Environmental impacts analysis of Moroccan olive cake combustion in Stirling motor cogeneration system: Case study

Morocco is the world's 5th largest olive oil producer with 160,000 tons in 2020/2021 and the production of 1 L of olive oil generated approximately 5 kilos of waste olive cake, this type of waste is dangerous for the environment and especially for groundwater. To address this issue and take into account the thermal properties of olive waste, our project's goal is to produce power and heat by using solid olive waste in a Stirling cogeneration system. Therefore, the goal of this article is to examine by using CFD tools the environmental impacts of the Moroccan solid olive waste burning in a CHP (combined heat and power) unit. The idea is to integrate a smart renewable energy system based on olive cake and the Stirling motor to produce electricity in order to employ this electrical energy for water pumping in rural areas. The impact of the excessive air ratio on temperature profile and exhaust has been investigated and discussed. In addition, the pollutant species in air has been presented, and compared with guideline values given by some international organization for health and environment. Results show that the highest excess air ratio gives high temperatures with a homogeneous distribution around the Stirling motor hot heat exchanger, and minimum emissions of CO, CO2, NO, NO2 and NH3 that do not exceed the values set by WHO, OSHA, and NIOSH.

The use of olive cake in the diet of dairy cows improves the mineral elements of Provola cheese

Mineral elements (Ca, Na, K, Mg, Zn, Ti, Sr, Fe, Ni, Ba, Cr, Mn, Cu, Se, Cd, Mo, B, V, As, Pb and Hg) in Provola cheeses obtained from dairy cows fed with two different integrated diets (Biotrak) and without olive cake (Control) were determined to discriminate between the two different cheeses. The results showed that cheeses from the Biotrak group presented higher values of essential elements. Selenium (Se) was found to be the most interesting: in Biotrak cheeses the content of Se was in the range of 0.112 to 0.281 mg/kg, about twice the content of Se in cheeses from the Control group. Among the toxic elements, only Cd was found in the samples, but at low levels (in average lower than 0.11 mg/kg). Therefore, the use of olive cake in animal feed is a good strategy to improve the mineral profile of the product obtained.

Rumen bacterial community profile and fermentation in Barki sheep fed olive cake and date palm byproducts

Rumen bacteria make the greatest contribution to rumen fermentation that enables the host animal to utilize the ingested feeds. Agro-industrial byproducts (AIP) such as olive cake (OC) and date palm byproducts (discarded dates (DD), and date palm fronds (DPF)) represent a practical solution to the deficiency in common feed resources. In this study, thirty-six growing Barki lambs were divided into three groups to evaluate the effect of untraditional diets including the AIP on the growth performance. Subsequently, nine adult Barki rams were used to evaluate the effect of experimental diets on rumen fermentation and rumen bacteria. Three rations were used: common concentrate mixture (S1), common untraditional concentrate mixture including OC and DD (S2), and the same concentrate mixture in S2 supplemented with roughage as DPF enriched with 15% molasses (S3). The animals in S2 group showed higher dry matter intake (DMI) and lower relative growth rate (RGR) as compared to the animals in S1 group. However, the animals in S3 group were the lowest in DMI but achieved RGR by about 87.6% of that in the S1 group. Rumen pH, acetic and butyric acids were more prevalent in animals of S3 group and rumen ammonia (NH3-N), total volatile fatty acids (TVFA), propionic acid were higher in S1. Rumen enzymes activities were higher in S1 group followed by S3 and S2. The bacterial population was more prevalent in S1 and microbial diversity was higher in the S3 group. Principal coordinate analysis revealed clusters associated with diet type and the relative abundance of bacteria varied between sheep groups. The bacterial community was dominated by phylum Bacteroidetes and Firmicutes; whereas, Prevotella, Ruminococcus, and Butyrivibrio were the dominant genera. Results indicate that diet S3 supplemented by OC, DD, and DPF could replace the conventional feed mixture.

Gut immune-related gene expression, histomorphometry and hematoimmunological assays in Nile tilapia (Oreochromis niloticus) fed Aspergillus oryzae fermented olive cake

Fermentation strategy is well documented to improve the nutritional value of agricultural waste by-products such olive cake (OC), which, in turn, provides healthy, safe, and affordable feedstuff. This study assessed the combined impact of Aspergillus oryzae-fermented OC (AFOC) on the growth performance, intestinal morphometry, blood biochemistry, lysozyme activity, gut immune-related genes, and flesh quality of Nile tilapia. We divided 225 fish into five groups and further subdivided into three replicates (n = 15 each) and fed them five diets (Control, AFOC5, AFOC10, AFOC15, AFOC20) to determine AFOC nutritional value and its optimized incorporation level in the diet. The trial continued for 3 months. The crude protein content of OC improved by 7.77% after A. oryzae fermentation, while lipid content decreased by 14.19%. In addition, growth and feed utilization significantly improved at (10.8-11.2) % AFOC dietary level. High-density lipoprotein (HDL) significantly improved, and the serum lysozyme level was significantly higher in the AFOC10 group compared to other groups. Interestingly, gut-related inflammatory cytokines tumor necrosis factor alpha (TNF- α) and interleukin 1 beta (IL-1β) revealed higher relative mRNA expression in the AFOC10 group compared to other groups. The histomorphometric parameters was greatly influenced by the AFOC incorporation level (10%-20%). These findings suggested that A. orzae fermentation modifies the nutritional quality of OC, as seen through its positive impact on the growth performance, local and systemic immunity, and intestinal absorptive capacity of Nile tilapia. The recommended dose for dietary AFOC was around 11.

