TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The fermenting step produces an effluent. The method further comprises: transferring at least a portion of the effluent from the anaerobic digester to the photosynthetic culture chamber; feeding a carbon dioxide-rich anaerobic exhaust gas from a hydrocarbon fuel combustion process to the photosynthetic culture chamber; separating carbon dioxide from the biogas and delivering it to aquatic medium in the photosynthetic culture chamber to enrich the aquatic medium with carbon dioxide; contacting at least a portion of the biogas with an aqueous volume outside the anaerobic digester and photosynthetic culture chamber to dissolve carbon dioxide from the biogas, generate a carbon dioxide depleted biogas; mixing the aqueous volume with the aqueous medium in the photosynthetic culture chamber, where the step (d) comprises converting at least a portion of the carbon dioxide depleted biogas to synthesis gas; and contacting at least a portion of the biogas with the aquatic medium in the photosynthetic culture chamber to dissolve carbon dioxide from the biogas in aquatic medium and generate a carbon dioxide depleted biogas. The step of transferring the effluent from the anaerobic digester to the photosynthetic culture chamber comprises transferring the effluent from the anaerobic digester to a treatment chamber, treating the effluent to generate a treated effluent and transferring the treated effluent to the photosynthetic culture chamber. The aquatic plants are planktonic and transferring of organic material of the aquatic plants to an anaerobic digester comprises transferring the aquatic medium containing the aquatic plants to the digester without separating the aquatic plants from the aquatic medium. The method further comprises between steps (a) and (b): harvesting the aquatic plants from the aquatic medium; and processing the aquatic plants to isolate oil and organic residue from the aquatic plants. The step (b) comprises transferring the organic residue to an anaerobic digester. The step (c) comprises fermenting the organic residue in the digester. Preferred Component: The effluent is liquid effluent comprising dissolved carbon dioxide of at least 3 mM when contacted with aquatic medium in photosynthetic culture chamber. The photosynthetic culture chamber is positioned above the anaerobic digester. The aquatic plants are duckweed or water hyacinth, or macro algae or micro algae. EXAMPLE - No suitable example given.