Study of internal and external temperatures and their influence on covered lagoon digester performance

Abstract

There is an evident gap in terms of understanding the interactions among variables that directly affect anaerobic digestion in full-scale biodigesters. The objective of this study was to assess the behavior of temperatures inside and outside the biodigesters and their relationship with organic matter removal and CH4 yield. The experiment was carried out in a pig farm located in the municipality of Teixeiras, Minas Gerais, Brazil, which has two parallel covered lagoon digesters (CLDs). According to the results, air and biogas temperatures largely varied throughout the day (24-h period), in contrast to the soil and substrate temperatures. The CLD system presented a low removal efficiency in terms of chemical oxygen demand (COD) and volatile solids (VS). The mean CH4 content in the biogas was 67%, and the mean biogas yield was 740.2 m³.d−1. When assessing the correlation matrix between internal and external temperatures, and their correlation with treatment efficiency, in terms of COD and VS removal, biogas yield presented a linear correlation with VS removal efficiency (r = 0.60). All temperatures inside and outside the CLD were intercorrelated.