The CO2 emissions and energy flows of a steel mill A (mill A) and petro-chemical industry B (PCI B) in southern Taiwan were investigated in this study. And the feasibility of integrating the energy flows of mill A and nearby waste management plant E (WMP E) was also evaluated in order to improve the energy efficiency and reduce the CO2 emission. The results show that the annual energy consumption of mill A and PCI B were 6,045,518 and 11,957,543 KLOE (kiloliter of crude oil equivalent), respectively. Mill A utilized less than 5% of Taiwan’s total annual energy consumption, but it used high CO2 emission coefficient fuels and accounted for 8–9% of Taiwan’s total CO2 emission inventory. However, the energy efficiency was improved, and at least 15% of total steam produced in mill A came from waste heat recycling. By recovering waste heat in mill A, 63,420 tonnes of heavy fuel oil (HFO) consumption was prevented, and thus 177,513 tonnes of CO2 were not emitted. Furthermore, WMP E is able to produce about 578,993 tonnes of process steam (17.6 kg/cm2G × 275°C) annually. These results show that creating a steam-network between mill A and WMP E can not only reduce the amount of energy consumed by the industrial park, but also brought an extra benefit of 95 million NTD/yr for WMP E. This is the first study of an innovative steam-network at an industrial park in Taiwan, and the results of this work can further be applied in other locations to improve energy efficiency and reduce CO2 emissions.