g p d ( p ile ) s e e d in g p d ( p ile ) s e e d in g p d ( p ile ) 40 20 0 14 21 28 35 42 49 56 63 70 77 84 composting time (day) Figure Temperature profiles during composting of cassava pulp with swine manure Changes in pH During the composting process, the pH of all piles dropped from approximately 7.8 to 5.5 during the first 18 days of composting (Figure 2) The pH of compost in piles and were lower than the other piles This may be due to the higher organic carbon content (around 45%) in these piles A large pH drop in the compost piles at the initial stage of composting might be due to the fact that organic carbon was degraded to organic acid by the acidforming bacteria existing in the compost pile (FAO, 1987) In addition, the pH drop might be caused by the mineralization of organic acid during the composting process as well as the large quantities of carbon dioxide released during the composting process (FAO, 1987; Tiquia et al, 1996; Tiquia et al, 1997a; Tiquia and Tam, 1998; Huang et al, 2004; Meunchang et al, 2005) - 38 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 pH C/N, C/N, C/N, C/N, C/N, C/N, 14 21 28 35 42 49 56 20/1 30/1 40/1 20/1 30/1 40/1 no seeding ( pile ) no seeding ( pile ) no seeding ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) 63 70 77 84 Com posting tim e, days Figure Changes in pH during composting of cassava pulp with swine manure After 18 days of composting, the pH of all piles increased and pH levels remained relatively unchanged after Day 35 The increase of pH in composting piles during the composting process could be due to the production of ammonium as a result of the ammonification process (Huang et al., 2004) The pH patterns were concomitant to the previous studies on the composting of other organic wastes (Meunchang et al, 2005; Tiquia and Tam, 1998) Tiquia and Tam (2002) studied the changes on composting of spent pig manure and sawdust litter They reported that the changes in temperature of composting had a strong correlation with some chemical parameters such as the pH and decided to use these parameters to determine the maturity of compost Moisture content Moisture content at Day and during the composting process in all compost piles were adjusted to 60 % because an optimum level of moisture content had strong effect on oxygen consumption rate of aerobic heterotroph microorganisms (Tiquia et al, 1996) It was reported that a suitable and efficient moisture content in composting of spent litter was between 50 % and 60 % At the initial stage of composting, the moisture content of all piles was around 62-64% and dropped gradually during composting time (Figure 3) When the temperature in the compost piles reached the ambient temperature, addition of water was stopped although the composting process continued Afterwards, the moisture content of all piles decreased slowly to around 38.82-46.62 % at the end of the composting period It was considered that the piles have achieved an acceptable level of quality of mature compost, i.e., ≤50% (Ta-oun et al., 2005) A decrease in moisture content was due to the release of moisture - 39 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 from the compost pile through water evaporation as a result of the heat generated from microbial activities during composting (Miller and Finstein, 1985) C/N C/N C/N C/N C/N C/N Moisture content (percent) 80 70 20/1 30/1 40/1 20/1 30/1 40/1 no seeding ( pile ) no seeding ( pile ) no seeding ( pile ) seeding ( pile ) seeding ( pile ) seeding ( pile ) 60 50 40 30 20 14 21 28 35 42 49 56 63 70 77 84 Composting time (day) Figure Changes in moisture content during composting of cassava pulp with swine manure Total organic carbon and total nitrogen During the composting process, total organic carbon in all piles sharply decreased in the first 28 days of composting and from 33 - 45% initial carbon content, it dropped to nearly 25% at the end of the composting period (Figure 4) Decrease in total organic carbon concentration resulted from the oxidation of carbon to carbon dioxide by microorganisms during composting (Tiquia et al., 1996) Throughout the composting process, total organic carbon loss in pile (24.28%) and pile (16.85%) was lower than those of the other piles (32% in pile 2, 39.44% in pile 3, 39.43% in pile and 39.74% in pile 6) The small decrease in total organic carbon in pile and pile could have resulted from a poor decomposition when the initial C/N ratio was low (Huang et al., 2004) In addition, recalcitrant organic wastes