TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The at least one metal ion is copper, iron, cobalt, nickel or molybdenum. The inhibitor of sulfate reduction is molybdate.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The methods further involve prior to the step of modifying, determining at least one environmental parameter of the deposit. The at least one environmental parameter is modified using information obtained from the step of determining. The step (i) involves inhibiting the consumption of hydrogen by methanogenic microorganisms, acetogenic microorganisms, sulfate-reducing microorganisms and/or iron-reducing microorganisms. The methods further involve characterizing at least one microorganism of the deposit or introducing at least one microorganism into the deposit so as to improve net hydrogen production in (M1) or molecular hydrogen, acetate or methane production in (M2). At least one microorganism of the deposit is genetically modified and reintroduced into the deposit so as to improve net production of molecular hydrogen by microorganisms in the deposit. At least one environmental parameter modified and/or determined is temperature, pH, salinity, sulfate concentration, acetate or other organic acid concentration, methane concentration, hydrogen concentration, water content, metal ion concentration and composition and/or hydrocarbon concentration and/or composition. The step of modifying involves addition of a composition consisting of water or an aqueous solution or aerosol comprising at least one component selected from complex nutrients, at least one vitamin, at least one metal ion, nitrogen, phosphorus, a trace element, an enzyme, a catalyst or a buffer, to the deposit by injecting the composition via fractures and/or cleats within the deposits; or addition of an aqueous composition or aerosol comprising an inhibitor of methanogenesis to inhibit methanogenesis; or introducing into the hydrocarbon-rich deposit an aqueous or aerosol composition comprising an inhibitor of acetogenesis to inhibit acetate production or an inhibitor of sulfate reduction to inhibit sulfate reduction, or a composition comprising air, oxygen, nitrate, nitric oxide or nitrous oxide in an amount sufficient to selectively inhibit metabolic activity of methanogens. The composition is injected into the deposit via fractures and/or cleats within the deposit. The environmental parameter modified is salinity. The step of modifying involves lowering pH in the hydrocarbon-rich deposit to an extent; or raising temperature to inhibit hydrogen- consuming microbial processes; or removing or precipitating nutrients required for hydrogen-consuming microbial processes. The method further involves fracturing the deposit and/or horizontal drilling. The steps of modifying, fracturing and/or horizontal drilling are carried out simultaneously. The hydrocarbon-rich deposit or its portion is removed from its formation location to a reactor. The hydrogen, methane or acetate is collected from the deposit via at least one recovery well or from the reactor.Preferred Components: The inhibitor is bromoethanesulfonic acid (BESA) or a derivative of para-aminobenzoic acid. The inhibitor of acetate production is rifampcin, rifampin, rifampicin or rifamycin.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The at least one metal ion is copper, iron, cobalt, nickel or molybdenum. The inhibitor of sulfate reduction is molybdate.