Quantifying Carbon Footprint in Industrial Heat Treatment Processes Through Life Cycle Assessment

Abstract Heat treatment processes are essential in manufacturing to enhance the properties of iron and steel components. However, they significantly contribute to greenhouse gas (GHG) emissions due to high process heating requirements. The Industrial Decarbonization Earthshot initiative by the U.S. Department of Energy (DOE) targets an 85% reduction in industrial GHG emissions by 2035, urging energy efficiency solutions for heat treatment furnaces. This emphasizes the need for accurate emissions estimation of existing heat treatment methodologies for decarbonization decision-making, and development of carbon reduction pathways. The current study provides a gas carburizing emissions calculation framework, along with a comprehensive emission profile for a 9-hour carburizing cycle in a preheated batch furnace. Through Life Cycle Assessment (LCA), Scope 1 (direct process emissions), Scope 2 (electricity-related emissions), and Scope 3 (supply chain emissions) are evaluated for a carburizing process. A detailed life cycle inventory (LCI) is compiled to quantify inputs, such as natural gas for combustion and furnace carburizing medium, endothermic gas for neutral hardening furnace atmosphere, electricity consumption, furnace insulation, and associated emissions. A heat transfer model is developed to calculate natural gas consumption, considering temperature profiles, furnace design, material properties, and energy losses. The model covers furnace heat-up and carbon diffuse-equalize phases. Natural gas combustion contributes 76% of GHG emissions followed by natural gas upstream supply chain at 22%. Endothermic gas accounts for 1% of emissions.