such as cellulose and lignin may affect a degree of organic carbon loss during the decomposition process (Huang et al, 2004) Total organic carbon in pile and pile was higher than those of the other piles in the first 70 days due to a larger amount of organic carbon supplied in these piles, specifically, large amount of cassava pulp was added into the compost mixture prior to the composting process - 40 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 50 C/N, C/N, C/N, C/N, C/N, C/N, Total Organic Carbon (%) 45 20/1 30/1 40/1 20/1 30/1 40/1 no seeding ( pile ) no seeding ( pile ) no seeding ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) 40 35 30 25 20 14 28 42 56 70 84 Composting time, days Figure Changes in total organic carbon during composting of cassava pulp with swine manure Total nitrogen increased slightly in all composting piles (Figure 5) The increase in total nitrogen during the composting process might be due to the activity of nitrogen fixing bacteria which was expected to exist in the compost pile These bacteria have the capability to fix N2 from the air to NO3 contained in the pile (Bishop and Godfrey, 1983) Huang et al (2004) found the same results where the nitrogen content in the compost slightly increased after 63 days of composting At the end of composting, piles 1, 2, and contained higher total nitrogen content (2.33%, 2.19%, 2.46% and 2.11%, respectively) than pile and (1.72 % and 1.89 %, respectively) The nitrogen in the compost pile mainly came from the swine manure added Thus, the nitrogen content in pile 1, 2, and (where larger amount of swine manure was added) was found to be higher than in pile and at the end of composting - 41 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 C /N , C /N , C /N , C /N , C /N , C /N , Total Nitrogen (%) 20/1 30/1 40/1 20/1 30/1 40/1 no seeding ( pile ) no seeding ( pile ) no seeding ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) 0 14 28 42 56 70 84 C om posting tim e, days Figure Changes in total nitrogen during composting of cassava pulp with swine manure Changes in total phosphorus and total potassium The changes of total P and K followed a similar trend as total nitrogen wherein there was a gradual increase throughout the composting period Increase in total P and K may be due to the net loss of dry mass which generally concentrated the phosphorus and potassium in composting pile (Huang et al, 2004) In addition, Tiquia and Tam (2002) explained that an increase in P and K during composting of poultry litter in forced-aeration piles were due to losses of organic C, H, N, and O from composting piles as CO2 and H2O At day 84 of composting, as seen in Figure 6, total P in pile 1, 2, and were 2.51 %, 2.44 %, 2.52 % and 2.56 %, respectively, and were higher than pile and pile (1.61% and 1.97 %, respectively) The amount of swine manure added to piles and was lower than those added into pile and pile which could have resulted to a lower amount of total phosphorous detected in these compost piles since the phosphorous detected in the compost was mainly released from swine manure - 42 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 C/N, C/N, C/N, C/N, C/N, C/N, Total Phosphorus (%) 20/1 30/1 40/1 20/1 30/1 40/1 no seeding ( pile ) no seeding ( pile ) no seeding ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) seeding p.d.1 ( pile ) 0 14 28 42 56 70 84 Composting time, days Figure Changes in total phosphorus during composting of cassava pulp with swine manure Total K in every pile slightly increased during the decomposition process (Figure 7) Total potassium in pile 1, 2, 4, and were 2.03 %, 1.89 %, 2.1 % and 1.97 %, respectively At the first day of composting, total K in pile and were lower than those of the other piles may be due to the lower amount of swine manure added to these piles to obtain higher initial C/N At the end of composting, the percentage of total K in pile and pile were also lower than those of the other piles (1.41 % and 1.58 %, respectively) indicating that the percentage of K depended on the amount of swine manure added into the compost piles Total K content in all piles were above the minimum acceptable level (K2O ≥ 0.5%) according to the qualifications of mature compost recommended by Land Development Department (2003) This suggested that cassava pulp and swine manure could be effectively used for composting and would result to satisfactory composts in terms of potassium content - 43 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 C/N, 20/1 