Carbon intensity is defined as emissions relative to another specific unit, for example, emissions per unit of produced energy, revenue, or other metrics relevant to the activity.

Carbon Intensity

ON Power produces electricity for its customers and hot water which is sold wholesale to Veitur Utilities. The emission intensity of the electricity is given in grams of CO₂ equivalents per kilowatt-hour (gCO₂eq/kWh) and for hot water in grams of CO₂ equivalents per cubic meter (gCO₂eq/m³).

In 2023, the emission intensity of electricity was 7.3 gCO₂eq/kWh, which is a 26% reduction compared to the emission intensity in 2016, see the table below and appendix. This achievement can be attributed to the initial steps taken in Reykjavík Energy's (RE) plan to make Hellisheidi Geothermal Power Plant carbon-neutral by 2025 and Nesjavellir Geothermal Power Plant by 2030, meaning that 95% of carbon dioxide from the plants will be captured, sequestered in rock, or utilized, see the image below.

In 2023, the emission intensity of hot water was 205.2 gCO₂eq/m³, which is a 16% decrease compared to the emission intensity in 2016, see the table below. The reason for this is the increased processing of hot water from the power plants compared to the total production of hot water.

In 2023, the proportional capture and sequestration of carbon dioxide from Hellisheidi Power Plant was about 25% of the plant's emissions. In 2023, the capture and sequestration of carbon dioxide began on a trial basis at Nesjavellir Power Plant and reduced emissions by 9%, see images below.

Monitoring is conducted on the concentration of CO₂ and H₂S in several production wells of Hellisheidi Power Plant. The flow from the injection back into the production field appears to be less than one year, and indications are that the concentration has only slightly increased in two monitoring wells closest to the injection field. Efforts continue to optimize the method and direct the gas injection into injection wells farther from the production field.

Carbon emissions from data transmission at Reykjavík Fibre Network have increased per unit of data transmission due to extensive construction activities in 2023.

RE does not release ozone-depleting substances due to its operations.

* Carbon footprint of low-temperature geothermal fields has been rated as approximately 0 gCO_2eq/kWh.

According to the Environmental Agency's guidelines on emission factors (6th edition) the emission factor (EMF) per kWh electricity is 8.54 gCO₂eq and EMF per m³ hot water 434 gCO₂eq.

Hydrogen sulphide emission intensity

The hydrogen sulphide emission intensity from each produced kWh at the geothermal power plants has been reduced since 2015, or from 2.2 g per kWh to approximately 1.5 g, see appendix.

The emissions of hydrogen sulphide from Nesjavellir and Hellisheidi Geothermal Power Plants amounted to 9.7 thousand tons in 2023. The concentration of hydrogen sulphide (H₂S) in populated areas never exceed limits. Proportionate injection of hydrogen sulphide from the Hellisheidi geothermal power plant was approximately 64%. Injection of hydrogen sulfide began on a trial basis at Nesjavellir geothermal power plant in 2023 and accounted for 8% of the plant's emissions. See more details in the figure and table below.

Work is being carried out according to a plan for Hellisheidi power plant to become carbon-neutral by 2025 and Nesjavellir power plant by 2030, which means that nearly all hydrogen sulphide from the plants will be captured and sequestered in bedrock.