There are areas where geothermal heat is available
at a reasonable cost. In some locations, hot water is
pumped from below ground to provide heat for the
greenhouse. In deep mine areas, warm air can be
pumped from the mines to heat greenhouses. There
are disadvantages to using both sources. Salts in the
water can precipitate out and foul heat distribution
equipment. Corrosive gaseous elements in the mine
air can create problems with equipment, structures,
and plants. There are a few greenhouses using
geothermal water, but expansion is limited