TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Culture: In the culture, the exogenous acyl-ACP thioesterase is a Fat B thioesterase. The exogenous acyl-ACP thioesterase is a Fat B thioesterase derived from the genus Cuphea. Also, the exogenous acyl-ACP thioesterase is ChFatB2. The recombinant photosynthetic microorganism has further been modified to produce an exogenous beta -ketoacyl synthase (KAS), where the exogenous KAS preferentially produces acyl-ACPs having the chain length for which the thioesterase has preferred activity. The recombinant photosynthetic microorganism is further modified so that one or more genes encoding beta-oxidation pathway enzymes are inactivated or down-regulated, or the enzymes are inhibited. The recombinant photosynthetic microorganism is further modified so that one or more genes encoding acyl-ACP synthetases are inactivated or down-regulated, or the synthetases are inhibited. The recombinant photosynthetic microorganism is further modified so that one or more genes encoding an enzyme involved in carbohydrate biosynthesis are inactivated or down-regulated, or the enzymes are inhibited. The enzyme involved in carbohydrate biosynthesis is a branching enzyme. Preferred Method: In converting inorganic carbon to fatty acids, the fatty acids are recovered from the culture by contacting the medium with particulate adsorbents, where the particulate adsorbents circulate in the medium and are contained in a fixed bed column. The pH of the medium is lowered during the contacting, where the pH lowering process comprises adding carbon dioxide (CO2). The medium is recirculated to the culture. The particulate adsorbents are lipophilic and are ion exchange resins. Preferred Composition: The composition is a biocrude. Alternatively, the composition comprises a derivative of the fatty acid produced by the culture. The composition is a finished fuel or fuel additive, and/or a biological substitute for a petrochemical product. The derivative is an alcohol, an alkane, or an alkene. EXAMPLE - No suitable example given.