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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #294749
Title: Poultry litter and switchgrass blending for biochar production

Author
item Cantrell, Keri
item Martin, Jerry
item Novak, Jeffrey

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2014
Publication Date: 5/14/2014
Citation: Cantrell, K.B., Martin, J.H., Novak, J.M. 2014. Poultry litter and switchgrass blending for biochar production. Transactions of the ASABE. 57(2):543-553.

Interpretive Summary: Biochar’s performance as either a soil amendment or bioenergy resource is affected by the type of feedstock and the pyrolysis production temperature. Selecting those properties can generate a specifically designed biochar suited for an intended application—“A Designer Biochar.” In this study, we investigate the composition, energy characteristics, and pellet durability of biochars produced from single manure (poultry litter) and plant (switchgrass) sources along with their blends. After pelletizing the feedstocks, they were slow pyrolyzed at three temperatures. The results indicated that blended poultry litter-switchgrass biochars had lower pH, electrical conductivity, and ash contents than the pure poultry litter biochars; this suggests a blended biochar is more appropriate for soil application. Blended biochars compared to pure poultry litter biochars also had a higher energy content and readily combusted; this was due to the increase in carbon in the biochars. Pure poultry litter biochar pellets were more durable than pure switchgrass biochar pellets, as indicated by less dust emissions during testing. Even though a blended biochar pellet becomes more prone to degradation with constant handling, blending manure and plants for biochar production alleviates some of the other application issues when using pure manure-based biochars for soil improvement or energy conversion applications.

Technical Abstract: Biochars for both soil improvement and bioenergy applications are affected by the choice of both the parent feedstock and 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 an 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. Two such feedstocks (poultry litter and switchgrass) have been blended at different ratios (100, 75, 50, 25, 0% litter), pelletized (6-millimeter diameter), and then underwent slow pyrolysis at different temperatures (350, 500, 700 degree Celsius) to create test biochars. These biochars have been tested for energetic characteristics, pellet durability, and proximate composition. The results indicated blended poultry litter-switchgrass biochars had lower pH, electrical conductivity, and ash contents than the pure poultry litter biochars; this suggests a blended biochar is more appropriate for soil application. Blended biochars also have higher energy contents (HHV) and the rate of mass loss during combustion was largely due to the increase of biochar carbon content; but blending decreased the end temperature of combustion (compared to pure poultry litter biochars) suggesting the blends to contain more labile carbon. Structurally, pure poultry litter pellets, regardless of pyrolysis temperature, are more durable, as indicated by less dust emitted, than pure switchgrass pellets. Even though a blended biochar pellet becomes more prone to degradation with constant handling, blending manure and plants for biochar production alleviates some of the other application issues when using pure manure-based biochars for soil improvement or energy conversion applications.