Composting of solid and sludge residues from agricultural and food industries. Bioindicators of monitoring and compost maturity

Effect of biochar on transformation of dissolved organic matter and DTPA-extractable Cu and Cd during sediment composting

This study investigated the influence of biochar on temperature, pH, organic matter (OM), seed germination index (GI), the fluorescent components of dissolved organic matter (DOM), and bioavailability of DTPA-extractable Cu and Cd during composting and analyzed the relation between DTPA-extractable metals with pH, OM, and the fluorescent components of DOM. Results showed that the addition of biochar shortened the thermophilic phase, reduced the pH at maturation period, accelerated the decomposition of OM, and raised GI. Besides, it promoted the formation of components with benzene ring in FA and HyI and the degradation of protein-like organic-matters in FA and HA, which was mainly related with the decrease of DTPA-extractable Cd and the increase of DTPA-extractable Cu. After composting, DTPA-extractable Cd in pile A and pile B were decreased by 37.15% and 27.54%, respectively, while the bioavailability of Cu in pile A and pile B was increased by 65.71% and 68.70%, respectively. All these findings demonstrate positive and negative impact produced by biochar into various heavy metals and the necessary of optimization measures with biochar in sediment composting.

Water hyacinth (Eichhornia crassipes (Mart.) Solms.) as an alternative raw material for the production of bio-compost and handmade paper

Water hyacinth (WH) is considered as the worst aquatic weed in the world because of its rapid growth and fast spread into new areas of fresh water bodies. We investigated the potentiality of using WH as a raw material for production of handmade paper and compost in Bangladesh. Potash pulping was done using potassium hydroxide (KOH) at different alkali concentrations (8-12%) with a liquor to solid ratio of 7:1 at 145 °C for 2 h. The pulp was bleached using hydrogen peroxide (H₂O₂), and pulp properties (brightness, tear index and tensile index) of bleached and unbleached pulps were analyzed following the respective TAPPI standards. The produced black liquor was mixed with WH along with kitchen bio-wastes to produce compost. The properties of the compost were tested following the published protocols, i.e., wet digestion, Kjeldahl, vanadomolybdophosphoric acid, and Flame Spectrophotometry methods. Brightness, tensile index and tear index of bleached hand sheets were found to be 37.2%, 49.2 N m/g and 6.79 m.Nm²/g, respectively suggesting significant contribution of bleaching on WH paper quality. Addition of black liquor significantly increased the nitrogen and potassium content of bio-waste compost. Thus, WH can be used as a raw material for making handmade paper while the process by-product can be supplemented to improve the nutritional quality of compost. Such cottage-industry fabrication of WH green products could be developed to control the infestation of WH in water bodies, and this technology may provide for new possible sustainable livelihood option.

Thermogravimetry Applicability in Compost and Composting Research: A Review

Composting could be a suitable solution to the correct treatment and hygienization of several organic waste, producing compost that can be used in agriculture. The evolution and maturity of this process has been studied using a variety of techniques. One very promising technique for these studies is thermogravimetric analysis. On the other hand, the compost can be used for a variety of purposes different to the agricultural one, such as direct energy by combustion or energy and products by pyrolysis and its suitability can be measured by thermogravimetric techniques. With these goals, a bibliographic analysis has been done, applying Preferred Reporting Items for Systematic Reviews and Meta-Analyses PRISMA methodology, to the use of thermogravimetric equipment applied to the study of composting and compost uses. According to the methodology for PRISMA systematic reviews, the following databases have been searched Google Scholar, Web of Science, Mendeley, Microsoft Academic, World Wide Science, Science Direct, IEEE Xplore, Springer Link, Scopus, and PubMed by using the terms “thermogravimetry AND (compost OR composting) AND NOT plastic”.

Physiological Behavior of the Aquatic Plant Azolla sp. in Response to Organic and Inorganic Fertilizers

The present investigation aims to evaluate the impacts of organic and inorganic fertilizers on the water parameters and physiological behaviors of an aquatic plant (Azolla sp.). The experiment used three groups: treatment with organic or inorganic fertilizer and a group with no fertilization as a control. Azolla sp. were grown in cement ponds that received different treatments. For water analysis, the obtained results clarified that fertilization resulted in no variation in the temperature or total hardness among different treatments. Organic fertilizer increased the dissolved phosphorus content, total hardness, and bicarbonate alkalinity, as well as the total phosphorus content, whereas inorganic treatment increased the pH, total ammonia content, and total nitrogen content. Regarding the biochemical composition of Azolla sp., the chlorophyll content showed no variation among different treatment groups, while organic matter showed high variation among different treatment groups. The highest values for ash and fat content were recorded in control ponds. The highest protein content was found in organic treatment ponds. The addition of fertilizers led to an increase in the tissue contents of N and P compared to the control. This increase was highest when Azolla sp. was fertilized with organic fertilizer. The atomic N:P ratio was low in tissues subjected to either treatment compared with the control. The doubling time of Azolla sp. was decreased by fertilization. It is concluded that different fertilizer systems have significant effect on physico-chemical and biological parameters of water. Fertilization positively affects Azolla sp. growth. Organic fertilizer was more efficient for the growth of Azolla sp., so it can be considered as a source of biofertilizer and green manure in areas where it spreads.

