Linking Industrial Ecology and Ecological Economics: A Theoretical and Empirical Foundation for the Circular Economy

The circular economy (CE) is a new model for the production and consumption of goods, which has attracted wide political attention as a strategy toward sustainability. However, the theoretical foundation of CE remains poorly structured and insufficiently explored. Recent studies have shown that the CE model draws on different schools of thought and that its origins are mainly rooted in fields such as industrial ecology (IE) and ecological economics (EE). In this article, we investigate the links between CE, IE, and EE and provide an overview of the similarities and differences between these fields. At the same time, we analyze to what extent the linkages between IE and EE can create a coherent body of knowledge for CE, and be used to identify further research opportunities. This paper shows that, until now, research on CE seems to be mainly rooted in the field of IE and based on concepts and tools that already exist in other fields, rather than inventing new ones. The reconciliation of IE and EE could provide a mechanism to extend beyond such a narrow focus, and increase knowledge of the theoretical and practical framework of CE to benefit sustainability.     

“Escherichia coli‐milk” biofilm removal from stainless steel surfaces: Synergism between ultrasonic waves and enzymes

Three different methods to standardize biofilm removal for in situ sanitary control of closed surfaces in the food industry have been developed and compared, i.e. sonication, enzymatic treatment and a combined treatment which involved the application of ultrasound to enzyme preparations. The biofilm studied was an Escherichia coli model biofilm, made with milk on stainless steel sheets. Plate counting and epifluorescence microscopy were used to assess the efficiency of each treatment. The results are expressed in percentages, 100% denoting total removal, obtained with a flat ultrasonic transducer (T1) developed and presented in a previous study. The application of ultrasound by a patented curved transducer, T2 (10 s, 40 kHz), specifically devised for closed surfaces, was not sufficient to completely remove the biofilm (30 ± 7%). This biofilm was dislodged by two proteolytic enzyme preparations tested by immersion, viz. a 15‐min application of protease (84±1%) and a 30‐min trypsin application (95±8%). Using a combined treatment, the results showed a synergism between ultrasonic waves and proteolytic or glycolytic enzyme preparations, with removal of a significant amount of biofilm, i.e. 61–96% depending on the conditions tested, i.e. two to three times greater compared to sonication alone (30%). This application was in agreement with an industrial control, i.e. a good reproducible recovery of the biofilm in 10 s compared with 30 or 15 min with the enzyme alone.     

Common dolphins form unexpected strong social bonds: insights into social plasticity of delphinids

When a social species inhabits disparate environments with different requirements, it presents an ideal study framework for investigating plasticity in social structure. Common dolphins (Delphinus delphis) are wide-ranging offshore delphinids that generally form societies with fission-fusion dynamics within large schools and exhibit weak social bonds. In Port Phillip, southeastern Australia, common dolphins of the same species are, against expectations, resident to an embayment. Residency in this species provides a unique opportunity to investigate whether their social structure resembles that of their offshore conspecifics with weak social bonds, or whether bay living leads to stronger social bonds. We investigated the social structure of 12 resident adult common dolphins, between 2007 and 2014, in Port Phillip. Network analyses revealed nonrandom associations and several strong bonds, a social structure unusual for this species. The study shows that the social structure of a wide-ranging gregarious species in Port Phillip reflects the requirements of a confined environment with limited but predictable resources. Their social structure in the bay resembles that of inshore delphinids, rather than of its own species. Our study highlights the extreme plasticity in social structure that common dolphins are capable of and the importance of the environment for social bonds.