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Microalgae have the potential to become the primary source of biodiesel, catering to a wide range of essential applications such as transportation. This would allow for a significant reduction in dependence on conventional petroleum diesel. This study investigates the effect of biostimulation techniques utilizing nanoparticles of Magnesium oxide MgO, Calcium hydroxyapatite Ca10(PO4)6(OH)2, and Zinc oxide ZnO to enhance the biodiesel production of Chlorella sorokiniana. By enhancing cell activity, these nanoparticles have demonstrated the ability to improve oil production and subsequently increase biodiesel production. Experimentally, each nanomaterial was introduced at a concentration of 15 mg L−1. The results have shown that MgO nanoparticles yielded the highest biodiesel production, with a recorded yield of 61.5 mg L−1. Hydroxyapatite nanoparticles, on the other hand, facilitated lipid accumulation. ZnO nanoparticles showcased a multifaceted advantage by enhancing both growth and lipid content. Thus, it is suggested that these nanoparticles can be used effectively to increase the lipid content of microalgae. These findings highlight the potential of biostimulation strategies utilizing MgO, hydroxyapatite, and zinc oxide nanoparticles to bolster biodiesel production. [ABSTRACT FROM AUTHOR]

Environmental issues are brought up concerning the production of Portland cement. As a result, biocement serves as a reliable substitute for Portland cement in green construction projects. This study created a brand-new technique to create high-quality biocement from agricultural wastes. The technique is based on nanomaterials that improve and accelerate the "Microbially Induced Calcite Precipitation (MICP)" process, which improves the quality of the biocement produced. The mixture was further mixed with the addition of 5 mg/l of graphitic carbon nitride nanosheets (g-C3N4 NSs), alumina nanoparticles (Al2O3 NPs), or silica nanoparticles (SiO2 NPs). The cement: sand ratio was 1:3, the ash: cement ratio was 1:9, and water: cement ratio was 1:2. Cubes molds were prepared, and then cast and compacted. Subsequent de-molding, all specimens were cured in nutrient broth-urea (NBU) media until testing at 28 days. The medium was replenished at an interval of 7 days. The results show that the addition of 5 mg/l of g-C3N4 NSs with corncob ash delivered the highest "Compressive Strength" and the highest "Flexural Strength" of biocement mortar cubes of 18 and 7.6 megapascal (MPa), respectively; and an acceptable "Water Absorption" (5.42%) compared to all other treatments. This treatment delivered a "Compressive Strength", "Flexural Strength", and "Water Absorption" reduction of 1.67, 1.26, and 1.21 times the control (standard Portland cement). It was concluded that adding 5 mg/l of g-C3N4 NSs to the cementitious mixture enhances its properties, where the resulting biocement is a promising substitute for conventional Portland cement. Adding nanomaterials to cement reduces its permeability to ions, increasing its strength and durability. The use of these nanomaterials can enhance the performance of concrete infrastructures. The use of nanoparticles is an effective solution to reduce the environmental impact associated with concrete production. [ABSTRACT FROM AUTHOR]

Summary: Biogas generation from the latent energy in biomass is one of the most attractive renewable energy sources. This can be attributed to the environmental friendly nature of the process and its less energy requirements. This article reviews the anaerobic digestion of biomass (livestock manure and crop residues) for biogas and methane production as a source of renewable energy. Furthermore, this study investigates the enhancement of biogas and methane production using light and laser radiations. The laser radiation accelerates bacterial division and growth, where this process is termed as "photobiostimulation." Additionally, laser radiation photoactivates the inactive enzymes. The results of this literature review showed that the irradiation of methanogenic bacteria with laser sources increased the biogas production by one and a half fold the traditional method of biogas production. The simultaneous irradiation of both nanomaterials and methanogenic bacteria using laser radiation increased the biogas volume by twofolds the biogas volume resulted from the traditional method of biogas production. [ABSTRACT FROM AUTHOR]

In this work, titanium dioxide nanoparticles (TiO2 NPs) and modified TiO2 NPs with silver (Ag) or platinum (Pt) dopant were developed through photodeposition method for the NOx conversion into nitric acid (HNO3) under visible light irradiation. The formed photocatalysts TiO2, Ag/TiO2, and Pt/TiO2 nanocomposites were characterized by utilizing TEM, SEM, energy-dispersive X-ray analysis (EDX), XRD, UV/visible diffuse reflectance spectroscopy (UV-Vis DRS), and FT-IR. It had been investigated that an enhancement within the conversion of NOx into HNO3 was increased from 34.3 to 78.3% for Ag/TiO2 and from 35.2 to 78.5% for Pt/TiO2 under visible light irradiation conditions at room temperature for less than 2 h. The photodegradation rate order of NOx under visible light irradiation is Pt/TiO2 ~ Ag/TiO2 > TiO2. A possible mechanism for the catalytic conversion of NOx gases has been proposed, which depends on the photogeneration of electrons and holes after the excitation of nanocatalysts under visible radiation that promoted superoxide and hydroxyl ions, which can depredate NOx gases. This approach of NOx photocatalytic conversion is characterized by its chemical stability, low cost, high efficiency, simple operation, and strong durability than traditional methods. [ABSTRACT FROM AUTHOR]

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Kinetic modeling helps in the process designing, reactor dimensioning, and up scaling of any system. A kinetic study of batch anaerobic digestion (AD) of food waste (FW), which is the organic fraction of municipal solid waste was conducted. Iron oxide (Fe3O4) nanoparticles (NPs) were added and their impact on methane generation and volatile solids (VS) removal was modeled through the existing kinetic models. AD of FW was carried out at a mesophilic temperature (37 ± 0.5 °C) for 60 days. Four different concentrations of Fe3O4 NPs, at 50, 75, 100, 125 mg L−1, were added, and the performance was evaluated by comparing it with the control (without NPs) and by kinetic modeling. The rate of reactions (k) was evaluated by using pseudo-first-order reaction kinetics by considering the initial and final data. The modified Gompertz model, Logistic, and Transference functions were fitted to the cumulative methane generation. The best fits of models were statistically determined by estimating the coefficient of correlation (R2), standard deviation residual (SDR) and least significant difference tools. The k values for all concentrations and the control were determined to be 6.1 × 10−3, 1.4 × 10−2, 1.8 × 10−2, 9.6 × 10−3, and 7.1 × 10−3 (day−1), respectively. The results of the study indicated that the modified Gompertz model produced a perfect fit with highiest R2 and the smallest value of SDR. Furthermore, more than 50% of VS reduction was achieved with the addition of 75 mg L−1 Fe3O4 NPs. The modified Gompertz model predicted the experimental results with a higher R2 and a lower SDR value at all concentrations of NPs. [ABSTRACT FROM AUTHOR]