System (100, 200, 300) comprising: (a) a structure defining a melting chamber, (b) at least one feedstock supply structure (33, 33A) fluidly connected to the structure defining the melting chamber, (c) one or more exhaust conduit (22, 22A, 22B, 22C, 22D, 22E, 22F) fluidly connected to the structure defining the melting chamber, (d) a heat exchange area, (e) the feedstock flowing through the heat exchange area to the melting chamber, (f) at least some of the exhaust flowing from the melting chamber flowing through the heat exchange area, (g) the heat exchange area being configured for allowing heat exchange from the at least some of the exhaust to at least some of the feedstock, (h) wherein the heat exchange area comprises at least one section which is positioned at an angle (θ, θ 1, θ 2, θ 3) to the vertical ranging from 0 to 90 degrees, (i) wherein at least one exhaust conduit (22, 22A, 22B, 22F) is connected to the heat exchange area, and (j) wherein the heat exchange area comprises a heat exchange substructure, (k) wherein at least one of the one or more exhaust conduits (22, 22A, 22B, 22F) comprises an angled exhaust conduit serving as the heat exchange substructure, characterized in that the angled exhaust conduit fluidly connecting the melter chamber to a 3-way flow connector, (m)the 3-way flow connector fluidly connecting the angled exhaust conduit with an angled feedstock supply conduit and to a vertical exhaust conduit, (n) the feedstock supply structure (33, 33A) comprises a feedstock supply container fluidly connected to the angled feedstock supply conduit, (o) the angle (θ, θ 1, θ 2, θ 3) is ranging from 10 to 75 degrees. (a) a structure defining a melting chamber, (b) at least one feedstock supply structure (33, 33A) fluidly connected to the structure defining the melting chamber, (c) one or more exhaust conduit (22, 22A, 22B, 22C, 22D, 22E, 22F) fluidly connected to the structure defining the melting chamber, (d) a heat exchange area, (e) the feedstock flowing through the heat exchange area to the melting chamber, (f) at least some of the exhaust flowing from the melting chamber flowing through the heat exchange area, (g) the heat exchange area being configured for allowing heat exchange from the at least some of the exhaust to at least some of the feedstock, (h) wherein the heat exchange area comprises at least one section which is positioned at an angle (θ, θ 1, θ 2, θ 3) to the vertical ranging from 0 to 90 degrees, (i) wherein at least one exhaust conduit (22, 22A, 22B, 22F) is connected to the heat exchange area, and (j) wherein the heat exchange area comprises a heat exchange substructure, (k) wherein at least one of the one or more exhaust conduits (22, 22A, 22B, 22F) comprises an angled exhaust conduit serving as the heat exchange substructure, the angled exhaust conduit fluidly connecting the melter chamber to a 3-way flow connector, (m)the 3-way flow connector fluidly connecting the angled exhaust conduit with an angled feedstock supply conduit and to a vertical exhaust conduit, (n) the feedstock supply structure (33, 33A) comprises a feedstock supply container fluidly connected to the angled feedstock supply conduit, (o) the angle (θ, θ 1, θ 2, θ 3) is ranging from 10 to 75 degrees.