Aeration frequency on accelerated composting of animal carcasses

Frequência de aeração em compostagem acelerada de cadáveres de animais

ABSTRACT

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.

Index terms:
Rotary drum reactor; poultry and pig; gas emission