The share of biomass in the transformation sector of Latvia accounts for only 15%, at the same time natural gas share in transformation sector is about 80%. Nonetheless, an ongoing natural gas price growth stimulates its full replacement with biomass. The goal of the research was to construct an experimental pilot device, where could be possible to combust biomass with gaseous fossil fuel. The pilot device was equipped with the following measurement instruments: thermocouples for local temperature measurements and gas analyzer for measurements of flue gas composition, temperature, and combustion efficiency.