Life cycle assessment of a domestic gas-fired water heater: Influence of fuel used and its origin

Abstract

The objective of this study is to apply a cradle-to-grave life cycle assessment to a gas-fired instantaneous water heater for domestic uses in order to identify the stages and processes with the largest impacts, as well as to evaluate the influence of different fuels (natural gas and liquefied petroleum gas) and country of use when natural gas is used as fuel. Primary data supplied by a Portuguese manufacturer contributed for achieving accurate life cycle inventory data that were then modelled in SimaPro 8.5.0 complemented with data from Ecoinvent database 3.4. The assessment was performed using the Recipe 2016 Midpoint V1.01 at the Hierarchist perspective. The results of the study show that the use stage (mainly owing to water consumption and fuel pre-combustion and combustion) is by far the largest contributor to the environmental burdens, followed by the raw materials production stage. The comparison between the two fuels considered demonstrates that liquefied petroleum gas leads to higher impacts than natural gas, mainly as a result of emissions from its own life cycle. The environmental damage varies noticeably in some impact categories depending on the country where this water heater is used, due to different natural gas origins. Practical implications of this work will enable the manufacturer to identify where to focus on the new water heaters that will be developed to achieve better levels of environment-friendliness.