| Title | Reducing greenhouse gas emissions from NZ geothermal power stations |
|---|---|
| Authors | K. McLean, I. Richardson, F. Hanik, F. Siega, B. Gibson |
| Year | 2024 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Geothermal emissions, greenhouse gases, carbon, non-condensable gases (NCGs), New Zealand ETS, CO2 reinjection, NCG reinjection |
| Abstract | Geothermal reservoirs contain naturally-occurring greenhouse gases, in the form of CO2 and methane. In most cases the process of generating electricity using geothermal reservoir fluids results in the release of some greenhouse gases into the atmosphere. This means that the operational emissions intensity (scope 1 emissions) of geothermal power stations is not zero. The operational emissions from the geothermal power stations in NZ have been collated and published each year since 2018 by the New Zealand Geothermal Association Emissions Working Group. The full lifecycle emissions are also estimated, to allow comparison to emissions from other renewable energy sources. The five previously published datasets are reviewed in this paper, along with the latest dataset from calendar year 2023. Changes and trends are identified, for the industry overall, and for individual power stations. The change of most interest is the elimination or reduction of emissions from some power stations. This has been achieved by reinjection of the greenhouse gases back into the reservoir. This method effectively closes the loop on the gases and returns them to where they came from. This has so far been achieved at three geothermal power stations – Ngāwhā, Te Huka and Ngā Tamariki. This common and important emissions challenge has given rise to a cooperation between all the geothermal generators in New Zealand, enabling the decarbonisation effort to progress faster. The effect of this effort on the emissions can be seen in this paper. |