Soybean and Soybean/Beef‐Tallow Biodiesel: A Comparative Study on Oxidative Degradation During Long‐Term Storage

Abstract

Vegetable oils are the primary raw materials used in biodiesel production; however, they usually present oxidative stabilities inferior to the EN 14214 specifications. An alternative to improve the oxidative quality of vegetable oil biodiesel is blending it with animal fat biodiesel. In this paper, we studied the oxidative degradation of soybean/beef‐tallow biodiesel (SB) 70/30 and 50/50 (w/w) during long‐term storage. Soybean biodiesel (SO) was used as a control sample. The biodiesel samples were stored for 350 days and analyzed periodically via oxidative stability, tocopherol content, peroxide value, polar compounds, and kinematic viscosity. The results showed that SB 70/30 and 50/50 biodiesel samples presented higher oxidative stabilities than SO biodiesel. Additionally, the blends met the limits proposed by EN 14214 for oxidative stability (8 h). During long‐term storage, the SB biodiesel showed greater resistance to oxidative degradation, which was indicated by the lower formation of hydroperoxides and polar compounds. Similarly, the decline in the tocopherol content was slower in SB biodiesel. Blends of soybean and beef‐tallow biodiesel at levels of 70/30 and 50/50 are, therefore, proper alternatives to improve the oxidative quality of this biofuel.

Biodiesel Production Processes and Sustainable Raw Materials

“…Some authors claim that animal fat-based biodiesel is less stable for oxidation due to the absence of natural oxidants as compared to biodiesel from vegetable oil [63][64][65]. On the other hand, others, claim that from the content of saturated fatty acid, the addition of animal fat improves the oxidative stability of biofuel [36,66,67]. Feedstocks rich in polyunsaturated fatty acids are more susceptible to oxidation, due to the presence of double bonds in the chains, than feedstocks rich in saturated or monounsaturated fatty acids [68].…”

Effect of kinematic viscosity variation with blended-oil biodiesel on engine performance and exhaust emission in a power tiller engine

“…This is due to the high FFA content in beef tallow, the high moisture content in raw material oils, and the high concentration of SFA. Table S5 shows the composition of FAME in TASO3 BD, soybean BD (SO BD) [9], and tallow BD (TA BD) [17]. The contents of SFA and UFA in TASO3 BD were 25.3% and 72.3%, respectively.…”

“…This composition of FAME has significant effects on the fuel properties such as cetane number, calorific value, and kinematic viscosity [58,60]. Table S6 shows the fuel properties of TASO3 BD, CD, SO BD [3,9,21,22,31,51,61,62], and TA BD [3,22,26,[61][62][63][64][65]. Among the fuel properties, cetane number is closely related to combustion qualities, such as combustion delay and diffusion combustion.…”

“…In Europe, vegetable oil from these three crops makes up over 95% of BD production [8]. In Brazil, 81% of BD is produced from soybean oil [9]. Since these raw materials are also used as food, their heavy use to produce biofuel can lead to food shortage and increase in food price [10,11].…”

Valorization of Wastes for Biodiesel Production: The Brazilian Case

“…An interesting approach was made by Pereira et al [43] who studied an alternative to improve the oxidative quality of vegetable oil biodiesel by blending it with animal fat biodiesel. They studied the oxidative degradation of soybean/beef-tallow biodiesel (SB) 70/30 and 50/50 (w/w) during long-term storage (up to 350 days).…”