Volume 3 Special Issue 1 2009
Compost II

How to reference: Artola A, Barrena R, Font X, Gabriel D, Gea T, Mudhoo A, Sánchez A(2009) Composting from a Sustainable Point of View: Respirometric Indices as Key Parameter. In: Martín-Gil J (Ed) Compost II. Dynamic Soil, Dynamic Plant 3 (Special Issue 1), 1-16

Guest Editor

Jesús Martín-Gil
University of Valladolid, Spain

www.universityofvalladolid.uva.es/

CONTENTS AND ABSTRACTS

Adriana Artola, Raquel Barrena, Xavier Font, David Gabriel, Teresa Gea (Spain), Ackmez Mudhoo (Mauritius), Antoni Sánchez (Spain) Composting from a Sustainable Point of View: Respirometric Indices as Key Parameter (pp 1-16)

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Invited Review: Composting at an industrial scale can be performed using low technology processes, such as windrows, or by implementing more complex technologies such as tunnels or, in general, in-vessel systems. In both cases process control can be done via measurement of oxygen content in the exhaust gases (or as interstitial oxygen in the material) and/or by monitoring the temperature evolution of the material. However, the use of respiration indices (RIs) as a control parameter to obtain reliable information on the actual microbial activity is being increasingly studied. Also RIs are used to determine the biological stability of the final product or the biodegradability of the wastes intended to be composted. In this case, the RI value can be related to the amount of biodegradable organic matter content. As a new application, RIs can also be used to determine the environmental impact of composting plants. Indeed, emission factors of pollutant gases (ammonia, Volatile Organic Compounds, etc.) or consumption of resources (water, energy, electricity) can be referred to the resulting reduction of RI obtained during the entire composting process. In this case, RI might be a promising parameter for the comparison of composting technologies from the point of view of its sustainability or to define the critical phases of the process in terms of environmental impact (for instance, treatment of exhaust composting gases by biofiltration). In fact, studies on composting sustainability should consider not only the composting process but the equipment used for the treatment of its emissions, which has an important effect on the global environmental impact of waste treatment plants. This paper discusses the above mentioned topics, with RIs as the key parameter in the analysis of composting processes. The discussion will be based on the experience of our previous research on composting and gas cleaning.

ABSTRACT

Invited Review: In this review we discuss the transformation of organic matter during municipal solid waste (MSW) composting and the suitability of chemical and biochemical parameters in defining the stability and maturity of the end product. The dynamics of chemical and biochemical parameters, such as several hydrolase activities and water-soluble fractions (i.e. water soluble carbon, water soluble nitrogen, water soluble carbohydrate) during MSW composting is discussed along with their suitability as tools for compost characterization. Besides, the evolution during the MSW process of the molecular structure of humic acid (HA), based on Fourier transform infrared (FTIR), ¹³C NMR spectroscopy and thermal analysis, is also discussed. The data presented highlight the suitability of several enzymatic activities and water soluble fractions as indicators of the evolution of the organic matter during MSW composting. However, since the extent of each enzyme activity at the end of composting depends on the starting material used, single point determinations appear inadequate for compost characterization. Moreover, the importance of the characterization of the dynamics of enzymatic activities and water-soluble fractions during the process has been emphasized. FTIR and ¹³C NMR spectra appeared useful tools reflecting the rate of change in HA structure during MSW composting. Thermoanalitical analyses (TG/DTG and DSC curves) also revealed valuable in order to characterize the organic matter during composting and distinguish between well and poorly stabilized organic matter.

Luke Chimuka, Thomani E. Manungufala (South Africa) Sources, Bioavailability and Fate of Heavy Metals and Organic Contaminants in Compost Manure (pp 32-38)

