Nitrogen transformation during organic waste composting by the Rutgers system and its effects on pH, EC and maturity of the composting mixtures

The evolution of the different forms of nitrogen during the composting of several wastes was studied, as well as its relation to the pH, electrical conductivity and parameters of maturity of the composts obtained. Four mixtures were prepared from different organic materials: sewage sludge, municipal solid waste, brewery sludge, sorghum bagasse, cotton waste and pine bark. The evolution of the different forms of nitrogen during composting depended on the material which supplied the nitrogen to the mixtures and the organic matter (OM) degradation rate during composting. The greatest concentration of ammonium was observed during the first weeks of composting, coinciding with the most intense period of OM degradation, and ammonium then decreased gradually to reach final values of below 0.04%. The use of urea as a nitrogen source in the mixtures led to high ammonium levels during the first weeks as a result of its rapid hydrolysis. The nitrification process began only when the temperature of the mixtures had dropped below 40 degrees C and its intensity depended on the quantity of ammonium present when the process began. The highest concentrations of NO3-N were always produced at the end of maturation, reaching values of 0.52%, 0.53%, 0.12% and 0.20% in the four mixtures studied. Nitrogen losses during composting depended on the materials used and on the pH values of the mixtures. Mixtures with the highest lignocellulose content showed the lowest losses (below 25%), while those containing municipal solid waste lost more than 40% of the initial content. Statistically significant correlations at a high probability level were found between the NO3-N concentration and pH and electrical conductivity. confirming that nitrification was responsible for the falling pH values and increasing electrical conductivity. The ratio of NH4-N and NO3-N concentrations was shown to be a clear indicator of the maturity of the mixtures during composting, the final values of 0.08, 0.04, 0,16 and 0.11 for the four mixtures being equal to, or below the maximum value established as a maturity index in other materials.     

猪粪堆肥化处理过程中的氮素转变及腐熟度研究

经过63d堆肥化处理后,猪粪与木屑混合堆肥及猪粪,木屑与树叶混合堆肥的T－N分别从开始的1．57％和1．78％增加到2．0％和2．11％;水溶性NO3－N／水溶性T－N均从接近于0的水平增加到3％左右;水溶性有机N／水溶性T－N分别增加到70％和76％;水溶性NH4－N／水溶性T－N则分别从开始52％和61％下降至堆肥结束时的30％和24％。种子发芽系数的测定结果表明,加入树叶有利于猪粪的腐熟化,可使猪粪堆肥化处理所城的时间从42d缩短至35d。化学指标与种子发芽系数的相关分析结果表明,水溶性NH4－N／水溶性T－N,水溶性NO3－N／水溶性T－N和水溶性有机N／水溶性T－N均与种子发芽系数呈显著相关,可作为堆肥的腐熟度评价指标。     

Aerobic biodegradation of sludge from the effluent of a vegetable oil processing plant mixed with household waste: physical-chemical, microbiological, and spectroscopic analysis

Sludge from a sewage treatment plant dealing with the effluent produced during the processing of crude vegetable oil (Lesieur-Cristal, Morocco) was composted in two mixtures (M1 and M2) with household waste obtained from landfill. The different physico-chemical characteristics of the final composts after 5 months of composting were, for M1 and M2, respectively: pH: 8.5 and 7.08; C/N: 10 and 16; proportion of decomposition: 78% and 55%, NH(4)(+)/NO(3)(-): 0.78 and 1.02. Monitoring the levels of lipid and total polyphenols showed a reduction of 81% and 72% for lipids and of 75% and 76% for polyphenols in M1 and M2, respectively. These reductions were paralleled by a rise in the humic acid content to reach 22 and 36mg/g, respectively. Overall, these results were confirmed by the FTIR spectroscopy study of the two mixtures. For M1, the FTIR spectra taken at different stages showed that during composting, biodegradation of the aliphatic compounds occurred as the proportion of aromatic structures increased. The transformations observed qualitatively were then confirmed quantitatively by the changes occurring in the various absorption ratios during composting. Mixture M2, however, presented strong absorbance of aliphatic compounds. These results were statistically confirmed by correlation tests and principal components analysis, which confirmed the maturity of the two composts, M1 having matured more than M2.     

