A system for introducing gas from an unconventional source into a gas grid pipeline includes a passive blender (10) that introduces gas from an unconventional source (1) into a gas grid (2), the passive blender (10) having gas inputs (3, 11) from the unconventional source (1) and the gas grid (2) and a blended gas output (12), and wherein an internal flow path within the passive blender (10) is shaped and sized to provide entraining and mixing of the gases. The passive blender (10) acts to entrain gas from a gas grid (2) through input (11) by utilising the flow of gas from an unconventional source (1) through input 3, proportionally blending inputs 3 and 11 before outputting the blended gas back to the main gas grid (2). The system comprises the passive blender (10) of the present invention, a first gas input pipe (11) from a grid gas pipeline (2) into the passive blender (10) a second gas input pipe (3) from the unconventional source (1) into the passive blender (1), and an output pipe (12) from the passive blender (10) into the grid gas pipeline (2). The blender (10) and system are advantageous in that they can greatly reduce the necessary conditioning of unconventional gas before it is introduced into a gas grid supply (2) without additional flow motivation or controls.