NOVELTY - Producing volatile fatty acid from organic waste through anaerobic fermentation, by subjecting high solid content containing sludge of solid mass (3.7-12%) to heat pre-treatment, inoculating acclimatized sludge seed culture (sludge containing anaerobic microorganisms) (10 g VS/L) to pre-treated sludge, passing nitrogen into fermenter for 1-5 minutes and fermenting the sludge at 35 degrees C for 4-10 days on table concentrator at rotation speed of 120 r/minute, where pH of the fermenting liquid is 8-12, and obtaining fermentation liquor containing volatile fatty acid.    USE - The method is useful for producing volatile fatty acid e.g. acetic acid from organic waste through anaerobic fermentation (claimed).    ADVANTAGE - The method is simple, rapid, cost-effective and produces high amount of volatile fatty acid (0.23 g) which is 20.1-61% higher than fermenting untreated sludge. The method reduces the organic solid waste, thus prevents the pollution caused by organic solid waste.    DETAILED DESCRIPTION - Method for producing volatile fatty acid from organic waste through anaerobic fermentation, involves (a) subjecting the high solid content containing sludge (substrate) of solid mass (3.7-12%) to heat pre-treatment by adjusting pH of sludge to 8-12 and heating the sludge at 20-90 degrees C for 1-10 hours with slow stirring, (b) inoculating acclimatized sludge seed culture (sludge containing anaerobic microorganisms) (10 g VS/L) to pre-treated sludge, passing nitrogen into the fermenter for 1-5 minutes and fermenting the sludge at 35 degrees C for 4-10 days on table concentrator at rotation speed of 120 r/minute, where the pH of the fermenting liquid is 8-12, and (c) obtaining the fermentation liquor containing volatile fatty acid, mainly acetic acid. The heat pre-treatment of the sludge is performed to transform organic matters, especially persistent organic biomass into soluble organic matter that can be treated by microorganisms. The acclimatized sludge seed culture is prepared by placing sludge in up-flow anaerobic sludge reactor (UASB) for 24 hours, removing supernatant from sludge, heating the sludge at 105 degrees C for 2 hours to remove non-sporulating methanogenic microorganisms, adding chemical oxygen demand (COD) glucose nutritive organic waste water (20000 mg/L) to sludge in UASB and acclimatizing the sludge at 35 degrees C for 10 days.