Rapeseed Acid Oil

About This Product

Rapeseed acid oil is produced from soapstock, the alkaline by-product drawn off when crude rapeseed oil is neutralised during chemical refining. Treating that soapstock with sulphuric acid splits the soaps back into free fatty acids, which separate as an oily layer. It is a dark, variable liquid and a genuine residue of refining rather than a manufactured grade. Its value as a fuel feedstock is largely regulatory. Because it comes from a processing residue rather than a crop, it is classified as a waste or residue under RED II and equivalent schemes, which carries stronger incentives and avoids the land-use constraints applied to virgin oils, and it trades at a discount to crude rapeseed oil. The processing consequence of that origin is high free fatty acid content, commonly above 50 percent. Alkali transesterification cannot handle that, because the caustic reacts with the free acids to form soap instead of ester and the catalyst is destroyed, so acid oils are processed by acid-catalysed esterification, by pre-esterification followed by transesterification, or by hydrotreating. Residual sulphate from acidulation is a specification point, as sulphur poisons hydrotreating catalysts. It is used for FAME biodiesel via esterification, hydrotreated renewable diesel, industrial soap and animal feed energy. Bio Green Fuels supplies rapeseed acid oil to specification on free fatty acid, moisture and impurities, sulphur and residual sulphate, iodine value and unsaponifiable matter.