Quantifying biochar content in a field soil with varying organic matter content using a two-temperature loss on ignition method

While the use of biochar as a soil amendment for agronomic and environmental management is gaining popularity, quantification of biochar in soil is still challenging. The objective of this work was to develop a fast, simple and inexpensive method to quantify biochar content in field soil with varying organic matter content - the two-temperature loss on ignition (LOI) method. In this approach, biochar mass fraction in a biochar-amended soil is computed by measuring the dry mass of biochar/soil mixture after heating sequentially at two temperatures: low temperature (LT), and high temperature (HT). This method requires the LOI profile for pure soil and pure biochar that are representative of soil and biochar in the field. Although the soil LOI profile may vary due to spatial variation in soil organic matter (SOM) content, the method only requires that the relative soil LOI at LT with respect to LOI at HT is uniform because of similarity in SOM chemical composition. In this method, LT and HT are selected such that the maximum difference in LOI exists at these temperatures between pure soil and biochar. The method was tested by quantifying the biochar content in roadway filter strips with and without a wood biochar pyrolyzed at high temperature (550 °C). The estimates of biochar content from the method matched independent measurements for soils with low (-0.23 ± 0.09 CI%, CI = 95% confidence interval, versus actual 0%) and high (3.9 ± 0.3 CI% versus actual 4.0 ± 1.1 CI%) biochar mass fraction. The method is applicable when SOM content is low to moderate (e.g. <15%) and mostly composed of labile organic compounds, and when biochars are pyrolyzed at moderate to high temperatures (i.e. >400 °C) and composed of relatively low ash content (e.g. <30%).

Current Scenario of the Tehran Municipal Solid Waste Handling Rules towards Green Technology

This study aims to study the waste management process and recycling of municipal waste in Tehran. Currently, Kahrizak is the defined landfill area which collects the waste generated from 22 districts of Tehran. The organic wastes undergo to the windrow composting method in order to manage the partial of the waste generated in the city. Samples from the compost pile generated in Kahrizak were examined to evaluate its fertilizer value to be used further by the farmers. The results show that the obtained compost does not reach the acceptable quality to be used further in agriculture, due to lack of homogeneity, aeration and presence of heavy metals. Overall, it has been concluded that, due to the improper waste segregation and management prior to sending to landfill and presence of non-organic materials such as hazardous metals and medical wastes, causes difficulties in proper waste management, implementation and producing high quality compost. Based on this study the existence of stakeholders, society, economy and proper handling rules can effectively improve the waste management system in the country and leads to the sustainable green environment.

Application of quadratic regression orthogonal design to develop a composite inoculum for promoting lignocellulose degradation during green waste composting

The aims of this study are to determine the feasibility of applying QROD (quadratic regression orthogonal design) to optimize a combination of microorganisms and to develop a composite inoculum for promoting lignocellulose degradation during GWC (green waste composting). This feasibility was studied in a laboratory scale experiment, using three lignocellulolytic microorganisms, isolated from the mature phase of GWC by the dilution plating method. After the feasibility was confirmed, a composite inoculum was developed through the results of the optimization, whose effect was evaluated by comparing it with Phanerochaete chrysosporium and EM (Effective Microorganisms) in a pilot scale experiment of GWC. The use of QROD to finish this optimization was proven feasible, because the p value of the regression equation was less than 0.05 (0.0108), meaning that the quadratic regression model is suitable for describing the relationship between the combination of the three microorganisms and their ability to degrade lignocellulose. Additional proof of this feasibility is that the composite inoculum in the quadratic regression orthogonal experiment demonstrated lignocellulose degradation ability similar to the GWC experiment. Although the lignin degradation ability of the composite inoculum did not surpass Phanerochaete chrysosporium, it was stronger than EM. Meanwhile, cellulose degradation ability and humus synthesis ability of the composite inoculum were stronger than for Phanerochaete chrysosporium and were close to EM. It is hard to tell which inoculum is the best since each inoculum had advantages in different aspects, while the composite inoculum still showed a considerable effect of lignocellulose degradation during GWC.

