Joeri Kaal

Bio: Joeri Kaal is an academic researcher from University of Santiago de Compostela. The author has contributed to research in topics: Organic matter & Soil organic matter. The author has an hindex of 24, co-authored 64 publications receiving 1741 citations. Previous affiliations of Joeri Kaal include Spanish National Research Council & University of Amsterdam.

Differentiation between pine woods according to species and growing location using FTIR-ATR

Abstract: Attenuated total reflectance-Fourier transform infrared (FTIR-ATR) spectroscopy was applied to 120 samples of heartwood rings from eight individual pine trees from different locations in Spain. Pinus sylvestris cores were collected at the Artikutza natural park (Ps-ART). Pinus nigra cores were collected in Sierra de Cazorla (Pn-LIN) and in La Sagra Mountain (Pn-LSA). Three discriminant analysis tests were performed using all bands (DFT), lignin bands only (DFL) and polysaccharides bands only (DFP), to explore the ability of FTIR-ATR to separate between species and growing location. The DFL model enabled a good separation between pine species, whereas the DFP model enabled differentiation for both species and growing location. The DFT model enabled virtually perfect separation, based on two functions involving twelve FTIR bands. Discrimination between species was related to bands at 860 and 1655 cm-1, which were more intense in P. sylvestris samples, and bands at 1425 and 1635 cm-1, more intense in P. nigra samples. These vibrations were related to differences in lignin structure and polysaccharide linear chains. Discrimination between growing locations was mainly related to polysaccharide absorptions: at 900, 1085 and 1335 cm-1 more representative of Pn-LIN samples, and at 1105 and 1315 cm-1 mostly associated to Pn-LSA samples. These absorptions are related to β-glycosidic linkages (900 cm-1), cellulose and hemicellulose (C-O bonds, 1085 and 1105 cm-1) and content in amorphous/crystalline cellulose (1315 and 1335 cm-1). These results show that FTIR-ATR in combination with multivariate statistics can be a useful tool for species identification and provenancing for pine wood samples of unknown origin.

Review of the stability of biochar in soils: predictability of O:C molar ratios

Abstract: Biochar is not a structured homogeneous material; rather it possesses a range of chemical structures and a heterogeneous elemental composition. This variability is based on the conditions of pyrolysis and the biomass parent material, with biochar spanning the range of various forms of black carbon. Thereby, this variability induces a broad spectrum in the observed rates of reactivity and, correspondingly, the overall chemical and microbial stability. From evaluating the current biochar and black carbon degradation studies, there is the suggestion of an overall relationship in biochar stability as a function of the molar ratio of oxygen to carbon (O:C) in the resulting black carbon. In general, a molar ratio of O:C lower than 0.2 appears to provide, at minimum, a 1000-year biochar half-life. The O:C ratio is a function of production temperature, but also accounts for other impacts (e.g., parent material and post-production conditioning/oxidation) that are not captured solely with production temperature. Th...

Characterization of slow pyrolysis biochars: effects of feedstocks and pyrolysis temperature on biochar properties.

Abstract: Biochars are increasingly used as soil amendment and for C sequestration in soils. The influence of feedstock differences and pyrolysis temperature on biochar characteristics has been widely studied. However, there is a lack of knowledge about the formation of potentially toxic compounds that remain in the biochars after pyrolysis. We investigated biochars from three feedstocks (wheat straw, poplar wood, and spruce wood) that were slowly pyrolyzed at 400, 460, and 525°C for 5 h (straw) and 10 h (woodchips), respectively. We characterized the biochars' pH, electrical conductivity, elemental composition (by dry combustion and X-ray fluorescence), surface area (by N adsorption), water-extractable major elements, and cation exchange capacity (CEC). We further conducted differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffractometry to obtain information on the biochars' molecular characteristics and mineralogical composition. We investigated trace metal content, total polycyclic aromatic hydrocarbon (PAH) content, and PAH composition in the biochars. The highest salt (4.92 mS cm) and ash (12.7%) contents were found in straw-derived biochars. The H/C ratios of biochars with highest treatment temperature (HTT) 525°C were 0.46 to 0.40. Surface areas were low but increased (1.8-56 m g) with increasing HTT, whereas CEC decreased (162-52 mmol kg) with increasing HTT. The results of DSC and FTIR suggested a loss of labile, aliphatic compounds during pyrolysis and the formation of more recalcitrant, aromatic constituents. X-ray diffractometry patterns indicated a mineralogical restructuring of biochars with increasing HTT. Water-extractable major and trace elements varied considerably with feedstock composition, with trace elements also affected by HTT. Total PAH contents (sum of EPA 16 PAHs) were highly variable with values up to 33.7 mg kg; irrespective of feedstock type, the composition of PAHs showed increasing dominance of naphthalene with increasing HTT. The results demonstrate that biochars are highly heterogeneous materials that, depending on feedstock and HTT, may be suitable for soil application by contributing to the nutrient status and adding recalcitrant C to the soil but also potentially pose ecotoxicological challenges.

Characterization of biochar from fast pyrolysis and gasification systems

Abstract: Thermochemical processing of biomass produces a solid product containing char (mostly carbon) and ash. This char can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. The most advantageous use of a given char depends on its physical and chemical characteristics, although the relationship of char properties to these applications is not well understood. Chars from fast pyrolysis and gasification of switchgrass and corn stover were characterized by proximate analysis, CHNS elemental analysis, Brunauer-Emmet-Teller (BET) surface area, particle density, higher heating value (HHV), scanning electron microscopy, X-ray fluorescence ash content analysis, Fourier transform infrared spectroscopy using a photo-acoustic detector (FTIR-PAS), and quantitative 13C nuclear magnetic resonance spectroscopy (NMR) using direct polarization and magic angle spinning. Chars from the same feedstocks produced under slow pyrolysis conditions, and a commercial hardwood charcoal, were also characterized. Switchgrass and corn stover chars were found to have high ash content (32–55 wt %), much of which was silica. BET surface areas were low (7–50 m2/g) and HHVs ranged from 13 to 21 kJ/kg. The aromaticities from NMR, ranging between 81 and 94%, appeared to increase with reaction time. A pronounced decrease in aromatic CH functionality between slow pyrolysis and gasification chars was observed in NMR and FTIR-PAS spectra. NMR estimates of fused aromatic ring cluster size showed fast and slow pyrolysis chars to be similar (∼7–8 rings per cluster), while higher-temperature gasification char was much more condensed (∼17 rings per cluster). © 2009 American Institute of Chemical Engineers Environ Prog, 2009