Improving the Environmental Performance of Manufacturing Systems via Exergy, Techno-ecological Synergy, and Optimization

Increasing world population, dwindling resources, and the degradation of natural ecosystems make thermodynamic and environmental improvement of industrial processes a prominent goal for the engineering community for the foreseeable future. The present work contributes to this effort by exploring the application of life cycle assessment, first law energy analysis, and exergy analysis to emerging technologies. A process for producing titanium dioxide nanoparticles is investigated at both the local process and broader life cycle scales. This case study reveals that decisions made at one level of analysis are not always ideal when the boundaries are expanded to include the supply chain and environmental impacts. In addition, the insights gained from exergy analysis are not available from any other method of evaluation, suggesting that it should be broadly embraced as a process improvement tool. Traditional engineering design is concerned with technological details and economics. Operating conditions and design alternatives are balanced with the bottom line. The second portion of this work shows how environmental considerations can be included in the design process in such a way that both the technological and ecological spheres can benefit. This is illustrated through two case studies pairing engineered systems with carbon sequestration available in natural systems. The first case study looks at the CGAM cogeneration plant from the industrial ecology literature. By simulating a hypothetical carbon network, allowing for sequestration through afforestation and underground geological storage, possible economic scenarios for complete or partial carbon mitigation for the power plant are explored. The second case study considers a biosolids network for the City of Columbus. Biosolids produced at two wastewater treatment plants in the City are allocated between four end-of-life alternatives: incineration, landfilling, composting, and land application as fertilizer. Most stages of the wastewater and biosolids treatment release greenhouse gases. A subnetwork of greenhouse gas mitigation techniques has been simulated using the EcoFlow software package. The overall system was optimized, and the results show significant improvements from the base case with respect to both the economic and environmental objectives. The effects of a carbon tax on the optimal solutions are also examined.

Where to find

Author Geoffrey Grubb
Institution The Ohio State University
Advisor Bhavik R. Bakshi
Expected graduation 2010