Integrating G2G, C2C and resource flow analysis into life cycle assessment framework: A case of construction steel's resource loop

This paper presents a new life cycle assessment (LCA) approach to model life cycle impact of materials that integrates both Cradle-to-Grave (C2G) and Cradle-to-Cradle (C2C) approaches. The new approach, also known as the resource loop, has the capability to capture both C2G and C2C lifecycles of most products, processes or policies. The C2C LCA model represents the footprint of a product, process or policy that never ends (i.e., recycled or reused). It reflects the footprint of a product, process or policy that terminates at the end of its useful life (i.e., disposed or landfilled). In this paper, Material and Energy Flow Analysis (MEFA) is integrated into the C2C LCA model to enhance the model's capability to capture and integrate material and energy information internal and external of LCA. The flows are relabeled “leaks” and “feeds”, of which the material and energy could leak out of or feed into the life cycle system. The “leaks” and “feeds” reflect the flows of materials and energy in and out of the life cycle process. They can also be integrated with the life cycles of other product, process or policy. Such integration is a step closer toward a more comprehensive LCA model for a finished product that contains multiple material and energy flows (e.g., a building). Resource loop (RL) reflects the material and energy flows and loops of one or more complex systems more accurately. The RL incorporates leaks and feeds that reflect the reality of a product's lifecycle. Through data collected from selected sources, the paper illustrates the use of the construction steel RL. For every 1 kg of construction steel product made and disposed, 0.74 kg was found to remain in the loop through reuse or recycling. The remaining 0.26 kg ends up in landfills representing unrecoverable “leaks”.