No abstract

In Mediterranean areas, olive mill wastes pose a major environmental problem owing to their important production and their high polyphenolic compounds and organic acids concentrations. In this work, the evolution of polyphenolic compounds was studied during co-composting of olive mill wastewater sludge and poultry manure, based on qualitative (G-50 sephadex) and quantitative (Folin-Ciocalteu), as well as high pressure liquid chromatography analyses. Results showed a significant polyphenolic content decrease of 99% and a noticeable transformation of low to high molecular weight fraction during the compost maturation period. During this step, polyphenols disappearance suggested their assimilation by thermophilic bacteria as a carbon and energy source, and contributed to humic substances synthesis. Polyphenolic compounds, identified initially by high pressure liquid chromatography, disappeared by composting and only traces of caffeic, coumaric and ferulic acids were detected in the compost. In the soil, the produced compost application improved the chemical and physico-chemical soil properties, mainly fertilising elements such as calcium, magnesium, nitrogen, potassium and phosphorus. Consequently, a higher potato production was harvested in comparison with manure amendment.

Purpose The most important factor affecting soil quality is soil humic fraction. Effects of adding carbon in soil humic compounds in arid environments have only been slightly investigated. The change in soil humic acids' structures in relation with manure and palm compost application and the evolution of humic acids' structures during palm composting have not been sufficiently investigated. The purpose of this study is to evaluate if date palm compost is suitable for the sustainable increase of soil carbon content with increasing soil humic compounds. Methods Soil was amended with date palm compost and sheep manure, which represented two treatments, in addition to a control represented by unamended soil. Soil samples were taken from depth layers of 0-20 cm and 20-40 cm. Physicochemical and spectroscopic analyses were used to study humic acids extracted from organic amendment and soil. Results The neutral pH and the C/N ratio of 11.9 revealed that the palm/manure compost was mature. Date palm compost application on soil showed its effectiveness in improving soil quality. Spectroscopic studies of humic compounds extracted from date palm compost and manure, showed the abundance of aromatic structures, confirmed by the low E4/E6 ratio associated with an increase in polycondensation and polymerization. Infrared spectroscopy of humic acids extracted from amended soil revealed its enrichment with aromatic structures. Conclusions Using date palm compost for a short term suggests that this compost may be useful as an alternative to increase the soil fertility by increasing the humic acids quantity with enhancing aromaticity degree and functional groups.

In order to increase organic matter availability, date palm waste was co-composted with goat manure according to an industrial ecological approach for a sustainable development. During the composting process, the organic matter biodegradation and compost quality were controlled using physico-chemical and biological parameters associated to spectroscopic techniques. To promote the composting process, date palm waste was previously water soaked in basin for 5 days and the resulted wastewater was used to humidify the windrow. The results showed a rapid temperature increase during the first 6 days and a relatively long compost maturity phase. Organic matter content was reduced by 36% and C/N ratio shifted from 60 to 20 at the process end that held 6 months. The microbial activity and the germination index exceeding 80% indicated respectively the compost stability and its phytotoxicity lack. UV-visible spectra confirmed the organic matter biodegradation by the SUVA 254 , SUVA 269 and SUVA 280 values increase. During the process, the fourier transform infrared spectroscopy (FTIR) analysis of the different collected samples showed qualitatively similar spectra differing in the absorbance bands intensity, proving the organic matter 1 biodegradation and mineralization. A total of 12 fluorescence excitation emission matrixces of composts were successfully decomposed into a four-factor model using PARAFAC analysis. For the 4 main evidenced components, the excitation/emission (Ex/Em) wavelengths were of 350/450 nm, 400/500 nm 450/530 nm and 325/400 nm attributable respectively to humic-like and fulvic-like substances.

No abstract