Composting of biodegradable organic wastes for sustainable agriculture


Courtesy of BioCycle Magazine

Investigators: M.A. Ali Khan, Manoj Kumar, Kavita Kashyap, Ruby Rani, Sanjay Yada, Priti Kaushik Siraohi Environmental Science Lab. Dept. of Botany, Simbhaoli, Ghaziabad, India

Objectives: To recycle, reduce and reuse hazardous distillery spent wash (DSW). Pressmud cake (PMC) fly ash, Eicchornia/Azolla/trash/litter and DSW inoculated with Trichoderma viride were observed for temperature based decomposer phases (psychrophilic, mesophillic, thermophilic, stabilization and poikilothermic). N. Mineralization in immature (IMC) and mature compost (MC) was evaluated by C/N ratio and plant bioassay test (Vigna radiata L). DSW rapidly decomposes green manure (Sesbania aculeata) for soil health management. Trichoderma showed early decomposition by humus-enzyme complex and hastened the decomposition rate of residuals in soil, essential for reactions and sustainability. Holistic effect was investigated of ferti-irrigation (liquid fertilizer) of treated distillery effluent on presown (priming) and postsown crop productivity and soil fertility. Partially treated effluent was further treated through reverse osmosis to remove inorganic solids and relacitrant compounds for healthy ecosystems.

Factors Affecting Air Pycnometer Performance For Its Use In The Composting Process

Investigators: L. Ruggieri, T. Gea, A. Artola, A. Sánchez, Composting Research Group, Department of Chemical Engineering, Escola Tècnica Superior d’Enginyeria, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola, Barcelona, Spain

Objectives: To study the potential error sources in Air filled porosity (AFP) determination in composting material samples by air pycnometry and to suggest the procedures to minimize the uncertainty of obtained AFP values. AFP is a determinant factor in composting to guarantee aerobic conditions within the composting matrix. Among the different methods proposed to measure AFP in composting processes, air pycnometry is defined as the most adequate. There is a lack of a standard methodology for air pycnometry utilization for AFP determination in heterogeneous samples as those from composting materials. Air pycnometers currently used for this purpose are custom made instruments operating under different conditions (sample volume, initial pressure, etc.). All factors affecting air pycnometry accuracy in the composting process are related to the proper maintenance and handling of the air pycnometer and the composting sample. In this study, AFP measurements have been performed for more than 50 samples of a wide range of composting materials in two different custom made pycnometers, one of them coupled to a composting reactor allowing in situ AFP measurement. While temperature variation during AFP measurement has been discarded as an error source, the determination of the volume of the sample has been found to be a significant factor affecting the air filled porosity calculation. Regarding to the initial pressure to use, a compromise value between accuracy and practicality has to be established for each pycnometer design as AFP values obtained with diverse initial pressures (from 200 to 500 kPa) were found to present no statistical differences. An initial pressure in the range of 300-500 kPa is recommended. In conclusion, there is a need for a standard methodology for AFP determination or prediction at industrial scale.

Compost-Based Nursery Substrates: Effect Of Peat Substitution On Organic Melon Seedlings

Investigators: F. Tittarelli , E. Rea, S. Canali, A. Trinchera and C.M. Rivera, Agricultural Research Council - Research Centre of soil-plant system (CRA-RPS), Rome, Italy; F. Ceglie and V. Verrastrob, Mediterranean Agronomic Institute (CIHEAM-IAMB), Valenzano, Bari, Italy; J.A. Pascual, Department of Soil Water Conservation and Waste Management, Centro de Edafologia y Biologia Aplicada del Segura (CEBAS-CSIC), P. Espinardo, Murcia, Spain

Objectives: To evaluate a bovine manure compost (BMC) and a green compost (GC) as components of substrates in partial substitution of peat for organic melon seedlings production. In particular, to accomplish this objective, composting parameters were monitored during the whole process to guarantee the necessary uniformity of the final products characteristics for their utilisation as quality organic components of substrates. The performances of the compost-based growing media were evaluated in two greenhouse experiments in which melon seedlings for organic farming were grown. Treatments, differentiated on the basis of the volume percentage of the two analyzed composts, were compared to the control (a mixture of peat, coconut fiber and perlite). In order to respect the guidelines of organic production, all the treatments were fertilized, at the beginning of the trial, with guano. Compost-based substrates were analyzed for physical, physico-chemical and chemical parameters (bulk density, porosity, pH, EC, nutrients content etc.). Even though significant differences were observed, recorded values were in the range of acceptability for growing media. In terms of performance, seedling growth in treatments containing 30% and 50% of composts was significantly higher than in control.

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