Identifying Characteristics of Verticillium Wilt Suppressiveness in Olive Mill Composts

The aims of this study were to assess the potential suppressive effects of different olive mill composts on Verticillium wilt and to elucidate the suppressive mechanisms. To this end, four olive mill composts from different crop areas with two maturation levels were selected. After conducting the Verticillium wilt bioassays in cotton, the suppressive effect was observed in only one compost. Compost maturation level did not affect disease development. The standardized area under the disease progress curve and microsclerotia concentration were associated with low API-ZYM enzymatic diversity, β-glucosidase activity, pH, and high electrical conductivity (EC). To assess the nature of suppressiveness in the suppressive compost, additional bioassays were performed with three treated compost-amended growing media (N-supplemented, autoclaved, and heat treated at 60°C for 6 days). Suppressiveness was partially reduced with heat treatments, where N-acetyl-β-glucosaminidase activity disappeared. In this compost, high oligotrophic actinomycete populations were associated with disease reduction. Therefore, plant growth media amended with different olive mill composts do not always show suppressiveness against Verticillium wilt. Enzymatic diversity, β-glucosidase activity, pH, and EC may be sufficient to predict where olive mill compost plant growth media will be effective in reducing Verticillium wilt and microsclerotia concentration. General and specific suppressiveness are involved in the mechanism of compost suppression.

Maturation of green waste compost as affected by inoculation with the white-rot fungi Trametes versicolor and Phanerochaete chrysosporium

Green waste was separately inoculated on day 0 and day 14 with either Trametes versicolor or Phanerochaete chrysosporium to determine their effects on composting time and compost quality. Inoculation with T. versicolor and P. chrysosporium caused more rapid and higher increases in compost temperatures, increased the duration of the thermophilic temperature stage, and reduced the maturity time. Inoculation with T. versicolor and P. chrysosporium greatly increased the quality of the final composts in terms of pH, electrical conductivity, organic matter concentration, C/N ratio, germination index, and nutrient content. Inoculation with T. versicolor and P. chrysosporium also significantly increased the degradation of lignin by 7.1% and 8.2%, respectively, and increased the degradation of cellulose by 10.6% and 13.6%, respectively.

Enhancing rock phosphate integration rate for fast bio-transformation of cow-dung waste-paper mixtures to organic fertilizer

Rock phosphate (RP) addition in cow-dung waste-paper mixtures at rates above 2% P has been reported to increase the rate of bio-transformation and humification of organic waste mixtures during vermicomposting to produce organic fertilizer for organic farming. However, the optimization of RP for vermicomposting was not established. The objective of this study was to determine the optimal amount of RP integration rates for effective bio-transformation of cow-dung waste-paper mixtures. Arrays of RP integration degrees (0, 0.5, 1, 1.5, 2, and 4% P as RP) were thoroughly mixed with cow- dung waste-paper mixtures to achieve an optimized C:N ratio of 30 and allowed to vermidegrade following the introduction of earthworms at a stocking mass of 12.5 g-worms kg⁻¹. The bio-transformation of the waste mixtures was examined by measuring C:N ratios and humification index (HI) and per cent ash and volatile solids. Application of 1% P as RP resulted in fast bio-transformation and maturation of cow-dung waste-paper mixtures. A scanning electron microscopy (SEM) was used to evaluate the morphological properties of the different vermicomposts affected by rates of RP showing the degree of degradation of initial compacted aggregates of cellulose and protein fibres in the mixtures at maturity. A germination test was used to further determine phytotoxicity of the final composts and microbial biomass assessment. The final vermicompost (organic fertilizer) had a C:N ratio of 7, MBC of 900 mg kg⁻¹ and HI of 27.1%. The RP incorporation rate of 1% P of RP investigated is therefore, recommended for efficient vermidegradation and humification of cow-dung waste-paper mixtures. However, higher rates of RP incorporation should be considered where greater P enrichment of the final vermicompost (organic fertilizer) is desired.

Evolution of microbial dynamics during the maturation phase of the composting of different types of waste

During composting, facilities usually exert greater control over the bio-oxidative phase of the process, which uses a specific technology and generally has a fixed duration. After this phase, the material is deposited to mature, with less monitoring during the maturation phase. While there has been considerable study of biological parameters during the thermophilic phase, there is less research on the stabilization and maturation phase. This study evaluates the effects of the type of starting material on the evolution of microbial dynamics during the maturation phase of composting. Three waste types were used: sludge from the fish processing industry, municipal sewage sludge and pig manure, each independently mixed with shredded pine wood as bulking agent. The composting system for each waste type comprised a static reactor with capacity of 600L for the bio-oxidative phase followed by stabilization and maturation phase in triplicate 200L boxes for 112days. Phospholipid fatty acids, enzyme activities and physico-chemical parameters were measured throughout the maturation phase. The evolution of the total microbial biomass, Gram + bacteria, Gram - bacteria, fungi and enzymatic activities (β-glucosidase, cellulase, protease, acid and alkaline phosphatase) depended significantly on the waste type (p<0.001). The predominant microbial community for each waste type remained present throughout the maturation process, indicating that the waste type determines the microorganisms that are able to develop at this stage. While fungi predominated during fish sludge maturation, manure and municipal sludge were characterized by a greater proportion of bacteria. Both the structure of the microbial community and enzymatic activities provided important information for monitoring the composting process. More attention should be paid to the maturation phase in order to optimize composting.

