The mass balance method is a method in which raw materials with certain characteristics (e.g., biomass-derived raw materials) are mixed with other raw materials (e.g., petroleum-derived raw materials) in the processing and distribution process from raw materials to finished products, and the characteristics are assigned to a portion of the finished products according to the input amount of raw materials with those characteristics.

Using this mass balance method, biomass is allocated to a portion of the finished resin product according to the amount of biomass-derived ethylene feedstock input, and the product is sold as a bioproduct resin. Resin that has not been allocated biomass will be sold as conventional resin.