Fatty-acid residue as plant oil asphalt (FA-POA) is a neglected biomass. The main objectives of this study were to identify the composition of FA-POA and to investigate the vacuum pyrolysis of FA-POA to synthesize liquid biofuel. Proximate and ultimate analysis of FA-POA was performed. The physical properties were also examined according to ASTM standards. The composition of FA-POA was inferred from FTIR spectra and thermal gravimetric analysis. GC–MS was conducted to determine the composition in the pyrolytic oil and biogas. Results showed that FA-POA is a polymerization product of fatty acids. It is formed by the combination of CC addition or association and carboxyl dehydration. In vacuum pyrolysis, a pyrolytic-oil yield of 71 wt % was achieved on a FA-POA basis. The pyroltyic oil mainly consists of fatty acids, paraffins, cycloparaffins, olefins, and aromatics. It was upgraded to pyrolytic biodiesel, which is characterized as having a high calorific value and moderate oxygen content. A pyrolysis reaction scheme of FA-POA was proposed from the experimental results. It is concluded that FA-POA is an attractive biomass source for liquid biofuels, chemicals, and biochar.