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The purpose of this work is to analyze the efficiency of natural adsorbents (rice husk ash (RHA) versus corn husk ash (CHA)) for the dry purification of ethyl biodiesels obtained by transesterification via homogeneous catalysis of nonedible oils (Balagnites aegyptiaca, Azadirachta indica, and Jatropha curcas). The characterization of RHA and CHA was achieved by N 2 adsorption/Brunauer−Emmett−Teller analysis and by scanning electron spectroscopy with microanalysis by energy dispersive X-ray spectroscopy. The quality of the three biodiesels, before and after dry treatment on adsorbent, was evaluated by various analytical methods ( 1 H nuclear magnetic resonance, gas chromatography with a flame ionization detector, Karl Fischer titration, and inductively coupled plasma−atomic emission spectroscopy). Several operating conditions (presence of activated carbon in the ashes, temperature, contact time, and number of treatment cycles) were tested in order to define the best procedure. RHA combined with the selected procedure showed very satisfactory results for removal of impurities from the produced biodiesels (residual glycerides, free glycerin, water, catalyst, and metals introduced during the oil extraction) and thus may be an alternative to the conventional wet purification process (acidic water washing).

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<em>Jatropha curcas</em> seed oil can be used for numerous purposes including fuel, soap and cosmetics. Better quality oil is obtained by cold pressing, the effectiveness of which is unfortunately limited by a low extraction rate. The objective of this study was to optimize cold hydraulic extraction parameters of <em>Jatropha curcas</em> seed oil by increasing the oil recovery and characterising the extracted oil. The key extraction parameters (dwell time, pressure, compression speed, and press cage charge) were determined using a laboratory hydraulic press. The results show that the unhulled and dehulled seeds contained 5.1 and 2.9% moisture, as well as 33.6 and 51.7% fat, respectively. Under the optimal operating conditions and at ambient temperature (25 °C), the oil recovery from whole (crushed) material was 38.2 (42.5)% unhulled seeds and 71.3 (69.5)% dehulled seeds. The physicochemical characteristics of cold-extracted Jatropha oil were 10ppm phosphorus, 1.9 ppm iron, 0.0 ppm copper, 0.15% water-volatile matter, 0.918 (15 °C) density, and 37.72 cSt (37.8 °C) kinematic viscosity, respectively. In conclusion, the optimized cold hydraulic extraction of jatropha seed oil leads to high oil recovery and good oil quality suitable for industrial applications.

Nutritional requirements in the fermentation process are key parameters for optimal yeast development and ethanol production. Natural nutritional supplements rich in nitrogen, phosphorus, sulfur, and micro-elements can improve the performance of yeasts and offer a sustainable, cost-effective, and environmentally friendly alternative to synthetic chemicals. This study aimed at investigating the effect of a natural yeast nutrient (fermented Parkia biglobosa seeds) on bioethanol production from cashew apple juice by Saccharomyces cerevisiae. The proximate and mineral compositions of fermented seeds were evaluated. Their powder was added to yeast medium at a concentration of 4–12 g/L. The behavior of two yeast strains (Angel brand super alcohol (S1) and Angel brand thermal-tolerant alcohol (S2)) was inspected. Titratable acidity, pH, °Brix, and density were evaluated during 144 h of fermentation. Sugar consumption was maximal after 72 and 48 h of fermentation for S1 and S2 yeast strains, respectively. The best ethanol yields of 0.19 and 0.22 g/g were obtained with S1 and S2 yeast strains, respectively, using 12 g/L of nutrients for the first and without nutrient supplementation for the second (control sample). The non-conventional nutrients from fermented P. biglobosa seeds seem to be favorablefor ethanol production using only S1 yeast strain.