Can natural antioxidants be used to stabilize the properties of some biodiesels?

Antioxidants have become one of the most popular buzzwords when it comes to human health, and for good reason: They protect the body from aging and inflammation, and can even help us with weight loss. However, a study published in the Australian Journal of Basic and Applied Sciences indicates that they could soon be used for cars, based on their findings which revealed that adding antioxidants can improve oxidative stability in biodiesel and other forms of alternative fuel.

Biodiesel is one type of renewable fuel that’s currently experiencing rapid growth in industrial countries. In the U.S. and Asia, the market for biodiesel is increasing in double digits, with countries like China and India leading the charge. The former, in particular, is aiming to have biodiesel replace petrodiesel by 15 percent in 2020. Australia, on the other hand, has seen a record-level increase in biodiesel consumption at 19 percent in recent times. The growth, of course, is mainly driven by the benefits that biodiesel brings to the table: It’s low in hydrocarbon, particulate, and carbon monoxide emissions, but it still can improve lubricity and lower sulfur while having a high cetane number. This makes biodiesel both environment-friendly and efficient at the same time.

However, a challenge with using biodiesel is its long-term effects on machines. It’s known for having high acid numbers and being very viscous, which can lead to the formation of sediments that can clog filters. Over time, these three factors can lead to the degradation of biodiesel, making it unusable.

For the study, researchers looked at adding antioxidants to increase the stability of biodiesel. In particular, the team used the following commercial antioxidants:

To note, these synthetic antioxidants, when used in food and cosmetics, may lead to adverse side effects; however, they are highly beneficial when used as fuel additives, based on earlier studies. These were then evaluated for their ability to reach the degree of oxidation needed for biodiesel under normal temperature and humidity. The combinations were blended at concentrations which ranged from 250 to 1,000 parts per million (ppm), and their oxidative stability was evaluated using ASTM D6751-11 to monitor changes using peroxide values (PV) and total acid number (TAN). Researchers found 500 ppm of either PG, a TBHQ-PG combination, or TBHQ had the best result in terms of PV content.
For TAN content, the team discovered that samples that had 500 ppm of PG were optimal. (Related: Olive and Grape Extracts Work Better as Food Preservatives than Synthetic Antioxidants.)

“This study showed the effectiveness of synthetic antioxidants butylated hydroxyanisole (BHA), butyl-4-methylphenol (BHT), t-butyl hydroquinone (TBHQ) and propyl gallate (PG) in improving the oxidative stability of grease trap oil-based biodiesel (B100) at the varying concentrations between 250 and 1000 ppm,” the researchers wrote in their report. Of the four antioxidants, the team chose the PG blend as the best formulation, suggesting that it could be developed into suitable blends in the future.

Learn more about biodiesels and other types of alternative fuel at

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