Water-free process for biodiesel production

Portuguese researchers are developing methods for purifying biofuels without the use of water. Their work has been published in the journal Fuel Processing Technology.

The global production of biofuels - such as ethanol and biodiesel - has increased by over 600% in a decade to more than 100 billion litres in 2011. Dr David Brown, chief executive of the Institution of Chemical Engineers (IChemE), noted, “In some countries like Brazil, biofuels provide nearly a quarter of their road transport needs. In the European Union, negotiations are underway to increase biofuels for transport to 10%. And Indonesia … has announced plans to increase biodiesel production to reduce its reliance on crude oil imports.”

However, the researchers said, “The technologies conventionally used for biodiesel purification imply high consumptions of both energy and water.” Biofuel production has been criticised for causing deforestation, adding to the pressure on agricultural land needed for food production and the environmental impact of wastewater produced during their production. Traditional methods also use high volumes of water to remove impurities or ‘soaps’ to meet stringent quality standards. For palm oil production, 50% of water used becomes palm oil mill effluent - the largest pollutant of rivers in Malaysia.

The researchers, from the University of Porto, are studying water-free methods for purifying biofuels, including those made from waste cooking oils, animal fats and other fatty wastes derived from industrial activities. Instead of water, they used catalysts to pre-treat and target calcium soaps in the biodiesel. The impurities were then removed by absorption into resins or passing through ceramic membranes.

The researchers stated that their most successful method involved pretreating the biodiesel with sodium carbonate. In this instance, they said, “The purification was effective using biodiesel produced from both soybean oil and waste frying oil and the quality of the product agreed with the one obtained using the conventional water washing process.”

“Demand for biofuels is clearly increasing,” said Dr Brown, “and advancement in chemical engineering processes, such as the use of heterogeneous catalysis and water-free methods using membranes, are very welcome to consolidate biofuels as a globally accepted and sustainable source of renewable energy.”