NOVELTY - A heat transfer composition comprises: (i) a first component selected from trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), cis-1,3,3,3-tetrafluoropropene (R-1 234ze(Z)) and mixtures; (ii) carbon dioxide (R-744); and (iii) a third component selected from difluoromethane (R-32), 1,1-difluoroethane (R152a), fluoroethane (R-161), 1,1,1,2-tetrafluoroethane (R-134a), 2,3,3,3-tetrafluoropropene (R-1234yf), and 3,3,3-trifluoropropene (R-1243zf).    USE - The composition is useful in a heat transfer device; for producing a blowing agent, a foamable composition, a foam and a sprayable composition; for cooling an article; for heating the article; for extracting a substance from biomass; for cleaning an article; for extracting a material from an aqueous solution; for extracting a material from a particulate solid matrix; and for reducing the environmental impact arising from the operation of a product (all claimed).    ADVANTAGE - The composition has a higher flammable limit, a higher ignition energy, a lower flame velocity, environment friendly, and the use of the composition of the invention results in a lower total equivalent warming impact, and/or a lower life-cycle carbon production than is attained by use of the existing compound or composition.    DETAILED DESCRIPTION - A heat transfer composition comprises: (i) a first component selected from trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), cis-1,3,3,3-tetrafluoropropene (R-1 234ze(Z)) and mixtures; (ii) carbon dioxide (R-744); and (iii) a third component selected from difluoromethane (R-32), 1,1-difluoroethane (R152a), fluoroethane (R-161), 1,1,1,2-tetrafluoroethane (R-134a), 2,3,3,3-tetrafluoropropene (R-1234yf), 3,3,3-trifluoropropene (R-1243zf), 1,1,1-trifluoropropane (R-263fb), 1,1,1,2,3-pentafluoropropane (R-245eb), propylene (R-1270), propane (R290), n-butane (R-600), isobutane (R-600a), ammonia (R-717) and mixtures. INDEPENDENT CLAIMS are:    (1) a heat transfer device containing the composition;    (2) a blowing agent comprising the composition;    (3) a foamable composition comprising one or more components capable of forming foam and the composition, where the one or more components capable of forming foam are selected from polyurethanes, thermoplastic polymers and resins, such as polystyrene, and epoxy resins, and mixtures;    (4) a foam obtainable from the foamable composition;    (5) a sprayable composition comprising material to be sprayed and a propellant comprising the composition;    (6) a method for cooling an article, comprising condensing the composition and thereafter evaporating the composition in the vicinity of the article to be cooled;    (7) a method for heating the article, comprising condensing the composition in the vicinity of the article to be heated and thereafter evaporating the composition;    (8) a method for extracting a substance from biomass, comprising contacting biomass with a solvent comprising the composition, and separating the substance from the solvent;    (9) a method of cleaning an article, comprising contacting the article with the solvent comprising the composition;    (10) a method of extracting a material from an aqueous solution, comprising contacting the aqueous solution with the solvent comprising the composition, and separating the substance from the solvent;    (11) a method for extracting a material from a particulate solid matrix, comprising contacting the particulate solid matrix with the solvent comprising the composition, and separating the material from the solvent;    (12) a mechanical power generation device containing the composition;    (13) a method of retrofitting a heat transfer device, comprising removing an existing heat transfer fluid, and introducing the composition;    (14) a method for reducing the environmental impact arising from the operation of a product comprising an existing compound or composition, comprising replacing at least partially the existing compound or composition with the composition;    (15) a method for preparing the composition, and/or the heat transfer device, where the composition or heat transfer device contains R-134a, the method comprising introducing R-1243ze(E), R-744, any additional third component, and optionally R-125, a lubricant, a stabilizer and/or a flame retardant, into a heat transfer device containing an existing heat transfer fluid which is R-134a; and    (16) a method for generating greenhouse gas emission credit, comprising: (i) replacing an existing compound or composition with the composition, where the composition has a lower global warming potential (GWP) than the existing compound or composition; and (ii) obtaining greenhouse gas emission credit for the replacing step.