Sugar catalysts can turn waste vegetable oil into biodiesel, researchers have revealed.  

As fossil fuel reserves start to run dry, alternative fuel sources such as biodiesel, which is made from renewable biological material, are needed.  Now, Min-Hua Zong at the South China University of Technology, Guangzhou, and colleagues have used a sugar catalyst to prepare biodiesel from waste vegetable oil.  Sugar catalysts, made by the sulfonation of partially carbonized D-glucose, have previously been used for making biodiesel from new vegetable oils, but had never been successfully used in making biodiesel from waste oil.  

According to Zong, one factor holding back the wide-spread use of biodiesel is the cost of the vegetable oil starting materials.  And the presence of free fatty acid impurities in waste vegetable oil makes it difficult to convert this cheap and readily available potential fuel source into biodiesel. A number of solid acid catalysts, such as zeolites, have found limited success in converting waste oil to biodiesel, but they can't operate effectively under the required harsh conditions. Sulfated zirconia has shown to be a very effective catalyst for the reaction, but the cost of the rare zirconium metal is prohibitive. Zong's sugar catalysts have a higher activity than zeolites, and are cheaper to prepare than the zirconia catalysts. 

Zong is committed to further research in this area. 'Environmentally-friendly production of cheap renewable fuels is very important,' she said. 'I am sure that biodiesel research is a growth area and that sugar catalysts will be an important part of it.'

Mark Keane, a chemical engineer at Herriot-Watt University, Edinburgh, UK, agreed that this work could be significant. 'The use of sugars as catalytic agents to convert waste oils is certainly intriguing and could potentially serve as a progressive approach to a burgeoning waste treatment issue,' he said.

 Rebecca Gillan