Accelerated coffee pulp composting

The effect of two abundant, easily available and very low-cost agro-industrial organic residues, i.e., filter cake from the sugar industry and poultry litter, on the composting stabilization time of coffee pulp and on the quality of the produced compost, was evaluated. Piles of one cubic meter were built and monitored within the facilities of a coffee processing plant in the Coatepec region of the State of Veracruz, Mexico. Manual aeration was carried out once a week. A longer thermophilic period (28 days) and a much lower C/N ratio (in the range of 6.9–9.1) were observed in the piles containing the amendments, as compared to the control pile containing only coffee pulp (14 days and a C/N ratio of 14.4, respectively). The maximum assimilation rate of the reducing sugars was 1.6 g kg-1 d-1 (from 7.5 to 5.3%) during the first two weeks when accelerators were present in the proportion of 20% filter cake plus 20% poultry litter, while they accumulated at a rate of 1.2 g kg-1 d-1 (from 7.4 to 9.13%) during the same period in the control pile. The best combination of amendments was 30% filter cake with 20% poultry litter, resulting in a final nitrogen content as high as 4.81%. The second best combination was 20% filter cake with 10% poultry litter, resulting in a compost which also contained a high level of total nitrogen (4.54%). It was concluded that the use of these two residues enhanced the composting process of coffee pulp, promoting a shorter stabilization period and yielding a higher quality of compost.     

八角下脚料、甘蔗滤泥、桐麸联合堆肥的腐熟度指标研究

测定八角下脚料与甘蔗滤泥、桐麸联合堆肥过程中温度、C/N比、种子发芽指数(GI)等腐熟度指标,研究各项指标在堆肥进程中的变化情况。结果表明:GI可作为八角下脚料与甘蔗滤泥、桐麸联合堆肥评价堆肥腐熟度的主要评价指标。在起始C/N比为31.45条件下进行八角提油下脚料、甘蔗滤泥、桐麸的联合高温好氧堆肥,堆制21 d和26 d时,三种腐熟度指标未全部显示堆肥腐熟;堆制31 d时,C/N比为18.55,T值为0.59(小于0.6),发芽指数GI为93.7%(大于80%)。从温度、发芽指数和C/N比三个指标均可认为堆肥已达到腐熟。     

The influence of mineral amendments on the changes in the organic nitrogen components of composts

Summary A series of straw composts, containing two levels of ammonium nitrate, were incubated with mineral amendments. Rate of decomposition was at a maximum over the first twenty days and was not influenced by the level of added nitrogne. The presence of bentonite and kaolinite reduced the loss of organic material slightly over the period of 150 days. In the low-N series, all the added inorganic nitrogen was immediately immobilized but in the high-N series inorganic N was slightly in excess of the microorganisms requirements. Little or no remineralization occurred. As a result of immobilization there was a rapid increase in amino acid and amino sugar nitrogen over the first 30 days and the values then remained fairly constant. The amino acid and amino sugar levels were slightly higher in the composts containing bentonite and kaolinite.In the early stages of the composting process, approximately half the organic nitrogen was soluble in phosphate buffer but the amount decreased with time of composting. Similarly, the amount of extracted nitrogen which could be hydrolysed by proteolytic enzymes, decreased with time. The composition of amino sugars liberated by acid hydrolysis suggested that chitin, probably of fungal origin, accounted for much of the amino sugar nitrogen and there is some evidence from oxidation studies for this. As composting proceeded, the amount of galactosamine increased and eventually muramic acid was identified indicating an increase in the bacterial flora.     

