(521e) life Cycle Optimization with Ecosystems As Unit Operations

Sustainable Process Design: Sustainable Process Design(SPD) is a widely prevalent approach in the chemical engineering field to account for environmental impact due to manufacturing technologies. Multi-objective approaches to account for emissions along with the economic objective (1) and treatment of the environment as an objective rather than a constraint (2) were some important steps towards development of SPD. The environmental profiling in SPD was achieved using Life cycle assessment (LCA) that traced the "cradle to gate" emissions and resource use of the concerned process. However, this method resulted in unintended and unexpected negative effects due to the system boundary cutoff of conventional life cycle analysis where only a part of the upstream life cycle of the process was captured by SPD. A framework was developed to bridge this gap by introducing a Hybrid LCA approach to SPD. Conventional SPD was modified by introducing a hybrid LCA model incorporating an economy scale to create the three scale Process to Planet framework (3). It was later expanded to integrate byproducts and include multiple objectives in economic and environmental dimensions.

Techno-Ecological Synergy:Life cycle oriented methods generally assess the impact to the ecosystem, in terms of emissions and resources used. However, they ignore the capacity of ecosystems to provide such remediation services or resources (4). The Techno-Ecological Synergy(TES) framework explicitly accounts for the supply of ecosystem services and interconnects technological systems with ecosystems through a symbiotic and synergistic relationship while maintaining that the demand of ecosystem services by technological systems do not exceed the capacity of ecosystems to provide the same. The framework has been applied successfully to determine services provided by forest and wetland ecosystems and their integration with a bio-diesel manufacturing facility.

Objectives:

This presentation presents a novel approach to bind the P2P framework with TES to perform sustainable process design while considering the supply of ecosystem services. The motivation of this study arises from the fact that technological systems can find unconventional solutions to negate their environmental impacts by harnessing the power of remediation services supplied by ecosystems. The easiest example would be a manufacturing facility directs effluents into a well-managed wetland for treatment. To do this, the plant operators should estimate supply of the treatment service through TES while SPD manages the design variables of the process to keep the effluent concentration within treatable limits. While this is an example at a local site, the same can be extrapolated over the entire life cycle of the process, extending integration of ecosystems and technologies at regional and national scales. This study currently includes ecosystems only at the equipment scale with future goal to include ecosystems at all the scales of P2P framework.

Results:

Inclusion of ecosystems as process units in system design is expected to expand the solution space leading to the discovery of "win-win" solutions that address multiple objectives. Initial analysis of a bio-diesel manufacturing case study with forest ecosystem has shown promising results for carbon dioxide emission and sequestration flows. It was observed that emission credit that the facility gets for sequestration by the managed forest can be utilized to expand the design space and improve the economic profitability of the industry while keeping total net emission quantities fixed. Hence, results demonstrated that "win-win" solutions are possible when synergistic relationships are established. The profit of the facility increases while the facility undertakes the responsibility of properly managing the forest. A comprehensive case study for the P2P-TES framework based on a power generation model or an HDA process integrated with multiple ecological systems will be undertaken with assessment of various emission flows – CO2, SO2, PM10 etc.

References:

(1)Bakshi, B. R., “Methods and tools for sustainable process design, ” Current Opinion in Chemical Engineering, vol. 6, pp. 69–74, 2014. [Online] Available: http://linkinghub.elsevier.com/retrieve/pii/S2211339814000768

(2)Cano-Ruiz, J. and McRae, G., “Environmentally conscious chemical process design, ”Annual Review of Energy and the Environment, vol. 23, no. 1, pp. 499–536, 1998.

(3)Hanes, Rebecca J., and Bhavik R. Bakshi, "Sustainable process design by the process to planet framework." AIChE Journal 61.10 (2015): 3320-3331.

(4)Bakshi, Bhavik R., Guy Ziv, and Michael D. Lepech. "Techno-ecological synergy: A framework for sustainable engineering." Environmental Science and Technology Letters 49.3 (2015): 1752-1760.