studied anaerobic digestion of pig manure under semi-continuous
operation applying the same HRT. In this case, the authors obtained
a yield of 217 mL CH4 g VS1
added. Thus, the better performance of R1
with the decrease in HRT (from 25 to 15 d) would be the consequence
of a higher OLR applied to the system and consequently a
higher amount of substrate available for microorganisms. Bo values
calculated for this reactor at both HRT resulted in an increase of biodegradability
with the reduction in digestion time. However, the increase
observed in the methane yield with the decrease in HRT was
considerably higher. This result may indicate the existence of a
threshold value associated to the organic nature of the feeding material.
Alvarez and Lidén [12] reported modifications in the methane
yield associated with variations in the OLR, these authors reported