Evaluation of maturity and stability parameters of composts prepared from agro-industrial wastes

The objective of this study was to evaluate changes in physical, chemical and biological parameters to assess the maturity and stability of composts prepared from mixture of different farm and agro-industrial wastes over a period of 150 days. All the composts appeared granular, dark grey in color without foul odor and attained an ambient temperature at 120 days of composting indicating the stable nature of composts. Correlation analysis showed that the optimal values of the selected parameters for our experimental conditions are as follows: organic matter loss >42%, C:N ratio <15, water soluble organic carbon (C(w)):organic N (N(org)) ratio <0.55, humic acid (HA):fulvic acid (FA) ratio >1.9, humification index (HI) >30%, cation exchange capacity (CEC):total organic carbon (TOC) ratio >1.7 and germination index (GI) >70%. Compost enriched with sewage sludge, pressmud and poultry waste matured earlier compared to composts either enriched with distillery effluent or un-enriched.     

Effect of the raw materials and mixing ratio of composted wastes on the dynamic of organic matter stabilization and nitrogen availability in composts of Sub-Saharan Africa

The effect of raw materials and their proportions in initial mixtures on organic matter (OM) stabilization and nitrogen (N) availability during pit composting in Sub-Saharan Africa was assessed using biochemical fractionation and laboratory incubations to characterize composts sampled throughout the composting process. Stabilization of OM occurred more rapidly in mixtures with slaughter-house wastes, it was progressive in mixture with household refuses while tree leaves compost remained unstable. Carbon mineralization from compost samples was positively correlated to water soluble and hemicellulose-like organic fractions. Mixtures containing large proportions of household refuses reached the highest stability and total N but available N remained weak. Slaughter-house wastes in the initial mixtures made possible to reach good OM stabilization and the largest N availability. The nature of initial mixing influenced composting parameters, OM stabilization and N availability. It is suggested mixing household refuses and slaughter-house wastes with tree leaves to reach better amending and fertilizer qualities of composts.     

Quality evaluation of co-composted wheat straw, poultry droppings and oil seed cakes

Poultry droppings, neem cake, castor cake, jatropha cake and grass clippings were used separately as organic nitrogen additives to decrease the high C:N ratio of wheat straw. Composting was carried out aerobically in presence of fungal consortium developed by including Aspergillus awamori, Aspergillus nidulans, Trichoderma viride and Phanerochaete chrysosporium. The degraded product was characterized to assess the technical viability of organic nitrogen supplements as well as fungal consortium in improving the quality of compost and hastening the process of decomposition of high lignocellulolytic waste. Evaluation of maturity showed that mixture of wheat straw, poultry dropping and jatropha cake had the lowest C:N ratio of 10:1, the highest humic acid fraction of 3.15%, the lowest dehydrogenase activity and a germination index exceeding 80% in 60 days of decomposition. Inoculated and grass clipping amended wheat straw–poultry dropping mixture resulted in compost with highest humus content of 11.8% and C:N ratio of 13.5, humic acid fraction of 2.84% and germination index of 59.66%. Fungal consortium was effective in improving the humus content of all the composted mixtures. In some treatments, germination index could not be correlated with C:N ratio. Non edible oil seed cake supplemented substrate mixtures did not respond to fungal inoculation as far as C:N ratio was concerned.     

蚯蚓处理猪粪与秸秆的最适碳氮比及混合物腐熟度评价

以猪粪和水稻秸秆混合作饵料,通过90 d的室内培养试验,用平均体质量、日均质量增加倍数、日均产茧量和累计繁殖量等指标衡量4个处理（C/N 20、C/N 25、C/N 30和C/N 35）中蚯蚓的生长繁殖状况,并通过35 d的混合物（C/N 25、C/N 30和C/N 35）腐熟试验,采用pH、C/N和水溶性有机碳（DOC）3个指标综合评定混合物腐熟度.结果表明: 处理C/N 30的蚯蚓生长繁殖状况显著优于其他处理.35 d的混合物腐熟试验以21 d为拐点,pH和DOC均呈现先下降后上升的趋势,C/N则呈现持续下降趋势;但综合3个指标衡量,混合物至试验结束尚未完全腐熟.处理C/N 25在7～35 d时C/N＜20,表明C/N＜20不适宜作为衡量混合物腐熟与否的单一指标,应结合其他指标综合判定混合物的腐熟情况.     

