Application of Thermogravimetric Analysis for the Proximate Analysis of Livestock Wastes

There is worldwide interest in deriving increasing amounts of energy from bio-based agricultural materials including not only lignocellulosic residues but also a significant quantity of available livestock manure. This manure can be used as a feedstock for various thermochemical conversion processes such as pyrolysis and gasification. In order to apply these processes, the manure must be properly characterized for volatile matter VM and ash contents. The determination of these components is not mentioned specifically in current ASTM standards for livestock manure. In this study, we employed the use of thermogravimetric analysis TGA for the rapid assessment of VM and ash content in swine, dairy, rabbit, and poultry manures using references from the ASTM coal and coke standards. The TGA assessment of VM in the manures were the same as those values found by non-automated means ASTM D3175-07 ranging from 47 to 78 wt%db. The TGA assessment of the ash was also the same when compared to ash results via non-instrumental means following ASTM D3174-04. Ash values ranged from 4 to 47 wt%db. There was one exception when testing a high ash containing swine lagoon sludge. Under the TGA method, this sludge underwent more complete devolatilization and oxidation. This was primarily attributed to the small sample size leading to uniform internal heating. The modification of the TGA ash method aimed at shortening the run time generated similar results as both the original TGA method and non-automated method. Thus, TGA ash determination in manure should occur above 600°C with preferences for the following method: Zerograde air at 2–4 furnace volumes/min, heating rate of 11°C·min 1, temperature range of 110–950°C, and isothermal hold at 950°C for 10 min. VM determination via TGA should follow ASTM D3175-07.