Roberto Altieri

Olive orchard amended with two experimental olive mill wastes mixtures: Effects on soil organic carbon, plant growth and yield

Amendments of olive orchard soil with two different preparations of olive mill solid waste (OMWMs) at the rate of 9tonha(-1) per year for five years in two different plots were compared with an industry standard soil amendment using urea. Both the OMWMs amendments showed significant increases in total organic carbon and humic substances in soil of approximately 40% and 58%, respectively, without negative effects on tree growth and yield. This work has shown that olive oil mill waste (OMW) can be recycled safely using the bioremediation system used in this study. We suggest that this system is particularly beneficial to organic farming and is an alternative solution to direct spreading of raw OMW on farm lands.

Two-phase olive mill waste composting: community dynamics and functional role of the resident microbiota.

In this study, physico-chemical modifications and community dynamics and functional role of the resident microbiota during composting of humid husk from a two-phase extraction system (TPOMW) were investigated. High mineralization and humification of carbon, low loss of nitrogen and complete degradation of polyphenols led to the waste biotransformation into a high-quality compost. Viable cell counts and denaturing gradient gel electrophoresis (DGGE) profiling of the 16S rRNA genes showed that the thermophilic phase was characterized by the strongest variations of cell number, the highest biodiversity and the most variable community profiles. The isolation of tannin-degrading bacteria (e.g. Lysinibacillus fusiformis, Kocuria palustris, Tetrathiobacter kashmirensis and Rhodococcus rhodochrous) suggested a role of this enzymatic activity during the process. Taken together, the results indicated that the composting process, particularly the thermophilic phase, was characterized by a rapid succession of specialized bacterial populations with key roles in the organic matter biotransformation.

Complexation capacity of dissolved organic matter from pig slurry: a gel filtration and dialysis study

The purpose of this research was to evaluate the apparent molecular weight distribution of dissolved organic matter (DOM) from pig slurry and the binding ability of its fractions toward copper (Cu2+) ions. In addition, the binding ability (maximum complexing capacity – MCC) of the DOM was compared with that of humic (HA) and fulvic (FA) acids from a clay-loam soil. The study was performed using Cu2+ ions since this metal is widely used as a supplement in pig diets and, consequently, is present in pig slurry. The techniques adopted were gel filtration chromatography (GFC) and dialysis. GFC showed that the DOM from pig slurry is mainly composed of a fraction with an apparent molecular weight higher than 5000 Da and the copper naturally present in the slurry is completely complexed by this fraction. The dialysis procedure enabled MCC to be determined. The MCC of pig slurry DOM and soil HA, which contained a similar concentration of carboxylic groups, were analogous, while MCC of soil FA, which contained double the concentration of carboxylic groups, was higher.

Effects of amendment with olive mill by-products on soils revealed by nitrifying bacteria

We investigated the effect of amending soil with olive mill by-products by examining soil characteristics and nitrifying and heterotrophic bacteria content, in comparison with non-amended soils. The effect of the amendment on organic carbon content was also evidenced. No differences were revealed in terms of heterotrophic bacteria, whereas the addition of olive mill by-products increased nitrifying bacteria content in soils with the addition of organic mixtures containing olive mill wastes. Two nitrifying bacterial strains were isolated from amended soils and given the names ISAFOM-B3 and ISAFOM-C2; 16S rDNA gene sequencing assigned them to the genus Arthrobacter and to the α-Proteobacteria subclass, respectively. A higher nitrate content was revealed in enrichment cultures prepared with amended soils when compared to non-amended ones. Nitrifying bacteria were imaged by fluorescent in situ hybridisation. A high total organic carbon content was detected in the amended soils, with an improvement of the humification indexes. This study suggests a positive effect of the addition of olive mill by-products on soils.

Measuring the Biodegradability of Plastic Polymers in Olive-Mill Waste Compost with an Experimental Apparatus

The use of biodegradable polymers is spreading in agriculture to replace those materials derived from petroleum, thus reducing the environmental concerns. However, to issue a significant assessment, biodegradation rate must be measured in case-specific standardized conditions. In accordance with ISO 14855-1, we designed and used an experimental apparatus to evaluate the biodegradation rate of three biopolymers based on renewable resources, two poly(-caprolactone) (PCL) composites, and a compatibilized polylactic acid and polybutyrate (PLA/PBAT) blend. Biodegradation tests were carried out under composting condition using mature olive-mill waste (OMW) compost as inoculum. Carbon dioxide emissions were automatically recorded by infrared gas detectors and also trapped in saturated Ba(OH)2 solution and evaluated via a standard titration method to check the results. Some of the samples reached more than 80% biodegradation in less than 20 days. Both the experimental apparatus and the OMW compost showed to be suitable for the cases studied.