Co-composting of oil exhausted olive-cake, poultry manure and industrial residues of agro-food activity for soil amendment

The co-composting of exhausted olive-cake with poultry manure and sesame shells was investigated. These organic solid wastes were watered by the confectionary wastewater which is characterized by its high content of residual sugars raising its COD. Four aerated windrows were performed to establish the effects of confectionary by-products on the compost process. Different mixtures of the agro-industrial wastes were used. During the composting process, physico-chemical parameters (temperature, moisture, pH, electrical conductivity, total carbon and total nitrogen) were studied. The stability of the biological system was noticed after 70 days. The final products were characterized by their relatively high organic matter content, and low C/N ratio of 14-17. The humidification of the windrows with the wastewater seemed to have accelerated the composting process in comparison to a windrow humidified with water. In addition, the organic matter degradation was enhanced to reach 55-70%. The application of the obtained composts to soil appeared to significantly improve the soil fertility. Indeed, field experiments showed an increase in potato yield; the production was 30.5-37.5 tons ha(-1), compared to 30.5 tons ha(-1) with farm manure.     

Effect of matured compost as a bulking and inoculating agent on the microbial community and maturity of cattle manure compost

Cattle manure composts were consecutively manufactured. Compost that reached maturity first was used as a bulking and inoculating agent for subsequent compost production. The microbial community was measured through phospholipid fatty acid analysis. Changes in the content of fatty acid methyl esters derived from phospholipids were similar in all the composts. The diversity index for the fatty acid methyl ester content increased in the secondary-produced compost from the onset of composting. Microbial succession was accelerated using matured compost. The proportion of biomarker fatty acids for gram-positive bacteria also increased in the secondary-produced compost from the early stage of composting. Changes in germination index indicated the maturity stage of the compost. The proportion of biomarker fatty acids for gram-positive bacteria was positively correlated to the germination index, indicating that phospholipid fatty acid analysis is an indicator for evaluating the maturity of cattle manure composts.     

Influence of different organic waste materials on the transformation of nitrogen in soils

Organic waste materials like crop residues, well-decomposed cow dung, composts, and other rural and urban wastes are considered highly useful resources in enhancing soil fertility and also in build-up of soil organic matter. Organic matter decomposition provides plant nutrients in soil, which in turn increases crop productivity. Availability of nutrients and nitrogen (N) and phosphorus from organic waste materials is dependent upon the nature of organic residues, climatic conditions, and soil moisture activity. Keeping these factors in view, the present investigation was undertaken to study the transformation of N from different organic waste materials in two contrasting soils from an eastern India, subtropical region. The results showed that the amounts of ammoniacal-N (NH4-N), nitrate-N (NO3-N), hydrolysable N (HL-N), and nonhydrolysable (NHL-N) were increased for up to 60 days of soil submergence and increased further with the increase (1% by weight of soil) of organic residue application. Considering the effect of various organic waste materials, it was found that the amounts of NH4-N, NO3-N, HL-N, and NHL-N were higher with the application of groundnut hull as compared to wheat straw and potato skin, which may be due to relatively narrow carbon:N ratio of groundnut (22:43) than that of wheat straw (62:84) and potato skin (71:32); however, the results showed that the release of NH4-N, NO3-N, HL-N, and NHL-N was in the order of groundnut hull > wheat straw > potato skin.     

