Slow Pyrolysis Kinetics of Two Herbaceous Feedstock: Effect of Milling, Source, and Heating Rate

Biocarbon from peanut hulls and their green composites with biobased poly(trimethylene terephthalate) (PTT)

There are millions of tons of post-food processing residues discarded annually. Currently, these waste materials are discarded to landfill, used as animal feed or incinerated. This suggests that there are potential uses for these materials in value-added applications. This work focuses on the characterization and valorization of peanut hulls through the generation of green composites. Peanut hulls were pyrolyzed at 500 °C and analyzed to discover their unique surface morphology and relatively low ash content. Raman spectral analysis determined I_D/I_G values of 0.74 for the samples, suggesting greater graphitic content than disordered carbon content. Such results were confirmed in X-ray diffraction analysis by the presence of (002) and (100) planes. Partially biobased engineering thermoplastic, poly(trimethylene terephthalate) (PTT), was combined with 20 wt.% biocarbon. The tensile and flexural moduli improved with the addition of biocarbon, and the bio-content increased from 35 to 48 wt.% as compared to neat PTT. The higher temperature biocarbon was found to have superior performance over the lower temperature sample. The enhanced sustainability of these materials suggested that peanut hulls can be valorized via thermochemical conversion to generate value-added products. Future works could focus on the optimization of these materials for non-structural automotive components or electrical housings.

Biomass microspheres - A new method for characterization of biomass pyrolysis and shrinkage

A method for manufacturing biomass microspheres is introduced. Biomass microspheres between 100 and 400 µm in diameter were produced from crystalline cellulose, switchgrass, and tall fescue using spray drying. The biomass microspheres were characterized using X-ray computed tomography (XCT), thermal gravimetric analysis (TGA), and real-time optical imaging: density, pore structure, and size effects were studied. Dynamic shrinkage was video-captured using a CMOS camera and parallel (paired, side-by-side) weight loss experiments were performed using TGA. The combined data was used to correlate the extent of pyrolysis to gross morphological change (shrinkage). The results show that manufactured biomass microspheres are uniform and that, in the absence of heat and mass transport limitations, pyrolysis shrinkage is an intrinsic property dependent only upon the final processing temperatures.