NOVELTY - Recovering and using (P1) carboxylic acids from fermentation broth involves: obtaining fermentation broth containing free carboxylic acid or mixture of carboxylic acids, or free carboxylic acid and its associated alkali or alkaline earth metal salts; drying the broth containing free carboxylic acid into powder; and synthesizing ester by reacting carboxylic acid in powder with alcohol solvent under CO2 atmosphere in absence of other acid catalyst at temperature and/or pressure which corresponds to supercritical, critical or near critical conditions for alcohol or CO2.    USE - For recovering and using carboxylic acids (such as formic acid, acetic acid, propionic acid, lactic acid, butyric acid) from fermentation broth to synthesize ester, predominantly diester, where ester is further converted into pharmaceutical, cosmetic, food or feed ingredient, polymer materials or biofuel (claimed); and also useful in production of chemical compounds, e.g. 4C platform compounds, polymers or fuels.    ADVANTAGE - The process provides an easier way to isolate and extract carboxylic acids from fermentation broth; converts corresponding esters (i.e. monoester, diester or triester) from carboxylic acids in a relatively efficient and cost effective manner; and eliminates 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 carboxylic acids are converted into esters, which are simpler to process and extract by distillation or other purification techniques without use of expensive and complicated chromatographic separation columns or resins. In 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 organic acids to their corresponding esters, we can avoid such issues. With optimization, esterification conducted at 250 degrees C under either same or greater CO2 pressure, the yield would be nearly quantitative (i.e. greater than 95%) and up to 99.9% conversion. The esters can be refined to achieve 90-98% purity. An advantage of recovering carboxylic acids from fermentation in the form of their corresponding esters is that downstream processing of esters is less energy intensive than hydrogenation of free acids. Another advantage of present esterification process is that one will find the present process simpler and easier, as compared to other approaches, to refine carboxylic acids for 4C chemical platforms from fermentation. It simplifies efforts to separate esters from other insoluble materials, as well as minimizes the amount of salt that one needs to separate. In an integrated process enables one to directly esterify a combination of free acid and salts that is produced in low-pH fermentation, in which, the fermentation is operated at pH of less than the pKa of carboxylic acids. The process can be less energy intensive that current recovery approaches.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) esterification method (P2) for polycarboxylic acid involving providing solution of free carboxylic acid from fermentation broth; reacting the solution of free carboxylic acids with alcohol in CO2 atmosphere without acid catalyst; and selecting operational reaction temperature or pressure corresponding to supercritical, critical or near critical conditions for alcohol or CO2 to yield ester corresponding to free carboxylic acid; and    (2) processing (P3) agricultural product or biomass involving obtaining carbohydrates from agricultural product or biomass; fermenting the carbohydrates to produce fermentation broth; drying the fermentation broth to produce fermentation broth powder; transporting the fermentation broth powder to second processing site; and reacting at least free carboxylic acid or mixture of free carboxylic acids and its associated salts in dried fermentation broth at second processing site with alcohol solvent under CO2 atmosphere in absence of extrinsic catalyst at reaction temperature and pressure that corresponds to supercritical, critical or near critical conditions for alcohol or CO2 to synthesize ester.