Thermochemical characterization of cattle manure relevant to its energy conversion and environmental implications

In this work, we used three manure resources from common cattle ruminants (i.e., dairy, beef, and buffalo) to evaluate their thermochemical properties, including elemental analysis, lignocellulosic constituents, calorific value, mineral components, thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy–energy-dispersive spectroscopy, which were relevant to the utilization as biofuel feedstocks. The fuel-related properties of manures from three different kinds of cattle were very similar. The cattle manure was rich in lignocellulosic constituents with about 80 % on a dry basis, indicating that its calorific value was as high as around 20 MJ/kg in connection with the contents of about 45 % C and 6 % H. More significantly, the contents of sulfur and nitrogen in the cattle manure are relatively low, suggesting that the biomass represents a promising fuel feedstock without concern in the excessive emissions of acidic gases. From the analyses of inorganic elements for the manure, there were no detectable concentrations of heavy metals such as Mn, Cu, and Zn. Based on the results of thermochemical characterization, cattle manure could be directly reused as a fuel feedstock in the direct combustion and co-firing systems or further converted into biochar, activated char, and bio-oil in the thermochemical processes.