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A novel miniaturized, transparent reactor system for use as either a research or educational tool was developed for investigating biomass char gasification with oxygen to determine the kinetic parameters. Parametric temperature and pressure data taken can be used to distinguish the validity of assumptions inherent in the Avrami, the random pore (RPM), the unreacted core shrinking (UCSM), and a UCSM hybrid models (HM). The results demonstrate the UCSM for spherical and cylindrical geometries, and an HM variation with a best-fit exponent, that yields residual sums of squares 2 to 4 orders of magnitude lower than other models. An Arrhenius evaluation yielded an activation energy of 84.8 kJ/mol and pre-exponential factor of 1.34 x 103 s-1. An O2 reaction order of 0.85 indicates O2 adsorption on the char surface is the primary ratecontrolling step. Data are consistent with a rapidly decreasing surface area as the reaction nears completion, suggesting available corresponding active sites for rapid chemisorption decrease as the reaction progresses. More importantly, the design of the system is safe to take into the classroom while simultaneously allowing students to view real-time reactions and produce repeatable data; this pushes the bounds on classroom interventions and learning. [ABSTRACT FROM AUTHOR]

Highlights • Nitrogen-based blowing agents interact with cellulose during pyrolysis reactions. • Blowing agent reactions can yield biochar structures with nitrogen-doping. • N-doping is achieved with solid state additives in the absence of added gaseous NH 3. • Dicyandiamide decomposes into NH 3 , allowing for N-doping of cellulose char. Abstract Pyrolysis of cellulose mixed with blowing agent additives containing high nitrogen content has been investigated in this work. The additives used are dicyandiamide (DCD), 5-aminotetrazole (5AT) and 5-phenyl-1H-tetrazole (5PT), in concentrations of 0.25, 0.50, 1.0, 2.0 and 4.0% (weight). Blowing agents are of particular interest as a cellulose pyrolysis additive for two reasons: as a first case, if these additives and their decomposition products are chemically inert with respect to cellulose pyrolysis reactions, then they can serve to enhance the ejection of high-molecular weight aerosols from the liquid intermediate phase that is known to form during pyrolysis; as a second case, if these additives are not chemically inert, then the reactions between blowing agent decomposition products (e.g., NH 3 and HN 3) can provide a pathway by which nitrogen-doped carbonaceous char structures can be readily produced. Pyrolysis studies were carried out using thermogravimetric analysis and analytical Py-GC/MS of the pure compounds (DCD, 5AT, 5PT) and mixtures with cellulose, as well as proximate/ultimate analyses of the resulting chars from slow pyrolysis. Experiments showed that there is a reactive interaction between the additives and cellulose during pyrolysis, leading to greater char yields. Analysis of slow pyrolysis chars showed that DCD is promising for producing biochar with higher nitrogen content. This was attributed to the evolution of ammonia from DCD and due to its thermal decomposition occurring in a temperature range coincident with that of cellulose pyrolysis reactions. [ABSTRACT FROM AUTHOR]

The effect of pyrolysis temperature on the morphology, bulk and surface chemistry of cellulose, xylan and lignin chars has been examined. Chars were produced between 300 and 700 °C. Raman, X-ray photoelectron, nuclear magnetic resonance spectroscopic techniques, scanning electron microscopy and surface area analysis were used to characterize each sample. Formation of polyaromatic structures were found to be prevalent at 400 °C for both cellulose and lignin chars, and showed development at 300 °C for Xylan. The low A bands identified in the lignin char produced at 400 °C indicate that crosslinking at low temperatures preferentially forms hexagonal or larger rings. Aromatic condensation increased until 500 °C, and remained stable up to 700 °C. The sharp drop in oxygen content as temperature is increased up to 500 °C and the formation of ether (C-O-C) groups indicates that oxygen is a primary reaction component for crosslinking and polycondensation. Despite the considerable increase in ring size for char produced at 700 °C compared to 500 °C, only very mild loss of oxygen is identified, suggesting that C-C bonds are forming with minimal oxygen mediation The increased broadness of the NMR peak and the Raman G band suggest that at these temperatures the increase in ring size occurs largely in a 3 dimensional manner rather than planar with contributions from non-hexagonal rings and out-of-plane distortion. By comparing the NMR dephasing data to the I(D)/I(G) ratio an approximate relation between this Raman data and cluster size has also been derived. [ABSTRACT FROM AUTHOR]

