Effect of inhibition treatment, type of inocula, and incubation temperature on batch H2 production from organic solid waste

Two types of induction treatments (heat‐shock pretreatment, HSP, and acetylene, Ac), inocula (meso and thermophilic) and incubation temperatures (37 and 55°C) were tested according to a full factorial design 23 with the aim of assessing their effects on cumulative H2 production (PH, mmol H2/mini‐reactor), initial H2 production rate (Ri,H, µmol H2/(g VSi × h)), lag time (Tlag, h), and metabolites distribution when fermenting organic solid waste with an undefined anerobic consortia in batch mini‐reactors. Type of inocula did not have a significant effect on PH, Tlag, and Ri,H except for organic acids production: mini‐reactors seeded with thermophilic inocula had the highest organic acid production. Concerning the induction treatment, it was found that on the average Ac only affected in a positive way the PH and Tlag. Thus, PH in Ac‐inhibited units (6.97) was 20% larger than those in HSP‐inhibited units (5.77). Also, Ac favored a shorter Tlag for PH in comparison with HSP (180 vs. 366). Additionally, a positive correlation was found between H2 and organic acid production. In contrast, solvent concentration in heat‐shocked mini‐reactors were slightly higher than in reactors spiked with Ac. Regarding the incubation temperature, on the average mesophilic temperature affected in a positive and very significant way PH (10.07 vs. 2.67) and Ri,H (2.43 vs. 0.76) with minimum Tlag (87 vs. 459). The positive correlation between H2 and organic acids production was found again. Yet, incubation temperature did not seem to affect solvent production. A strong interaction was observed between induction treatment and incubation temperature. Thus, Ac‐inhibited units showed higher values of PH and Ri,H than that HSP‐inhibited units only under thermophilic incubation. Contrary to this, HSP‐inhibited units showed the highest values of PH and Ri,H only under mesophilic conditions. Therefore, the superiority of an induction treatment seems to strongly depend on the incubation temperature. © 2006 Wiley Periodicals, Inc.