In recent years, it has become clear that the rapidly acidifying chemical oxygen demand (RACOD) content of the waste water and the surface tension of the reactor liquid contribute to the phenomenon of granular growth in upflow anaerobic sludge-blanket reactors (UASB). By adding 20% of directly soluble RACOD, in the form of a sucrose;starch mixture, on top of the original COD load and by adjusting the reactor liquid surface tension below 50 mN m(-1) with linear alkylbenzenesulphonate, granular growth and sludge-bed stability could be enhanced significantly within 40 days, Carrot pulp, a waste product having a high short-chain fatty acid precursor potential, was applied as an alternative fibrous RACOD source. Best results were obtained when adding the carrot pulp freshly to the laboratory-scale UASB reactor in an in-recycle liquefying chamber. This concept of adding carrot pulp waste product as a granular growth supplement by means of an in-recycle liquefying chamber therefore merits testing in practice.