Olive Mill Solid Waste Research Articles

Mathematical modeling of olive mill waste composting process

The present study aimed at developing an integrated mathematical model for the composting process of olive mill waste. The multi-component model was developed to simulate the composting of three-phase olive mill solid waste with olive leaves and different materials as bulking agents. The modeling system included heat transfer, organic substrate degradation, oxygen consumption, carbon dioxide production, water content change, and biological processes. First-order kinetics were used to describe the hydrolysis of insoluble organic matter, followed by formation of biomass. Microbial biomass growth was modeled with a double-substrate limitation by hydrolyzed available organic substrate and oxygen using Monod kinetics. The inhibitory factors of temperature and moisture content were included in the system. The production and consumption of nitrogen and phosphorous were also included in the model. In order to evaluate the kinetic parameters, and to validate the model, six pilot-scale composting experiments in controlled laboratory conditions were used. Low values of hydrolysis rates were observed (0.002841/d) coinciding with the high cellulose and lignin content of the composting materials used. Model simulations were in good agreement with the experimental results. Sensitivity analysis was performed and the modeling efficiency was determined to further evaluate the model predictions. Results revealed that oxygen simulations were more sensitive on the input parameters of the model compared to those of water, temperature and insoluble organic matter. Finally, the Nash and Sutcliff index (E), showed that the experimental data of insoluble organic matter (E>0.909) and temperature (E>0.678) were better simulated than those of water.

Micronutrient dynamics after thermal pretreatment of olive mill solid waste

This study investigated metal dynamics, and their bioavailability, before and after thermal pretreatment of olive mill solid waste (OMSW), using a sequential metal extraction scheme. The 11.5% increase of cobalt in the most available fraction after the pretreatment coupled to the increase of methane production rate have been a good indicator that the OMSW anaerobic digestion might be metal limited due to the lack of cobalt.

Performance of a household boiler fed with agropellets blended from olive mill solid waste and pine sawdust

Abstract The main purpose of this present work is to study the combustion characteristics of a domestic boiler (12 kW) when fired with biofuels prepared by blending an industrial by-product (pine sawdust, PS) and an agro-industrial by-product (Olive Mill Solid Waste, OMSW). The boiler and combustion efficiencies as well as gaseous emissions were determined and compared to EU normalization standards (EN 303-5). It was found that the main exhaust gases (CO, CO 2 C x H y and NO x ) are emitted in acceptable concentrations comparing to other biofuels in the literature. The analysis of bottom ash compositions shows the presence of three oxides, namely CaO, K 2 O and SiO 2 as well as a significant amount of unburned carbon. Hence, the boiler control through the primary and secondary air injections should be adapted to the different pellets properties. Additionally, both combustion efficiency and boiler efficiency results are encouraging for considerations of prepared agropellets as alternatives to woody biofuels.

Plant Growth Promoting Rhizobacteria: Mechanism and Current Prospective

Despite the phytotoxicity of olive-mill solid waste (OMSW) due to its high polyphenols content, OMSW have fertilizer characteristics, which make it a potential source for organic fertilization. Composting of OMSW treatment process was conducted in this study to eliminate the phytotoxicity and solve the environmental impact of this waste. Recycling of OMSW was carried out via composting of six batches of trials using equal proportions of OMSW, cow manure (C) and wheat straw (W). The treatment process was performed at two time intervals (two and five months), after each one, the recipient species (Vicia faba L.) was planted. The results showed the efficiency of composting in reducing OMSW original toxicity after two months than five months. The germination percentage and the plumule and radicle lengths of V. faba showed a significant improvement when the OMSW was composted with C at different proportions before using as soil amendments. Besides, the total biomass was noticeably increased at the high concentration of C-OMSW. Similarly, the total pigments concentration in V. faba was increased by using various composts after two months, where the highest pigment content was observed at 40% W-OMSW treatment. The maximum uptake of potassium and sodium was recorded through the application of W-OMSW compost to soil after two months. Furthermore, the C-OMSW composts showed the highest concentration of nitrogen, calcium, iron and manganese. However, the C-W-OMSW composts recorded the highest concentration of phosphorous, magnesium and copper. Finally, this study developed a low cost treatment that will enable the growers to convert OMSW into a natural nontoxic compost rich with essential nutrients which have positive effects on plants growth.

