Compostagem de esterco de galinha: composiÃÃo quÃmica da matÃria orgÃnica e extraÃÃo de substÃncias hÃmicas / Chicken manure composting: organic matter composition and humic substances extraction

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The agro-industrial activities are responsible for the generation of large amounts of organic waste, and composting is an efficient process for the treatment of such waste; humification degree is an important parameter for determining the quality of the compost produced. This study aims to evaluate the dynamics of humification of organic matter during composting of chicken manure, by using several chemical and spectroscopic analysis (Infrared â IF-TR; nuclear magnetic resonance â NMR), and alkaline solutions to extract humic compounds formed during composting and, the nutrients contents in the humic extracts. Three mixtures were prepared by mixing chicken manure with different structuring agents, such as: charcoal, coffee husk and sawdust originating from the furniture industry. The materials mentioned were mixed in the proportion of 1:1 (fresh weight), and subsamples were collected from each waste after 0, 30, 60, 120 and 210 days after compost incubation. Evaluating the effects of structuring agents in the degradation of organic matter and in the process of humification, it was verified that, despite the inert nature of biochar, the composting mixture prepared with this agent underwent an organic matter degradation of 70% of its initial content. The chemical nature of organic matter of the poultry manure-biochar mixture is characterized by a high polymerisation degree of the humic-like substances, with a relative high proportion of humic acids in relation to fulvic acids. At the end of the composting process, the humic acid fraction represented more than 90% of the alkali extractable fraction, reflecting the intense humification of this material. Enrichment of poultry manure with biochar reduces the nitrogen loss in the mature composts, although the use of wood sawdust would be more efficient in preserving the organic matter and nitrogen in the mature compost. Thermogravimetry showed an increase in the humic materials resistance to termodegradation with increasing humification. The infrared spectra showed the presence of aliphatic, aromatic, phenolic-OH, carboxylic and carbohydrates. Increases were observed in the absorption related to the aromatic groups and a decrease in the carbohydrate for the samples of organic compounds, especially for the mixture of chicken manure with charcoal. The 13C NMR spectroscopy indicated a small increase in the content of aromatic groups and a decrease in aliphatic content during the composting process. In the study conducted to evaluate the potential for extraction of humic substances in organic compounds, it was found that, in general, the extractor KOH, in the concentration 0.5 mol L-1 presented the highest efficiency in the humic substances extraction for all the organic composts analyzed. Increase of the concentration of KOH and NaOH extractants affects the ratio C-HAF/C-FAF, and both the extractants favor the increase in the humic acid contents in relation to the fulvic acid extracted due, probably, to increased solubilization of humic acids. None of the three evaluated concentrations of NaOH solution was efficient in extracting the humic substances present in the organic waste/composts studied. The higer contents of nutritients were found in the poultry manure composite with coffee husk, however, the chemical elements contents varied for each extractor, not being possible to identify which alkaline solution enables the higher humic extract enrichment in nutrients.

ASSUNTO(S)

carvÃo humification index biochar ft-ir ft-ir chemical extractors ciencia do solo extratores quÃmicos termodegradaÃÃo termodegradation Ãndice de humificaÃÃo rmn 13c 13c nmr

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