The 10-mlb thrust, concentric-tubes resistojet, which was life tested on hydrogen and ammonia propellants for 8000 hours, is being developed* for use with biowaste propellants. Thrusting performance is presented for H2, H2O, CH4, and CO2 as well as typical biopropellant mixtures CO2-CH4, H2O-CH4 and CO2-H2O. Using Pt-Ir alloy heater tubes, 235 and 575 seconds were obtained for water and hydrogen propellants. Overall total power efficiencies were 66% which includes losses for a pre-evaporator close-coupled for the water tests. Vibration to 1.0 g2/Hz with an overall G rms of 36, shock at 30 g's and acceleration to 8 g's simulating a launch were passed by the thruster.