Detoxification of Olive-mill Solid Waste and its Probable Application as Organic Fertilizer

Despite the phytotoxicity of olive-mill solid waste (OMSW) due to its high polyphenols content, OMSW have fertilizer characteristics, which make it a potential source for organic fertilization. Composting of OMSW treatment process was conducted in this study to eliminate the phytotoxicity and solve the environmental impact of this waste. Recycling of OMSW was carried out via composting of six batches of trials using equal proportions of OMSW, cow manure (C) and wheat straw (W). The treatment process was performed at two time intervals (two and five months), after each one, the recipient species (Vicia faba L.) was planted. The results showed the efficiency of composting in reducing OMSW original toxicity after two months than five months. The germination percentage and the plumule and radicle lengths of V. faba showed a significant improvement when the OMSW was composted with C at different proportions before using as soil amendments. Besides, the total biomass was noticeably increased at the high concentration of C-OMSW. Similarly, the total pigments concentration in V. faba was increased by using various composts after two months, where the highest pigment content was observed at 40% W-OMSW treatment. The maximum uptake of potassium and sodium was recorded through the application of W-OMSW compost to soil after two months. Furthermore, the C-OMSW composts showed the highest concentration of nitrogen, calcium, iron and manganese. However, the C-W-OMSW composts recorded the highest concentration of phosphorous, magnesium and copper. Finally, this study developed a low cost treatment that will enable the growers to convert OMSW into a natural nontoxic compost rich with essential nutrients which have positive effects on plants growth.

Detoxification of Olive-mill Solid Waste and its Probable Application as Organic Fertilizer

Detoxification of Olive-mill Solid Waste and its Probable Application as Organic Fertilizer

Efficacy of olive oil mill extract in replacing sulfur dioxide in wine model

Olive oil industry produces high amounts of olive mill solid waste. These have been described as natural source of hydroxytyrosol, which shows high antioxidant and antimicrobial properties joint to health-promoting effects. In the present work, an olive mill solid waste extract dissolved in model wine was evaluated to determine its potential capacity to replace and/or reduce sulfur dioxide in winemaking. Olive oil mill extract is a potent antioxidant of biological origin. The extract resulted in 4 and 40 mmol/L Trolox/mg extract by DPPH and ORAC respectively. Its antimicrobial activity was approaching to that of SO2 for Hanseniaspora uvarum, Candida stellata, Lactobacillus plantarum, Pediococcus damnosus and Acetobacter aceti, higher for Oenococcus oeni and lower for Dekkera bruxellensis and Botryotinia fuckeliana.Additionally, GC-olfactometry analysis showed that the most important odorants from the extract are naturally present in wines. However, some odorant zones might be significantly increased in wine after extract addition.It can be concluded that olive mill solid waste extracts is a source of bioactive compounds of low cost, with high antioxidant activity and good antimicrobial properties.

Selection of management option for solid waste from olive oil industry using the analytical hierarchy process

This paper considers the process of selecting a appropriate olive mill solid waste management option in Jordan. Six alternatives were found to be possible options for olive mill solid waste management. Those alternatives are: animal feed, energy recovery, extraction of useful materials, co-combustion, fertilizers, and disposal without treatment. Prioritization of these six alternatives was performed through the analytical hierarchy process. Management options were prioritized based on three criteria: environmental effects, economical benefits, and the technology involved. Priorities given to each of criteria were evaluated through soliciting experts and olive mills owners opinions. Analytical hierarchy process model results revealed that co-combustion option is most favorable followed by the animal feed alternative and lease favorable is disposal without treatment. Sensitivity of the proposed analytical hierarchy process model was addressed as the priorities may change. Model sensitivity analysis showed that our model decision is robust to moderate changes in priorities. Unless the environmental criteria given a very high priority, co-combustion remains as the most favorable management option.