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Invited Mini-Review: This paper reviews the sources, bioavailability and fate of heavy metals and organic contaminants in compost manure and in soils of which the manure is applied. The toxicity of heavy metals and organic compounds in soil of which would have come from applied compost is also discussed. Type of materials, their background and where collected for use in composting contribute to the sources of heavy metals and organic compounds in compost manure. The materials that are major sources include sawdust, sewage sludge and municipal solid waste (MSW). Sewage sludge usually is collected from wastewater and or sewage treatment plants while sawdust is collected from timber industries that manufacture different items from raw wood. MSW is found at municipal operated landfills and dumping facilities. Both inorganic and organic contaminants are highest in sewage sludge because of enrichment that occurs during wastewater treatment process. Heavy metals such as iron (Fe), manganese (Mn), chromium (Cr), nickel (Ni), zinc (Zn) and copper (Cu) are found in sawdust and come from wood cutting metal component. The extent of heavy metals and organic compounds in sewage sludge depends on the type of wastewater being treated. Sewage sludge from industrial wastewater treatment plants has generally higher levels of heavy metals (copper, zinc, lead, iron, cobalt, nickel, chromium, cadmium) and organic compounds (polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins/furans and polyaromatic hydrocarbons) than that from household wastewater treatment plants. Electronic waste, metal (soft drink cans) and glass (food bottles) components in MSW are the major contributor to heavy metals. Source separation of the biodegradable waste from electronic waste, metal and glass components in MSW has been observed to reduce the level of Cu, Zn, Lead (Pb) and Fe in compost. Bioavailability and toxicity are influenced by factors such as type and amount of contaminant in the soil and compost, type of soil, amount of organic matter in the compost and other environmental conditions such as pH.

Gabriele Alfano, Giuseppe Lustrato, Giuseppe Lima, Giancarlo Ranalli (Italy) Present and Future Perspectives of Olive Residues Composting in the Mediterranean Basin (CompMed) (pp 39-56)

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Invited Review: For many years, olive mill wastewater (OMW) from oil production plants has been the most pollutant and troublesome waste produced by the olive industry in all Mediterranean countries. Olive wastes (OMW and three-and two-phase olive husks) are generated in large quantities in short periods of time and represent a substantial economic and environmental problem for the sector. Inappropriate management has in the past led to dramatic environmental disasters involving rivers and low-lying farmland in various parts of Europe and across the Mediterranean basin, posing a constant threat to small producers. In addition, either the management of OMW or its disposal by expensive specialised service companies represents a substantial economic burden for the small enterprises that constitute the Mediterranean olive oil sector. The challenge of achieving cost-efficient management of olive wastes has been extensively investigated during the last 50 years without finding a single universally valid solution than may be considered as technically feasible, economically viable and socially acceptable. However, it is well known that olive waste contains valuable resources such as a large proportion of organic matter, a wide range of nutrients and high added-value antioxidants that could be utilised. However, to date, this has not been the case because there are some technological barriers linked to specific processes. This paper reports a synthesis and an overview of recently-developed solutions for the treatment of these wastes, with a special emphasis on olive waste composting as a sustainable solution suitable for small medium-sized agricultural farms and olive mills, which represent the vast majority in Mediterranean agriculture. Furthermore, a review of the Italian and European legal framework on olive waste disposal and treatment is reported.

Anurag Garg (India), Ibtisam E. Tothill (UK) A Review of Solid Waste Composting Process – The UK Perspective (pp 57-63)

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Invited Review: Due to increasing political and environmental pressures, a sustainable solid waste management scheme is required. The urgency of scheme is more in countries heavily relied on landfilling such as the UK. Imposition of the European Union Landfill Directive (1999/EC/31) placed tremendous pressures on local authorities and waste management industries in the UK. In this paper, we review the composting process, one of the principle treatment options for biodegradable waste. This process not only produces useful end-product in the form of compost but also contributes in meeting landfill diversion and recycling targets. Informations regarding the parameters controlling the process, suitable feedstocks for composting and types of processes are also provided. In addition, previous studies were used to compile the information on the product quality and its impacts on plant growth. It has been suggested that immature compost and high heavy metal content are most likely to inhibit plant growth. In addition, the most significant air emissions from the compost sites are identified and data available in the open literature related to the release of these pollutants is being presented. Preventive measures to reduce the release of air pollutants to the atmosphere are also suggested. Apart from this, current regulatory climate in the UK is also reviewed to assess the feasibility of the process. Recommendations for future work include the need for the improvement in risk assessment methods and sampling strategies for air pollutants.

