Biodiesel from rice bran lipids: resource assessment and technological review

The biodiesel (BD) industry struggles to compete with petroleum diesel because of its high cost, primarily attributed to the costs of raw material and production. Rice bran (RB) is an oleaginous agro-industrial residue which has been of interest as a feedstock for BD production. Although RB has been found to be a potential resource for various products of commercial interest, its current bulk but limited utilization is either as a source of edible oil or as an ingredient of feeds. A key challenge in processing lipids from rice bran is its significant free fatty acid content but is not necessarily a setback when utilized for biodiesel production. Despite the perceived potential, the sheer number of published researches, and even patented processes, there has been no quantitative assessment of the resource availability, and no commercialized process reported. In this work, a localized resource assessment with biodiesel yield estimates has been conducted to identify priority areas for adapting rice bran for biodiesel production. As leading paddy rice producers, Southern, Eastern, and Southeastern Asian regions were found to have potential in adapting RB as a biodiesel feedstock. Alongside this, detailed technological comparisons were described in this review, from lipid extraction, reaction systems or schemes, reactants, catalysts, reactor configurations and strategies, to emerging and patented technologies with economical and scalable potential. In addition, opportunities in (RB) processing and related government policies, foreseen impacts on economics, social, and environmental aspects, as well as existing challenges, were identified and discussed for future prospects and developments