no seeding ( pile ) C/N, 30/1 no seeding ( pile ) C/N 40/1 no seeding ( pile ) C/N, 20/1 seeding p.d.1 ( pile ) C/N, 30/1 seeding p.d.1 ( pile ) C/N 40/1 seeding p.d.1 ( pile ) Total Potassium (%) 0 14 28 42 56 70 84 Composting time, days Figure Changes in total potassium during composting of cassava pulp with swine manure Changes in C/N ratio The C/N ratio is one of the factors used to indicate compost maturation A C/N ratio of 20 or less is accepted as mature compost (Land Development Department, 2003) The C/N ratios of all piles in this study decreased, with the increase in composting time, to approximately 15 at the end of composting (Day 84) indicating that the compost reached maturity (Figure 8) Reports on the C/N ratio of compost at a maturity phase stated 13.27 for the co-composting of chestnut burr and leaves with solid poultry manure (GuerraRodriguez et al., 2001) and 11-17 for the composting of bagasse with sewage sludge (Negro et al., 1999) Percent loss of C/N ratio in pile 2, 3, and were 59.72 %, 62 %, 62.5 % and 64.9, respectively, which were slightly higher than piles and (48.28 % and 46.31 %, respectively) Lower percentage loss in pile and indicated that decomposition was poor when the initial C/N ratio was low There was no difference in the changes of C/N ratio in the compost pile with the same initial C/N ratio with or without p.d (Figure 8) These results indicated that p.d.1 did not play an important role in the decomposition process of the composting piles in this study The initial C/N ratio was the main factor affecting the time to reach maturity of the compost suggesting that it was not necessary to add the microorganisms as activator for composting Our results were supported by the work of Tiquia et al (1997b) who studied - 44 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 the role of various commercial bacterial products during the composting of pig waste They discovered that an addition of the commercial bacterial product during the composting process with moisture adjustment in windrow composting was not important If moisture content was adjusted, addition of bacterial product during composting would not be needed 50 C/N, 20/1 no seeding ( pile ) C/N, 30/1 no seeding ( pile ) C/N, 40/1 no seeding ( pile ) C/N, 20/1 seeding p.d.1 ( pile ) C/N, 30/1 seeding p.d.1 ( pile ) C/N, 40/1 seeding p.d.1 ( pile ) C/N ratio 40 30 20 10 0 14 28 42 56 70 84 Composting time, days Figure Changes in C/N ratio during composting of cassava pulp with swine manure Faecal coliforms elimination Faecal coliforms are used as indicator organism for the maturity of compost The survival of faecal coliforms depends on environmental factors including pH, temperature, moisture content, sunlight and nutrients (USEPA, 1995) Yanko et al (1987) reported that the faecal coliforms could grow after thermophilic phase of the sewage sludge composting if they were poorly composted and nutrient resource still remained The USEPA recommended that faecal coliforms should be less than 3.00 Log10 MPN g-1 in compost pile when it reached maturity (USEPA, 1995) Tiquia et al (1998) reported that the numbers of faecal coliforms were reduced to 2.27 Log10 MPN g-1 at a final date of spent pig litter composting At the beginning of our composting, the faecal coliforms were in the range of 5.07 – 7.09 Log10 MPN g-1 in all piles (Table 3) The faecal coliform numbers in pile and reduced slightly over time and may be due to the fact that these two piles had lower maximum temperature and slower rise in temperature (Figure 1) than other piles USEPA (1995) stated that a temperature higher than 40°C, for days, was sufficient to reduce pathogens - 45 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 However, when piles 1, 2, 3, and reached maturity, although the numbers of faecal coliform were reduced to around 3.11 -3.96 Log10 MPN g-1, these were still slightly higher than the USEPA limits Throughout the composting time, the faecal coliform numbers of pile reached 2.87 Log10 MPN g-1 at day 42 and were found to be less than those of the other piles This value was lower than the USEPA limit (Table 3) In addition, the final composts obtained were of pleasant earthy smell and dark brown in color indicating a good compost appearance Table Changes in the number of faecal coliforms during composting of cassava pulp with swine manure Faecal coliform numbers (Log 10 MPN g-1) Time (days) Type of composting Without seeding p.d Seeding with p.d 20/1 ‡ 14 28 42 56 70 84 30/1 40/1 20/1 30/1 