# Oxidative stability and emission profiles of biodiesel from hemp, karanja, castor, and amla oils: impact of natural antioxidants

## TL;DR

This study evaluates how natural and synthetic antioxidants affect the stability and emissions of biodiesel made from non-edible oils like hemp and karanja.

## Contribution

The paper introduces the use of natural antioxidants like olive pomace and Moringa oleifera to improve biodiesel stability and reduce harmful emissions.

## Key findings

- BHA provided the best oxidative stability among tested antioxidants.
- Moringa oleifera extract reduced NOx emissions in biodiesel combustion.
- Biodiesel emissions remained lower than conventional diesel despite antioxidant use.

## Abstract

Biodiesel is a renewable fuel with great potential, but its quality can decline over time due to oxidation, which forms harmful compounds like peroxides, aldehydes, and alcohols. This study examines the oxidative stability and storage life of biodiesel made from non-edible oils such as hemp, karanja, castor, and amla. The stability was evaluated using parameters, like peroxide value, totox value, conjugated diene and triene values, and para-anisidine value. To improve stability, both synthetic and natural antioxidants were tested. Butylated hydroxyanisole (BHA) was used as a synthetic antioxidant, while natural antioxidants used were aqueous extract of Moringa oleifera leaves, citrus fruit residues, and olive pomace. BHA provided the best overall protection, and among the natural antioxidants, olive pomace extract performed the best. Engine emission tests were also carried out to study the environmental impact of these additives. The results showed that Moringa oleifera extract reduced the high NOx emissions commonly seen with biodiesel, while all antioxidants caused only a slight increase in CO and unburned hydrocarbons. Overall, the emissions from biodiesel remained lower than those from conventional diesel fuel.

Effect of natural and synthetic antioxidants on the oxidative stability and emission profiling of combustion of hemp, karanja, castor, and amla oil-based biodiesels.