In Koekoekspolder, a horticultural area in the province of Overijssel, a geothermal power plant has been operational since 2012. This power plant provides sustainable heat to six horticultural businesses, a equestrian facility, and several commercial buildings. The power plant uses geothermal energy, a sustainable energy source that harnesses heat from deep underground to warm greenhouses and other facilities. This project marks an important step towards a more sustainable energy system in the Dutch horticultural sector, which traditionally relies heavily on natural gas for heat. In this blog, we delve deeper into how geothermal energy works, the results of our recent life cycle analysis (LCA), and the contribution that geothermal energy can make to the Dutch energy transition.
What is Geothermal Energy and How Does it Work?
Geothermal plants rely on a technology that extracts heat from deep underground. Through boreholes often more than a kilometer deep, warm water is extracted to the surface. The water, with temperatures ranging from 50°C to sometimes over 100°C, is then used to heat buildings or for industrial processes. The cooled water is subsequently pumped back into the same underground layer, making it a virtually closed system. This process significantly reduces greenhouse gas emissions, as the use of fossil fuels, such as natural gas, becomes largely unnecessary. However, electricity is required to pump the hot water up and return it to the same underground layer. In the Netherlands, most geothermal plants have a COP (coefficient of performance) between 15 and 25. This means that one unit of electricity (e.g., 1 MWh) produces 15 to 25 MWh of heat.
In the Netherlands, geothermal energy is an emerging technology with great potential, especially for sectors that require large amounts of heat, such as greenhouse horticulture. Due to the presence of suitable geological layers, many parts of the Netherlands are attractive for geothermal project development. Radboud Vorage, director of the geothermal project in Koekoekspolder, agrees: “For every kilometer you drill, the ground temperature increases by over 30 degrees. In Koekoekspolder, the deep layers of groundwater have a temperature of about 74 degrees Celcius. A perfect temperature to heat greenhouses growing cucumbers, tomatoes, and peppers. Some of our customers have already managed to reduce their natural gas usage by 70-90%."
Goal and Scope of the LCA Study
To properly map the enviornmental impacts of the Koekoekspolder power plant, investor Meewind decided to comission a life cycle analysis (LCA). Meewind, which finances several geothermal projects, was interested in the environmental impacts of the projects in which it has invested. The goal of this LCA was to analyze the environmental effects of the entire life cycle of the geothermal plant, and compare these to other energy sources, such as natural gas. The focus of the analysis was on the Global Warming Potential (GWP), which is the contribution to climate change expressed in CO2 equivalents.
This study provides insight into the extent to which specific components and activities of the installation contribute to the ecological footprint. Moreover, it identifies opportunities for reducing environmental impacts. The scope of the study included all relevant activities and materials needed to set up and exploit the geothermal installation. This includes the production of steel pipes, borehole drilling, material transport, and the energy required for the operational phase of the plant. It also looked at the infrastructure needed to distribute the heat to connected horticultural businesses, such as pipes and pumps. Finally, maintenance work and the final decommissioning of the plant were included in the analysis.
Geothermal Energy: a Sustainable Alternative to Natural Gas
One of the key advantages of geothermal energy is that it offers an attractive alternative to the demand for heat from natural gas. By utilizing geothermal heat, horticulturalists in Koekoekspolder can drastically reduce their dependence on natural gas. This not only provides environmental benefits but also economic ones, given fluctuations in gas prices and increasing taxes on fossil fuels. Moreover, during the operation of the geothermal plant, natural gas is also captured from the underground layers. This reduces the demand for natural gas extraction elsewhere.
Based on our analysis, it is estimated that the geothermal plant in Koekoekspolder has a Global Warming Potential of 2.4 to 7.3 kg CO2-equivalent per GJ of geothermal heat generated. This is significantly lower compared to the GWP of natural gas, which averages 67.3 kg CO2-equivalent per GJ. This shows that the GWP of geothermal energy in the Netherlands can be considerably lower compared to conventional energy generation based on natural gas. Especially when a mix of sustainable electricity sources is used during the operational phase.
A crucial factor is the efficiency of the geothermal plant, which directly affects the heat output per unit of energy. Efficiency can be influenced by various factors, such as the temperature of the deep-water layers, the composition of the underground, and the maintenance of the installation. Higher efficiency results in greater heat output per invested unit of energy, which lowers the GWP per GJ produced. Conversely, the GWP per GJ can increase if efficiency is lower due to suboptimal conditions. Therefore, it is important to emphasize that these results are specific to Koekoekspolder.
"Dispersed’s LCA has provided us with valuable insight into the opportunities for reducing our CO2 footprint. This allows us to take major steps toward ‘fossil-free’ cultivation." - Radboud Vorage (Director, Geothermal Power Koekoekspolder)
Life Cycle Impacts: Energy Use, Steel, and Cement
The results of the LCA study show that the lifecycle GWP is most strongly affected by the assumed composition of the electricity mix during the operational stage. When grey electricity is used, the operational phase plays a dominant role in the total GWP, accounting for as much as 81%. This is a result of the required energy consumption by the geothermal pumps. In the grey electricity scenario, this processes is largely dependent on fossil fuels.
However, when a mix of renewable electricity sources, such as wind and solar energy, is assumed, the GWP can be reduced by up to 67%. This demonstrates the crucial role that renewable energy sources may play in limiting the environmental impact of geothermal energy during the operational phase.
In addition to electricity, the materials used in the construction of the geothermal installation contribute significantly to the environmental burden. Especially the production of steel and cement, which are essential for the boreholes and the heat distribution network, have a substantial impact. These production of these materials is highly energy-intensive, and therefore leads to significant greenhouse gas emissions.
Conclusion: Geothermal Energy in a Sustainable Energy System
Our LCA study into the geothermal power plant in Koekoekspolder shows that geothermal energy can make a significant contribution to the sustainability of the horticultural sector in the Netherlands. While the initial construction of geothermal plants has considerable environmental effects, these are offset in the long term by the benefits of avoiding natural gas usage.
In a broader sense, geothermal energy fits within the Dutch strategy to reduce greenhouse gas emissions and accelerate the transition to a sustainable energy system. With the right incentives and further technological developments, geothermal energy can grow into a key pillar of the Dutch energy mix, especially in sectors such as greenhouse horticulture, which require a lot of heat. The geothermal plant in Koekoekspolder is an excellent example, and can serve as a model for future projects across the country.
Our research also offers concrete starting points for further improving the sustainability of geothermal plants in the future. For instance, the impact of the operational phase can be significantly reduced by using electricity from renewable sources. Additionally, the relative impact of the initial material use can be reduced by optimizing the installation’s lifespan and by introducing recycling and reuse schemes at the end-of-life.