Abstract: Biodegradable, frost proof heat-transfer fluid, use thereof in near-surface geothermal installations, and a concentrate: subject matter of the present invention is the use of a triazole-free composition which as well as water comprises a) 9.2% to 49.5% by weight of at least one C2 to C3 alkylene glycol, C2 to C3 polyalkylene glycol or glycerol, b) 0.1% to 4% by weight of at least one corrosion inhibitor, with the provisos that c) the composition is readily degradable biologically in accordance with test method OECD 301 A, d) the composition has an anaerobic biodegradability of at least 75% in accordance with test method OECD 311, e) the corrosion inhibitor or all corrosion inhibitors used are readily degradable biologically in accordance with OECD 301 A (for water-soluble corrosion inhibitors) or OECD 301 B (for corrosion inhibitors of low water-solubility), in near-surface geothermal installations as a heat-transfer fluid.

Abstract: Biodegradable, frost proof heat-transfer fluid, use thereof in near-surface geothermal installations, and a concentrate: subject matter of the present invention is the use of a triazole-free composition which as well as water comprises a) 9.2% to 49.5% by weight of at least one C2 to C3 alkylene glycol, C2 to C3 polyalkylene glycol or glycerol, b) 0.1% to 4% by weight of at least one corrosion inhibitor, with the provisos that c) the composition is readily degradable biologically in accordance with test method OECD 301 A, d) the composition has an anaerobic biodegradability of at least 75% in accordance with test method OECD 311, e) the corrosion inhibitor or all corrosion inhibitors used are readily degradable biologically in accordance with OECD 301 A (for water-soluble corrosion inhibitors) or OECD 301 B (for corrosion inhibitors of low water-solubility), in near-surface geothermal installations as a heat-transfer fluid.