in softening the s2 layer proper application of the agent such as the chemical agent in the primary refiner fibrillation and the biological agents in the fiberizer refiner defibration step is desired to yield enhanced pulp quality following treatment with agent s a further mechanical refining device or other pulp device s may apply shear and compressive forces to the wood chips to further fibrillate and provide other beneficial properties to the pulp including brightness enhancement extractives removal optical enhancement and fiber development tensile elasticity fiber length high specific surface etc the application of an agent e g a chemical or biological agent to a process stage may provide a reduction of operating costs by improved energy efficiency and optimized chemical usage further by introducing an agent e g chemical agent to the fillibration process the agent may provide improved optical properties of the refined pulp including properties of enhanced light scattering and opacity of the pulp an enhanced scattering coefficient may be achieved by the agent contributing to a high specific surface of the fibers the use of agents may also allow for a simplification of the refining process stages and related reductions in investment costs another benefit of applying agents to a refining process is increased extractives removal which is consideration particularly relevant.