Production and characterization of biochar from three-phase olive mill waste through slow pyrolysis

The influence of temperature and heating rate on the yield and properties of biochar derived from pyrolysis of solid olive mill waste (pomace) was investigated. Three pyrolysis temperatures (430 ± 10 °C, 480 ± 10 °C and 530 ± 10 °C) and 3 heating rates (25 °C min−1, 35 °C min−1 and 45 °C min−1) were studied. The biochar production was carried out using a vertical downdraft gasifier. Increasing the pyrolysis temperature, and/or the heating rate, the biochar yield lowered, the C content and biochar aromaticity increased and the surface functional groups were reduced. The highest biochar yield was obtained by low pyrolysis temperature (430 ± 10 °C) and low heating rate (25 °C min−1). This biochar is characterized by a high heating value (31 MJ/kg) that makes it a possible fuel candidate and, in the meantime, due to its high concentration in C (70.2%–84.1%), low electrical conductivity (0.28 dS m−1–0.47 dS m−1) and the lack of phytotoxicity it is suitable for amendment in agricultural soils and for long term carbon sequestration.

Characterization and modeling of pyrolysis of the two-phase olive mill solid waste

In this work, first, the two-phase olive mill solid waste was characterized in terms of its physical–chemical properties, which can be useful for its use in pyrolysis units. Then, its behavior on pyrolysis processes was studied by dynamic thermogravimetry and derivate thermogravimetry. For the simulation of pyrolysis processes a kinetic model including three independent parallel reactions was used. The characterization results showed that the solid presents a size distribution with about 66% of particles >1.00mm, while the percentage of fines (<0.250mm) is only of 1.50%. The moisture content is very high (around 70%), being one of the main characteristics of the solid that makes its direct use as a fuel difficult. However, the low sulfur value (<0.1%) is very suitable from the environmental point of view, reducing SO2 emissions. The results of the proximate analysis are within the range of most biomass waste and the gross calorific value obtained was 4897kcal/kg. The thermal decomposition in an inert atmosphere can be modeled by separate decomposition of each of the three fractions which constitute the material. The results of both, physical–chemical characterization and thermogravimetric study show that the two-phase olive mill solid waste could be treated in energy recovery installations.

Composting of three phase olive mill solid waste using different bulking agents

Pilot-scale experiments were carried out to produce good quality, low-cost composting technology from three phase olive mill solid waste (olive pomace, OP) using rice husk (RH) and olive leaves (OL) as bulking agents. A series of parallel experiments was carried out to examine the effect of: (a) initial moisture content, (b) water addition during the composting process, and (c) material ratios. To monitor the composting process and evaluate compost quality, physicochemical parameters (temperature, moisture content, pH, electrical conductivity, organic matter, volatile solids, total organic carbon, total nitrogen, total phosphorus, potassium, sodium, and water soluble phenols) were measured at different phases of the composting period. Experimental results showed that even after short composting periods, the quality of the final product remained high. To achieve higher quality of the final product, OP should be used in higher quantities than the other two materials (OL and RH). A full-scale compost unit was designed based on the experimental results. For a typical small-sized olive mill, processing 30 tonnes of olives per day for a 90 days operation period, a total area of about 500 m2 is needed to compost the mill's entire waste production.

Assessment of two-phase olive mill solid waste and microalgae co-digestion to improve methane production and process kinetics

Olive mill solid waste (OMSW) is a pollutant waste coming from olive oil elaboration by the two-phase centrifugation system. OMSW has a high organic matter content and unbalanced carbon to nitrogen (C/N) ratio, 31/1, which avoids obtaining high methane yields in the anaerobic digestion of this waste. In the present study a microalgae, Dunaliella salina, was employed as co-substrate for the OMSW anaerobic digestion in order to decrease the C/N ratio and increase its biodegradability. Different co-digestion mixtures (C/N ratios) were studied. The increase of D. salina from 25% to 50% in the co-digestion mixture clearly increased the biodegradability of the sole substrates. The highest biodegradability was found for the co-digestion mixture 50% OMSW-50% D. salina. Nevertheless, the maximum methane production, 330mLCH4/gVSadded, and the highest methane production rate were obtained for the co-digestion mixture 75% OMSW-25% D. salina, keeping a C/N ratio near to 26.7/1.

