Poultry litter and switchgrass blending and pelletizing characteristics for biochar production

Abstract

Biochar characteristics for both soil and energy applications have been documented to be affected by both the parent feedstock and pyrolysis production temperature. Controlling these two variables may yield an ideal product with engineered properties—“A Designer Biochar.” Manure-based biochars are known to be extremely alkaline with high ash contents while lignocellulosic biochars are known to be carbon-rich with more neutral to acidic pH. Poultry litter and switchgrass feedstocks were blended at different ratios, pelletized, and then underwent slow pyrolysis at different temperatures to determine the effect that blend ratio and pyrolysis temperature had on the final biochar’s energetic, pellet durability, and proximate composition characteristics. Comparing pure poultry litter biochars to the blended poultry litter and switchgrass biochars, the high pH, EC, and ash contents were mediated suggesting a more appropriate biochar for soil application. Blending poultry litter and switchgrass increased both the energy content (HHV) and the rate of mass loss largely due to the increase of biochar C; but blending decreased the end temperature of combustion suggesting more labile C in the blends.Structurally, pure poultry litter pellets, regardless of pyrolysis temperature, were more resistant to degradation and less dustier than pure switchgrass pellets. Even though a blended biochar pellet will become more prone to degradation with constant handling, a manure-plant blended pellet alleviates some of the other application issues when using pure manure-based biochars.