Chemical, Thermal and Spectroscopic Methods to Assess Biodegradation of Winery-Distillery Wastes during Composting

The objective of this work was to study the co-composting process of wastes from the winery and distillery industry with animal manures, using the classical chemical methods traditionally used in composting studies together with advanced instrumental methods (thermal analysis, FT-IR and CPMAS ¹³C NMR techniques), to evaluate the development of the process and the quality of the end-products obtained. For this, three piles were elaborated by the turning composting system, using as raw materials winery-distillery wastes (grape marc and exhausted grape marc) and animal manures (cattle manure and poultry manure). The classical analytical methods showed a suitable development of the process in all the piles, but these techniques were ineffective to study the humification process during the composting of this type of materials. However, their combination with the advanced instrumental techniques clearly provided more information regarding the turnover of the organic matter pools during the composting process of these materials. Thermal analysis allowed to estimate the degradability of the remaining material and to assess qualitatively the rate of OM stabilization and recalcitrant C in the compost samples, based on the energy required to achieve the same mass losses. FT-IR spectra mainly showed variations between piles and time of sampling in the bands associated to complex organic compounds (mainly at 1420 and 1540 cm^-1) and to nitrate and inorganic components (at 875 and 1384 cm^-1, respectively), indicating composted material stability and maturity; while CPMAS ¹³C NMR provided semi-quantitatively partition of C compounds and structures during the process, being especially interesting their variation to evaluate the biotransformation of each C pool, especially in the comparison of recalcitrant C vs labile C pools, such as Alkyl /O-Alkyl ratio.

Development of an ATP measurement method suitable for xenobiotic treatment activated sludge biomass

Activated sludge consumes a large amount of energy to degrade a xenobiotic organic compound. By tracking the energy inventory of activated sludge biomass during the sludge's degradation of a xenobiotic, any disadvantageous effect on the sludge's performance caused by energy deficiency can be observed. The purpose of this study was to develop a reliable and accurate method for measuring the ATP contents of activated sludge cells that were to degrade a xenobiotic organic. Cell disruption and cellular ATP extraction were performed by a protocol with which xenobiotic degrading activated sludge biomass was washed with SDS, treated by Tris and TCA, and followed by bead blasting. The suspension of disrupted cells was filtered before the filtrate was injected into HPLC that was set at optimal conditions to measure the ATP concentration therein. This extraction protocol and HPLC measurement of ATP was evaluated for its linearity, limits of detection, and reproducibility. Evaluation test results reported a R(2) of 0.999 of linear fit of ATP concentration versus activated sludge concentration, a LOD=0.00045mg/L, a LOQ=0.0015mg/L for HPLC measurement of ATP, a MDL=0.46mg/g SS for ATP extraction protocol, and a recovery efficiency of 96.4±2%. This method of ATP measurement was simple, rapid, reliable, and was unburdened of some limitations other methods may have.

Obtaining edaphic biostimulants/biofertilizers from different sewage sludges. Effects on soil biological properties

We studied the influence of six edaphic biostimulants/biofertilizers (BSs) manufactured by the pH-stat method from different sewage sludge (SS): SS1 (an anaerobic mature sludge, one year old), SS2 (an aerobic young sludge, without maturation) and SS3 (an aerobic mature sludge, four months old), not previously autoclaved (A) and autoclaved (B), by analysing their effects on soil biological properties. Soil enzymatic activities were measured at 1, 3, 5, 7, 15, 30 and 60 days of the incubation period, whereas the 16S rDNA-DGGE profiles were determined at 0, 5 and 60 days. The enzymatic activities were significantly stimulated. The highest stimulation was found in the B2 treatment followed by B3, A2, A3, B1 and A1 treatments. Increasing the number of lower molecular weight proteins in the BS enhances the stimulation of soil enzymatic activities. The application of BS caused at 5 days of the incubation period temporal variations in the soil bacterial community structure.

Thermophysical characterization of the seeds of invasive Chinese tallow tree: importance for biofuel production

The limited supply of traditional fossil based fuels, and increased concern about their environmental impact has driven the interest in the utilization of biomass based energy sources, including those that are underutilized or otherwise nuisance species such as Chinese tallow trees (Triadica sebifera [L.]). This species is a prolific seeds producer, and this paper shows that they contain more than 50% lipids by mass that are suitable for conversion into biodiesel. We present here, for the first time, the seeds' thermophysical properties important for biofuel production. The seeds were characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and ultimate analysis; their thermal conductivity, thermal diffusivity, and specific heat were determined. The characterization results were correlated to fatty acid composition and lipid content for whole seeds and individual layers, as well as to the protein, hemicellulose, cellulose, and lignin content. The TGA analysis indicated the presence, in addition to lipids, of hemicellulose, cellulose, lignin, and proteins, depending on the layer analyzed. Thermal conductivity and specific heat were, respectively 0.14 ± 0.007 W/mK and 3843.5 ± 171.16 J/kgK for wax, 0.20 ± 0.002 W/mK and 2018.7 ± 5.18 J/kgK for shells, 0.13 ± 0.0 W/mK and 1237 ± 3.15 J/kgK for internal kernel, and 0.13 ± 0.000 W/mK and 2833.9 ± 104.11 J/kgK for whole seeds. These properties and characterization method can be further used in engineering analysis used to determine the most optimum processing method for production of biofuels from this feedstock.

