P.L. Genevini

Organic Matter Evolution Index (OMEI) as a Measure Of Composting Efficiency

The significance of the organic matter evolution index (OMEI) related to the composting process degree was tested on a full-scale windrow process for 239 days. Analytical data from many samples collected during the process and kinetics were in agreement regarding the insufficient degree of stability and maturity reached by the compost obtained. As expected, the OMEI at the end of the process was low (OMEI = 0.46) confirming its validity to composting degree evaluation. New analytical methods for humic substances quantification were developed by monitoring humic acids concentration versus composting time and ligno-humic fraction.

A New Index of Organic Matter Stability

A new organic matter stability index (S.I.) has been developed determining the humic acid content in samples of compost, both as they stand and when subjected to treatment with apolar and polar solvents and acid hydrolyses for the purpose of eliminating substances (pseudo-humic substances) that interfere with analytical determination of the same. The index, which registers values between zero and one, easily relates to the degree of stability and maturity of organic matter. Checks on the reliability of the index when applied to 10 different types of organic matrices have confirmed its usefulness for direct measurement of the degree of stability (SI > 0.6) and maturity (SI > 0.8) of organic matter, as well as the effectiveness of the analytical method proposed for determining the humified fraction content in organic matter, as a means of obtaining more realistic values, especially in the case of immature substrates.

Respiration Index Determination: Dynamic And Static Approaches

Forty-five organic matrices of different types and origin were subjected to the test for the determination of biological stability by means of dynamic respirometric measurement (DRI) and static respirometric measurement (SRI). The results obtained from the comparison between the two indexes indicated that the SRI, compared with the DRI, underestimates the consumption of oxygen by the biomasses and consequently their rate of biological stability by a factor equal to 2. From the analysis of the data it is possible to define the biological stability as DRI<1000 mgO2kg−1VSh−1. The DRI data were correlated with the temperatures of the biomasses showing a linear correlation (R2=0.81, p<0.01) only for stable matrices while for nonstable matrices no significant correlation is found.

Composting And Humification

The development of humic substances in the course of four composting processes was monitored quantitatively, recording both relative and absolute contents. Relative data showed contrasting results if the humic substances (HS) were related to the dry matter (d.m.) or to volatile solids (VS). Humic substances were apparently formed because of a concentration effect due to organic matter degradation. If absolute contents were considered, a decrease in the humic substances was observed, above all in the early stages of the process, due, probably, to degradation of the organic material, such as proteins, carbohydrates and lipids, coextracted with the humic substances. Processing of the data in respect of humic substance content over 13 composting processes and one study on the degradation of plant residues in soils, confirmed that no net humic substances are formed during composting and that the humification should be interpreted merely as degradation of the organic matter associated with the humic substances,...

Heavy Metal Content in Selected European Commercial Composts

Thirty commercial composts from biogenic wastes and raw materials from vegetable fruit gardens (VFG) were analyzed for heavy metal content. Results obtained were discussed with respect to metal contents for composts from municipal solid waste (MSW), composts from MSW source separation and literature green composts, and the limits for heavy metal contents stipulated by European laws. The data obtained showed that, except for Cd content, the majority of the composts analyzed including MSW source separation and green composts could be considered as compost of very high quality or high quality. At the same time, the majority of composts analyzed must be classified as being contaminated compost or compost of low quality on the basis of their Cd contents. The results suggest that for these composts cadmium contamination of raw materials defined the compost quality and that the legal limits suggested for this trace element should be reviewed.

Evolution and qualitative modifications of humin-like matter during high rate composting of pig faeces amended with wheat straw

Abstract During a 4-week period of composting of wheat straw-amended pig faeces, humin (HU)- and core-HU-like matter were isolated by NaOH-Na4P2O7 treatment of the compost bed, respectively, without and with previous extraction by organic solvent and by H2SO4. The changes in the content and elemental composition of both fractions in the compost bed were monitored. Evidence of the compositional changes was also obtained by NMR spectroscopy and by pyrolysis-GC / MS studies. The results indicated that core-HU-like matter was mainly aromatic, while HU contained both core-HU-like and other types of easily degradable organic matter. Correlation of the data found in this study with data from previous studies on humic acid (HA)- and core-HA-like matter in the same composting process indicated that in the time range from 2 to 4 weeks, the weight loss of the core-HU-like matter amounted to 788 g, whereas the weight of total core-HA-like matter increased by 87 g. In spite of the high weight loss, the NMR and pyrolysis-GC / MS spectra failed to reveal significant changes in the chemical nature of the core-HU-like residue. However, the chemical composition of the core-HA-like matter changed significantly and tended to become similar to that of the core-HU-like matter when the composting time increased. The data suggest that, during composting, core-HU-like matter undergoes both conversion to new core-HA-like soluble matter and biodegradation to volatile products.

Chromium ions toxicity on the membrane transport mechanism in segments of maize seedling roots

Abstract Chromium ions affect the proton extrusion and the potassium uptake capacity in segments of maize seedling roots. The hypothesis that these effects can explain the chromium ions toxicity in plants is discussed.

Effect of nickel on proton extrusion in segments of maize seedling roots

Abstract Nickel affects the proton extrusion capacity in segments of maize seedling roots; as in the field condition, this effect is enhanced by phosphate and counteracted by Ca++ and Mg++. The effect of nickel on the proton‐extruding activity can explain either nickel toxicity and its stimulating effect on plant growth. Such hypothesis is discussed in this paper.

Dairy Cattle Slurry and Rice Hull Co-composting

A liquid dairy cattle slurry was composted using rice hull as absorbing matrix and bulking agent. The main results obtained were as follow: 1) The structure and size of rice hulls as well as their absorption capacity, made it possible to obtain a good compo sting mixture (moisture: 71.42 %; C/N ratio: 28.80 %; bulk density: 0.429 kg / dm3) 2) The compost stability was reached after 56 days of composting, obtaining the follow data (% D.M.): ignition loss: 73.00: C/N: 18.36; TKN: 1.98; K: 1.84; P: 1.13; humified carbon: 4.60; respirometric index: 0.88 mg O2/gVS x h; dry matter yield: 57.34 %; organic matter yield: 50.05 %, water losses: 56.99 %; airflow-rate: max: 2.96 m3/kg D.M. x day., min: 0.28 m3/kg D.M., men 0.75 m3/kg D.M.. 3) The curing phase determined as aspected the reaching of a high compost maturity degree. After 256 composting days the data obtained (% D.M.): ignition loss: 65.89; C/N: 13.52; TKN: 2.51; K: 2.00; P: 1.27; humified carbon: 10.81; dry matter yield: 46.36 %; organic matter yield: 36.91 %, water losses: 63.99 %. 4) As shown by the organic matter yield, the mixture presented high degradability, in contrast to the literature (Chino et al., 1983). This can be explained by the composting temperature obtained (30 –45 °C) wich permitted high cellulose-like material degradation. 5)The compost data obtained, suggests that two marketable products are obtained: the first after 56 composting days, utilizable in field applications, and the second after 254 days, as substitute for organic substrata (e.g., peat) in greenhouses and on sensitive plants.