Comparative Life Cycle Assessment among Three Polyurethane Adhesive Technologies for the Footwear Industry

This study presents an environmental assessment involving three polyurethane adhesive technologies used in the footwear industry: a solvent-based adhesive (SBA), a water-based adhesive (WBA), and a powder-based adhesive (PBA). SBA is a versatile adhesive, but the presence of volatile organic compounds has some disadvantages regarding both environmental and workers' welfare issues. On the other hand, PBA and WBA require more complex processing than SBA. PBA is a hot-melt adhesive in powder form and a solvent free thermoplastic material, presenting lower risks to workers' health and flammability, but its application requires electric energy because it is carried out by machine. Thus, a comparative study among these three polyurethane adhesive technologies using a life cycle assessment methodology was conducted from "cradle-to-gate". Primary data for environmental emissions, wastewater, chemical components, and technical specifications were collected during visits in local. Based on the results, PBA decreased environmental impacts in all categories evaluated except in the respiratory organic category. Therefore, if the purpose of this analysis is to look at the footwear workers' health, WBA would be considered the best technology. This work shows that any actions that seek to minimize these impacts should begin in "the footwear industry", more specifically; in the stage of use due to the electricity required during the adhesive application. Besides that, all three technologies offer possibilities to minimize some of the environmental impacts. Therefore, it is suggested that better management of the energy expended during the application step from renewable energy sources, improvement of equipment energy efficiency, and development of new formulations are potential alternatives for solutions seeking to reduce impacts involving all adhesive technologies and consequently shoe production.