Life Cycle Comparison of Manual and Machine Dishwashing in Households

Abstract

Machine dishwashers are a unique consumer appliance since they are often substituted with manual dishwashing. Although some studies indicate machine dishwashers use less energy and water than manual dishwashing, their scopes are limited to the use phase. Our study evaluates the full life cycle burdens for both manual and machine dishwashing following typical and recommended behaviors. Use phase behaviors are observed through a laboratory study and survey, while burdens are calculated using a life cycle assessment framework. We find that typical manual dishwashing behaviors result in the greatest greenhouse gas emissions (GHG). Even when recommended behaviors for machine dishwashers are not followed, they outperform typical manual dishwashing. Although manufacturers do not include typical behaviors like pre-rinsing when estimating their value-chain emissions profile, these activities can increase lifetime GHG emissions by 17%. The sustainability of the average American household can be significantly enhanced by following recommended machine dishwashing instead of typical manual dishwashing, thereby reducing GHG emissions by 72%.