Abstract: A positive displacement mixer and method for mixing a product that mixes at least two materials into a homogenous product. The positive displacement mixer has at least one positive displacement element having a length, a primary compartment, and a moving element, and two or more minor positive displacement elements each having a length, a minor compartment, and a moving element. The primary compartment and the minor compartments are fluidly connected and during mixing the primary compartment and minor compartments are closed to the atmosphere.