Sustainability by cyclic manufacturing: Assessment of resource preservation under uncertain growth and returns
2015
Tsiliyannis, Christos Aristeides
Resource preservation (RP) and homeostasis is a key aspect of sustainability and a prime target of policy considerations. Heralded as an efficient means towards sustainable production and consumption of manmade products, cyclic manufacturing (CM) is fundamentally different from traditional open loop manufacturing: raw materials are not merely resources extracted from the natural environment, but products returned by the consumer as well. RP via CM strongly depends on the quantity and quality of returns. Affected by several factors (economic cycles, income, technological innovation, energy efficiency, social trends, etc.), the majority of returns, including end-of-life (EoL) returns, are random and unobservable. The present work reveals the intricacies of RP under real market conditions, including uncertainty in growth, stock and returns. It is shown that the recycling rate, the reuse rate and key parameters, including mean lifetime, number of reuse cycles and cyclic frequency, may not discern RP enhancement. A simple dimensionless rate is proposed and shown suitable for RP assessment. Its efficacy is demonstrated under leveled consumption/sales, growth or contraction: the minimal rate for reduced virgin material demand is higher under rising sales/consumption and lower in periods of economic austerity. The results may be useful for RP monitoring and proactive sustainable policy.
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