(718c) Towards Integration of Design and Operation of Techno-Ecological Synergistic Systems

Over the last few decades, the engineering community has dedicated an immense amount of effort to minimize its impact on environment. Innovations like integrated mass and heat exchange network, waste reduction algorithms and eco-industrial parks are such examples that have helped reduce the impact of the chemical industry on environment [1]. Life cycle assessment and optimization methods were developed to avoid shifting of impacts and ensure individual unit scale reductions are reflected across the supply chain and product life cycle. Although these innovations have enhanced quality of human life and ecosystems, environ- mental issues like lake eutrophication, global climate change and air pollution in major cities across the global and in US persist. The currently developed impact reduction methods failed to determine the appropriate level of reduction in order to avoid ecological overshoot.

To address this fundamental challenge, there is a need to shift engineering design paradigm to explicitly consider capacity of ecosystems in technological designs. The framework of Techno-Ecological Synergy (TES) is one such approach that enables the explicit inclusion of ecosystem capacity in design and operation of manufacturing process by proposing sustainability metrics across local, regional and global scales [2]. As opposed to previously developed methodologies, TES aims to reduce emissions through a synergistic improvement in process efficiency and ecological capacity by investing in ecosystems as unit operations. Increased reliance on ecosystems for efficient functioning of technological systems incentivizes their expansion and protection while providing economically and environmentally win-win solutions.

Inclusion of ecosystems like forestry, wetlands, etc. as unit operations in design and optimization of technological systems are accompanied with their novel set of design and operational challenges. While the design challenges are often spatial placement and service shed boundary delineation problems, the temporal nature of operational challenges can be partitioned across three scales: (i) long-term planning, (ii) mid-term scheduling and (iii) short-term control problems. Typically, the planning scale would be concerned with an increase in ecosystem capacity over span of years such growth of forest or maturation of wetland. The month-to-month variation in the ecosystem capacity due to seasonal variation is accounted by the mid-term scheduling problem to maximize the operational performance of the plant. Lastly, the minutes-to-hour scale local control decisions ensure satisfaction of critical sustainability and safety constraints. Along with above challenges, the TES design and operation problem also need to immunize against the inherent uncertainty in predicting weather on which the ecosystem’s productive is dependent.

Bakshi and co-workers have applied the framework of TES in design of sustainable biofuel supply chain [3], biodiesel manufacturing [4] and watershed management to demonstrate a possibility of win-win solutions using ecosystems as unit operations. The applications have largely ignored operational challenges involved with inclusion of ecosystems. Previously, Shah and Bakshi [5, 6] solved an integrated design and planning problem over a span of 20 years to demonstrate that a TES design for air quality regulation case study can lead to environmentally, societally and economically win-win solutions. They considered a forest ecosystem along with technocentric selective catalytic reducer (SCR) to design and operate a chloralkali production facility under monthly aggregated NO2 sustainability requirement. The sustainability constraint was based on extensive mass-based emission requirement, while the practical human well-being constraints are based on intensive property like concentration in form of Air Quality Index (AQI).

In this work, we expand the integrated design and planning framework to explicitly ac- count for AQI constraints on hourly scale as well as incorporate the shorter-term scheduling scale in the long-term design and planning problem. We define and solve the integrated de- sign and operation problem at various scales namely hourly, weekly and monthly to demonstrate the effect of aggregation on the optimal design and operation. We further bridge the scheduling and planning operational scale using an approximate dynamic problem formulation, where the smallest scale hourly decisions are approximated using a surrogate deep neural network model. Availability of hourly scale modified intensive resultant concentration data allows calculation of accurate hourly scale damages and benefits to human life due to NO2 emissions. This work is a step toward a fully integrated design and operation framework for engineering design in the presence of dynamic ecosystem services.

References

[1] B. R. Bakshi. Toward Sustainable Chemical Engineering: The Role of Process Systems Engineering. Annual Reviews in Chemical and Biomolecular Engineering, Accepted, 2019.

[2] B. R. Bakshi, G. Ziv, and M. D. Lepech. Techno-ecological synergy: A framework for sustainable engineering. Environmental science & technology, 49(3):1752– 1760, Feb 3, 2015.

[3] T. Ghosh, X. Liu, and B. R Bakshi. Including ecosystem services in sustainable process design across multiple spatial scales. In Computer Aided Chemical Engineering, volume 44, pages 1837–1842. Elsevier, 2018.

[4] M. Charles, G. Ziv, G. Bohrer, and B. R Bakshi. Connecting air quality regulating ecosystem services with beneficiaries through quantitative serviceshed analysis. Ecosystem Services, 41:101057, 2020.

[5] U. Shah and B. R. Bakshi. Accounting for nature’s intermittency and growth while mitigating no 2 emissions by technoecological synergistic design-application to a chloralkali process. Journal of Advanced Manufacturing and Processing, 0(0):e10013, Mar 28, 2019.

[6] U. Shah and B. R Bakshi. Quantification of physical and monetary benefits of forest ecosystem: A case study for net positive impact manufacturing. In 2019 AIChE Annual Meeting. AIChE, 2019.