A gronomy J our n al • Volu me 102 , I s sue 2 • 2 010 623 ABSTRACT Pyrolysis is the anaerobic thermal conversion of biomass for energy production. It off ers an option of returning carbon and nutrients to the soil while producing energy. Th e Ultisols in the southeastern United States have inherently low soil organic carbon and fertility, and may benefi t from the addition of biochar from pyrolysis. Our objectives were to evaluate the eff ect of peanut hull and pine chip biochars on soil nutrients, corn (Zea mays L.) nutrient status and yield in a Kandiudult for two growing seasons (2006 and 2007). Experiments for each biochar source were conducted as completely randomized designs with the biochar applied at 0, 11, and 22 Mg ha -1 with and without N fertilizer. Nitrogen in the peanut hull biochar (209 kg ha -1 at 11 Mg ha -1 rate) was not available during the study based on corn tissue concentrations. Th e peanut hull biochar linearly increased Mehlich I K, Ca, and Mg in the surface soil (0-15 cm). Th e increased available K was refl ected in the plant tissue analysis at corn stage R1 in 2006, but not in 2007. Pine chip biochar decreased soil pH, but had no eff ect on other nutrients except Mehlich I Ca. In the peanut hull biochar experiment, grain yields decreased at the 22 Mg ha -1 rate in the fertilized treatments. In the pine chip biochar experiment, grain yields decreased linearly with application rate in 2006, but this did not persist in 2007. Overall yield responses to biochar were smaller than expected based on previous studies.

A three-step bio-oil production process involving torrefaction pretreatment (at 225, 250, or 275°C with a 20 min hold time), pyrolysis (at 500°C with two heating rates), and secondary catalytic processing over 450, or 500°C ) was studied to determine process effects, particularly of torrefaction, on the yield of liquid and aromatic hydrocarbons and the quality of upgraded bio-oil. When bio-oils derived from torrefied biomass were catalytically cracked, average yields (%, w/w of feed) of reactor char (100% reduction), catalyst coke (21.4%), and catalyst tar (8.1%) were significantly reduced relative to the best-case conditions using non-torrefied feedstock. The reduction in coke (%, w/w of feed) as a result of torrefaction was 28.5% relative to the respective control for slow-pyrolysis bio-oil upgrading and 34.9% for fast-pyrolysis bio-oil upgrading. The concentration of aromatic product (benzene, toluene, ethylbenzene, and xylene, i.e., BTEX) was highest at 95 g L −1 for upgraded (at 500°C) fast-pyrolysis bio-oil derived from biomass torrefied at 275°C. Catalyst effectiveness for BTEX production significantly increased with increased torrefaction and catalytic cracking temperatures.

A three-step bio-oil production process involving torrefaction pretreatment (225, 250, or 275 °C at 20 min hold time), pyrolysis (500 °C, two heating rates), and secondary catalytic processing over HZSM-5 (at 400, 450, or 500 °C) was studied to determine how treatments affected byproduct formation and catalyst properties and function. Torrefaction pretreatment significantly reduced average yields (%, w/w of feed) of reactor char (100% reduction), catalyst coke (21.4%), and catalyst tar (8.1%) relative to the best-case conditions using non-torrefied feedstock. The yields of chemical components, including levoglucosan, formic acid, acetic acid, and 5-hydroxymethylfurfural (5-HMF), were significantly reduced in intermediate fast-pyrolysis bio-oil (FPO) derived from torrefied feedstock, while for intermediate slow-pyrolysis bio-oil (SPO), yields of levoglucosan, acetic acid, and 5-HMF were reduced. However, in terms of concentration, only furfural showed a significant correlation with the torrefaction temperature. Both furfural and formic acid indicated correlations with coke formation, although these were negative correlations. For formic acid, a decreased coke yield with an increasing concentration was attributed to the formation of H 2 from the thermal decomposition. Combined coke, char, and tar yield significantly decreased with an increasing torrefaction temperature, decreasing formic acid, acetic acid, and furfural concentrations, and an increasing levoglucosan concentration to a minimum of 14.4% (w/w of bio-oil feed). Torrefaction also increased catalyst effectiveness for minimizing changes to pore size, pore volume, and surface area upon upgrading FPO but reduced effectiveness for SPO processing. Torrefaction of biomass prior to slow pyrolysis more effectively maintained weak and strong acid site density after catalytic processing, although no clear effect of torrefaction was seen for FPO-processing catalysts.

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