(525b) Process Simulation with Trees As Unit Operations for Improving Air Quality, Sequestering Carbon, and Reducing Cost

To reduce the environmental impacts of chemical processes, engineers have focused on limited components such as reducing waste and process integration. Other efforts focused on increasing the efficiency of the process by minimizing the consumption of raw materials or energy use. However, these efforts do not address the impact of the process on natural ecosystems and local communities. To achieve a sustainable design, chemical processes must account for the burden of using ecosystems goods and services and their limited capacities.

Frameworks such as techno-ecological synergy (TES) intend to find synergistic designs that combine the efficiency and performance of technology with nature’s ability to provide similar services and tasks to technology[1]. Such services include carbon sequestration, air, and water quality regulations, and renewable energy. Ecosystem services also provide other benefits to the process and local communities like heat reduction from trees and habitat for biodiversity. Integrated design of manufacturing processes with supporting ecosystems can enhance the process by reducing raw material consumption and emissions and preserving the ecosystem.

However, ecological systems have been ignored in chemical process design, resulting in a huge gap between engineering and ecological science. Although models for ecological systems are readily available in the literature, engineers are hesitant to utilize these models without familiar tools and the traditional undervaluation of ecosystem services' role and the uncertainty of their performance.

To overcome some of these barriers, ecosystems can be classified as unit operations since they can be designed to achieve specific tasks[2]. Constructed wetlands, for example, can be designed to treat certain pollutants from wastewater. Capitalizing on this idea will allow easy and relative comparison to technological alternatives with the same function. In previous work, we developed a module for constructed wetlands used for wastewater treatment in the biodiesel manufacturing process[3].

In this work, we build on that concept by focusing on integrating vegetation as unit operations in process design. Trees provide numerous benefits relevant to the chemical industry, such as carbon sequestration and the removal of air pollutants. We developed a practitioner-friendly simulation module that utilizes sophisticated rural and urban forestry models developed by the online i-Tree assessment tool[4]. The developed module is available in popular simulation software such as CHEMCAD, ASPEN, and CAPE-OPEN interface standards.

The module will enable the testing, validating, and implementing of new and innovative designs that account for nature's capacity. It will also highlight the economic, social, and environmental benefits and the potential tradeoffs of the integrated design. Moreover, this will provide new insights that will aid the decision-making process toward sustainable design. We will also demonstrate the module through a case study of a combined heat and power plant and highlight some of the alternative integrated designs that are environmentally and economically superior.

References:

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

[2] Gopalakrishnan, V., & Bakshi, B. R. (2018). Ecosystems as unit operations for local techno‐ecological synergy: Integrated process design with treatment wetlands. AIChE Journal, 64(7), 2390-2407.

[3] Aleissa, Yazeed M., and Bhavik R. Bakshi. "Constructed Wetlands as Unit Operations in Chemical Process Design: Benefits and Simulation." Computers & Chemical Engineering 153 (2021): 107454.

[4] i-Tree Software Suite (2022), http://www.itreetools.org