Geothermal Vierpolders director Paul Grootscholten said: "It remains to be seen how high the efficiency of the source actually is, but we are convinced that it is the best and most sustainable solution to the energy needs of the greenhouses."
Grootscholten, who is also a partner at family-owned glasshouse salad plant supplier Globe Plant, one of the nine growers using the heat, added: "Now we use geothermal energy we burn 90 per cent less natural gas and emit 20 per cent less CO2."
The area's geology makes it well suited to geothermal. At 2,200m there is a porous sand layer with water of about 85 degsC that can be relatively easily pumped up then returned back to the soil when cool.
Eight years in development, the scheme has been subsidised by the EU, national government and agencies. "Like many new technologies, geothermal energy is also at this early stage not quite competitive with traditional sources of energy," the project's website explains. "But the prospects are promising and the social interest is large."
Globe Plant will be among several glasshouses opening their doors to the public this weekend (2 April) as part of the industry's ongoing Kom in de Kas (Come into the Glasshouse) programme.