NOVELTY - Producing biofuel involves a) obtaining fermentation broth containing at least one free carboxylic acid, or a mixture of carboxylic acid, or at least one carboxylic acid and its associated salts; b) drying fermentation broth containing free carboxylic acid into powder; and c) synthesizing ester by reacting carboxylic acid in powder with alcohol solvent under carbon dioxide atmosphere in substantial absence of any other acid catalyst; and d) subjecting ester to either hydrogenolysis or hydrogenation to form a biofuel.    USE - For producing biofuel such as alkane or an alcohol e.g. ethane, ethanol, propane, propanol, butane, 1-butanol, octane, and octanol (claimed).    ADVANTAGE - The process converts the carboxylic acid to its corresponding ester (e.g. mono-ester, di-ester, or tri-ester) in a relatively efficient and cost effective manner. The process allows discovery of a simple but effective way of producing esters from carboxylic acids that are otherwise costly and difficult to isolate. Using the process, one can use free carboxylic acids directly from a fermentation broth and generate corresponding esters from without, the need to isolate or purify the acids from the fermentation broth, as is necessary in conventional extractions from broth. In comparison to certain fermentation processes that neutralize or convert the organic acids to their salts, the present process provides an easier way to isolate and extract organic acids iron a fermentation broth. The present process eliminates a need for titration and neutralization of the fermentation broth that can precipitate metal salts, and certain purification steps to produce stock platform chemical. The free organic acids are converted into esters, which are simpler to process and extract by distillation or other purification techniques without the use of expensive and complicated chromatographic separation columns or resins. For instance in a conventional process, one would need to use ion exchange chromatography to isolate the acids. A small amount of salts may unavoidably carry-over after the ion exchange. Hence, one may require multiple units of operation to purify the acid to an acceptable quality level. With each added operational unit, the costs of the overall process increases. In contrast, with the present process, synthesizing the ester of the acid, one can recover the salt as a carbonate or hydroxide, which can be used to regenerate the fermentation broth, and minimize waste. By converting the carboxylic acids to their corresponding esters, can avoid, such issues. Using an amount of the alcohol solvent in excess of the carboxylic acid, one can produce a very clean esterification. The process provides a direct route by which biologically-derived carboxylic acids can be recovered in a simple, cost-efficient process from a fermentation broth, can simplify the transport and processing of crops for fermentation products.    DETAILED DESCRIPTION - Producing biofuel involves a) obtaining fermentation broth containing at least one free carboxylic acid, or a mixture of carboxylic acid, or at least one carboxylic acid and its associated salts; b) drying fermentation broth containing free carboxylic acid into powder; and c) synthesizing ester by reacting carboxylic acid in the powder with an alcohol solvent under carbon dioxide atmosphere in substantial absence of any other acid catalyst at either a reaction temperature and/or pressure that is at a supercritical, critical or near critical condition for at least one of alcohol or carbon dioxide; and d) subjecting ester to either hydrogenolysis or hydrogenation to form a biofuel.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram illustrating an iteration of the present process for esterifying an organic carboxylic acid derived from fermentation broth, and further downstream processes that can isolate the resulting esters and/or generate other compounds from such esters.