40/1 Pile1 6.04±0.43‡ 3.63±0.45 3.68±0.39 3.31±0.50 3.26±0.36 ND ND Pile 6.76±0.5 4.54±0.53 4.14±0.26 3.5±1.19 3.14±0.19 ND ND Pile 5.09±0.43 7.22±0.62 6.03±0.86 5.33±0.72 5.02±0.81 3.96±0.74 ND Pile 6.36±0.15 4.31±1.16 3.61±0.34 3.28±0.59 3.11±0.14 ND ND Pile 7.09±0.65 3.59±0.22 3.26±0.20 2.87±0.28 ND ND ND Pile 5.67±0.73 6.93±0.51 6.31±0.84 6.04±0.16 4.44±0.48 3.78±0.72 ND Mean ± standard deviation.ND-not determined as the piles had already reached maturity Main characteristics of final composts in all piles are shown in Table The main characteristics showed that the moisture content, total organic carbon, total nitrogen, pH, total phosphorus, and total potassium in all final compost products were in acceptable values according to Land Development Department (2003) indicating the high efficiency of final compost However, when considering the changes in temperature and faecal coliform elimination, the results suggested that the compost in pile (C/N, 30/1 with seeding p.d.1) was the finest compost This was due to the lowest number of faecal coliform (2.87 Log10 MPN g-1) presented in this pile suggesting the highest degree of sanitation compared to the other piles USEPA (1995) stated that the number of faecal coliform in final compost should not be greater than 3.00 Log10 MPN g-1 for sanitary use of the compost In addition, the compost in pile reached maturity in a shorter time (around day 42) compared to others Therefore, the final compost from pile (C/N ratio of 30/1 with a seeding of p.d.1) was considered as the most suitable compost to be used as soil conditioner to enhance soil chemical properties, nutrient accumulation in plants and plant growth - 46 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 Table Main characteristics of final composts Compost characteristics Parameter Moisture (%) Organic carbon (%) Total Nitrogen (%) C/N ratio pH Total Phosphorus (%) Total Potassium (%) Final Day Temperature (°C) Coliform Numbers (Log10 MPN g-1)/day reach maturity Without seeding C/N 20/1 (Pile1) 41.78± 1.03ab‡* 24.72± 1.33a 2.33± 0.08ab 10.85± 0.17a 7.49± 0.34a 2.51± 0.16a 2.03± 0.09a 30.23± 0.25a 3.26± 0.36ab /56 C/N 30/1 (Pile 2) 41.39± 1.71ab 26.34± 1.01ab 2.19± 0.50ab 11.99± 0.39a 7.46± 0.80a 2.44± 0.34a 1.89± 0.18a 29.83± 0.70ab 3.14± 0.18ab /56 C/N 40/1 (Pile 3) 48.62± 2.00c 27.16± 0.60a 1.72± 0.35d 15.81± 0.66b 7.45± 0.36a 1.61± 0.06b 1.41± 0.13b 36.23± 0.91b 3.96± 0.73b /70 Seeding with PD-1 C/N 20/1 (Pile 4) 38.92± 3.61a 26.89± 1.05a 2.46± 0.08a 11.07± 0.40a 7.9± 0.14b 2.52± 0.86a 2.10± 0.20a 29.0± 0.56ab 3.11± 0.14ab /56 C/N 30/1 (Pile 5) 38.82± 4.30a 25.05± 0.38a 2.11± 0.14bc 11.91± 0.99a 7.39± 0.57a 2.56± 0.29a 1.97± 0.08a 28.83± 1.53ab 2.87± 0.27a /42 C/N 40/1 (Pile 6) 46.15± 2.05bc 27.05± 0.80a 1.89± 0.31cd 14.62± 2.60b 7.46± 0.15a 1.97± 0.26b 1.58± 0.89b 34.87± 0.45b 3.78± 0.72b /70 * Means followed by the same letter within similar row are not significantly different using Duncan’ s multiple range test at 0.05 level of significance ‡ Mean ± standard deviation CONCLUSIONS The conclusions drawn from the study are as follows: 1) Compost with an initial C/N ratio of 30/1 (cassava pulp/swine manure) seeded with p.d.1 was the most satisfactory compost among the others due to a short time required to reach maturity (around day 42) and low faecal coliform number (2.87 Log10 MPN g-1) 2) The p.d.1 did not play an important role in the decomposition process of the composting piles The initial C/N ratio was the main factor affecting the time to reach maturity of the compost suggesting that it was not necessary to add an activator for composting - 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49 - Journal of Water and Environment Technology, Vol.4, No.1, 2006 Yanko, W.A (1987) Occurrences of pathogens in distribution and marketing municipal sludges Report No EPA/600/1-87/014 (NTIS : PB88-154273/AS) Springfield, VA : National Technical information Service - 50 - ... in total organic carbon concentration resulted from the oxidation of carbon to carbon dioxide by microorganisms during composting (Tiquia et al., 1996) Throughout the composting process, total... 77 84 Composting time (day) Figure Changes in moisture content during composting of cassava pulp with swine manure Total organic carbon and total nitrogen During the composting process, total... during the composting process could be due to the production of ammonium as a result of the ammonification process (Huang et al., 2004) The pH patterns were concomitant to the previous studies on the