(706d) Designing Climate-Resilient Chemical Processes and Supply Chains

Given the looming specter of climate change, it is essential that process systems are designed to be resilient to such a future. Chemical and manufacturing processes and their supply chains are major contributors to greenhouse gas (GHG) emissions, and thus to climate change. Many systems also rely heavily on water resources, both for generating steam and for cooling the process. However, water resources could be affected by drought under future climate change due to projected increase in temperature and variability in precipitation. To combat climate change and its impact, there is a need for implementation of technologies and policy changes that reduce CO2 emissions. In this work, we investigate how manufacturing processes and their supply networks could be affected by future changes in climate and how they could be designed or modified to maintain their productivity.

Representative Concentration Pathway (RCP) scenarios, which are adopted by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5), show future GHG concentration trajectories [1]. RCP 8.5 is a high emission scenario with no mitigation, and thus, shows the continuous increase in CO2 concentrations that reach more than 900 ppm in 2100. On the other hand, the RCP 4.5 exhibits suppressed increase in CO2 concentrations due to some mitigation strategies applied in the future.

Various climate models (CMs) have been developed to estimate future climate change based on the RCP scenarios. Those models are summarized in the Coupled Model Intercomparison Project Phase 5 (CMIP5), which is a standard experimental protocol for various climate model studies. In this study, to account for variance between different CMs, we employ five CMs from LOCA (Localized Constructed Analogs) statistically downscaled CMIP5 climate projections [2]. Those CMs estimate future daily temperature and precipitation. To account for future water scarcity risk, the Soil & Water Assessment Tool (SWAT) model simulates total water yield using future climate data. Average daily water temperature is also calculated from average daily air temperature [3].

To examine climate change impacts on process design and supply chain design problems, various design constraints, such as projected water availability, water temperature, and target CO2 emissions reduction, can be considered. For example, if water temperature gets warmer due to climate change, the systems that use water for cooling are likely to withdraw and consume more water to keep the same amount of cooling energy. If this is the case, the increased risk of water scarcity may be a critical constraint for process and supply chain design problems. Alternatively, equipment may need to be redesigned to increase heat transfer area or coefficients. This could incur a financial cost. Also, depending on which RCP scenario is considered, future chemical processes may need to regulate their GHG emissions and adopt greener supply chains.

In this work, a novel framework for designing climate-resilient processes and supply chains will be proposed. Economic and environmental trade-offs of such designs versus conventional designs that ignore climate change will be discussed. As a case study, we investigate how climate change could affect urea manufacturing processes and supply chain networks in the Muskingum River Watershed (MRW) in Ohio. Specifically, we examine the effectiveness of technologies that help reduce CO2 emission and water consumption to mitigate and adapt to climate change. For example, green urea production employs water instead of methane as feedstock to provide hydrogen to the urea since the electrolysis of water usually has smaller carbon footprints than the conventional steam reforming of methane. Another technology includes the use of renewable energy sources instead of fossil fuels. Additionally, we will address flexibility of urea production processes to climate change impacts [4].

Preliminary findings of this study show that urea production in MRW may not meet the expected future demand and could face monetary losses due to the increased risk of water scarcity and warm water temperature. The results indicate that more advanced mitigation technologies and strategies are needed to maintain future productivity.

References

[1] Meinshausen, M. et al. The RCP Greenhouse Gas Concentrations and Their Extensions from 1765 to 2300. Climate Change, 109, 213-241 (2011).

[2] Pierce, D.W., Cayan, D.R., & Thrasher, B.L. Statistical Downscaling Using Localized Constructed Analogs (LOCA)*. Journal of Hydrometeorology, 15, 2558–2585 (2014).

[3] Stefan, H.G. & Preud'homme, E.B. Stream Temperature Estimation from Air Temperature. Journal of the American Water Resources Association, 29, 27-45 (1993).

[4] Grossmann, I.E., Calfa, B.A., & Garcia-Herreros, P. Evolution of concepts and models for quantifying resiliency and flexibility of chemical processes. Computers and Chemical Engineering, 70, 22-34 (2014).