low value (90 ± 55) (Table 2) when compared to those obtained in
the study carried out by Kaparaju and Rintala [5]. These authors reported
values in the range of 130–150 mL CH4 g VS1
added for the
anaerobic digestion of hog manure. Moreover, the methane content
(49%) of the biogas registered in the present study was also low
when compared to results reported by other authors. The poor
methane yield obtained in this study may be rationalized by the
low content of organic material available for microorganisms. SM
used as substrate for R1 at an HRT of 25 d presented a low CODs/
CODt ratio (Table 1). The decrease in the HRT to 15 d resulted in an
OLR increase from 0.4 to 0.6 g VS L1 d1 and an improvement of
the methane yield with an average value of 201 mL CH4 g VS1
added.
Data obtained were in accordance to Panichnumsin et al. [6], who