Gabriele Alfano, Giuseppe Lustrato, Giuseppe Lima, Domenico Vitullo, Sebastiano Delfine, Roberto Tognetti, Giancarlo Ranalli (Italy) Physico-Chemical, Microbiological, Agronomical, and Phytopathological Aspects in the Recycling of Olive Waste Composted Residues (pp 64-72)

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Original Research Paper: Olive mill wastes might impact plants, soil, microbial population, aquatic ecosystems and air media unfavourably. In the present work, olive waste composting confirmed to be a suitable microbial biotechnology for transformation of these by-products into organic fertilizers (cured composted residues) with no phytotoxicity, free of pathogens and able to improve soil fertility and plant production. In our experimental conditions, physico-chemical, biochemical, phytotoxicity and microbiological analysis confirmed the negligible agronomical qualitative characteristics of the cured composted residues. Moreover, olive mill residues after the composting process showed positive properties which suppressed soil-borne plant pathogens. Composted olive waste evidenced good suppressive activity against microsclerotia of V. dahliae and other fungal plant pathogens. Agronomical trials on tomato and sunflower crops showed that seed and fruit production was not decreased by the exclusive addition of compost. Compost amendment caused an increase in soil organic matter, although crop yield and plant growth increased only after mineral fertilization. Furthermore, olive yield and olive oil quality were not negatively affected by compost distribution. These results are encouraging for the agronomic use of composted residues in addition to mineral fertilizers. This may represent an initial phase to increase organic matter in the soil and possibly to reduce mineral fertilization. This process may be considered a new environmental opportunity for greater agriculture sustainability. All these aspects take into consideration that the application of good quality cured composts with high agronomic, microbiological and suppressive characteristics seem to be a very promising strategy for organic and integrated agriculture systems and for organic matter re-integration of soil.

Gennaro Brunetti (Italy), Pedro Soler-Rovira (Spain), Nicola Senesi (Italy) Composting Exhausted Wastes of Mushroom Cultivation: Maturity Parameters and Organic Matter Stabilization (pp 73-77)

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Original Research Paper: The aim of this work was to study the parameters of the composting process of organic wastes originated from mushroom production industry. To accomplish these objectives three piles (P1, P2 and P3) obtained with a spent mushroom substrate (SMS) with different proportions of wheat straw (WS) and urea were composted for 90 days in a static-pile system with continuous monitoring of the process. Samples from each pile were periodically taken to assess physico-chemical properties (pH, E.C., TOC, N, C/N ratio), organic matter and humification parameters. The comparative examination of results obtained for original substrates and final composts showed an increased stability and maturation degree of the organic matter, especially for the piles with a higher proportion of straw. All the piles achieved the stabilization and maturity levels required for a safe application of compost as a soil organic amendment.

Manuel Dios, Maria Angeles Arcos, Maria Angeles Martín, Ana Belen Corredera, Arturo F. Chica (Spain) Relationship between Respirometric Stability and Agricultural Maturity in Compost from Municipal Solid Waste (pp 78-85)

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Original Research Paper: Composting of the Organic Fraction of Municipal Solid Waste (OFMSW) has become an increasingly widespread practice in many countries today. The final product, compost, must be stabilized and sanitized if it is to be used as an input of organic matter and nitrogen in agricultural soils without adverse effects. Respirometric determination of the Oxygen Uptake Rate is one of the most widely accepted methods in the literature for measuring the development of the composting process. This method allows the stability of samples taken during the composting process to be determined. On the other hand, mature compost is defined as the product which has no negative effect when it is applied to agriculture. Mature compost is often evaluated by means of germination or growth tests of plant species. In this paper we have studied the relationship between the two concepts and measurement techniques to evaluate the possibility of predicting maturity by means of determining stability. To this end, samples from two types of OFMSW compost were analyzed at different composting times through an assay of tomato seed germination and the degree of stabilization was determined by the SOUR respirometric method (Specific Oxygen Uptake Rate). Two other OFMSW compost samples were studied through assays of Latucca sativa growth using the Di.Pro.Ve. method developed at the University of Milan. The test was performed at different composting times and degrees of stabilization. In light of the results of the respirometric method and the growth and germination efficiency, we were able to correlate both variables (stability and maturity). We have found that by determining compost stability by means of a respirometric technique, we can obtain a good indicator of the maturity of the product and therefore predict its agronomic performance.

