|Avena Bustillos, Roberto|
|Glenn, Gregory - Greg|
|Orts, William - Bill|
Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2014
Publication Date: 11/20/2014
Citation: Chiou, B., Valenzuela-Medina, D., Bilbao-Sainz, C., Klamczynski, A., Avena Bustillos, R.D., Milczarek, R.R., Du, W., Glenn, G.M., Orts, W.J. 2014. Torrefaction of pomaces and nut shells. Bioresource Technology. 177:58-65.
Interpretive Summary: Torrefaction of biomass involves heating the sample under inert atmosphere at temperatures between 200-300'C for one hour or less. Most studies on torrefaction of biomass had involved different wood species. There had been very few studies focusing on pomaces and nut shells. In this study, we examined the torrefaction of apple, grape, olive, and tomato pomaces as well as almond and walnut shells. We characterized the effects of torrefaction temperature and time on mass and energy yields of the torrefied byproducts. Raw tomato pomace had the highest energy value due to its high carbon content. Also, temperature had a greater effect on the mass and energy yields of the torrefied byproducts than time. In addition, grape pomace generally had the highest mass and energy yields at high torrefaction temperatures.
Technical Abstract: Technical: Apple, grape, olive, and tomato pomaces as well as almond and walnut shells were torrefied at different temperatures and times in a muffle furnace. The fiber content and thermal stability of the raw byproducts were examined using fiber analysis and thermogravimetric analysis (TGA), respectively. Also, the moisture and ash contents, elemental composition, and gross calorific values (GCV) of the raw and torrefied samples were characterized using TGA, elemental analysis, and bomb calorimetry, respectively. Response surface methodology and a central composite design were used to examine the effects of torrefaction temperature and time on the mass and energy yields of the torrefied byproducts. Apple pomace had the highest hemicellulose and lowest lignin contents. In comparison, grape pomace had the highest lignin content. Tomato pomace had the highest gross calorific value because of its high carbon content. Also, apple pomace had the lowest thermal stability due to its high hemicellulose content. Consequently, apple pomace was torrefied at 200°C, 230°C, and 260°C rather than 230°C, 260°C, and 290°C for the other byproducts. Temperature had a larger effect on mass and energy yields of the torrefied byproducts than time. Also, grape pomace generally had the highest mass and energy yields at high torrefaction temperatures. In addition, energy yields of the byproducts could be predicted from mass loss values.