POULTRY LITTER AND SWITCHGRASS BLENDING FOR BIOCHAR PRODUCTION

Biochars for both soil improvement and bioenergy applications are affected by the choice of both the parent feedstock and the pyrolysis temperature. As such, controlling these two variables may yield an ideal product with engineered properties-a "designer biochar." The potential for a designer biochar comes from its ability to combine the properties of manure-based biochars, which are nutrient-rich and alkaline, with lignocellulosic biochars, which are carbon-rich and neutral to acidic. In this study, two such feedstocks (poultry litter and switchgrass) were blended at different ratios (100%, 75%, 50%, 25%, and 0% litter), pelletized (6 mm diameter), and then subjected to slow pyrolysis at different temperatures (350 degrees C, 500 degrees C, and 700 degrees C) to create test biochars. The biochars were tested for energy characteristics, pellet durability, and proximate composition. The results indicated that the blended biochars had lower pH, electrical conductivity, and ash contents than the pure poultry litter biochars. This suggests that a blended biochar is more appropriate for soil application. The blended biochars also had higher energy content (HHV), and the rate of mass loss during combustion was largely due to the increase of biochar carbon content. However, blending decreased the end temperature of combustion (compared to pure poultry litter biochars), suggesting that the blends contained more labile C. Structurally, the pure poultry litter pellets, regardless of pyrolysis temperature, were more durable, as indicated by less dust emitted, than the pure switchgrass pellets. Even though blended biochar pellets degrade more rapidly during handling and storage, blending manure and plant material for biochar production alleviates some of the other application issues when using pure manure-based biochars for soil improvement or energy conversion applications.