Composting of common organic wastes using microbial inoculants

It is important to use renewable resources to maximize crop yields and minimize the environmental hazards associated with chemical residues. Composting is an age old practice for the biological conversion of organic waste to a humus-like substance which can enhance physical, chemical and biological soil properties. To explore the effect of microorganisms in the composting process, three potent bacterial isolates were selected. Their morphological, cultural and biochemical characteristics were identified, and 16S rDNA studies identified isolates B1U/1 and D3L/1 as Bacillus subtilis and isolate RAT/5 as Pseudomonas sp. Common organic wastes were composted using the selected isolates individually and as a consortium. The C/N ratio of each substrate reduced gradually to 25–30:1 within 120 days and remained constant thereafter. The reduction in NH₄⁺ and NO₃⁻ ion concentrations also indicated compost maturity after 120 days. The pH of the mature compost was typically 7.0 ± 0.2, and the PO₄⁻³ ion concentration was high throughout the decomposition process. This study describes the optimization of the composting process using a consortium of isolates from composted soil.

Stabilization process within a sewage sludge landfill determined through both particle size distribution and content of humic substances as well as by FT-IR analysis

Landfill is largely considered as a reliable option for sewage sludge disposal in most metropolitan areas worldwide due to the huge quantities of this waste to be disposed of and the relatively low costs of such a kind of sludge management. It has been found that the sludge in the landfill degrades rapidly and becomes stabilized within a few years. In the present study, the sludge from different landfill stages was characterized by particle size distribution, humic substances contents and elemental composition, and Fourier transform infrared spectroscopy (FT-IR), as the landfill time increased. In general, the mean particle size of the sludge increased from 37 μm at day 0 to 143 μm at 300 days and the corresponding median particle size increased from 13 to 70 μm. The stability of particle size distribution can be assessed by the mean or median particle size. The humic acid (HA) and fulvic acid (FA) contents extracted from dry sludge after different landfill periods increased from 4.2 and 2.7% of day 0 to 5.6 and 3.1%, respectively, at 400 days, thereby indicating that the stabilization process of sludge in a landfill is also a humification process. The HA samples contained more carbon and nitrogen, and less hydrogen and oxygen than the FA samples, indicating a high degree of maturity and humification of these HA samples. The FT-IR spectra indicated that easily degradable organic matter components, such as aliphatic chains and protein, were distinctly decomposed during landfill. Based on the changes in the band relative intensity, it was concluded that after 300 days in a landfill the sludge is still in the process of degradation and maturity.

Production of well-matured compost from night-soil sludge by an extremely short period of thermophilic composting

The effect of various operational conditions on the decomposition of organic material during the composting of night-soil treatment sludge was quantitatively examined. The optimum composting conditions were found to be a temperature of ca. 60°C and an initial pH value of 8. Rapid decomposition of organic matter ceased by the sixth day of composting under these optimum conditions, and the final value of the cumulative emission of carbon (E(C)), which represents the degree of organic matter decomposition, was less than 40%, indicating that the sludge contained only a small amount of easily degradable organic material. A plant growth assay using Komatsuna (Brassica campestris L. var. rapiferafroug) in a 1/5000a standard cultivation pot was then conducted for the compost at various degrees of organic matter decomposition: the raw composting material, the final compost obtained on day 6, and the 2 intermediate compost products (i.e., E(C)=10% and 20%). It was found that the larger the E(C), the greater the yield of Komatsuna growth. It was also found that 6 days of composting is sufficient to promote Komatsuna growth at the standard loading level, which is equivalent to a 1.5 g N/pot, since the promotion effect was as high as that obtained using chemical fertilizer. It can therefore be concluded that well-matured compost could be obtained in a short period of time (i.e., as early as 6 days), when night-soil sludge is composted under optimum conditions.

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.

