Quantifying the indirect/direct water usage of common manufacturing processes

Jonathan Ogaldez, Purdue University

Abstract

The research conducted for this thesis involved investigating the water usage associated with different manufacturing processes. Following preliminary findings a more inventory-oriented methodology was used to account for the water consumption for both direct and indirect usage. Usable water in the form of freshwater is limited; much of the usable water forms a small percentage of what makes up the complete water resource on this planet. The impacts on the environment and the resources that are available are of great concern especially in regions where water is scarce. Water is used both directly and indirectly in manufacturing. One important manufacturing perspective of indirect use of water for manufacturing is related to power consumption. Energy use in the form of electricity drives many manufacturing processes and enables the creation of a variety of products. A mixture of electricity generating technologies provides energy to the power grid, used in the United States. Generally, the power generating technologies that are available and presently used are coal, nuclear, hydro, natural gas, and renewables. The mixture of electricity generating technologies differs from state to state depending what natural resources are available for that particular region. Developing an understanding of the state-to-state mixture differences and the mixture difference effect on the water footprint represented much of the initial research of this thesis. A database was identified that contained the power generation mixture for each state. The power grid and the means of sharing electricity between different states were not considered in this thesis and was beyond the scope of this study. The water energy relationship is still being studied by researchers and much of the impacts of system architectures and energy creation and use on water is still in its beginning stages. Researchers, engineers and manufacturers will be able to control and predict the impacts to our environment much more systematically as policy makers and governments become more supportive in these kinds of efforts. Initially, this research began by investigating the use of energy in machining processes. The machining processes that were chosen were drilling, milling, and turning. The energy required to power such processes was analyzed by using the unit process life cycle inventory (uplci) methodology for frequently used machining materials such as: steel, aluminum, and copper. The power use varies significantly due to the different material properties. For the water footprint in the machining process the results are significant, the Scope 1 definition was strictly for Metal Working Fluids (MWFs) and based on two different allocation methods. Scope 2 water footprint was larger than that of Scope 1 which factored in the power usage and power grid mixture. Quantifying the water and energy use per unit volume was the most practical method to investigate water usage in machining. Similar to a carbon footprint there are three scopes that had to be defined in order to capture the use of water. Water consumption and withdrawals with direct and indirect usage were defined to appropriately allocate water. Scope 1 is direct water usage from Metal Working Fluids (MWFs), Scope 2 is indirect water usage from energy use and Scope 3 all other embodied water usage. A manufacturing facility was chosen to investigate the water use for a six-month period. The facility's main manufacturing process was a stamping operation, for which material flows, and water and electricity consumption were recorded and analyzed. The water usage recorded for parts washing (cleanline) was based on the overall consumption that was experienced for sustaining the facility's production during the six month period. The water footprint for Stamping processes was also found to be very significant, although the use of water for these processes is normally considered to be minimal; however, it was found that the water usage defined in Scope 1 and Scope 2 is substantial. The water footprint will serve as a measure of the water use efficiency and water-energy relationship that exists in a process and to provide more information for industry in identifying areas that can have a potential reduction in the amount of energy and water required to function. This research provides a standard for identifying and quantifying water for direct manufacturing use and indirect water consumption for energy usage in production.

Degree

M.S.M.E.

Advisors

Zhao, Purdue University.

Subject Area

Industrial engineering|Mechanical engineering

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