RECENT STUDIES ON PREPARATION OF HUMIFIED COMPOST USING OLIVE MILL WASTE FOR HORTICULTURAL PURPOSES

This paper is a brief review of recent studies on the feasibility of using olive mill solid waste (OMW) as a major ingredient in the preparation of humified compost (HC), and the application of the HC to soil on the growth of horticultural crops such as Olea europaea (olive), Lycopersicon esculentum (tomato), Lactuca sativa (lettuce), Fragaria vesca (strawberry) and Agaricus bisporus (white button mushroom). OMW-based compost subjected to thermal composting process resulted in significant decrease in the level of polyphenols making it non-phytotoxic. Addition of the compost to olive orchard soil significantly increased total organic carbon and humic substances by 40 and 58% respectively. Similar results on elevated nutritional status and enhanced crop productivity were obtained in trials with other horticultural crops and the cultivated mushrooms. The outcomes of these studies have been the integration of soil health and environmental management practices to achieve sustainable crop production.

Effect of ultrasonic pretreatment on biomethane potential of two-phase olive mill solid waste: kinetic approach and process performance.

The effect of ultrasound (US) pretreatment on two-phase olive mil solid waste (OMSW) composition and subsequent anaerobic biodegradation was evaluated by chemical oxygen demand solubilization and biochemical methane potential (BMP) tests. OMSW was ultrasonically pretreated at a power of 200 W and frequency of 24 kHz for time periods of 20, 40, 60, 90, 120, and 180 minutes, corresponding to specific energies of 11367, 21121, 34072, 51284, 68557, and 106003 kJ/kg total solids, respectively. In order to evaluate the US pretreatment, a low, medium, and high exposure time, that is, 20, 90, and 180 min, were selected for BMP tests. Methane yields of 311 ± 15, 393 ± 14, and 370 ± 20 mL CH4/g VSadded (VS: volatile solids) were obtained for 20, 90, and 180 minutes, respectively, while the untreated OMSW gave 373 ± 4 mL CH4/g VSadded. From a kinetic point of view, the BMP tests showed a first exponential stage and a second sigmoidal stage. In the first stage, the kinetic constant obtained for US pretreated OMSW at 20 minutes was 46% higher than those achieved for the pretreated OMSW at 90 and 180 minutes and 48% higher than that for untreated OMSW. The maximum methane production rate achieved was 12% higher than that obtained for untreated OMSW.

Potential of bioethanol production from olive mill solid wastes

The main objective of this study was to screen endogenous microorganisms grown on olive mill solid wastes (OMSW) with the potential to ferment pentoses and produce ethanol. Two yeasts were isolated and identified as Issatchenkia orientalis, and Pichia galeiformis/manshurica. The adaptation of the strains displayed a positive impact on the fermentation process. In terms of xylose utilization and ethanol production, all strains were able to utilize xylose and produce xylitol but no ethanol was detected. Separate hydrolysis and fermentation process on hydrolysate undergo detoxification, strain I. orientalis showed the best efficiency in producing of ethanol when supplemented with glucose. Using simultaneous saccharification and fermentation process following pretreatment of OMSW, the average ethanol yield was 3 g/100 g dry OMSW. Bioethanol production from OMSW is not economic despite the raw material is cheap.

Mesophilic Fermentation of SOMW in a Micro Pilot-Scale Anaerobic Digester

One of the most promising processes to exploit Solid Olive-Mill Waste (SOMW) for energy production is anaerobic digestion. An experimental study has been carried out on SOMW and inoculum, consisting of Cattle Slurry Digested (CSD) and coming from an anaerobic digestion plant. A substrate with an optimal supply ratio equal to 2:1 has been investigated in a reactor at 37°C by analysing the biogas production. The Biochemical Methane Potential (BMP) test has been carried out, monitoring pH, biogas production (amount and composition). According to the tests results, SOMWs needed to be diluted and inoculated, moreover the pH control is foundamental in order to obtain a significant biogas production. Anaerobic digestion plant of SOMW should be promoted in Mediterranean countries as an environmentally sound option for waste management and energy production, since olive mills are very widespread agro-industries in this area.

