TNO presents sustainability options for geothermal in the Netherlands
Netherlands-based TNO presents a case for reducing the CO2 emissions of geothermal heating to make it a more sustainable alternative to natural gas
Although geothermal heating has CO2 emissions that are 90% lower compared to natural gas heat boilers, it is still not completely emission-free. Netherlands-based research organization TNO has proposed a few options for reducing the emissions of geothermal heating to zero.
Gases in geothermal fluids are a result of the chemical reactions between the fluids and the subsurface formation. The exact percentage of these gases can vary based on the type of formation of the geothermal source. Dorien Dinkelman of TNO cites the example of the geothermal fluids from the Westland area that have relatively higher gas concentrations because of the Delft Sandstone. This means that the approach for handling emissions may have to vary from one location to another.
Three options for reducing emissions
One method that TNO is proposing is to keep the formation gas in solution. In this case, the gases are simply pumped back into the aquifer. However, this solution demands that the pressure in the geothermal system be kept at high values. This will make the installation more expensive.
The second method is for the formation gas to be burned and the CO2 to be captured. The CO2 will then be reinjected into the formation along with the geothermal fluids. Although the technology to do this already exists, it is also the most expensive option. This method can be more economical if it can be scaled up. For instance, multiple geothermal sites can have a connected gas capture system.
The last method is for the formation gases to be upgraded to natural gas quality and sold to existing heating networks. While this does not reduce the CO2 emissions, it makes the Netherlands less dependent on natural gas importation.
Reducing emissions on usage phase yields the most benefits
As part of this study, TNO also looked at the total CO2 emissions associated with the construction of a geothermal facility. Based on a life cycle analysis (LCA) of a geothermal project from construction to decommission, 97% of the environmental impact comes from the usage phase. This means that making changes to the usage phase of the geothermal provides the biggest opportunities for making the industry more sustainable.
Sustainability before costs
“A sustainable alternative almost never starts with a good business case,” comments Hester Djikstra of TNO. The proposals made by TNO will almost certainly require additional expenses. However, the primary problem should be the emissions, not the money. “It is better to look at what the best solution is for the problem and then reason what will be needed from there.” added Hester.
Municipalities and regions have the power to push for more sustainable heating alternatives. Through subsidies or additional taxes on fossil fuels, alternatives such as geothermal energy can be given a push and help the country move forward towards energy transition.