Abstract:

Tartary buckwheat residue was used as raw material, and the fermentation broth with different total solid (TS) mass fraction was used to investigate the acidification experiment. After obtaining the mass fraction of acidified TS, it was readded with buffer solution for anaerobic fermentation. The changes of volatile fatty acids in the whole process of anaerobic fermentation were monitored. The results showed that when the mass fraction of TS was 4%, the gas production was good.When the mass fraction of TS exceeded 4%, acidification occurred in the system, which was caused by excessive accumulation of butyric acid. The conversion of butyric acid to acetic acid could be promoted by using buffer solution(30% NaOH solution) to adjust pH value for combined hydrogen and methane production fermentation, which could effectively solve the problem of acid accumulation and improve energy conversion efficiency. Under the same TS mass fraction, the energy conversion efficiency of the combined hydrogen and methane production group (4^# and 5^#) were 10.8 times and 12.8 times of those of the untreated group (2^# and 3^#), respectively. Adjusting pH value with buffer solution after acidification not only could quickly restore gas production, but also had a higher gas production rate than other recovery methods, and the gas production rate of TS could reach 1 267 mL/g. Modified Gompertz equation was used for fitting, and it was found that the correlation coefficients R were all above 0.99, and the fitting results were good.

Key words: tartary buckwheat residue, anaerobic digestion, acidification, hydrogen and methane production, volatile fatty acid