Performance of Barki Lambs Fed on Rations Containing Olive Cake with or Without Polyethylene Glycol

BACKGROUND AND OBJECTIVE

Olive by-products could be a suitable alternative feedstuffs ingredient in ruminants rations. This study was carried out to evaluate effects of replacing clover hay by olive cake with or without addition of poly ethylene glycol in growing lambs ration.

METHODOLOGY

Thirty five Barki lambs averaged 34 kg body weight and 5 months old were divided into 5 groups (7 animals of each) according to live weight for 90 days feeding trial. Olive cake was treated mechanically by hummer mill, screened to produce screening olive cake (treated olive cake, TOC).

RESULTS

Data of dry matter and organic matter digestibility were decreased with ration containing 20% TOC from ration or 67% from clover hay comparing with others. No significant differences were observed among groups in crude protein digestibility. Total digestible nutrients (TDN) as an energy measurement for the experimental rations cleared that replacing process of clover hay by TOC up to 20% of DM intake or 67% of clover hay, given lower values (65.32 and 66.80%). The rumen pH values were not affected by the different experimental rations including control. The highest rumen NH3 was recorded with lambs fed ration containing 33% TOC without PEG instead of clover hay, while the lowest values was recorded with that group fed ration containing 33% TOC with PEG. No significant differences were detected in total gain, ADG as well as feed efficiency among the experimental rations. Dry matter intake slightly increased with feeding growing lambs on TOC containing rations except R5 compared to the control group.

CONCLUSION

Summing up partially de-stoned olive cake by screening could be used in replacing clover hay for growing lamb rations, at inclusion levels up to 33 and 67% with or without poly ethylene glycol, with no adverse on performance of growing lambs.

Improvement of protein content and decrease of anti-nutritional factors in olive cake by solid-state fermentation: A way to valorize this industrial by-product in animal feed

The present work investigates the bioconversion of the olive cake (OC) generated by olive oil industries in Morocco through solid-state fermentation using selected filamentous fungi to increase its nutritional values for subsequent valorization as ruminants feed. The fungi, namely Beauveria bassiana, Fusarium flocciferum, Rhizodiscina cf. lignyota, and Aspergillus niger were cultured on OC for 15 days. Chemical composition as well as enzymes activities were determined. Results showed (i) an increase in protein content of up to 94% for treated OC and (ii) significant (P < 0.05) decreases of phenolic compounds, up to 43%, 70% and 42% for total phenolic content, total flavonoids content, and total condensed tannins, respectively. Moreover, the RP-HPLC analysis of fermented OC confirmed the degradation of individual phenolic compounds by the strains. These findings demonstrate that F. flocciferum and Rhizodiscina cf. lignyota are efficient enzymes producers leading to a nutritive enhancement of this by-product.

Kinetic study of thermal degradation of olive cake based on a scheme of fractionation and its behavior impregnated of metals

This research aims to provide a better knowledge of the thermal decomposition of the olive cake as well as this lignocellulosic material loaded, in a previous stage of biosorption, with heavy metals for its use in processes of energy recovery. Firstly, isolation of constituents of the olive cake was carried out. Then, experiments were performed by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) under inert and oxidative atmosphere at a heating rate of 15 K/min for each isolated fraction. Next, adequate reactions schemes were proposed to find kinetic parameters. Validation of these schemes were verified by the goodness of fitting between experimental and simulated data. Also, some important combustion characteristics such as ignition and burnout temperatures were determined. With regard to the effect of metals, cadmium, copper, chromium, nickel and lead present in metal-loaded olive cake did not modify values of kinetic parameters which described the thermal decomposition processes.

Extra CO2 sequestration following reutilization of biomass ash

Although combustion ashes are usually used in soils, little attention is paid to the CO₂ sequestration potential of this practice. The present study aims to quantify carbon sequestration as carbonate compounds in a tailored synthetic calcareous soil treated with biomass ash from a gasification power plant that uses olive cake. It is estimated that after ash amendment, 14.5g CO₂ remained fixed per kg of fly biomass ash, 16.5g CO₂ per kg of bottom biomass ash with plant cultivation and 19.7g CO₂ per kg of bottom biomass ash without plant cultivation. This inorganic C fixation plus the organic (black) C contained in the ashes made the reutilization of ashes as K fertilizer a relevant practice due to its C resilience and rate, with a yearly C sequestering potential of ca. 8% of 'Soil carbon 4 per mille' goal, an initiative launched at the COP21.

