To achieve net-zero emissions by 2045 in Sweden, bioenergy with carbon capture and storage (BECCS) has been identified as a key technology. Biomass fired combined heat and power plants (bioCHPs) constitute the second largest CO2 emission source after paper and pulp plants. Therefore, integrating BECCS in bioCHPs will contribute significantly to achieve Sweden’s climate goal. In the prerequisite of maintained heat generation for district heating (DH) sectors, this paper aims to estimate the aggregated negative emissions when integrating CO2 capture into existing 110 bioCHPs, in which the boiler load can be increased to the maximum capacity. A physical model was developed for bioCHP, and the operation of an example bioCHP can be determined by the objective function of maximizing the heat for CO2 capture. Based on results of example plant, the artificial neural network models were further established to predict the capture performance from other plants. Not only the amount of captured CO2, but also the amount of avoided CO2 was examined for a better understanding of the contribution of negative emissions. It is estimated that the heat generation used for DH is 33925.83 GWh/year. The aggregated amount of captured CO2 is estimated of 23.11 Mton/year; the aggregated amount of avoided CO2 is estimated of 20.22 Mton/year. The electricity generation is found to be decreased by 8810.82 GWh/year (63.6%) when BECCS is included.