A new low-power burner, where liquid fuel is sprayed with a high-speed jet of superheated steam, has been developed and tested. The possibility of combustion of low NOx liquid combustible waste in a low-power burner is shown. For the first time, the thermal and environmental characteristics of diesel fuel and waste oil combustion in the developed burner have been studied. In this study, the heat release, external flame temperatures, and amount of CO and NOx in equilibrium combustion products at various operating parameters were measured. The performances of spraying fuel with a steam jet or an air jet were compared. The developed burner design reduces significantly the amount of nitrogen oxides up to 55% when burning diesel and up to 25% when burning waste oil as compared to air at low concentrations of CO and high fuel combustion. This performance complies with EN:267. The results obtained are necessary to model mathematically the studied processes and create new environmentally friendly technologies for recycling liquid combustible waste for thermal energy generation.