Compost is used in bioretention systems to improve soil quality, water infiltration, and retention of contaminants. However, compost contains dissolved organic matter, nitrate, and phosphorus, all of which can leach out and potentially contaminate ground and surface waters. To reduce the leaching of nutrients and dissolved organic matter from compost, biochar may be mixed into the bioretention systems. Our objective was to test whether biochar and co-composted biochar mixed into mature compost can reduce the leaching of organic carbon, nitrogen, and phosphorus. There was no significant difference between the effects of biochar and co-composted biochar amendments on nutrient leaching. Further, biochar amendments did not significantly reduce the leaching of dissolved organic carbon, nitrate, and phosphorus as compared to the compost only treatment. The compost–sand mix was the most effective in reducing nitrate and phosphorus leaching among the media. [ABSTRACT FROM AUTHOR]

A well-defined methodology for constructing appropriate atomistic representations of biochar will aid in visualizing the structural features and elucidating biochar behavior with molecular dynamics (MD) simulations. Such knowledge will facilitate engineering biochars tailored to specific applications. To achieve this goal, we adapted modeling strategies applied in coal science by employing multi-cross-polarization 13C nuclear magnetic resonance, ultimate analysis, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy to identify functional groups. Helium density, surface area, and porosity were used to assess structural features. Biochar's aromatic cluster size distribution was proposed based on data from the benzene polycarboxylic acid method. The computational framework reduces bias by incorporating chemical information derived from density functional theory, reactive MD simulations, and advanced characterization data. The construction approach was successfully applied to cellulose biochars produced at four temperatures, obtaining independent representations with a relative error on the atomic contents of <10 % for oxygen and nitrogen and <5 % for carbon and hydrogen. The atomistic representations were validated using X-ray diffraction, electron spin resonance data, and laser desorption/ionization Fourier-transform ion cyclotron resonance-mass spectrometry. The code will assist others in overcoming structural creation barriers and enable the utilization of the generated structures for further simulations. [Display omitted] • Available code for creating large-scale atomistic models, capturing chemical and physical features. • A novel approach proposes the aromatic cluster size distribution of biochar. • Atomistic representations are validated with experimental and theoretical data. • The arrangement of aromatic size distributions aids in surface area and pore development. [ABSTRACT FROM AUTHOR]

Quantifying the content of surface nitrogen and oxygen containing functional groups in amorphous nitrogen doped carbons via deconvolution of C 1s x-ray photoelectron (XPS) spectra remains difficult due to limited information in the literature. To improve the interpretation of XPS spectra of nitrogen-doped carbons, the C 1s, N 1s and O 1s core level energy shifts have been calculated for various nitrogenated carbon structures via DFT. Furthermore, we propose an expanded method to improve the self-consistency of the XPS interpretation based on a seven-peak C 1s deconvolution (3 C–C peaks, 3 C–N/-O peaks, and π-π∗ transition peaks). With the DFT calculations, spectral components arising from surface-defect carbons could be distinguished from aromatic sp2 carbon. The deconvolution method proposed provides C/(N + O) ratios in very good agreement (error less than 5%) with those obtained from total C 1s, N 1s and O 1s peaks. Our deconvolution strategy provides a simple guideline for obtaining high-quality fits to experimental data on the basis of a careful evaluation of experimental conditions and results. Image 1 [ABSTRACT FROM AUTHOR]

Highlights • The properties of biochar depend on the production temperature and feedstock type. • Heavy metal content in biochars varies depending on type and origin of feedstock. • Acid washing biochar is effective in removing/reducing levels of some toxic metals. • Biochar should not be used for land amendment without prior characterization. Abstract The ever-increasing consumption of material goods with economic growth is resulting in an increasing generation of municipal solid waste (MSW) and the rapid filling of landfills. Fractions of municipal solid waste containing wood-based products have the potential to be used for the development of value added products. In this paper we produced and characterized biochar and pyrolysis vapors from municipal solid waste (MSW) woody fractions to demonstrate their suitability towards soil amendments. Carbonization work focused on compost overs, molded wood pallets, treated wood, sawmill cut ends, wood derived fuels, furniture, painted wood, plywood, oriented strand board and particle boards from Washington State recycling facilities. The goal of this research is to use these biochars as soil amendments; however, there are concerns with both the potential presence of condensed organic pollutants and trace metals. The presence of trace metals and polycyclic aromatic hydrocarbons (PAH) in all the biochars produced were examined. GC-MS analyses of liquid extracts did not reveal the presence of soluble PAH compounds. High concentrations of mercury (Hg) and arsenic (As) were found in the biochar made from painted wood and treated wood, respectively. Among the methods tested for the removal of trace metals, acid washing was found to be the most effective. The volatiles released from the analyzed MSW fractions were also analyzed in Py-GC-MS studies. Among these volatile compounds, many contained Cl, N, or S, which could be potential sources of pollution if the pyrolysis vapors are combusted. [ABSTRACT FROM AUTHOR]

