Session- Analytical Methods I
Solid-state 13C-NMR Studies of Composting of Agricultural, Industrial and Municipal Solid Waste
Yona CHEN
Dept. of Soil and Water Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Israel
Compost maturity or stability reflects the degree of decomposition of the OM. Since stability of natural OM is a relative term, defining it is not a trivial challenge. In addition, it requires a series of chemical, physico-chemical and spectroscopic determinations. Among the methods applied, 13C-NMR and FTIR (or DRIFT) have been shown to be of significance and therefore this review will be dedicated to studies focusing on the application of these methods to composting research. In fact, solid-state 13C-NMR spectroscopy has become the most important tool for examining the chemical structure of natural organic matter (NOM) and the chemical changes associated with OM decomposition. Changes can be measured on the bulk OM either fresh or composted, on humic substances (HS) extracted from the compost or on dissolved organic matter (DOM). Recently, 2D 1H NMR has been employed to study properties of HA extracted from MSW compost. In general, changes measured on decomposing OM are more distinct in the following order of tested materials: DOM > Bulk OM > HS > Core HS. In conclusion, compost HS which are young relative to soil HS were shown to differ from the latter mostly in their high levels of aliphatic and polysaccharide components, which tend to decompose during composting. 13C-NMR is the most effective instrument applied to-date to structural studies of NOM.
Evaluation of Compost Maturation and Quality Using Near Infrared Spectroscopy (NIR)
EDWARD JOHANSSON, Anders Brundin
Bedminster AB, Stora Vika, Sweden
Throughout the whole process of aerobic composting of municipal solid waste (MSW), the physical and chemical properties of the compost changes. This is valid for the period in the composting drum as well as during the compost maturation period. By using near infrared spectroscopy (NIR) in combination with multivariate analysis we have shown that it is possible to evaluate quality parameters of the compost. NIR spectroscopy detects overtone vibrations of molecules and light scattering effects of particles, and can therefore detect composition changes in the compost. From changes in the spectra it was possible to make calibration models for different purposes. It was thereby possible to evaluate e.g. maturation, water content and particle size of the compost.
Inoculum Standardization and Storage Affect Community Level Physiological Profiles of Compost Samples
MONDINI C.(1);Insam H.(2)
(1) Experimental Institute for Plant Nutrition, division of Gorizia (Italy); (2) Institute of Microbiology, University of Innsbruck (Austria)
The potential of Community Level Physiological Profiles (CLPPs) as a compost stability test is significant, given the sensitivity and the simplicity of the assay. Nevertheless, application of the technique to compost requires more methodological work because of the fast changes in physico-chemical and microbiological properties and the dependence of the rate of colour development on the inoculum density. The aim of this work was to investigate the reliability of a new approach to standardize inoculum density and the effect of storage on CLPPs of compost samples with different degree of stabilization. Compost samples (fresh, air dried, frozen and air dried-rewetted) were extracted with a two-batch procedure and then inoculated on Biolog Ecoplates. Standardization of inoculum density was performed according to microbial biomass content determined by substrate induced respiration (SIR) on fresh samples. Microplates were incubated at 30 C in the dark and optical density (OD) was measured at 592 nm every 8 hours for 7 days. Principal component analysis (PCA) was performed on various data set: OD values at fixed average well colour development (AWCD), kinetic parameters and area under the OD curve as a function of time. PCA of fresh samples showed that classification and ordination of samples according to their age were satisfactory with fixed AWCD and area under the curve data sets, suggesting the reliability of SIR for the standardization of inoculum density. These results support the most universally applicable approach to data collection, implying approximate standardization of inoculum density and continuous plate reading, but, at the same time, underline the importance of the data set construction for PCA analysis. Ordination patterns obtained from air dried samples showed a good resemblance with those obtained from fresh ones, suggesting that analyses aimed to evaluate the degree of compost stability could be successfully performed on samples with low water content.
Compost quality assessment and process control by Fourier Transform Infrared-Spectroscopy
Ena SMIDT (1), Peter Lechner (1)
Infrared spectroscopic investigations in the mid-infrared area of different waste materials revealed the possibilities of this tool for both product and process control. The spectrum of a sample offers a detailed insight in the state of organic matter and its development. Increase and decrease, the appearance and disappearance of distinct bands, which represent relevant functional groups, reflect the metabolic process. Spectral characteristics include the information about the fate of inorganic compounds and their relation to organic matter. The content of mineral components influences composting and stabilization processes. Changing relative absorbances of bands indicate the progress of a composting process. Dynamics and kinetics of processes can be investigated by calculating relative absorbances of selected bands. Spectra of a composting process in a biowaste outdoor plant will be presented. Spectral characteristics of the complete sample were compared to conventional parameters. Beside qualitative interpretation of the spectrum decomposition and stabilization were assessed by relative absorbances of relevant bands. This process was faced to an other composting process by comparing relative absorbances of the methylene band. Different slopes of its decrease demonstrated various developments that were also confirmed by conventional parameters. The nitrate concentration was determined by KNO3 addition to the waste material and calibration with relative absorbances of the nitrate bands. Spectra were also made from eluates and extracted precipitated humic acids. Spectroscopic investigations of the eluates were useful for the identification of some bands. IR-spectra of humic acids indicated changes during the composting process.