NOVELTY - Reducing (M1) or removing at least one contaminant from a gas-phase emission stream involves (a1) providing a gas-phase emissions stream comprising at least one contaminant; (b1) contacting the gas-phase emissions stream with an additive and activated carbon particles comprising a biogenic activated carbon composition to generate contaminant-adsorbed particles; and (c1) separating at least a portion of the contaminant-adsorbed particles from the gas-phase emissions stream to produce a contaminant-reduced gas-phase emissions stream.    USE - For reducing or removing at least one contaminant from a gas-phase emission stream; for reducing mercury emissions; for producing energy; for purifying a liquid; for removing at least a portion of a sulfur contaminant from a liquid; for reducing a concentration of sulfates in water; for removing a sulfur contaminant from a gas-phase emissions stream; and for reducing or removing at least one contaminant from a gas or liquid (claimed).    ADVANTAGE - The method reduces or removes contaminant from gas-phase emission stream, thus the method is more efficient; provides product quality; and maintains flexibility and adjustability for feedstock variations and product requirements.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) method (M2) of using a biogenic activated carbon composition to reduce mercury emissions;    (2) method (M3) of producing energy;    (3) method (M4) of using a biogenic activated carbon composition to purify a liquid;    (4) method (M5) of removing at least a portion of a sulfur contaminant from a liquid;    (5) method (M6) of reducing a concentration of sulfates in water;    (6) method (M7) of removing a sulfur contaminant from a gas-phase emissions stream;    (7) method (M8) of reducing or removing at least one contaminant from a gas or liquid;    (8) method (M9) of reducing or removing at least one contaminant from a gas or liquid;    (9) method of using graphene involving obtaining a biogenic activated carbon composition comprising, on a dry basis, greater than or equal to 55 wt.% total carbon, less than or equal to 15 wt.% hydrogen, and less than or equal to 1 wt.% nitrogen, where at least a portion of the carbon is present in the form of graphene; optionally separating the graphene from the biogenic activated carbon composition; and using the graphene, in separated form or as part of the biogenic activated carbon composition, in adhesive, sealant, coating, paint, ink composite material, catalyst, catalyst support, battery electrode, fuel cell electrode, graphene-based circuit or memory system, energy storage material or device, supercapacitor, sink for static electricity dissipation, material or device for electronic or ionic transport, high-bandwidth communication system, infrared sensor, chemical sensor, biological sensor, electronic display, voltaic cell, or graphene aerogel.