The effect of sewage sludge (SWS) addition on the H(2) fermentation of food waste (rev) was investigated. It was found that a slight addition of SWS (10:1 = FW:SWS on a COD basis) significantly enhanced the H2 fermentation performance, not only increasing the total amount of H(2) produced but accelerating the whole reaction, shortening the lag period, and increasing the H(2) production rate. Substrate degradation and microbial germination were also facilitated by SWS addition. A simple calculation reveals that the increased amount of H(2) production derived mostly from FW, indicating that SWS addition synergistically enhanced H(2) fermentation performance. This was attributed to the existence of Fe and Ca at much higher concentrations in the SWS compared to the FW. The batch process treating a mixture of FW and SWS was repeated and showed an average H(2) yield of 2.11 +/- 0.20 mol H(2)/mol hexose(added), which was 13% higher than that of FW treated alone. (C) 2011 Elsevier Ltd. All rights reserved.