Designing industrial symbiosis

The field of industrial ecology (IE) has grown rapidly in the two decades or so since the seminal paper “Strategies for Manufacturing” by Frosch and Gallopoulos appeared in Scientific American in 1989. This article described possibilities for establishing symbiotic relationships within industrial systems — in direct analogy with similar relationships found in natural ecosystems — in order to enhance efficiency of resource use and reduce generation of wastes. This field, which seeks to enhance the sustainability of industrial systems by emulating cyclic flows of materials in nature, has spawned specialized terms such as “industrial symbiosis” and “industrial ecosystems.” It has attracted intellectual contributions from researchers throughout the world with diverse backgrounds, including engineering, physical and life sciences, economics and business management. Two decades of IE research has also led to the emergence of key journals (e.g., Journal of Industrial Ecology and Journal of Cleaner Production), dozens of books, and countless research articles.

One of the key concepts in IE is industrial symbiosis (IS), which may be roughly defined as the exchange of waste streams among adjacent industrial plants for the explicit purpose of enhancing sustainability. By definition, the streams exchanged in IS are not the main products of the business entities involved; rather, they represent new opportunities that arise outside of normal operations. Hence, in principle, companies involved in IS schemes benefit not just from enhanced environmental performance, but also through added revenues (i.e., from the sale of “waste” streams that have been identified as being a useful input for another plant’s operations) or reduced costs (i.e., from the purchase of “wastes” as lower-cost substitutes for regular raw materials). The concept of IS has been proven in practice many times over, most notably through the celebrated case of the Kalundborg system in Denmark, where various waste streams are exchanged among key players that include a thermal power plant and a small city, among others. Early demonstrations of IS have led to the emergence of eco-industrial parks (EIPs), which are industrial parks planned to facilitate the emergence of precisely the type of symbiotic linkages idealized by IE researchers. Nowadays, such EIPs exist in various parts of the world, and have achieved various degrees of success in establishing sustainable closed-loop systems.

Among IE researchers, there has been a long-standing debate as to whether EIPs are best left to spontaneously emerge out of individual firms’ profit-maximizing decisions (as argued by Marian Chertow in here 2007 paper “Uncovering industrial symbiosis” in the Journal of Industrial Ecology), or whether they need to be planned using a top-down approach. The latter school of thought is particularly prevalent in Asia, and is reinforced by the growing body of literature on the use of various quantitative decision support methods for planning EIPs. Many such techniques have been proposed by researchers (myself included) in the related discipline of process systems engineering (PSE). Recent work in this field has resulted in the fusion of mathematical programming, artificial intelligence (AI) and game theory to account for the complex factors that govern the formation of EIPs. In addition to the physical considerations of material and energy flows among industrial plants, it is necessary to also account for the conflicts of interest that inevitably arise when companies interact with each other. The role to be played by governments acting as facilitators of the emergence of IS adds a complicating dimension (and thus, an interesting research challenge as well). One theoretical approach, developed by my colleague, Dr. Kathleen Aviso, as part of her Ph.D. thesis, makes use of a nested, two-tier optimization model that is then solved heuristically using an AI-based strategy; this work (co-authored with me, Dr. Alvin Culaba of De La Salle University, and Dr. Jose B. Cruz, Jr., then affiliated with Ohio State University) appeared in 2010 in the IChemE journal Process Safety and Environmental Protection, and was recently recognized in the editor’s report as the journal’s most cited article in the past three years. More recently, I have started work with a long-time collaborator and his Ph.D. student (Dr. Denny Ng and Rex Ng, based at the University of Nottingham’s satellite campus near Kuala Lumpur) on similar methods for planning EIPs based on the booming Malaysian palm oil industry. I have also started to conceptualize a novel (but to date hypothetical) symbiosis scheme with my DLSU colleague, Dr. Luis Razon, which involves a “calcium loop” between a power plant and a biochemical factory.

Clearly, there must be many more similar opportunities for any research team with the right mix of skills, imagination, energy and motivation to take up the challenge. Time will tell if such novel IS schemes actually come to fruition — but this is something I try not to worry too much about as a researcher. What is essential for now is that the ideas are developed rigorously, subjected to proper critical scrutiny, and disseminated broadly, to become a small but solid part of the global scientific enterprise.

* * *

Dr. Raymond R. Tan is a university fellow and professor of Chemical Engineering and De La Salle University. He is also the director of the university’s Center for Engineering and Sustainable Development Research (CESDR). He is a leading process systems engineering (PSE) researcher in Asia, and has published over 80 articles in various chemical, environmental and energy engineering journals in the past decade. His current Scopus h-index is 21. He is a member of the editorial board of Clean Technologies and Environmental Policy (Springer) and co-editor of the book Recent Advances in Sustainable Process Design and Optimization (World Scientific). In addition to being the recipient of multiple awards from the National Academy of Science and Technology (NAST) and the National Research Council of the Philippines (NRCP), he has also been recognized for three highly cited papers in journals of the IChemE (Institution of Chemical Engineers, UK). He can be contacted via e-mail ([email protected]).