Ecological Robustness as a Design Principle for Sustainable Industrial Systems

Ecology has acted as a source for sound design principles and studies have examined how ecological principles can enhance sustainability in human industrial networks. Engineered systems are often designed for maximum performance, but in many cases robustness is sought with respect to unwanted variations in input or other parameters. Taguchi’s signal to noise ratio and other quality engineering principles are well known fundamentals in the field of robust design. In this paper, we will introduce flow-based equations from ecological network analysis (ENA) to determine how to modify the flows and connections in industrial systems to balance efficiency and robustness against disturbances. In ENA, the robustness of a system is given by the relationship of flow path diversity to system efficiency. Systems with diverse flows are more resilient to a disturbance since there are redundant pathways, but are inefficient precisely because they contain many flow paths with the same endpoints. Efficient systems have increased capacity to transfer material and energy, but this is at the cost of fewer pathways so the system is brittle. Thus, given a disturbance, a robust system balances redundancy with efficiency/capacity. Ecological systems seem to occupy a narrow range of states that balance efficiency and resilience to confer robustness. Human networks, like trade networks, water reclamation facilities, etc. have been analyzed using these robustness principles and methods for flow based ecological network analysis. These analyses show that human networks may be more brittle than their ecological counterparts because of insufficient flow path diversity.