(681c) Designing Techno-Ecological Synergies While Accounting for Ecosystem Dynamics

Industrial processes are designed from a superstructure of multiple production pathways and the most optimal design is selected based on multiple objectives. Design objectives usually include economic goals such as maximizing net present value while simultaneously reducing impact from processes by choosing raw materials that are least toxic and identifying pathways that result in minimum emissions. However, this method towards designing industrial systems fails to address the underlying issue that the current demand for natural resources and ecosystem goods and services exceeds the rate at which these services can be supplied by ecosystems. This difference between the ecosystem service demand and supply is largely unaccounted for during design of industrial systems and ignoring the role of supporting ecosystems and the limit on ecosystem service supply has been one of the major causes for ecosystem degradation.

Originating from the concept of `unit operations', this work expands the scope of traditional process design methodologies to include ecosystem services within the design framework, by treating ecological systems as unit operations, with the goal of building process flowcharts based on the unit operation concept of ecosystems. Previous work on the use of Techno-Ecological Synergy (TES) framework for the assessment and design of systems including industrial sites [1], residential [2] and agricultural systems [3] have shown the economic and environmental benefits of using this approach. However, none of these studies consider interactions between detailed process-level decisions and the design of supporting ecosystem services. In this presentation, we show that simultaneous selection of process design variables and ecological variables while accounting for the variability and dynamics of ecosystems results in robust systems that tend towards absolute sustainability while being economically feasible. Variability and dynamics of ecological systems arises due to changes in meteorological conditions and seasonal variations. We show that, such robust systems can be designed by identifying a combination of technological and ecological alternatives.

The overall system is designed to maximize the total net present value and maximize the net ecosystem services supply with the goal of achieving absolute sustainability. A multi-period optimization problem formulated as a nonlinear program (Mo-NLP) is solved and tradeoffs are identified between maximizing the net present value of the system and the net ecosystem service supply for multiple ecosystem services for multiple time periods in a year.

Application of this framework to a biofuel production system along with a forest and wetland ecosystem indicates that systems designed by accounting for ecosystem service supply results in novel designs that have a higher economic value, and higher sustainability index. Preliminary results for the multi-period optimization problem revealed that selecting a combination of technological and ecological options during certain seasons have a higher economic and environmental performance compared to a purely technological design. Thus, coupled TES systems are expected to have economic and environmental advantages over conventional systems design, mainly due to the reduction in external inputs by moving towards a closed loop production system.

References:

[1] Gopalakrishnan, V., Bakshi, B.R. and Ziv, G., 2016. Assessing the capacity of local ecosystems to meet industrial demand for ecosystem services. AIChE Journal, 62(9), pp.3319-3333.

[2] Urban, R.A. and Bakshi, B.R., 2013. Techno-ecological synergy as a path toward sustainability of a North American residential system. Environmental science & technology, 47(4), pp.1985-1993.

[3] Hanes, R.J, Gopalakrishnan, V., Bakshi, B.R. Synergies and trade-offs in renewable energy landscapes: Balancing energy production with economics and ecosystem services. Submitted. Applied Energy.