Abstract Anaerobic digestion (AD) is an important technology to produce biogas from dairy manure. Although the AD of dairy manure results in the harnessing of the energy contained in manure, most of the nutrients (phosphorous and nitrogen) remain in the liquid effluent, representing an important source of pollution. Additionally, the biogas produced contains H 2 S and CO 2 , limiting its practical use as fuel. In this paper, we report the production and use of a carbonaceous adsorbent from AD fibers for the removal of hydrogen sulfide (H 2 S) from biogas and phosphate (PO 4 3−) from aqueous liquid effluents. The adsorbents studied were produced via slow pyrolysis between 350 and 800 °C followed by CO 2 activation. The elemental and proximate analyses, surface area and pore size distribution of each of the adsorbents studied are reported. Their adsorption capacities were assessed using H 2 S breakthrough and PO 4 3− batch equilibrium tests. The sorption capacity varied between 21.9 and 51.2 mg g−1 for H 2 S and between 4.9 mg g−1 and 37.4 mg g−1 for PO 4 3−. Commercially available activated carbon studied adsorbed 23.1 mg g−1 H 2 S and 15.7 mg g−1 PO 4 3−. The results show that the retention of H 2 S and PO 4 3− compounds were governed by the ash content, surface area and pH. Adsorption mechanisms for H 2 S and PO 4 3− sorption are proposed. Graphical abstract Image 1 Highlights • Anaerobically digested fiber is suitable for producing activated char. • The activated char produced demonstrated high capacity to adsorb H 2 S and PO 4 3−. • Production temperature has a major influence on the capacity of the resulting biochar towards H 2 S and PO 4 3−. • The content and composition of ash are critical for H 2 S and PO 4 3− removal. • Micropores volume is an important factor in H 2 S retention. [ABSTRACT FROM AUTHOR]

This paper reports the effects of pyrolysis temperature on biochar to oxidation by air. Eighteen biochars were produced from the pyrolysis of Douglas fir wood (DFW), Douglas fir bark (DFB), and hybrid poplar wood (HP) at six temperatures (623, 673, 723, 773, 823 and 873 K) in a lab scale spoon reactor. The oxidation step for all biochars produced was conducted at 523 K in the presence of air in a spoon reactor. The elemental and proximate analyses of all the oxidized and un-oxidized chars suggest that the carbonaceous materials produced at low temperature are more susceptible to oxidation than those produced at high temperature. A number of surface properties of resultant biochars were examined to better understand how pyrolysis temperatures and feedstock sources relate to the development of surface characteristics. The removal of volatiles during the pyrolysis step resulted in the gradual creation of microporosity detectable by CO 2 adsorption but which was difficult to detect with N 2 adsorption, suggesting that the chars contain micropores mostly less than 1 nm in entrance dimension. In some cases, the surface area decreased after being oxidized likely due to the blockage of micropores by oxygen-containing functional groups. The surface composition determined by XPS and Boehm titration confirms that greater quantities of carbonyl and carboxyl groups are formed on biochars produced at low temperature. The formation of these oxygenated functional groups contributes to add negative charges on the surface and consequently the pH at the point of zero charge increases for un-oxidized biochars. [ABSTRACT FROM AUTHOR]

