NOVELTY - Method for producing at least one organic chemical product from biomass comprises: heating an aqueous slurry comprising biomass and water in a pressure vessel at 150-500 degrees C in the presence of a phosphate catalyst to produce a mixture comprising a dispersion of an organic phase and an aqueous phase; and optionally separating the organic chemical product from the mixture.    USE - The method is useful for producing: chemical products including pyrazines (methyl pyrazine, dimethyl pyrazine, trimethyl pyrazine, ethyl pyrazine and ethyl methyl pyrazine), hydrocarbons (toluene), alkenes (1-nonene and pentadecene), alkanes (pentadecane and heptadecane), methylated pyrroles, imides (N-methyl and N-ethyl succinimide), amides (hexadecanamide and 9-octadecanamide), lactams (2-pyrrolidinone, N-methyl-2-pyrrolidinone, N-ethyl-2-pyrrolidinone, N-butyl-2-pyrrolidinone, 2-piperidinone and caprolactam), crotonaldehyde, saturated and unsaturated aldehydes, ketones (cyclopentanone, cyclopentenone, methyl cyclopentenone, dimethyl cyclopentenone, methyl furfural and hydroxymethyl furfural), carboxylic acids (acetic acid, propionic acid, octanoic acid, dodecanoic acid, methylated butyric and valeric acid), lipid acids (palmitic and oleic acid), phenol and cresol; alicyclic five-membered ketones from carbohydrates; ethyl benzene or styrene, which are useful for manufacturing polystyrene of biological origin; and dialkylated or polyalkylated pyrazines, which are useful for manufacturing (by oxidation) pyrazine dicarboxylic acids, pyrazine polycarboxylic acids or anhydrides for the precursors of condensation polymers of biological origin (all claimed), where the above organic chemical products are useful as e.g. biofuels, fuel additives, flavor enhancers and bioprecursors.    ADVANTAGE - The method: provides the organic chemical products in high yields, where the organic chemical products having high economic importance; uses the biomass e.g. microalgae (fastest growing plants) as the abundantly available raw material and thus it is economical; utilizes phosphate catalysts, which significantly increase the overall yield of the products and also increases the yield of desired products.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) the organic chemical product produced from the above method;    (2) the production of dianhydromannitol and dianhydroglucitol from seaweeds in the phaeophyta or from any alginate bearing material, by the above method;    (3) the production of alicyclic five-membered ketones from carbohydrates, by the above method; and    (4) producing pyrazines and lactams in the presence of other materials from microalgae, comprising (i) heating an aqueous slurry of microalgae in a pressure vessel at 330-450 degrees C to produce an organic phase and an aqueous phase and (ii) separating the pyrazines and lactams from the mixture.