Camilla Giovannini, Daniela Montecchio, Paola Gioacchini, Ornella Francioso, Claudio Ciavatta (Italy) Characterization of Compost-Based Growing Media. A Chemical, Thermal, Spectroscopic and Isotopic Approach (pp 86-92)

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Original Research Paper: Peat is the best substrate in growing media, but its rapid depletion needs at least a partial substitution. Composting of urban green wastes and agro-industrial by-products can produce good compost (Cm) for this purpose. Cm-based substrates are increasing in the market. However, physical and chemical characterization of Cm-based growing media is the first step for their proper use. This paper reports the results of the fractionation of the bulk organic matter (OM) of four growing media, containing increasing amount (v/v) of Cm [100% Peat; 80% Peat + 20% Cm (CP20); 40% Peat + 60% Cm (CP60); 100% Cm) into well-defined fractions: humic acid-like (HAL), non-humic fraction (NH) and dissolved OM (DOM) and their characterization by a combination of chemical, thermogravimetric (TG), differential thermal analysis (DTA), spectroscopic (Diffuse Reflectance Infrared Fourier Transform-DRIFT) and isotopic (δ ¹⁵N) techniques. TG-DTA of bulk growing media, HAL, NH and DOM showed significant differences among increasing Cm in Cm-based growing media. DRIFT spectra confirmed these differences. The N isotope ratio (δ ¹⁵N) of all the substrates increased with the amount of Cm in the substrate. The combination of chemical, TG-DTA, DRIFT and δ ¹⁵N techniques can be successfully applied for the chemical characterization of Cm-based growing media with a good identification of different matrices.

Ajay S. Kalamdhad, Muntjeer Ali, Meena Khwairakpam, A. A. Kazmi (India) Organic Matter Transformation during Rotary Drum Composting (pp 93-98)

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Original Research Paper: Organic matter transformation using chemical and spectroscopic methods was studied for composting of four carbon/nitrogen (C/N) ratio waste combinations (C/N 16, C/N 22, C/N 30 and C/N 38) of grass cuttings, mix vegetable waste, cattle manure, food waste and sawdust. Temperature, moisture content, ash content, total organic matter, C/N ratio and water-soluble organic carbon (WSOC) concentrations were observed in a rotary drum composter for 20 days. In addition, a spectroscopic method (Fourier-transform infrared) was used to study the chemical composition of the organic matter. Temperature reached above 50°C in all waste combinations indicating the immense oxidation within the rotary drum composter, resulting in a final higher ash content (62.28%) in C/N 16 compared to about 30-32% for C/N 22, 30 and 38. The C/N ratio decreased rapidly from initial values of 16, 22, 30 and 38 to 5.4, 10.9, 16.6 and 27.2 after 20 days of composting. Total organic carbon (TOC) of the compost displayed a similar trend to WSOC, which decreased to around 34, 31 and 18% in C/N 22, 30 and 38 compared to 58% in C/N 16. The infrared spectra of the all treatments exhibited the same band pattern, indicating unnoticeable qualitative changes during the composting process. The decrease of the 2930/1030, 2850/1030 (aliphatic C/aromatic C) and 2930/1630 (aliphatic C/polysaccharide) ratios monitored in all treatments (higher decrease in C/N 16) and an increase of the 1380/2930 ratio indicated progress of the composting process and consequently a higher degree of decomposition.

Ernesto Lahoz, Rosa Caiazzo, Luigi Morra, Angela Carella (Italy) Suppression of Lettuce Drop caused by Sclerotinia sclerotiorum in the Field using Municipal Solid Waste Compost and Fungistatic Effect of Water Extract (pp 99-102)

