Technological Aspects of Refuse Fats, Pretreatment and Retrofitting

Scope of the article is to discuss pretreatment of refuse, nonedible animal fats into biodiesel feedstock to improve yields of standard quality biofuel at low operational costs. Recommendations are equally viable for 2nd generation biodiesel processing technologies and to extend catalysts lifetime. Refuse fats are vulnerability to storage conditions having significant influence on loss of market value. Common concerns expressed in terms of high levels of FFA (Free Fatty Acid), moisture, impurities have been addressed. Detrimental constituents are present in these feedstocks in complicated, stubborn colloid chemical structures with direct impacts on processing. Common edible grade oil techniques have been revisited but failed to produce high market-value biodiesel feedstock at acceptable levels of yield and reliability. Petroleum refinery techniques, selective solvent refining and vacuum distillation have also not met expectations. Glycerolysis and direct esterification conversion techniques were efficient in reduction of FFA and impurities to acceptably low level at reasonable yield. Acid catalyzed direct esterification proved to be lower cost technique to produce good quality biodiesel feedstock that can be processed in first generation alkali-based transesterification and hydrotreatment techniques alike. Co-Sol apolar solvent born technology has been shown to be the best performing option in retrofitting. Direct esterification was demonstrated in a truly continuous, counter current, solvent born mode with substantial energy and resource efficiency gains.