(49f) A Hierarchical Techno-Ecological Decision Procedure for Sustainable Design

In 1985, J. M. Douglas published “A Hierarchical Decision Procedure for Process Synthesis”. This paper outlined tiers for decision-making in chemical manufacturing processes with a conceptual design approach aimed to reduce backtracking for project decisions. In practice, the idea is to generate and filter design alternatives at appropriate stages, adding details to the process flow sheet with each phase. This approach is widely adopted in chemical engineering curriculum and design software. With rapid growth of sustainable engineering and new approaches to process synthesis, there is a need for an updated hierarchical approach to incorporate more current sustainable design research. Such a hierarchy can be applied in many ways including determining the proper sustainability assessment methods to conduct, ensuring innovative solutions outside of the technological system boundary are considered, and assisting in the navigation of when to consider certain details or higher resolutions of variables.

Previous work on techno-ecological design has led to innovative approaches for manufacturing sites, supply chains, academic campuses, and others. These approaches include ecosystems and their services within design frameworks, leading to innovative solutions that can reduce environmental and health impacts and, in some cases, costs. Other parties, such as the Intergovernmental Panel on Climate Change, have also identified nature as a significant role in mitigating climate impacts and increasing community resiliency based on the many co-benefits provided by healthy ecosystems. In the pursuit of sustainability, this new hierarchical approach considers techno-ecological systems. Further, the approach is guided by six previously identified necessary (but not sufficient) considerations for claiming sustainability: impacts across multiple spatial scales, temporal changes, cross-disciplinary effects, interactions between multiple stocks and flows, ecosystem demands, and the capacity for ecosystems to supply demanded inputs. This approach is constructed based on previous experience, literature reviews, and within techno-ecological sustainable design.

This work provides both a new conceptual approach and an example toy problem that highlights potential benefits and insights for application to sustainable design projects. The approach presents hierarchical levels of analysis for both technological process design and the surrounding socio-ecological landscape. Each level considers different scales and resolutions of time and space along with decisions around choosing available technological and ecological solutions, or unit operations. One of the main benefits of utilizing this approach is to simplify quantitative analysis and limit decision variables and equations within computable limits. One challenge in designing techno-ecological systems is the inclusion of spatial variables and boundaries that landscapes inherently have. Further, the temporal dynamics of technological and ecological systems are drastically different where ecosystems take years to develop and mature while technological systems aim to control and adjust systems based on much finer temporal resolutions. This hierarchical techno-ecological decision procedure reveals a process for generating new techno-ecological design solutions and assists in limiting mathematical complexities and program size for optimization, or other quantitative design methods, based on its multi-phase approach. The goal of this concept is to bridge academic sustainable design work with industrial practice and curriculum in the classroom. Further, we aim to continue to highlight the opportunities of synergizing technological design with the functions of nature in the search for sustainable solutions.