Life cycle assessment of the Theistareykir geothermal power plant in Iceland

One of Iceland's key energy sources, geothermal energy, provides the country with more than 25% of its total electrical energy supply and nearly all of its heating supply. The country's latest installation is the 90 MW Theistareykir geothermal power station in northeast Iceland, which has been in full operation since 2018. A "cradle to grave" life cycle assessment in accordance with ISO 14040 and ISO 14044 was carried out for the power station, providing numerical results on a variety of environmental impacts throughout the life cycle, including the manufacturing of all construction materials and equipment, construction work, operation and end of life. The largest contributors to environmental impacts are direct CO₂ and H₂S emissions during the operation of the station during its lifetime, fuel use during construction, including the drilling of wells, and indirect emissions due to the manufacturing of all station components. The carbon footprint of electricity generation at Theistareykir is 13.9 g CO₂-eq per kWh leaving the station, and 14.8 g CO₂-eq per kWh when electricity transmission has been included. The carbon footprint is dominated by direct CO₂ emissions from the geothermal fluid during the 40-year lifetime, amounting to 10.9 g CO₂-eq per kWh or 78% (excluding transmission), while the manufacturing and construction of station buildings, infrastructure and machinery account together for 18% of the carbon footprint. Make-up wells and the renewal of machinery during the operation accounts for another 4% to the carbon footprint. The most carbon intensive units are the wells, in total constituting 8% of the carbon footprint during the entire life cycle. Direct hydrogen sulphide (H₂S) emissions at Theistareykir is the main contributor to the impact category acidification, another important contributor besides climate change after applying weighting and normalisation. The LCA results identify environmental hot spots and many opportunities for improvement of future development projects and for the operational years ahead, such as measures to reduce CO₂ and H₂S emissions from the geothermal fluid via CCS technologies or utilization of residual geothermal sources (hot water, steam, CO₂) as soon as possible, improving the station's capacity or extending its lifetime with good maintenance. Although there is uncertainty regarding the number of make-up wells needed during the station's lifetime, this LCA identifies opportunities to reduce their environmental impacts, for example via electrification of drilling and sustainable procurement practices for make-up wells.