Utilization of Jatropha deoiled seed cake for production of cellulases under solid-state fermentation

Toxic waste generated by Jatropha seed cake after utilization of biodiesel on one hand has stimulated the need to develop new technologies to treat the waste and on the other, forced us to reevaluate the efficient utilization of its nutritive potential for production of various high-value compounds and its conversion to non-toxic forms which could be used as animal feed stock. In this study, Jatropha seed cake was used for production of cellulases by new isolate of Thermoascus aurantiacus under solid-state fermentation. The interaction of nitrogen source concentration, moisture ratio, initial pH of the medium and inoculum size was investigated and modelled using response surface methodology (RSM) using Box-Behnken Design (BBD). Under optimized conditions endo-β-1,4-glucanase, β-glucosidase and filter paper activities were found to be 124.44, 28.86, 4.87?U/g of substrate, respectively. Characterization of endo-β-1,4-glucanase, β-glucosidase was done after partial purification by ammonium sulfate fractionation followed by desalting. The endo-β-1,4-glucanase and β-glucosidase showed maximum activity at 70?°C and pH 4. Saccharification studies performed with different lignocellulosic substrates showed that sugar cane bagasse was most susceptible to enzymatic hydrolysis. The study suggests that Jatropha seed cake can be used as a viable nutrient source for cellulase production without any pretreatment under solid-state fermentation by T. aurantiacus.     

畜禽粪便堆肥过程中各种氮化合物的动态变化及腐熟度评价指标

对不同畜禽粪便在堆肥过程中各种含氮化合物的动态变化进行了研究,结合综合性腐熟度评价指标——种子发芽指数（GI）,探讨了畜禽粪便堆肥过程中与氮有关的腐熟度评价指标.结果表明：随着堆肥的进行,除奶牛粪外,其它畜禽粪便的全氮（TN）含量均呈先下降而后平稳变化趋势,奶牛粪则呈先增加而后平稳变化趋势;各种畜禽粪便中,碱解性氮（HN）含量先增后降;NH₄⁺-N含量先下降而后保持平稳;NO₃^- -N含量则持续增加;NH₄⁺ -N/NO₃^- -N迅速降低.堆肥腐熟度指标中,除综合性评价指标GI值外,HN/TN和NH₄⁺ -N/TN也可作为评价畜禽粪便腐熟程度的优选指标,而NO₃^- -N/TN只能作为一般性评价指标.根据综合性评价指标GI值达到腐熟要求的标准（GI>0.50）,除仔猪粪外,其它畜禽粪便在HN/TN<20.77％、NH₄⁺ -N/TN<10.06％及NO₃^- -N/TN>0.38％时基本达到腐熟要求.     

Do earthworms affect dynamics of functional response and genetic structure of microbial community in a lab-scale composting system?

Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, NH(4)(+)-N and ash content) showed similar evolution in both systems except a higher NH(4)(+)-N in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters.     

Co-composting of soybean residues and leaves in Hong Kong

The goal of this project was to evaluate the feasibility of co-composting of soybean residues and leaves and the effects of turning frequency on compost quality. Soybean residues were mixed with leaves and sawdust in 1:1:3 (w/w wet weight) for achieving a C/N ratio of about 30. Three heaps of about 4 m3 of compost mixtures were prepared receiving a turning frequency of daily (pile A), 3-day (pile B) and weekly (pile C) turning. Different turning frequencies did not significantly affect the changes in pH and volatile solids throughout the composting period. High turning frequency caused a lower electrical conductivity and NH4-N contents as well as a shorter duration of thermophilic phase, because of a high heat loss by evaporation and volatilization of ammonia in the pile. The highest C decomposition of 4% occurred in the pile with a 3-day turning period, which coincided with the higher-nitrogen content in this treatment. All treatments with different turning frequencies reached maturation at 63 days as indicated by the soluble organic carbon, soluble NH4-N, C/N ratio and cress seed germination index. However, increasing the aeration during composting period was beneficial in accelerating the maturation process. Taking into consideration less labour and lower operation costs as compared to daily turning, it can be suggested that a 3-day turning frequency would be more appropriate for reaching acceptable quality of compost and ease in operation.     