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Original Research Paper: Sclerotinia sclerotiorum (Lib.) De Bary is the principal etiological agent of lettuce drop in Italy and worldwide. The objectives of this study were: i) to evaluate the efficacy of source-separated municipal waste compost when used as fertilizer at a rate of 25 t ha^-1 on a dry matter basis in suppressing S. sclerotiorum on lettuce; ii) to investigate the effect of compost water extract on myceliogenic germination of sclerotia; iii) to determine the effect of water extract on 6 pathogens of lettuce. In order to achieve these objectives, two lettuce crop cycles in open fields, two fungal bioassays and soil assays of sclerotial content in the laboratory were carried out in 2008. Results demonstrated that the incidence of S. sclerotiorum in open fields was significantly lower in compost than in mineral fertilized plots (-31% in average). Marketable yield was significantly higher for compost amended plots than those mineral fertilized (+ 6.5 t ha^-1 in average). No variation in soil population of the pathogen was observed. Sterile water extract from mature compost was able to inhibit growth of S. sclerotiorum and Rhizoctonia solani AG 2-1 with IC₅₀ values of 308 and 438 mg l^-1 respectively, while it was not effective toward four other pathogens tested, including R. solani AG 1. S. sclerotiorum myceliogenic germination of sclerotia was also affected by water extract. Fungistasis could be one of the possible mechanisms of action, but this hypothesis does not imply that biological rather than physical mechanisms should act contemporary. Water extract of mature compost demonstrated the potential for extraction of active molecules. In addition, the extract was not phytotoxic, as reported for certain immature compost teas.

Romeela Mohee, Vanessa Jumnoodoo, Nafiisa Sobratee, Ackmez Mudhoo, Geeta Unmar (Mauritius) Assessing the Suitability of the Composting Process in Treating Contaminating Pesticides and Pathogenic Wastes (pp 103-114)

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Original Research Paper: Composting is a treatment which has been employed for organic wastes such as household wastes, yard wastes, manure and municipal solid wastes. More and more, wastes, hazardous in nature, such as polychlorobiphenyls (PCBs), contaminated soils, oily/petroleum wastes and explosives are nowadays being treated through composting. By the inherent characteristics of the composting process, the toxicity of hazardous wastes is strongly reduced and the compost can be safely disposed as landfill cover or other less expensive methods. This paper assesses the suitability of the composting process in treating hazardous wastes, mainly livestock wastes and pesticide-contaminated wastes. It analyses in general the parameters involved in the degradation of the hazardous wastes. For livestock wastes composting, it focuses on the heat/temperature inactivation of microorganisms and the use of indicators to judge the outcome of the process. In the case of pesticide-contaminated green wastes composting, the degradation of the pesticide molecules during the composting process is studied. The composting of green wastes contaminated with chlorinated herbicides has shown that the composting process was favourable to the microbial metabolism of 2,4-dichlorophenoxyacetic acid (2,4-D) and atrazine. Various parameters contributed to the biodegradation such that loss of 2,4-D occurred at a faster rate than atrazine. The biodegradation of atrazine was initiated by nucleophilic displacement of chloride ion. During composting of livestock wastes, hygienisation was attained at a maximum temperature of 66.4°C and log₁₀ reductions of –8.03, –8.18 and –5.96 were noted for faecal coliforms (FC), Escherichia coli (EC) and faecal enteroccocci (FE). Hence, it has been demonstrated that FC and EC could be more rapidly destroyed at elevated temperatures compared to FE.

Manfred Sager (Austria) Trace Element Enrichment in Austrian Soils from Fertilization, and Regional Effects (pp 115-131)

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Original Research Paper: In all kinds of fertilizers sold on the Austrian market, 22 main and trace elements were determined in quasi total digests by ICP multi-element spectrometry, and total N by combustion. Accessory elements were expressed in terms of a fertilization rate of 100 kg N resp. 100 kg P/ha. The country was parted in regions due to geological and climate criteria. The rate of use of different kinds of fertilizers varied between the regions. Whereas there were no regional differences in composition of mineral fertilizers, some were found for commercial organic fertilizers, manures and garden moulds, which could be traced mainly to land use. Regional geology just explained differences in Al, Ba and Be in composts, population density effected Na and Pb, and Cu and Zn in manures reflected the amount of commercial animal feedstuff used. When fertilized with the same equivalents of P or N, composts supplied higher loads of accessory elements than mineral fertilizers, except for Cd-As-Be-V. For budgeting, atmospheric deposition as well as average concentrations and crop yields of wheat and potatoes were taken into account. If an organic farmer takes organics from the local market at the same N- or P-rate per area, accumulations in the soil growing wheat or potatoes are more probable, unless these excesses can be used for other special crops. It will be necessary to budget not only N, P and C, but also trace elements.