Valorization of solid waste products from olive oil industry as potential adsorbents for water pollution control—a review

The global olive oil production for 2010 is estimated to be 2,881,500 metric tons. The European Union countries produce 78.5% of the total olive oil, which stands for an average production of 2,136,000 tons. The worldwide consumption of olive oil increased of 78% between 1990 and 2010. The increase in olive oil production implies a proportional increase in olive mill wastes. As a consequence of such increasing trend, olive mills are facing severe environmental problems due to lack of feasible and/or cost-effective solutions to olive-mill waste management. Therefore, immediate attention is required to find a proper way of management to deal with olive mill waste materials in order to minimize environmental pollution and associated health risks. One of the interesting uses of solid wastes generated from olive mills is to convert them as inexpensive adsorbents for water pollution control. In this review paper, an extensive list of adsorbents (prepared by utilizing different types of olive mill solid waste materials) from vast literature has been compiled, and their adsorption capacities for various aquatic pollutants removal are presented. Different physicochemical methods that have been used to convert olive mill solid wastes into efficient adsorbents have also been discussed. Characterization of olive-based adsorbents and adsorption mechanisms of various aquatic pollutants on these developed olive-based adsorbents have also been discussed in detail. Conclusions have been drawn from the literature reviewed, and suggestions for future research are proposed.

Biochemical methane potential of two-phase olive mill solid waste: Influence of thermal pretreatment on the process kinetics

The effect of thermal pretreatment on two-phase olive mill solid waste was evaluated by chemical oxygen demand solubilisation and biochemical methane potential (BMP) tests. Temperatures of 100, 120, 160 and 180°C were applied during 60, 120 and 180 min for each temperature studied. The highest chemical oxygen demand solubilisation after pretreatment (42%) was found for 120 and 180°C during 180 min in both cases. These two conditions were selected for the BMP tests. BMP tests showed two different stages: a first exponential stage and a sigmoidal zone after a lag period. No influence of the pretreatment was observed on the kinetic constant of the first-stage. Clear difference was observed in the maximum methane production rate of the second stage, 76.8 mL CH4/(g VS day) was achieved after pretreatment at 180°C (180 min), value 22% and 40% higher than that obtained for the untreated and pretreated OMSW at 120°C, respectively.

Characterization of olive mill wastes composts and their humic acids: stability assessment within different particle size fractions

Compost stability assessment within different particle size fractions was studied. Humic acids (HAs) were extracted from two kinds of co-composts prepared using evaporated olive mill wastewater (OMSW) or solid waste from olive oil extraction (OC) and poultry manure (PM). The elemental composition, Fourier-transform infrared spectroscopy (FTIR) and 13C-NMR (nuclear magnetic resonance) analysis and molecular weight distribution were investigated to assess the composted organic matter stability in different fractions. In both composts, organic matter content was higher in the>2 mm fractions than in the<2 mm fractions, because of fractions’ richness in hardly biodegradable compounds. Spectroscopic analysis revealed that OMSW compost fraction<2 mm and OC compost 2–4 mm fraction were rich in aromatic compounds and oxygenated groups but poor in aliphatic structure. Moreover, the HA distribution reflected a high stabilized compost<2 mm fraction, especially from evaporated effluent known as phytotoxic. However, the 4–6 mm fraction included high aliphatic compounds besides aromatic structures and did not exhibit any phytotoxicity, confirming compost fraction maturity. However, the low C/N ratio, the high OMSW compost mineral nutritive elements and the high aromatic C rate reflected highly stabilized products. Consequently, the performance of both prepared organic fertilizers for agriculture use contested the previous negative effect ascribed to olive mill wastewater.

Microbially-enhanced composting of olive mill solid waste (wet husk): Bacterial and fungal community dynamics at industrial pilot and farm level

Bacterial and fungal community dynamics during microbially-enhanced composting of olive mill solid waste (wet husk), used as a sole raw material, were analysed in a process carried out at industrial pilot and at farm level by the PCR-DGGE profiling of the 16 and 26S rRNA genes. The use of microbial starters enhanced the biotransformation process leading to an earlier and increased level of bacterial diversity. The bacterial community showed a change within 15days during the first phases of composting. Without microbial starters bacterial biodiversity increased within 60days. Moreover, the thermophilic phase was characterized by the highest bacterial biodiversity. By contrast, the biodiversity of fungal communities in the piles composted with the starters decreased during the thermophilic phase. The biodiversity of the microbial populations, along with physico-chemical traits, evolved similarly at industrial pilot and farm level, showing different maturation times.