Hydrogen and methane yields of untreated, water-extracted and acid (HCl) treated maize in one- and two-stage batch assays

In the present study, two-stage H2 and CH4 production was compared with one-stage CH4 production from maize subjected to water extraction and acid (HCl) treatment. In addition, the effect of duration (2 and 14 days) of the first-stage H2 process on the H2 yields and subsequent CH4 yields from the second-stage was also investigated. Results showed that the average H2 yields from untreated maize were 5.6 and 9.9 ml/g volatile solids added (VSadded) after 2 and 14 days, respectively. On the other hand, H2 yields from water-extracted and HCl-treated maize were 18.0 and 20.5 ml/gVSadded (14 d), respectively. On comparison to one-stage CH4 assays, the average increase in CH4 yields from two-stage assays with 2 d H2 stage were 7, 9 and 27% for untreated, water-extracted and HCl-treated maize, respectively.

► H2 yield from untreated maize was 9.9 ml/g volatile solids added (VSadded). ► 18 and 20.5 mlH2/gVSadded were obtained after water extraction and HCl-treatment. ► Two-stage H2 + CH4 process improved CH4 yields by 7–27%.