José Martín Soriano-Disla, Ignacio Gómez, José Navarro-Pedreño, Cesar Guerrero (Spain) The Use of a Respirometric Technique for Assessing the Evolution of the Stability of a Sewage Sludge Compost Developed under Full-Scale Conditions (pp 132-135)

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Short Communication: Composting is one of the best ways to properly manage the high production of sewage sludge with the aim of obtaining sanitized products with a stable organic matter. The evolution of the stability of a compost consisting of sewage sludge, straw and sawdust, developed under full-scale conditions, was analyzed. The stability was assessed by a respirometric assay performed for 30 days, where the O₂ consumption and CO₂ production was continuously measured by an automatic respirometer. Important reductions were observed in the respirometric parameters, changes which mainly occurred in the samples taken during the first 40-50 days of composting. After this period, the few changes observed and the low levels of respiration suggested compost stability. The maximum rates and the cumulative values of CO₂ and O₂ after 8 days of incubation seemed to be the most useful respirometric parameters for compost monitoring.

Siobhán N. Jordan, George J. Mullen, Ronan G. Courtney (Ireland) A Greenhouse Trial on the Effects of Spent Mushroom Compost on the Microaggregate Fraction of Lead-Zinc Tailings (pp 136-138)

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Short Communication: Particle size analysis was carried out on the microaggregate fraction (<53 µm) of spent mushroom compost (SMC) amended pyritic lead-zinc tailings using laser diffraction. A randomized factorial greenhouse trial of six-month duration was established using tailings originating from the surface (20 to 30 cm) of the partially vegetated 76-ha tailings management facility (TMF) in Gortmore, Silvermines, Co. Tipperary, Ireland. SMC was incorporated at application rates of 0, 50, 100, 200 and 400 t ha^-1 and Lolium perenne sown at a rate of 200 kg ha^-1. Following trial dismantlement, the effects of SMC treatment on the microaggregate fraction of the tailings was investigated using optical laser diffraction on a Malvern Mastersizer 2000^®. At SMC applications of 200 t ha^-1 and 400 t ha^-1 an increase in clay dispersion was observed as represented by low d(0.10) values, while a reduction in clay dispersion was noted at SMC applications of 50 t ha^-1 and 100 t ha^-1. Furthermore, microaggregate stability generally decreased with increasing SMC application as noted by a decrease in d(4,3) values. This is probably explained by the change in surface charge following SMC amendment, the low clay concentration and the mineralogy of the lead zinc-tailings, all of which did not prove favorable in the stabilization of the microaggregates present in pyritic lead-zinc tailings. Laser diffraction gave rapid, reliable and consistent results and for the most part showed a shift in particle size distribution between each SMC treatment.

S. Viveka, B. Leena Grace (India) Conversion of Water Hyacinth (Eichhornia crassipes) into Nutrient-Rich Fertilizer by Pit Methods (pp 139-142)

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Short Communication: Among the aquatic weeds, water hyacinth is considered to be the most obnoxious of all aquatic weeds and occupies eighth rank in the world. Water hyacinth caused lot of problems to human beings and animals in many ways. The present study is therefore aimed to develop an appropriate technology for recovery of resources from aquatic weeds by pit methods of composting. Compost was prepared from aquatic weed water hyacinth using three different pit methods namely Indore method, Bangalore method and phospho-compost method. Physical and chemical parameters of the compost were analyzed in the initial and final stage. The physical analyzes of composts showed that electrical conductivity, porosity, water holding capacity and moisture content were increased from initial to final stage in all pit methods especially in Bangalore method. The drastic reduction was noticed in lignin and cellulose level of composts especially in Bangalore compost. All the three compost have recorded higher macro and micro nutrients especially in Bangalore compost from initial to final stage. Among the three composts, Bangalore compost recorded the highest reduction in C: N ratio followed by phospho-compost and Indoor compost. Increased bacterial and fungal counts were observed in Bangalore compost than the Indore and phospho-compost. The generic compositions of bacterial and fungal strains of three composts were revealed that more or less same types of genera were present. In this context we conclude that all the three techniques of composting are best suitable to replenish the Eichhornia weed biomass. Water hyacinth based compost used as an organic fertilizer has appropriate macro and micro nutrients and microorganisms that will support the plant growth.