The use of ozone to increase the cation exchange capacity (CEC) of two chars produced from pyrolysis of Douglas fir ( Pseudotsuga menziessii ) and a control bituminous coal activated carbon (AC) is reported. Chars were produced from the wood fraction of Douglas fir (DFWC) and the bark (DFBC) at 500 °C using an auger driven reactor with a nitrogen sweep gas under mild vacuum. Five ozone treatment times, ranging from 5 min to 60 min, were investigated. The initial properties of each char were found to differ significantly from the other samples in terms of surface area, proximate composition, and elemental composition. DFWC did not show significant mass loss or temperature variation during ozone treatment; however, after 1 h of oxidation both DFBC and AC samples resulted in 20% and 30% mass loss, respectively, and reactor temperatures in excess of 60 °C. Analysis of the pore size distribution of each treatment shows that ozone treatment did not significantly affect small micropores after 30 min of treatment for any material, but did reduce the apparent surface area of mesopores. Increases in carboxylic groups were identified with ozone treatment and found to correlate strongly with changes in measured CEC. The formation of lactone was found to correlate positively with reactor temperature during oxidation. These results indicate that the properties of chars, including surface area, pore structure, and chemical composition, as well as reactor conditions strongly affect the ozone oxidation of chars. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoate (PHA) production generates a significant amount of residual bacterial biomass (RBB) after PHA extraction. The RBB as a zero-value waste contains proteins, carbohydrates, phenolics, and ash, which can be managed and converted to bio-oil and biochar products by pyrolysis. Thermogravimetric analysis (TGA) was used to investigate the thermodegradation kinetics of RBB and pyrolysis–GCMS studies were employed to determine potential chemical products. Pyrolysis was conducted on a laboratory-scale auger reactor at 500 °C. The bio-oil and biochar yield were 28 and 46%, respectively. The pyrolysis bio-oil was characterized by the combination of GCMS, high-pressure liquid chromatography (HPLC), and electrospray ionization mass spectrometry (ESI–MS). The bio-oil was dominated by nitrogen-containing, hydrocarbons, and aromatic compounds. The biochar was studied for its specific surface area and pore size, chemical functionality by Fourier transform infrared (FTIR) and Raman spectroscopies, and butane absorption activity. Biochar was comprised of a large part of polycondensed phenolic and majorly disordered amorphous carbon. [ABSTRACT FROM AUTHOR]

• Eggshell-modified biochar shows prominent phosphorous adsorption performance. • Chemical adsorption process is the controlled step for eggshell-modified biochar. • Ca-P precipitation, hydrogen bonding, electrostatic attraction are adsorption step. • Adsorbed phosphates are mainly distributed inside pore size range of 15–50 nm. Biochar modified with calcium source is acted as an effective adsorbent for phosphorous recovery. In this research, eggshell is used as a low-cost and environmentally friendly calcium source to replace chemical reagents such as CaCO 3 , Ca(OH) 2 and CaCl 2 used in the modified biochar production. Biochar derived from rape straw and modified with eggshell shows prominent phosphorous adsorption performance (e.g., equilibrium adsorption amount, 109.7 mg/g). The kinetic and isotherm analysis demonstrate that chemical adsorption process is performed as the main controlled step for the modified biochar adsorption, and the phosphate adsorption process is composed of both monolayer adsorption and multi-layer adsorption. Moreover, it is found from the physicochemical structures comparison before and after phosphate adsorption that Ca-P precipitation, hydrogen bonding and electrostatic attraction are identified as main adsorption mechanisms. In addition, the adsorbed phosphates are mainly distributed inside the space with pore sizes of 15–50 nm. [ABSTRACT FROM AUTHOR]

This study explores the use of an engineered char produced from the pyrolysis of anaerobically digested fiber (ADF) to adsorb phosphate from aqueous solutions. Two series of engineered chars were produced. The first series was a CO 2 activated (CA) char produced via slow pyrolysis between 350 and 750 °C. The second series was a nitrogen doped (ND) char activated in the presence of ammonia at comparable temperatures. Proximate analysis, elemental composition, gas physisorption, Inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray powder diffraction (XRD) techniques were used to characterize properties of resulting products. The surface area of the carbon product increased after nitrogen doping through ammonization (166.6–463.1 m2/g) compared to CO 2 activated chars (156.5–413.1 m2/g). Phosphate adsorption isotherms for both CO 2 activated and nitrogen doped chars can be described by the Langmuir- Freundlich and Redlich Peterson adsorption models. Nitrogen doped carbon phosphate sorption capacity in aqueous solutions was twice compared to CO 2 activated carbons. As carbonization/activation temperature increased the sorption capacity increased from 3.4 to 33.3 mg g-1 for CA char and 6.3–63.1 mg g-1 for nitrogen doped char. Image 1 • It is possible to produce a char with high capacity for PO43−from anaerobically digested fibers. • The presence of Ca, Mg, Fe and Al in the ash contributes to PO43− removal. • PO43− adsorption capacity doubles compared to CO 2 activated char, if the material is doped with nitrogen. • Most of the nitrogen added to the char is in the form pyridinic functional groups. • Chars with up to 9 atoms of N per 100 atoms of C were produced. [ABSTRACT FROM AUTHOR]