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This article in JEQ

  1. Vol. 32 No. 6, p. 2379-2386
     
    Received: July 26, 2002
    Published: Nov, 2003


    * Corresponding author(s): claudio.mondini@isnp.it
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doi:10.2134/jeq2003.2379

An Integrated Chemical, Thermal, and Microbiological Approach to Compost Stability Evaluation

  1. Claudio Mondini *a,
  2. Maria Teresa Dell'Abateb,
  3. Liviana Leitaa and
  4. Anna Benedettib
  1. a Istituto Sperimentale per la Nutrizione delle Piante, Via Trieste 23, I-34170 Gorizia, Italy
    b Istituto Sperimentale per la Nutrizione delle Piante, Via della Navicella 2/4, I-00184 Rome, Italy

Abstract

The evaluation of compost stability is of the utmost importance for the reliability of composting as a recycling strategy. To date there is no single parameter that can give a sure indication of the stability of composts from different starting materials. This paper investigates different methods of evaluating the dynamics of transformation of materials and the stability level of the end products in a composting process. The following parameters were determined on compost samples of different ages from cotton (Gossypium herbaceum L.) cardings and yard wastes: humification index (HI), degree of humification (DH), thermogravimetry (TG) microbial biomass C (BC), and ninhydrin-reactive N (BNIN). Finally, from TG, derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) thermal stability parameters were deduced. Humification parameters in the end products (0.2 and 81% for HI and DH, respectively) showed the effective stability reached by the organic matter (OM). Thermal analysis evidenced the presence of two main organic pools with different thermal stability. During composting a relative increase in the more stable organic pool was indicated by the variation of the thermostability index R1 from 0.41 to 0.74. The parameter R1 was significantly correlated with both HI (r = −0.94; P < 0.05) and DH (r = 0.97; P < 0.05). Microbial biomass content dynamics reflected the availability of readily decomposable substrates. The ratio between BNIN and total N in the end product was 0.96%, indicating a good stability level. The simultaneous application of different approaches, considering different properties of composting materials, provides a more complete description of the stability and quality reached by the organic materials.

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