NOVELTY - The method comprises pre-mixing biomass with a biotreatment reagent to prepare a first mixture, pre-mixing a bulking agent with an additional biodegradation reagent and an additional biotreatment reagent, adding the pre-mixed bulking agent to the first mixture after a time sufficient for the biotreatment reagent to have reacted with the biomass, mixing the added pre-mixed bulking agent with the first mixture to prepare a second mixture for forming a static solid state bioreactor, loading (1) dried biomass into a mixing vessel, and rehydrating (2) the dried biomass load in the mixing vessel.    USE - The method is useful for preparing biomass consisting of corn stover, corn fibers, wheat straw, wood wastes, urban wastes, switchgrass, rice straw, sugar beet pulp, citrus peels and/or sugarcane bagasse for biotreatment in a static solid state fermentation bioreactor (all claimed), where the biomass is an feedstock for producing fossil fuel substitutes.    ADVANTAGE - The method is capable of simply and economically preparing biomass with small carbon footprint, high product yield and improved permeability thus allowing good pH control and modifications in the static solid state bioreactor, and suppresses the proliferation of undesirable microorganisms thus avoiding the production of unwanted products.    DETAILED DESCRIPTION - The method comprises pre-mixing biomass with a biotreatment reagent to prepare a first mixture, pre-mixing a bulking agent with an additional biodegradation reagent and an additional biotreatment reagent, adding the pre-mixed bulking agent to the first mixture after a time sufficient for the biotreatment reagent to have reacted with the biomass, mixing the added pre-mixed bulking agent with the first mixture to prepare a second mixture for forming a static solid state bioreactor, loading (1) dried biomass into a mixing vessel, rehydrating (2) the dried biomass load in the mixing vessel, adding (3) reagent solutions sequentially to the rehydrated biomass in the mixing vessel, providing (4) sufficient mixing time for the reagent solutions and the rehydrated biomass in the mixing vessel, adding (5) the bulking agent to the mixing vessel, and adding (6) water to the mixing vessel to attain a target hydration level of mixed biomass and bulking agent solids. The prepared second mixture has a uniform distribution of bulking agent and biomass solids. The dried biomass is present in the form of dried sugar beet pulp and dried sugar beet cossettes. The bulking agent includes an organic material and an inorganic material, and consists of almond shells (screened and unscreened) and hulls, wood chips (bark and/or wood), beet chunks, corn cobs, corn stover, orange rinds, wheat and rice straw, plastic balls (spheres, bioballs), styrofoam peanuts, shredded tires, and rocks. The biotreatment reagent consists of enzymes, antibiotics, yeast nutrients, yeast, water, recycled solution, and fermentation agent. The mixing vessel is an agricultural feed mixer, a rotating drum, a screw mixer, and a vertical-auger batch mixer. An INDEPENDENT CLAIM is included for a system for preparing biomass for biotreatment static solid state bioreactor.    DESCRIPTION OF DRAWING(S) - The diagram shows a flowchart of a method for preparing biomass for biotreatment in a static solid state bioreactor.    Loading dried biomass into mixing vessel (1)    Rehydrating dried biomass load in the vessel (2)    Adding reagent solutions to rehydrated biomass (3)    Providing sufficient mixing time for the reagent solution (4)    Adding bulking agent to the vessel (5)    Adding water to the vessel. (6)