Rotary drum reactors (RDRs) for accelerated carcass composting are being installed in animal production units as an alternative for the disposal of pig and poultry carcasses in Brazil. The aim of the present study was to investigate the influence of aeration frequency on gas emissions (CO2-C, CH4-C, NH3-N and N2O-N) during composting of pig and poultry carcasses in RDRs. RDRs with a volume of 3.6 m3 (50% useful volume) were used. Aeration time was 24 minutes. Four intervals between aeration periods were tested (treatments) as follows: 1 hour (T1), 2 hours (T2), 3 hours (T3) and 4 hours (T4). Gas emissions were continuously monitored using a photoacoustic gas monitor (INNOVA 1412). Temperature was monitored using iButtons mixed with the biomass. Mathematical models of CO2-C and NH3-N emissions relative to the observed biomass temperature were proposed. Biomass temperature was affected by the treatments. The highest aeration frequency had the shortest thermophilic phase (>50 °C). No significant differences in total gas emissions were observed between treatments (p>0.05). CO2-C and NH3-N emissions were better fitted by non-linear models (R2=0.75 and R2=0.78, respectively). A minimum 2-hour interval should be adopted between aeration periods of 24 minutes to guarantee a longer thermophilic phase and elimination of possible pathogenic contaminants.

The contamination of coastal areas by petroleum and its derivatives is a relevant issue based on large-scale production and consumption. This study presents field and laboratory surveys on the detoxification enzymes on the estuarine/coastal catfish Genidens genidens to understand the enzymatic responses to oil derivatives and environmental conditions. Field catalase (CAT) and glutathione S-tranferase (GST) measurements suggest oxidative stress and acting repair mechanisms in fishes, but were not induced by diesel oil as indicated by laboratory studies. On the other hand, higher ethoxyresorufin-O-deethylase (EROD) activities following higher polycyclic aromatic hydrocarbon (PAH) concentrations in the estuarine waters suggested fish responsiveness to oil contamination, mainly due to the fact that such EROD values were similar to the magnitude measured in fish during a 24-h exposure to diesel oil in the laboratory. However, other environmental estuarine conditions may also act on field EROD activities since PAHs concentrations in the water-soluble fraction of diesel oil (WSFDO) were higher than those measured in estuarine waters.