One of the main obstacles to transfer to carbon neutral energy management is technological transition. An important task is to change fuel used in the boiler furnace from natural gas (fossil fuel) to biomass. The easiest but most expensive solution is the installation of biomass boiler. Other solutions include burner replacement or additional installation, but these options are more complex from the engineering and technical point of view. By replacing natural gas with wood particles, boiler output is reduced, because value of combustion heat, furnace load and specific combustion parameters are lower, as well as temperature and pollution with nitrogen oxides NOx decrease. It is especially important when energy end user improves energy efficiency and reduces energy consumption. As a result there is excess installed capacity in the boiler house. Feasibility of co-firing is calculated with Levelled Cost of Energy analysis. This research is important as natural gas will gradually become replaced by biogas that is carbon neutral. Moreover, biomass co-firing with solid wood particles will reduce the impact on climate change.