The United Nations Framework Convention on Climate Change (UNFCCC) states that Indonesia is committed to contributing to global climate change solutions. The government will also continue to encourage the development of a number of renewable energy (EBT)-based power generation projects. This is based on the use of renewable energy which is still low, namely around (1.9%) 8215.5 MW. Meanwhile, the potential for EBT to become energy can be around 443,208 MW. One source of EBT in Indonesia that can be utilized is Biomass. Co-firing of biomass is a relatively cheaper option and does not require investment in new power plants. However, Co-firing combustion has several aspects that need to be studied, such as temperature combustion and the generation of gas emissions. Therefore, this study aims to determine the temperature and the emissions resulting from co-firing of palm kernel shell biomass. This research was conducted using the Computational Fluid Dynamics method on stoker boiler model. The test parameters of the research was the maximum and average temperatures in the furnace, and the average and maximum fractions of CO2, SO2 in the stoker boiler furnace. From the research conducted, it was found that the resulting combustion temperature decreased as the co-firing fraction of the biomass increased. However, CO2 gas emissions increased and SO2 decreased with increasing fraction of co-firing biomass which showed a decrease in harmful gas emissions and complete combustion that occurred in the furnace.