Using headspace solid phase microextraction to evaluate the odor compounds in trap grease feedstock for biodiesel

Trap grease is a waste grease material that can be used as a biodiesel feedstock. Its commercial viability could be limited unless its inherent odor can be mitigated. Because trap grease can have many sources and is collected in a variety of ways it possesses many challenges in developing a characterization method and biodiesel conversion process. A headspace solid phase microextraction (HS-SPME) analysis method had been developed to provide rapid and quantitative identification of odor compounds in trap grease and its biodiesel product. Six trap grease samples were evaluated and several distinct classes of compounds were identified. A significant portion of the volatile odorant compounds in trap grease was identified as short and medium chain free fatty acids (FFA). The odorant components were identified using HS-SPME sampling analyzed by gas chromatography/mass spectrometry (GC/MS). Relative response factors and calibration curves were used to analyze the short chain FFA (SC-FFA) in trap grease. The results showed that the developed method is a suitable analysis tool for the fast and reliable identification of different classes of odorant compounds and quantitation of SC-FFA from trap grease or similar biofuel feedstocks.