Life cycle inventory of the automotive paint processes

JCT CoatingsTech, June, 2008 by Lindita Prendi, Edwin K.L. Tam

Automotive coating processes contribute significantly to the environmental burden of vehicle manufacturing, with significant emissions released to air, water, and land, and consumption of substantial amounts of energy and raw materials. In North America, the automotive industry is currently quantifying the environmental impacts incurred during an automobile's manufacturing processes. Detailed and up-to-date life cycle inventory (LCI) data does not exist at this time for the majority of the vehicle painting processes associated with the North American-based. automotive industry. The complexity of the contemporary automobile and the numerous processes required for its manufacture and assembly, however, poses a significant set of challenges for completing a manufacturing LCI and for the practical application of manufacturing LCI information. This article presents the findings from a major LCI research project conducted in order to populate a newly emerging North American LCI database. Typical data from selected processes within a representative vehicle painting facility are discussed, as well as the challenges faced and lessons learned from completing the study.

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INTRODUCTION

The automotive manufacturing industry is one of the largest industrial sectors in North America. Millions of cars, of sizes ranging from small economy cars to large commercial vehicles, are manufactured every year. These millions of cars supply not only the demand in North American markets, but also worldwide.

In North America, the automotive industry is currently attempting to quantify and inventory the environmental impacts incurred during the automobile manufacturing processes. This data is being used to populate a public database of environmental impacts intended to enable both the private and public sector in North America to use life cycle assessment (LCA) techniques for environmentally oriented decision-making. (1)

The complexity of the contemporary automobile and the many different processes in its manufacture and assembly, however, poses a significant set of challenges for completing a manufacturing life cycle inventory (LCI). Consequently, detailed and up-to-date LCI data does not exist at this time for the majority of the manufacturing/assembly processes associated with the North American-based automotive industry.

This article will develop an LCI for automotive paint pretreatment, the first portion of the automotive paint process. Pretreatment is an ideal candidate for an LCI because of the complexity of the process stages and the resources involved, and their interrelationships with the environment. To date, a complete life cycle inventory of the pretreatment process has not been reported in literature. Previous studies have instead been comparative in nature (e.g., waterborne versus solvent paints, (2) powder coating (3) ) and so discuss relative differences, rather than focusing on absolute performance levels. This article will thus contribute valuable environmental impact information for an environmentally significant manufacturing process, and will furthermore be relevant to other industries beyond vehicle manufacture (e.g., white goods manufacturing).

BACKGROUND

Life Cycle Inventory in the Automotive Industry

One method used to evaluate the environmental impacts of a product or process is life cycle assessment (LCA). This technique quantifies the environmental impacts associated with a product or process at its various life cycle stages and can identify stages that are most significant. (3) It also identifies the stages where trade-offs between alternatives chosen arise. (4) As recognized by many authors, the most difficult part of the LCA is data collection, the part of the LCA known as the life cycle inventory (LCI). (5) This resource-intensive process is a careful inventory of a product's or process' associated materials use, energy use, and emissions, thereby yielding a quantifiable measure of the overall environmental impact.

It is common in LCA studies to use data from different sources such as real plant data, engineering calculations, patents, etc. As reported by Tam and Abdulrahem, (5) this can lead to uncertainties of the LCA results. The authors found that theoretical LCI data for materials, compositions, and emissions were different than site-specific data and the need arose for scaling factors (i.e., correction factors). However, due to the inconsistent differences between theoretical and real values, there was no single scaling factor that could be assigned for the conversion of theoretical LCI data to real plant data. (5) Yet, very few studies have been conducted to assess the life cycle material use, energy use, and emissions of these paint processes.

NREL LCI Database Project

The United States Life Cycle Inventory Database Project (hereafter referred to as NREL LCI Database) is being developed by the United States National Renewable Energy Laboratory (NREL), working with the Athena Sustainable Materials Institute and several industry and academic research partners.