Assessment of natural and pyrolytic antioxidants as additives to biodiesel production

Abstract

Brazil is one of the largest producers and consumers of biodiesel in the world, with a production of 6.7 million m 3 in 2021. Its main sources for biodiesel production are soybean oil and animal fat. The low oxidative stability of biodiesel is a problem that has not yet been satisfactorily solved and represents the main barrier to market expansion. Therefore, a promising approach to improve oxidative stability is the addition of antioxidants. This study evaluated the effect and performance of natural extracts of Scenedesmus obliquus (S. obliquus), Haematococcus pluvialis (H. pluvialis), curcuma sp. (turmeric), Bixa Orellana (annatto) seeds, coffee husk (C. husk), and commercial Haematococcus pluvialis (C.H. pluvialis) as antioxidants during long-term storage of biodiesel matrices from soybean (Glycine max), canola (Brassica napus), and macauba (Acrocomia aculeata). In addition, the antioxidant properties of bio-oils produced from the slow pyrolysis of biodiesel synthesis of soybean, canola, macauba, and depigmented S. obliquus biomass were also investigated. Among the natural extracts, turmeric and S. obliquus stood out, which at the concentration of 3000 ppm produced increased stability time (35.0% for soybean, 51.8% for canola, and 338.4% for macauba) and (36.0% for soybean, 46.7% for canola, and 122.0% for macauba) respectively. Furthermore, the addition of S. obliquus bio-oil at a concentration of 4000 ppm produced an increase in stability time of 116.8 % (13.2 h) for soybean, 194.5% (17.7 h) for canola, and 563.5% (13.21 h) for macauba, which meets the Brazilian standard requirement (ANP resolution no. 798/219) of a minimum stability time of 12 hours for biodiesel. Keywords: Biodiesel. Catalysis. Natural antioxidants. Microalgae. Oxidation stability. Pyrolysis antioxidant