Changes in chemical and biological parameters during co-composting of anaerobically digested sewage sludges with lignocellulosic material

This study reports a pilot experiment of composting of anaerobically digested sewage sludges deriving from the production of biogas in a wastewater treatment plant. Two composting piles (about 15 m(3) each) were prepared by mixing 50% and 30% (v/v) sludges with lignocellulosic material. The composting process was monitored through determination of the main physicochemical properties. The stability of the composts was assessed by determination of the respiration index and dehydrogenase activity. The collected data indicated that, at both sludges concentrations, the process produced a compost suitable for agricultural applications as far as the physicochemical properties were concerned. On the other hand, in the pile containing 50% sludges, the maximum temperature of the thermophilic phase was lower than the temperature required (55°C) to ensure the sanitization of the compost. The germination and growth indexes of Lepidium sativum indicated the lack of phytotoxicity of the final materials. The suitability of the composts as field improvers and horticultural substrates has been attested through plant bioassays conducted on maize and chrysanthemum.

A stepwise-cluster microbial biomass inference model in food waste composting

A stepwise-cluster microbial biomass inference (SMI) model was developed through introducing stepwise-cluster analysis (SCA) into composting process modeling to tackle the nonlinear relationships among state variables and microbial activities. The essence of SCA is to form a classification tree based on a series of cutting or mergence processes according to given statistical criteria. Eight runs of designed experiments in bench-scale reactors in a laboratory were constructed to demonstrate the feasibility of the proposed method. The results indicated that SMI could help establish a statistical relationship between state variables and composting microbial characteristics, where discrete and nonlinear complexities exist. Significance levels of cutting/merging were provided such that the accuracies of the developed forecasting trees were controllable. Through an attempted definition of input effects on the output in SMI, the effects of the state variables on thermophilic bacteria were ranged in a descending order as: Time (day)>moisture content (%)>ash content (%, dry)>Lower Temperature ( degrees C)>pH>NH(4)(+)-N (mg/Kg, dry)>Total N (%, dry)>Total C (%, dry); the effects on mesophilic bacteria were ordered as: Time>Upper Temperature ( degrees C)>Total N>moisture content>NH(4)(+)-N>Total C>pH. This study made the first attempt in applying SCA to mapping the nonlinear and discrete relationships in composting processes.

Study of the composting process of winery and distillery wastes using multivariate techniques

Physico-chemical, chemical and biological parameters were studied throughout the composting process of four winery and distillery composts and the data set of compost characteristics was analysed using multivariate techniques: factorial analysis (FA) and linear discriminant analysis (LDA), in order to classify the different parameters studied and thus, to establish those that better describe the composting process of this type of wastes. Through factorial analysis (FA) of the parameters studied throughout the composting process, four components that explained 85.6% of the variability were established. The parameters associated to compost maturity, agronomic character, water-soluble fraction and ammonia and temperature increment were grouped in the components F1, F2, F3 and F4, respectively, which can reduce the number of determinations needed to ascertain the maturity and quality of the composts. In addition, the linear discriminant analysis on the factorial components makes possible to classify the four composts with a percentage of success around 95%.

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.

Evaluation of carbon degradation during co-composting of exhausted grape marc with different biowastes

In this work the carbon biodegradation of exhausted grape marc (EGM) combined with other organic wastes using the turned pile composting system was studied. Four different piles were made of EGM in Pile 1, EGM mixed with cow manure and straw (CMS) in Pile 2, EGM mixed with municipal solid waste (MSW) in Pile 3 and EGM mixed with grape stalks (GS) in Pile 4. The results obtained were modelled to determine the main kinetic and stoichiometric parameters. Regarding to the rate constants of the composting processes they were increased from 0.033d(-1), the value obtained when EGM was composted alone, to 0.040 and 0.044d(-1) when MSW and GS were added, respectively as co-substrates. However, the addition of CMS reduced the rate constant. About the biodegradable carbon fractions, it was observed that the co-composting reduced significantly the remanent carbon concentration after composting in all the piles whilst increased the readily biodegradable carbon fractions from 35, the value obtained when EGM was composted alone, to 50 and 60%, respectively when MSW or GS were added. As regards the temperature profiles, only Piles 1 and 4 achieved thermal hygienization values and about the nitrogen losses, the lowest percentage of nitrogen loss took place when GS were added, because of its optimum pH and C/N initial ratio. Thus, though any of these wastes could be used for co-composting with EGM, the use of GS as co-substrate and bulking agent for the co-composting process of EGM was recommended.

Agrochemical characterisation of the solid by-products and residues from the winery and distillery industry

The winery and distillery industry produces a great quantity of residues, whose management and disposal are environmental problems due to their seasonal character and some polluting characteristics. The main solid by-products and residues generated are grape stalk, grape pomace or marc, wine lee, exhausted grape marc and winery sludge. In this study, 87 samples of winery and distillery residues were collected from different Spanish wineries and distilleries. Electrical conductivity, pH, total organic matter, organic carbon, polyphenols and contents of plant nutrients and heavy metals were determined. The purpose of this research was to study the composition of these wastes and to find relationships in order to use easily analysable parameters to estimate their composition. In general, the winery and distillery residues showed low pH (mean values ranged from 3.8 to 6.8) and electrical conductivity values (1.62-6.15 dS m(-1)) and high organic matter (669-920 g kg(-1)) and macronutrient contents, especially in K (11.9-72.8 g kg(-1)). However, a notable polyphenol concentration (1.2-19.0 g kg(-1)) and low micronutrient and heavy metal contents were also observed, some of these properties being incompatible with agricultural requirements. Therefore, conditioning treatments are necessary prior to possible use of these wastes. In all wastes, significant correlations were found between easily determined parameters, such as pH, electrical conductivity and total organic matter, and most of the parameters studied. The regression models obtained are also discussed.

