Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/27/2011
Publication Date: 2/14/2012
Citation: Cantrell, K.B., Hunt, P.G., Uchimiya, S.M., Novak, J.M., Ro, K.S. 2012. Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar. Bioresource Technology. 107:419-428. Interpretive Summary: Pyrolysis of livestock manure generates a nutrient-rich, value-added biochar. This biochar has potential uses as a soil amendment or alternative fertilizer. It is important to characterize biochars from a wide selection of available manures made under the same processing conditions. In this study, we generated five manure-based biochars pyrolyzed at 350 and 700 degrees Celsius: separated swine solids, paved feedlot manure, dairy manure, poultry litter, and turkey liter. Pyrolysis of manure regardless of animal variety generated a high pH biochar with predominately stable carbon structures right in inorganic nutrients. Detailed structural analyses indicated (1) similarities with turkey and poultry litter biochars, (2) similarities with feedlot and dairy manure biochars, and (3) distinct properties for swine waste biochars. High biochar mass recovery was linked to the raw feedstock ash and volatile matter. Feedstock nutrient concentrations were not found to predict actual (numerical) biochar nutrient compositions. However, the high concentrations of plant minerals like phosphorous, calcium, and potassium may prove beneficial for use of manure-based biochars as an alternative fertilizer.
Technical Abstract: Pyrolysis of livestock manures generates a nutrient-rich biochar with potential uses as a soil amendment or alternative fertilizer. This paper reports on selected physicochemical results for five manure-based biochars pyrolyzed at 350 and 700 degrees Celsius: separated swine solids; paved feedlot manure; dairy manure; poultry litter; and turkey litter. Elemental and FTIR spectroscopic analyses of these alkaline biochars confirmed pyrolytic temperature increases led to a reduction in volatile matter and increases in both aromatic-carbon character and ash containing elevated potassium, calcium, and phosphorus. Heavy metal concentrations in all biochars were at acceptable concentrations for land applications, as long as feedstock concentrations were initially acceptable. Manure biochar mass recovery demonstrated an inverse response to temperature increases and strongly correlated to the feedstock proximate (ash and volatile matter) and elemental (carbon, nitrogen) characteristics. Feedstock nutrient concentrations did not affect reactions equally and would not be considered a quantitative predictor of biochar nutrient compositions.