The gas data results showed that SA was a good substrate for
biogas production, and the DSAwas also a good material for biogas
production. Cumulative biogas yield of SA in the first stage was
388 ± 22 ml g1 TSadded which was much higher than that of DSA
(with 210±2 ml g1 TSadded). After two stages anaerobic digestion,
cumulative biogas yield and TS removal rate of SA were
495 ± 24 ml g1 TSadded and 76.85 ± 1.94%. However, average
methane content of DSA in the secondwas 70.78 ± 2.11% whichwas
much higher than that of SA in the first stage.
After NaOH treatment, some lignin structure and carbohydrate
were partially destructed and lots of lignin fragment and carbohydrate
entered into aqueous extract. However, the destruction of
DSA's structure was limited, and there was slightly chemical
structural alteration between untreated and NaOH-treated DSA on
the whole. The skeleton structure of lignin and cellulose of DSA
were not destructed significantly by NaOH treatment. Although the
destruction of skeleton structure of DSA was slight, the biodegradability
of DSA was improved obviously. After NaOH-treatment,
cumulative biogas yield of DSA was increased by 68.17%~153.29%.
Therefore, NaOH treatment is still a good pretreatment for biogas
production of DSA.