Ensiling in the presence of 0.5% formic acid preserved the sugar content of sweet sorghum, while in enzyme-assisted ensiling (ENLAC) with in situ produced enzymes, the sugar loss in 30 days was 28.6%. The ENLAC silage contained 1.5% lactic acid and 0.6% ethanol which might be recovered as value-added secondary products, ira addition to the high quality residue as animal feed. Overall the formic acid ensiling is the better choice for sugar preservation, storage and prolonged bioprocessing for biofuel production. (C) 1997 Elsevier Science Ltd.