GEOTHERMAL DISTRICT HEATING SYSTEM IN ICELAND: A LIFE CYCLE PERSPECTIVE WITH FOCUS ON PRIMARY ENERGY EFFICIENCY AND CO2 EMISSIONS

This paper presents a cradle-to-gate life cycle assessment (LCA) of Stykkisholmur’s geothermal district heating system based on a functional unit of 1 MWhth of delivered heat to consumers. The study is largely based on primary data collected for the construction and operation of the system and is representative for a modern design of such a system. The LCA was performed using the SimaPro 7 software and results were obtained using CML baseline impact categories and Cumulative Energy Demand (CED) analysis, with special focus set on primary energy demand and carbon footprint of the functional unit. The primary energy demand of producing 1 MWhth of delivered heat to consumers in the Stykkisholmur DHS was calculated to be 2.73 MWhth. Thereof, 0.03 MWhth originate from non-renewable sources used in the construction stage, mainly for production of steel used in the various pipes within the system. Use of geothermal energy in the operational stage dominates the renewable part of the primary energy demand. The carbon footprint was calculated to be 5.8 kg CO2 eq/MWhth of district heat delivered to customers. Other impact categories were also investigated in the study.