NOVELTY - The method involves providing a liquid medium in a vessel, where the liquid medium comprises hydrocarbon containing material and target molecule. Sufficient flow of the liquid medium comprising the target molecule is effectuated from the vessel through a cross-flow filtration cassette. Filtration fractions generated by cross-flow filtration modules are sequentially generated, where the target molecule is physically separated by the cross-flow filtration and the physical separation of a target product is based on different molecular weights, size and operating conditions.    USE - Method for separating target molecule from hydrocarbon containing material. Uses include but are not limited to ethanol, biobutanol, proteins, enzymes such as cellulase, xylanase and hemicellulose, sugars, starches, short chain fatty acids, long chain fatty acids, energy containing hydrocarbons, serum components and renewal fuel, from corn grain, con cobs, corn husks, con stover, grasses, wheat, wheat grain, wheat straw, barley, barley straw, hay, rice straw, switch grass, waste paper, sugar cane bagasse, sorghum, roots, leaves, wood chips, sawdust, shrubs, bushes, vegetables, fruits, flowers, animal manure municipal waste as plants (all claimed), root crops, animal tissue and cell cultures such as yeast e.g. Saccharomyces cerevisiae or Pichia stipitis, algal, bacteria such as Zymomonas mobilis and Escherichia coli, fungi species, milk, milk products, fruits and fruit juices.    ADVANTAGE - The method enables cellulosic biomass such as agricultural waste/residue, to be utilized for conversion to ethanol as less expensive feedstock. The method enables eliminating need for centrifuge and filtration by utilizing the cross-flow filtration cassette. The method enables large particles from a feed stock to be reduced in a particle reduction system, thus providing fairly consistent source material for processing.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for producing renewable fuel molecule from cellulosic biomass.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of components of a cross-flow filtration cassette used in separation of renewable fuels.    Partition element (6)    Channel opening (8)    Inlet basin opening (10)    Outlet basin opening (12)    Permeate passage openings (13)