A Systemic Evaluation of Reuse, Recycling, and Reduction Strategies in the Circular Economy for Global Sustainability Using an Integrated Planetary Model

Circular economy (CE) has been proposed as a promising approach for sustainable resource management. CE includes reduce, reuse, and recycle (3R) as the three main levers. Their relative impacts and synergistic effects to achieve overall sustainability need to be assessed for policy prioritization. This work uses an integrated planetary model (IPM) to compare these three CE practices. The IPM is a food web model representing the global system in compartmental form. It includes multiple trophic levels, a human society, a traditional industry, and the recycling industry. The study first extends the IPM to implement the reuse component of CE to complement recycle and reduce options. Reuse is captured by modeling extended use of industrial goods over multiple time steps by humans. Reduce option is modeled through steady reduction in the demand for products, while recycle option is modeled through a circulation industry post use phase. The integrated model is simulated for different combinations of these 3R options. Additionally, fractions of population practicing reuse is also varied. Simulation results show that by doubling the reuse time, there is a 50% reduction in minimum recycling rate and fraction of the population engaged in reusing required to achieve sustainability. However, very aggressive reuse practice is counter-productive, as it leads to human domination of resources and extinction of open-access grasslands. This must then be balanced by lower recycling rates. Results also show that as we move beyond a human centric view, the sustainable operating zone of 3R shrinks significantly to ensure the survival of all components of the ecosystem.