Effects of olive mill wastewater addition in composting of agroindustrial and urban wastes

In order to study the suitability of olive mill wastewater (OMW) for composting, thisliquid waste was added to two different mixtures of agroindustrial and urban wastesand the composting process was compared with two other piles of similar composition,but without OMW. These four piles were studied in a pilot plant using the Rutgers staticpile system. The addition of OMW produced a greater proportion of degradable organic matter or a higher degradation rate, higher electrical conductivity values, greater losses of total N and lower nitrification than in piles without OMW. Its addition also restricted the increase of the cation exchange capacity and provoked the appearance of phytotoxicity or a longer persistence of phytotoxicity. However, in general, all the composts showed increases in the cation exchange capacity, the percentage of humic acid-like carbon, the polymerisation ratio of these humic substances (which revealed that the organic matter had been humified during composting) and the germination index, the latter indicating the reduction of phytotoxicity during the process.     

Effect of turning regime and seasonal weather conditions on nitrogen and phosphorus losses during aerobic composting of cattle manure

Cattle manure from stock bedded on straw was aerobically composted under ambient conditions, turning with either a tractor-mounted front-end loader or a rear discharge manure spreader. Three composting experiments, each of approximately four months duration, were conducted to investigate the effect of turning regime and seasonal weather conditions on nitrogen and phosphorus losses during aerobic composting of cattle manure. Manure stacks of 12-15 m(3) initial volume were constructed in separate 5 x 5 m concrete compartments. Experiment 1 (January-April 1999) compared manure heaps turned once (T1) or three times (T3) using a front-end loader with an unturned static (S) control manure stack. Experiment 2 (June-September 1999) compared the same treatments as Experiment 1. Experiment 3 (September-December 1999) compared T1 and T3 turning regimes using a front end loader with turning by a rear-discharge spreader (TR1 and TR1T2) for more effective aeration of the manure. Turning took place at 6 weeks for the one turn treatments, and after 2, 6 and 10 weeks for the three turn treatments. Leachate losses were dominated by NH(4)-N during the first three weeks of composting, after which time NH4-N and NO3-N concentrations in leachates were approximately the same, in the range 0-20 mg N l(-1). The concentrations of both NH4-N and NO3-N in leachate were higher after turning. Molybdate-reactive P concentrations in leachate tended not to be significantly influenced by turning regime. Gaseous losses of NH3 and N2O rose quickly during the initial phases of composting, peaking at 152 g N t(-1) d(-1) for the T3 treatment. Mean NH3 emission rate (25-252 g N t(-1) d(-1)) for the first two weeks of Experiment 2 conducted during the period June-September were an order of magnitude greater (1-10 g N t(-1) d(-1)) than Experiment 3, conducted during the colder, wetter autumn period (September-December). Nitrous oxide emission rates ranged between 1-14 g N t(-1) d(-1) and showed little influence of turning regime. Total N and P concentrations in turned (T) and static (S) manure were elevated at the end of all experiments, due to loss of dry matter. Mean total N losses were 30.4% (T1) and 36.8% (T3) and total P losses 28.2% (T1) and 27.4% (T3).     

Composting of high moisture content swine manure with corncob in a pilot-scale aerated static bin system

Pilot composting experiments of swine manure with corncob were conducted to evaluate the performance of the aerated static bin composting system. Effects of temperature control (60 and 70 degrees C) and moisture content (70% and 80%) were monitored on the composting by measuring physical and chemical indexes. The results showed that (1) the composting system could destroy pathogens, converted nitrogen from unstable ammonia to stable organic forms, and reduced the volume of waste; (2) significant difference of NH(4)(+)-N (P(12) = 0.074), and (NO(3)(-) + NO(2)(-))-N (P(12) = 0.085) was found between the temperature control treatments; (3) anaerobic reaction in the treatment with 80% moisture content resulted in significant difference of pH (P(23) = 0.006), total organic matter (P(23) = 0.003), and germination index (P(23) = 0.040) between 70% and 80%. Therefore, the optimum initial moisture content was less than 80% with the composting of swine manure and corncob by using the composting system.