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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Publications at this Location » Publication #313493

Research Project: Developing Technologies that Enable Growth and Profitability in the Commercial Conversion of Sugarcane, Sweet Sorghum, and Energy Beets into Sugar, Advanced Biofuels, and Bioproducts

Location: Commodity Utilization Research

Title: Influence of carbonization methods on the aromaticity of pyrogenic dissolved organic carbon

item Uchimiya, Sophie
item HIRADATE, SYUNTARO - National Institute For Agro-Environmental Sciences
item ANTAL, JR, MICHAEL - University Of Hawaii

Submitted to: Energy and Fuels
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2015
Publication Date: 3/5/2015
Citation: Uchimiya, M., Hiradate, S., Antal, Jr., M.J. 2015. Influence of carbonization methods on the aromaticity of pyrogenic dissolved organic carbon. Energy and Fuels. 29(4):2503-2513.

Interpretive Summary: Biochar is a promising soil amendment to improve crop yields and to reduce carbon footprint. Biochar production (slow pyrolysis) units often suffer from low efficiency and capacity to produce enough quantity for field-scale soil amendment. This study focused on 2 patented high-yield, high-throughput pilot-scale biochar production technologies called flash and high-yield carbonization processes. The amount and structure of carbon extractives correlated with the measurable parameters (heat resistance and spectroscopic peaks) of biochars. The quantity of available nutrient elements (K, Na, S) could be predicted from the conductivity of the extractives. These correlations will help end-users predict how much organic and inorganic nutrients will be available from biochar to food crops.

Technical Abstract: Dissolved organic carbon (DOC) components of soil amendments such as biochar will influence the fundamental soil chemistry including the metal speciation, nutrient availability, and microbial activity. Quantitative correlation is necessary between (i) pyrogenic DOC components of varying aromaticity and ionizable (carboxyl, hydroxyl) substituents and (ii) bulk and solution properties of biochars. This study employed fluorescence excitation-emission (EEM) spectrophotometry with parallel factor analysis (PARAFAC) to understand the influence of pyrolysis platform (flash and high-yield carbonization, slow pyrolysis, and fast pyrolysis) and solution pH on the DOC structure of carbonaceous materials. The PARAFAC fingerprint representative of conjugated, polyaromatic DOC correlated (Pearson’s r = 0.6, p < 0.005) with (i) volatile matter content and (ii) total organic carbon and nitrogen concentrations in water and base (50-100 mM NaOH) extracts. Electric conductivity of the extracts correlated with S (indicative of labile sulfate species) and Na+K concentrations (r > 0.9, p < 0.0005). The pH-dependent changes in fluorescence peak position and intensity suggested (i) protonation of carboxylate/phenolic functionalities and (ii) acid-induced aggregation of colloidal particles for =350 °C slow pyrolysis biochars; DOC of high-yield/flash carbonization charcoals and =500 °C slow pyrolysis biochars were less sensitive to pH. Solid state 13C cross polarization and magic angle spinning NMR analysis of bulk aromaticity (-C=C- peak at 110-160 ppm) suggested that both recalcitrant and labile fluorescence DOC fingerprints are composed of polyaromatic structures that begin to form near 350 °C. These biochar-borne DOC of varying aromaticity and carboxyl substituents will participate in hydrophobic and H-bonding interactions with soil components that will ultimately impact the biogeochemical cycles.