Composting of lead-contaminated solid waste with inocula of white-rot fungus

The treatment of the simulated lead-contaminated solid waste by composting with white-rot fungus was studied at laboratory scale. The composting system without the inocula of white-rot fungus was prepared as control, and the composting of the uncontaminated solid waste with the inocula of white-rot fungus was carried out as the other control. The results indicated that the solid waste inoculated with white-rot fungus could be successfully processed. The final compost was mature with 70.5% of lead (Pb) in residual fraction and none in exchangeable fraction. Germination index reached 120%. All the results indicated that the bioavailability of Pb in compost was reduced and the potential harm of Pb in compost was alleviated by composting with the inocula of white-rot fungus.

An electrochemical on-field sensor system for the detection of compost maturity

A maturity sensor system was developed, based on the combination of three electrically measured parameters, pH, NH(4)(+) concentration, and phosphatase activity in the water extracts of compost samples. One of these parameters, the apparent phosphatase activity in crude test solutions was determined using screen-printed carbon strips (SPCSs) coated with alpha-naphthyl phosphate (alpha-NP) in Nafion film. The phosphatase activity was monitored in connection with differential pulse voltammetry (DPV) with an aliquot (30 microL) of the test solution on SPCS. The phosphatase activity sensor was validated using alkaline phosphatase (ALP) in Tris-HCl buffer (pH 8.0) and acid phosphatase (ACP) in citric acid buffer (pH 5.0). The activity of the spiked enzymes in the water extract of the compost sample could be confirmed with the change of corresponding oxidation peak current signal of the product, alpha-naphthol. The water extracts of compost samples (n=24) collected in various composting days were applied to our compost maturity sensor system, and the conventional germination tests. Using multiple regression analysis, the germination index (GI) was expressed by the multi-linear regression equation consisting of pH, NH(4)(+) concentration, and the phosphatase activity. The calculated GI from the regression equation had a good correlation with the measured GI of the corresponding composts (r=0.873). As a result, we have determined an equation for the determination of the compost stability using our portable sensor system rapidly at the composting site.

Estimation of maturity of compost from food wastes and agro-residues by multiple regression analysis

The composting process of food wastes and tree cuttings was examined on four composting types composed from two kinds of systems and added mixture of microorganisms. The time courses of 32 parameters in each composting type were observed. The efficient composting system was found to be the static aerated reactor system in comparison with the turning pile one. Using the multiple regression analysis of all the data (159 samples) obtained from this study, some parameters were selected to predict the germination index (GI) value, which was adopted as a marker of compost maturity. For example, using the regression model generated from pH, NH(4)(+) concentration, acid phosphatase activity, and esterase activity of water extracts of the compost, GI value was expressed by the multi-linear regression equation (p<0.0001). High correlations between the measured GI value and the predicted one were made in each type of compost. As a result of these observations, the compost maturity might be predicted by only sensing of the water extract at the composting site without any requirements for a large-size equipment and skill, and this prediction system could contribute to the production of a stable compost in wide-spread use for the recycling market.

Optimization of adenosine 5'-triphosphate extraction for the measurement of acidogenic biomass utilizing whey wastewater

A set of experiments was carried out to maximize adenosine 5'-triphosphate (ATP) extraction efficiency from acidogenic culture using whey wastewater. ATP concentrations at different microbial concentrations increased linearly as microbial concentration decreased. More than 50% of ATP was extracted from the sample of 39 mg volatile suspended solids (VSS)/l compared to the sample of 2.8 g VSS/l. The ATP concentrations of the corresponding samples were 0.74+/-0.06 and 0.49+/-0.05 mg/l, respectively. For low VSS concentrations ranging from 39 to 92 mg/l, the extracted ATP concentration did not vary significantly at 0.73+/-0.01 mg ATP/l. Response surface methodology with a central composite in cube design for the experiments was used to locate the optimum for maximal ATP extraction with respect to boiling and bead beating treatments. The overall designed intervals were from 0 to 15 min and from 0 to 3 min for boiling and bead beating, respectively. The extracted ATP concentration ranged from 0.01 to 0.74 mg/l within the design boundary. The following is a partial cubic model where eta is the concentration of ATP and x ( k ) is the corresponding variable term (k=boiling time and bead beating time in order): eta=0.629+0.035x (1)-0.818x (2)-0.002x (1) x (2)-0.003x (1) (2) +0.254x (2) (2) +0.002x (1) (2) x (2). This model successfully approximates the response of ATP concentration with respect to the boiling- and bead beating-time. The condition for maximal ATP extraction was 5.6 min boiling without bead beating. The maximal ATP concentration using the model was 0.74 mg/l, which was identical to the experimental value at optimum condition for ATP extraction.

