Biodiesel has become more attractive material for its properties such as biodegradability, renewability and very low toxicity of its combustion products. A higher quality of this fuel is essential in its potential commercialization. Analytical methods used in biodiesel analysis are constantly refined. The most popular analytical techniques include chromatography and molecular spectroscopy. The ATR-FTIR spectroscopy is one of the most important methods of spectroscopy. This paper presents the results of studies on selected oils of natural origin using ATR-FTIR infrared absorption spectroscopy. Three types of oils from pumpkin seeds and winter rapeseed were analysed. The main fatty acids were also determined in all the samples.

This study investigated the effects of particle size and ultrasonic parameters on the yields of bioactive compounds extracted from the leaves and inflorescences of hemp. The total flavonoid and anthocyanin contents were determined using the spectrophotometric method. The response surface methodology (RMS) was employed to optimize the yield of bioactive substances. On the basis of the developed model, the highest flavonoid yield was obtained under the following extraction conditions: particle size, 0.59 mm; extraction time, 10.71 min; ultrasound intensity, 7.13 W∙cm−2; extraction yield, 9.28 mg QE∙g−1; determination coefficient, R2 = 0.97. The optimal conditions for extracting anthocyanins were as follows: particle size, 0.25 mm; extraction time, 15 min; ultrasound intensity, 8.60 W∙cm−2; extraction efficiency, 20.27 mg Cy-GE∙100 g−1; determination coefficient, R2 = 0.87. This study helped confirm the importance of pulsed ultrasound-assisted extraction in obtaining bioactive compounds from hemp.

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Abstract. Anaerobic decomposition of plant residues from which biogas is produced, generates very large amounts of digestate. Due to its physicochemical properties post-digestion liquid can be used as a fertilizer. Postdigestion liquid was used in the field cultivation of fodder alfalfa and winter wheat. The content of macroelements and the content of protein in the grains of winter wheat fertilized with digestate were on the same levels as in the grains of wheat fertilized with mineral fertilizers. The analysis showed a similar content of macroelements in alfalfa leaves fertilized both with post-digestion liquid and mineral fertilizers as well. Fertilizing fields with digestate brings destruction of possible pathogens. Digestate utilization as a fertilizer brings tangible benefits in agricultural production, but it is also a product, the application of which can reduce the negative effects of mineral fertilization and contribute to development of sustainable agriculture. The study has shown that digestate can be used as a fertilizer.

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