Thursday, December 8, 2016

Sustainability and Operations Research: A Trek Down Memory Lane from Transportation to Supply Chains

Given the interest my blogpost on Professor Joe Sarkis' talk on greening supply chains generated I thought that I would write this piece on sustainability and operations research from the perspective of how we got interested in the subject and where it has taken us.

Professor Sarkis also mentioned in his presentation that he, like I and my research group, have been working on sustainability for a while - actually two decades and since we are hearing that "sustainability" is some fields, including operations management, is being perceived as being relatively new, I thought it deserved some commentary.

I have always been one who loves nature and I get some of my best ideas on hikes. Clean air, clean water, fresh food, and a healthy, peaceful environment we all deserve and they are essential to our well-being  and that of future generations.
As a research topic, I became interested in sustainability while working with two doctoral students at the Isenberg School of Management: Kanwalroop "Kathy" Dhanda and Padma Ramanujam in the 1990s.

Together we wrote the Environmental Networks book, which was published in 1999, and the year after, my Sustainable Transportation Networks book was published.

Vice President Al Gore wrote me a nice letter on the publication of my Sustainable Transportation Networks book, which now hangs in my office at the Isenberg School.

Prior to the publication of these books, I had co-authored several papers, which also provided the seeds for our sustainability work. These included a 1996 paper in Operations Research, written with Sten Thore and one of my first PhD students, Jie Pan, who tragically died of an autoimmune disease shortly after having receiving tenure. With Padma, that same year, we had also published a paper in Transportation Science.

Padma's dissertation,  Transportation Network Policy Modeling for Congestion and Pollution Control: A Variational Inequality Approach, was awarded a Transportation Science & Logistics dissertation prize from INFORMS in 1999, a great honor.

Some other early papers on various sustainability of ours included: "A Multimodal Traffic Network Equilibrium Model with Emission Pollution Permits: Compliance versus Noncompliance," published in Transportation Research D in 1998 and "Marketable Pollution Permits in Oligopolistic Markets with Transaction Costs," which appeared in Operations Research in 2000. I also wrote several papers on emission paradoxes, one with another doctoral student of mine, now Professor June Dong.

Hence, we were proposing tradeable pollution permits even for transportation networks in the 1990s. Padma is now working at SAS, a fabulous analytics firm, and is based in Cary, North Carolina, whereas Kathy has had several tenured professorships at different universities and continues to work on sustainability issues.

Interestingly, the Virtual Center for Supernetworks, which I founded in 2001 and continue to serve as Director of, was initiated because of three NSF grants that I had received at that time plus two AT&T Industrial Ecology Fellowship grants, which envisioned such a center. Hence, the sustainability theme has been central to our research.

In 2005, with a doctoral student from Japan, Fuminori Toyasaki, who is now a professor at York University in Toronto, I published a paper that is highly cited: "Reverse Supply Chain Management and Electronic Waste Recycling: A Multitiered Network Equilibrium Framework for E-cycling." This paper was recognized by Transportation Research E as a most cited paper.

In 2002, I had co-authored the paper, "A Supply Chain Network Equilibrium Model," with June Dong and Ding Zhang and this paper, which introduced multiple tiers of interacting decision-makers, who compete across a tier but cooperate between tiers, generated new frameworks for work on sustainability and supply chains as well. We also conducted research on energy supply chains and I have a series of papers in this area, some of which also include carbon taxes. An example is the paper, "Modeling Generator Power Plant Portfolios and Pollution Taxes in Electric Power Supply Chain Networks: A Transportation Network Equilibrium Transformation," co-authored with Kai Wu, Zugang Liu (another former PhD student of mine who is now a tenured professor), and John Stranlund, a faculty member at UMass in Resource Economics.

Another former very successful doctoral student of mine, Trisha Anderson Woolley, now a tenured professor,  also published several papers with me on sustainability, energy, and supply chains, as well as policy interventions. 

As the news about climate change resonated and its negative impacts, we continued to explore modeling of supply chains and an example of a paper reflecting this is: "Environmental Impact Assessment of Transportation Networks with Degradable Links in an Era of Climate Change, " which was published in 2010 and written with Patrick Qiang, my co-author of the Fragile Networks book (and whose dissertation received the Charles Wootan Award from the CUTC), and the "other" Professor Nagurney - Ladimer S. The paper, "Sustainable Supply Chain Network Design: A Multicriteria Perspective," written by the two Nagurneys, which was also published in 2010, remains one of the most highly cited articles in the International Journal of Sustainable Engineering.

Our more recent research on sustainability and supply chains has focused on numerous different applications, and these are quite fascinating. Much of the impetus has come from outside - such as our work on fashion and sustainability - but some of it has also been internal - as in the case of our blood supply chain sustainability research and driven by common interests and passion that I share with both students and collaborators. Examples of such papers are: Sustainable Fashion Supply Chain Management Under Oligopolistic Competition and Brand Differentiation, Anna Nagurney and Min Yu, International Journal of Production Economics, Special Section on Green Manufacturing and Distribution in the Fashion and Apparel Industries 135: (2012) pp 532-540 and Supply Chain Network Design of a Sustainable Blood Banking System, Anna Nagurney and Amir H. Masoumi, in Sustainable Supply Chains: Models, Methods and Public Policy Implications, T. Boone, V. Jayaraman, and R. Ganeshan, Editors, Springer, London, England (2012) pp 49-72.

In 2014, I was delighted to co-author a paper with two of my former PhD students, Toyasaki, already mentioned, and Professor Tina Wakolbinger, and her first PhD student, Thomas Nowak, who has since received his PhD: When and for Whom Would E-waste be a Treasure Trove? Insights from a Network Equilibrium Model of E-waste Flows, Tina Wakolbinger, Fuminori Toyasaki, Thomas Nowak, and Anna Nagurney, International Journal of Production Economics 154: (2014) pp 263–273.

Some of our other recent research has included my collaborator in Sweden, Professor Jonas Floden, since I had a fabulous Visiting Professorship at the University of Gothenburg over a 4 year period. Examples are the papers: Supply Chain Network Sustainability Under Competition and Frequencies of Activities from Production to Distribution, Anna Nagurney, Min Yu, and Jonas Floden, Computational Management Science 10(4): (2013) pp 397-422 and Fashion Supply Chain Network Competition with Ecolabelling, Anna Nagurney, Min Yu, and Jonas Floden, in Sustainable Fashion Supply Chain Management: From Sourcing to Retailing, T.-M. Choi and T.C.E. Cheng, Editors, Springer (2015) pp 61-84.

Another paper that I am quite proud of in which I move from transportation to supply chains to sustainable cities is, "Design of Sustainable Supply Chains for Sustainable Cities," invited paper for the Complex-City Workshop, December 5-6, 2011, Amsterdam, The Netherlands, Environment & Planning B 42(1): (2015) pp 40-57.

Our research on food supply chains, conducted with Professor Min Yu (yes, another former terrific Isenberg UMass PhD alumna in Management Science), and published in the European Journal of Operational Research, also has components of sustainability since we consider waste. The same holds for our work on pharmaceutical supply chains.

And, for those of you interested in perishable product supply chains, including food and medical nuclear ones, in which waste is a big issue, our Networks Against Time: Supply Chain Analytics for Perishable Products, is recommended.
And the research continues into its third decade!