The fate of the recombinant DNA in corn during composting

In order to make regulations that safeguard food and the environment, an understanding of the fate oftransgenes from genetically modified (GM) plants is of crucial importance. A compost experiment including mature transgenic corn plants and seeds of event Bt 176 (Zea mays L.) was conducted to trace the fate of the transgene cryIA(b) during the period of composting. In bin 1, shredded corn plants including seeds were composted above a layer of cow manure and samples from the corn layer were collected at intervals during a 12-month period. The samples were tested for the transgene persistence and microbial counts and also the compost was monitored for temperature. In bin 2, piles of corn seeds, surrounded by sheep manure and straw, were composted for 12 months. A method combining nested polymerase chain reaction (PCR) and southern hybridization was developed for detection of the transgene in compost. The detection sensitivity was 200 copies of the transgene per gram of dry composted corn material. Composting commenced on day 0, and the transgene was detected in specimens from bin 1 on days 0 and 7 but not on day 14 or thereafter. The transgene in corn seeds was not detectable after 12 months of composting in bin 2. Temperatures in both bins rose to about 50 degrees C within 2 weeks and remained above that temperature for about 3 months, even when the ambient temperature dropped below -20 degrees C. Extracts from compost were inoculated onto culture plates and then were incubated at 23 to 55 degrees C. Within the first 2 weeks of composting in bin 1, the counts of bacteria incubated at 55 degrees C increased from 3.5 to 7.5 log10, whereas those incubated at 23 degrees C remained at about 7.5 log10. The counts of fungi incubated at 45 degrees C increased slightly from 2.5 to 3.1 log10, but those incubated at 23 degrees C decreased from 6.3 to 3.0 log10. The rapid degradation of the transgene during composting of Bt corn plants suggested that the composting process could be used for safe disposal of transgenic plant wastes.

The fate of a genetically modifiedPseudomonasstrain and its transgene during the composting of poultry manure

The fate of the genetically modified (GM) Pseudomonas chlororaphis strain 3732 RN-L11 and its transgene (lacZ insert) during composting of chicken manure was studied using plate count and nested polymerase chain reaction (PCR) methods. The detection sensitivity of the nested PCR method was 165 copies of the modified gene per gram of moist compost or soil. Compost microcosms consisted of a 100-g mixture of chicken manure and peat, whereas soil microcosms were 100-g samples of sandy clay loam. Each microcosm was inoculated with 4 × 1010CFU of P. chlororaphis RN-L11. In controlled temperature studies, neither P. chlororaphis RN-L11 nor its transgene could be detected in compost microcosms after incubation temperature was elevated to 45 °C or above for one or more days. In contrast, in the compost microcosms incubated at 23 °C, the target organism was not detected by the plate count method after 6 days, but its transgene was detectable for at least 45 days. In compost bins, the target organism was not recovered from compost microcosms or soil microcosms at different levels in the bins for 29 days. However, the transgene was detected in 8 of the 9 soil microcosms and in only 1 of the 9 compost microcosms. The compost microcosm in which transgene was detected was at the lower level of the bin where temperatures remained below 45 °C. The findings indicated that composting of organic wastes could be used to reduce or degrade heat sensitive GM microorganisms and their transgenes.Key words: composting, genetically modified Pseudomonas strain, transgene, polymerase chain reaction.

Microbiological aspects of humid husk composting

The feasibility of composting as disposal practice of husk mixed with olive mill wastewaters (OMW) was studied in the present research. The process was investigated with regards to some reliable and easy to be determined microbial activity parameters such as the ATP content, the activity of a pool of enzymes and the viable counts, keeping in mind the well known bias of this last technique. Two different composting technologies were compared: static pile and reactor by studying the cured composts obtained. Among the bioindicators tested, the composting process trend was described better by the ATP content and the activity of some enzymes. In fact, the ATP content showed an increase during the thermophilic phase in both the pile and the reactor, and decreased at the end of the process, it was also higher in the bioreactor-pile technology than in the pile. With regard to the enzymatic activity, with the reactor technology experiment, two peaks were evidenced in the thermophilic phase and during the curing phase in pile, and a drop during the transfer of material from the reactor to the pile. The quality of the cured product obtained using the reactor technology has been evaluated considering phytoxicity and hygienic features: the stabilised compost resulted to have neither phytoxical effect, nor faecal indicator contaminants.