Reducing emissions of CO2, providing efficient, reliable power generation and good cooperation with renewables are only a few requirements of today’s world power plants. Even though in the distant future distributed power systems relying on renewables are expected to become the core of power grids, there will still be need for green and high – efficient combustion power plants during the transition process. Classical gas-steam (CCGT) combined heat and power (CHP) plants with some ecological improvements are expected to be one of the most suitable technologies for this task. This paper presents a retrofit of a CCGT, CHP plant in Zielona Góra, regarding possible solutions of reducing CO2 emissions and cooperation with renewables producing hydrogen. Two modernization variants were considered: CO2 capture during the combustion of syngas from sewage sludge gasification and zero-emission combustion of hydrogen in gas turbine. Both technologies were shortly described and paths of future development have been shown. All the calculations were conducted using numerical modelling with computational tools, which help verifying the concepts at an early stage of development. Avoided CO2 emissions for both solutions and other relevant indicators for CO2 emission level assessment were shown, taking into account the net power and efficiency penalties. The proposed retrofits were compared to the base case and for other conventional, gaseous fuels such as methane and nitrogen-rich natural gas. Preliminary calculations showed 5-10% efficiency penalty depending on fuel considered and CO2 concentration, for 90% capture efficiency. Indicators for CO2 emissions for hydrogen combustion came out much better than for CO2 capture from syngas combustion. This comparison was made to draw conclusions on the legitimacy of using such solutions and to propose further development possibilities.