Exergetic performance and exergoeconomic analyses of a small-scale turbojet engine fuelled with either conventional aviation fuel or biofuel are conducted; and the performance and cost flow of the engine are assessed. The analyses are performed through component-based exergy and cost calculations. The main components of the engine are the air compressor, the combustion chamber and the high-pressure turbine. The results show that the exergy efficiencies of the engine components are obtained as 74.52% for the air compressor, 47.68% for the combustion chamber, and 99.00% for the high-pressure turbine for the biofuel test case. On the other hand, when the engine is fed with the conventional aviation jet fuel, the exergy efficiencies of the air compressor, the combustion chamber, and the high-pressure turbine are calculated as 75.22%, 48.34% and 98.44%, respectively. In addition, the cost rate of thrust is calculated as 79.08 US$/h.kN for the jet fuel case and 91.89 US$/h.kN for the biofuel test case. (C) 2017 Elsevier Ltd. All rights reserved.