A conceptual model of a sustainable system based upon observations of biodegradable plastic packaging film experiments and material flow

Abstract

One can imagine full knowledge of a system allows for optimal decision making when problems arising within that system need to be solved. In reality, solutions involving any non-trivial system must be pursued with incomplete knowledge. In light of the complexity and diversity of current industrial economic systems and the decision-making processes pertaining to them, integrating streams of knowledge would improve problem solving outcomes on such scales. More specifically, it could potentially address how to compare the rate of problem proliferation to solution implementation within a system. However, successfully integrating knowledge of diverse systems towards a common purpose requires careful and consistent analogies to be constructed between the entities of those systems. The current work investigates the merits of such an approach for resolving sustainable development issues. The hypothesis is that knowledge of what influences the flow and transformation of matter, (that is, what influences a common phenomenon throughout life-supporting systems), can facilitate this integration. The problem of accumulating material waste is used as a vehicle to focus the discussion. To this end, the foundation of the work is an experimental study into the development of a starch based biodegradable plastic packaging film. The two main constraints on sample production were to minimise cost and maximise biodegradability. Slit die rheological data is gathered for five samples selected from polymer extrusion trials as part of describing their viscous behaviours via a semi-empirical model incorporating die temperature (measured at 120, 140 and 160°C) and shear rate (altered by screw speeds of 5-50 rpm). The samples differ in additive content and extrusion passes from a baseline starch/water/glycerol (~73/18/9.0 wt% total) combination extruded once to the addition of cross-linking agents and surface modifiers (<1 wt% total) extruded twice. GPC, DSC, tensile strength and moisture absorption analyses join the rheological data to explain observed flow behaviour in terms of the influence of sample constituents, processing conditions and the ensuing molecular transformations. Regression coefficients, R2, between 0.957 and 0.981 are obtained for model predicted viscosity versus observed viscosity suggesting a satisfactory fit of the model for the five samples within the experimental parameters. The experimental study represents a typical analytical approach to developing a technical solution. Yet while technology will remain indispensable to problem solving, there is a iii need to realise that splintering knowledge into disciplines of the ever finer detail required to extend technical accomplishment, must also be complemented by a synthesis of associated facts and relevant theories to address more encompassing problems associated with sustainability of the modern industrial economy. Therefore, considering the relative success of modelling the viscous behaviour of the starch based plastic samples, it was proposed to extend the concepts of rheology used to explain the flow of matter on the molecular scale to the flow of matter on the scale of the industrial economy. To whatever extent possible, the advantages of being able to predict how such flows respond to industrial economic decisions would contribute to the research of sustainable systems. The assumption is made here that an apt material flow undergirds a sustainable system. A conceptual model is constructed based on this assumption that aims to simplify the impediments associated with mediating the complexity of the industrial economic system with an ecologically sustainable one. Ultimately, a system is described in which a fundamental unit, or monad, is defined composed of a set of resource entities, a set of product entities, and the set of process entities that transforms the former to the latter over time. Extrapolating this monad description to define humanity as the set of process entities, any system can then be defined as a nexus of three flows: matter/energy, knowledge/information/data and money/value, where matter/energy forms the set of resource entities and money/value forms the set of product entities. Aspects of the model are demonstrated by applying it to parts of the experimental study and to the operation of a material reuse business. The model has immediate practical benefit as a framework for organising information for the purpose of assessing and developing the sustainability of a system. It has further potential as a basis for a mathematical model that could take advantage of well-defined techniques of analogy and system integration to assist in determining the ratio between the rate of problem proliferation and the rate of solution implementation within a complex system.