A method for regulating the heat and the CO2 concentration of the air in an enclosed space within which plants or crops are grown, in which method an oxygen-containing gas and a hydrocarbon-containing gas are alternately passed over a bed of particles that are capable of binding oxygen, wherein the oxygen-containing gas is passed over the bed of particles at a temperature of 100 to 1,500° C. and a pressure in a range of 1 to 100 bar whereby the particles are oxidised and heat is released, after which at least part of the heat is provided to the enclosed space, and wherein the hydrocarbon-containing gas is passed over the bed of the oxidised particles at a temperature of 300 to 1,500° C. and a pressure of 1 to 100 bar whereby the oxidised particles are chemically reduced and water and CO2 are formed, after which at least part of the CO2 so obtained is provided to the enclosed space.