Three different waste animal fats (bone, chicken, and tallow) have been studied to evaluate whether they could be used as bioliquids according to the European Regulation (EC) No.1069/2009. The analyses showed that they contained an unsuitable amount of free fatty acids (FFA) and impurities content (total sediment) if compared with the standards for power generation (set by UNI 6579:2009), with the exception of tallow fat (class C, UNI/TS 11163:2018). A series of physical-chemical processes already applied at industrial scale have been considered to manage the acid value and the impurities content. The FFA esterification was carried out with methanol, comparing two acid catalysts (sulfuric acid or Amberlyst – 15), followed by neutralization of the residual acidity with two different bases (ammonia solution or solid sodium carbonate monohydrate) when necessary. The final purification has been achieved by treatment with powdered activated carbon. In particular, the bone fat was studied as reference material, having the worst initial physical-chemical characteristics. The UNI/TS 11163:2018 standard would allow to classify the bioliquid from bone fat belonging to class B, while the one from chicken would require further degumming and purification processes to reduce the metals, sulfur, and phosphorus content.