Co-Firing biomass in the form of wood dust or sawdust with natural gas is a new concept, which was performed in a specialized burner from the Riga Technical University. In order to test the burner, primary experimental test runs were performed to get an overview of flue gas behaviour. The addition of sawdust increased CO values but O2 values remained very low in the flue gases. This was due to technical problems with the fuel. Co-Firing has the potential to reduce CO2 emissions of energy production and wood dust is an abundant byproduct of forestry, therefore the potential has to be explored in future research.