TNO presents sustainability options for geothermal energy in the Netherlands

Rijswijk Center for Sustainable Geo-energy, geothermal laboratory, The Netherlands (source: TNO)

Netherlands-based TNO presents a case to reduce CO2 emissions from geothermal heating to make it a more sustainable alternative to natural gas

Although geothermal heating has 90% lower CO2 emissions compared to natural gas boilers, it is still not completely emission free. The Netherlands-based research organization TNO has come up with a few options for reducing emissions from geothermal heating to zero.

The gases in geothermal fluids are the result of chemical reactions between the fluids and the underground formation. The exact percentage of these gases may vary depending on the type of geothermal source formation. Dorien Dinkelman of TNO cites the example of geothermal fluids from the Westland region which have relatively higher gas concentrations due to the Delft sandstone. This means that the approach to dealing with emissions may need to vary from location to location.

Three options to reduce emissions

One method proposed by TNO is to keep the formation gas in solution. In this case, the gases are simply reinjected into the aquifer. However, this solution requires that the pressure in the geothermal system be maintained at high values. This will make the installation more expensive.

The second method consists of burning the formation gas and capturing the CO2. The CO2 will then be reinjected into the formation with the geothermal fluids. While the technology to do this already exists, it is also the more expensive option. This method can be more economical if it can be extended. For example, several geothermal sites may have a gas collection system connected.

The last method consists of upgrading the formation gases to natural gas quality and reselling them to existing heating networks. While this does not reduce CO2 emissions, it makes the Netherlands less dependent on importing natural gas.

Reducing emissions during the use phase offers the most benefits

As part of this study, TNO also examined the total CO2 emissions associated with the construction of a geothermal facility. Based on a life cycle assessment (LCA) of a geothermal project from construction to deconstruction, 97% of the environmental impact comes from the use phase. This means that making changes to the geothermal use phase offers the greatest opportunities to make the industry more sustainable.

Sustainability before costs

“A sustainable alternative almost never begins with a good business case,” comments Hester Djikstra of TNO. The proposals made by TNO will almost certainly require additional expenditure. However, the main issue should be the emissions, not the money. “It’s best to find out what is the best solution to the problem and then determine what will be needed from there. Hester added.

Municipalities and regions have the power to lobby for more sustainable heating alternatives. Through subsidies or additional taxes on fossil fuels, alternatives such as geothermal energy can be boosted and help the country move forward towards the energy transition.

Source: EBN