Upgrading fuel characteristic of poultry sludge via wet torrefaction

The main barriers to the use of biomass as an energy source are high humidity, ash, and oxygen content which can be eliminated by wet torrefaction (WT). In this study, dewatered poultry sludge (DPS), as being complex biomass to dispose of, was subjected to WT by considering the reaction temperature, time, and feed concentration as the independent process parameters. The parameter range is determined using response surface methodology and the experiments were carried out in a laboratory-scale batch reactor. The optimum conditions for both maximum solid yield (SY) and calorific value (CV) were evaluated for the reaction temperature, time, and feed concentration of 268°C, 47 min, 50wt%, respectively. According to the results, the feed concentration was the most influential parameter on calorific value and solid yield, whereas the reaction time has the lowest effect. In addition to their individual effects, the interactive effects of process parameters on CV and SY were also analyzed by two and three-dimensional contour plots. Besides, the proximate analysis revealed that the fixed carbon was observed to be increased while the amount of ash and volatile matter in the torrefied DPS (TDPS) decreased under optimum conditions. Through the ultimate analysis, a remarkable reduction in the atomic ratio of oxygen to carbon was reported. According to the results it is concluded that the WT significantly enhances and converts raw poultry sludge to a more efficient solid fuel.