Combustion Potential of Raw and Torrefied Zoo Animals Faeces

Raw and torrefied faeces from four zoo animals (giraffe, deer, camel, reindeer) and a sample of zebra manure pellets were studied to assess their energy potential using combustion calorimetry and thermoanalytical (TG/DTA) methods. Marked differences (ca 12%) in the torrefaction yield of the faeces were found depending on the animal species. Using the standard deviation of torrefaction yield, the heterogeneity of the droppings within one animal species was estimated to be up to 4%. Torrefied faeces demonstrated an increase in higher heating values by about 30% compared to raw samples. The differences between the higher heating values of samples torrefied at 300 °C and 250 °C were found to be relatively insignificant, both leading to completely comparable values of the energy densification ratio. According to elemental composition, higher heating value and combustion characteristics, torrefied faeces proved to be quite comparable to these parameters of lignite.