Optimization of ultrasound-assisted extraction (UAE) of phenolic compounds from olive cake

The use of ultrasound in ultrasound-assisted extraction (UAE) is one of the main applications of this technology in food industry. This study aimed to optimize UAE conditions for olive cake extract (OCE) through response surface methodology (RSM). The optimal UAE conditions were obtained with extraction temperature of 56 °C, extraction time of 3 min, duty cycle of 0.6 s, and solid to solvent ratio of 3.6%. At the optimum conditions, the total phenolic compounds (TPC) content and antioxidant activity (AA) were measured 4.04 mg/g and 68.9%, respectively. The linear term of temperature had the most effect on TPC content and AA of OCE prepared by UAE. Protocatechuic acid and cinnamic acid were characterized as the highest (19.5%) and lowest (1.6%) phenolic compound measured in OCE extracted by UAE. This research revealed that UAE is an effective method to extract phenolic compounds from olive cake. RSM successfully optimized UAE conditions for OCE.

Effect of mixed feeds containing different levels of olive cake on fattening performance, carcass, meat quality and fatty acids of lambs

In this study, the effects of diet including different levels of olive cake were investigated on the fattening performance, blood parameters, certain slaughtering traits, and carcass quality of lambs. Thirty-six male lambs were used in the experiment. The lambs were randomly assigned to three groups with 12 lambs each. Groups included control, 12.5 and 25% olive cake (OC). The mixed feeds were offered ad libitum. All lambs were also allowed to consume alfalfa hay (83.8 g DM/animal/day). The experiment lasted for a period of 56 days. The effect of different levels of olive cake was not found different in fattening performance values of lambs in 0-56 days (P > 0.05). Carcass weight, pH, and yield were not different (P > 0.05). While the values of color parameters, cooking loss, tenderness, and ether extract level of longissimus dorsi muscle (MLD) was not found different (P > 0.05), it was determined that the levels of olive cake increased the water-holding capacity of meat (P < 0.05). Furthermore, although the levels of olive cake were shown to decrease total n-3 and total saturated fatty acids (Σ SFA), they also increased total n-6, n-6/n-3 ratio, total monounsaturated fatty acids (Σ MUFA), and total polyunsaturated fatty acids (Σ PUFA) were not different (P > 0.05).

Biodetection of potential genotoxic pollutants entering the human food chain through ashes used in livestock diets

Ash derived from energy generation is used as a source of minerals in livestock feeds. The microbial biosensor recApr-Luc2 was built to detect genotoxic hazard in recycled ash. Escherichia coli SOS gene (recA, lexA, dinI and umuC) expression in response to cisplatin-induced DNA damage led to the selection of the recA promoter. The biosensor required functional RecA expression to respond to genotoxic heavy metals (Cr>Cd≈Pb), and polluted ash induced a strong recApr-Luc2 response. In human liver and intestinal cells, heavy metals induced acute toxicity (Cr>Cd>Pb) at concentrations sufficient to activate recApr-Luc2. Cytostatic effects, including genotoxicity, were cell- and metal-dependent, apart from Cr. In agreement with the recApr-Luc2 bioassay, Cr had the strongest effect in all cells. In conclusion, recApr-Luc2 could be useful for evaluating the genotoxic risk of pollutants present in ash that might be concentrated in animal products and, thus, entering the human food chain.

Effect of biomass-sulfur interaction on ash composition and agglomeration for the co-combustion of high-sulfur lignite coals and olive cake in a circulating fluidized bed combustor

This study aimed to investigate the effect of biomass-sulfur interaction on ash composition and agglomeration for the co-combustion of high-sulfur lignite coals and olive cake in a circulating fluidized bed combustor. The tests included co-combustion of 50-50% by wt. mixtures of Bursa-Orhaneli lignite+olive cake and Denizli-Kale lignite+olive cake, with and without limestone addition. Ash samples were subjected to XRF, XRD and SEM/EDS analyses. While MgO was high in the bottom ash for Bursa-Orhaneli lignite and olive cake mixture, Al2O3 was high for Denizli-Kale lignite and olive cake mixture. Due to high Al2O3 content, Muscovite was the dominant phase in the bottom ash of Denizli Kale. CaO in the bottom ash has increased for both fuel mixtures due to limestone addition. K was in Arcanite phase in the co-combustion test of Bursa/Orhaneli lignite and olive cake, however, it mostly appeared in Potassium Calcium Sulfate phase with limestone addition.