Tuning Biochar Properties via Partial Gasification: Facilitating Inorganic Nutrients Recycling and Altering Organic Matter Leaching

Sui Boon Liaw and Hongwei Wu (2015). “Tuning Biochar Properties via Partial Gasification: Facilitating Inorganic Nutrients Recycling and Altering Organic Matter Leaching.” Energy & Fuels Just Accepted Manuscript DOI: 10.1021/acs.energyfuels.5b01020.

Abstract: This study reports a systematic study on the potential of employing partial gasification at low conversions for tuning biochar for better properties and facilitating the recycling of inorganic nutrient species. The raw biochars were prepared from mallee wood and leaf at fast pyrolysis at 500 C (a temperature pertinent to bio-oil production) and subsequent tuning via partial steam gasification at 725°C and low conversions (5 and 10 % on a carbon basis). The favourable structure tuning is achieved at the expense of 8–23% carbon which would otherwise be available for sequestration during biochar application in soil. The development of pore structure and transformation of the chemical forms of inorganic nutrient species as results of partial gasification increase the leachability of the inorganic nutrient species in biochars via both water and Mehlich I solution. In addition, <1.5% of the organic matter in raw and tuned biochar are water soluble. The leaching of water-soluble organic matter from the tuned biochars after re-pyrolyssi and partial gasification (but absence in the same biochars after re-pyrolysis) suggests that partial gasification increases the accessibility of organic matter trapped in closed or blocked pores formed during pyrolysis. While some aromatic compounds can be leached from the raw biochar via solvent, no aromatic compounds are detected in the leachates from the tuned biochars. The tuning of biochar via partial gasification also improves the leaching kinetics of the inherent inorganic nutrient species. The overall recyclability of the inorganic nutrient species in the raw and tuned biochar shows that tuning biochar via partial gasification can be an effective strategy for facilitating the recycling of the inherent nutrient species in biochar.

New ISTC report: Antioxidants from Wood-derived Pyrolyzates (Bio-oils)

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Phenolic compounds with antioxidant activity toward soybean-derived fatty acid methyl esters (SME, used as a model for biodiesel) were obtained by pyrolysis from wood (birch hardwood), corn stover, and lignin. The lignins were either commercially available (Indulin AT kraft lignin from softwood) or isolated from whole plant material by acid-dioxane extraction. Phenols were isolated from the crude liquid pyrolyzate by extraction with alkali. Antioxidant activities were determined by ferric isothiocyanate spectrometry, Rancimat induction period determination, and pressurized differential scanning calorimetry. Preliminary evidence with hydrocarbon diesel-SME mixtures indicated that the mixtures differed from SME alone in their response to antioxidants. The total phenolic extracts from birch wood pyrolysis and kraft lignin were active antioxidants in all three analyses, comparable in effectiveness to the synthetic antioxidant BHT. However, many simple lignin-related phenolic monomers were found to have little or no activity when tested with SME. Chromatographic separation and analysis of the extracts indicated that the bulk of the activity was associated with a more complex fraction, made up principally of dimers in the size range of lignans, with molecular weights from 272 to 344. A model lignan, the naturally occurring nordihydroguaiaretic acid (molecular weight 302), was shown to have very good effectiveness, as good as or better than BHT. (However, it is not likely to be present in our extracts, based on its mass spectral characteristics.) A suggested mechanism for antioxidant effectiveness of lignin-like dimers was proposed based on steric effects – simultaneous hydrogen bonding and radical quenching.

Biochar in Co-Contaminated Soil Manipulates Arsenic Solubility and Microbiological Community Structure, and Promotes Organochlorine Degradation

Samuel J. Gregory, Christopher W. N. Anderson , Marta Camps-Arbestain, Patrick J. Biggs, Austen R. D. Ganley, Justin M. O’Sullivan, Michael T. McManus (2015). “Biochar in Co-Contaminated Soil Manipulates Arsenic Solubility and Microbiological Community Structure, and Promotes Organochlorine Degradation.” PLOSOne, April 29, 2015.
DOI: 10.1371/journal.pone.0125393

Abstract: We examined the effect of biochar on the water-soluble arsenic (As) concentration and the extent of organochlorine degradation in a co-contaminated historic sheep-dip soil during a 180-d glasshouse incubation experiment. Soil microbial activity, bacterial community and structure diversity were also investigated. Biochar made from willow feedstock (Salix sp) was pyrolysed at 350 or 550°C and added to soil at rates of 10 g kg-1 and 20 g kg-1 (representing 30 t ha-1 and 60 t ha-1). The isomers of hexachlorocyclohexane (HCH) alpha-HCH and gamma-HCH (lindane), underwent 10-fold and 4-fold reductions in concentration as a function of biochar treatment. Biochar also resulted in a significant reduction in soil DDT levels (P < 0.01), and increased the DDE:DDT ratio. Soil microbial activity was significantly increased (P < 0.01) under all biochar treatments after 60 days of treatment compared to the control. 16S amplicon sequencing revealed that biochar-amended soil contained more members of the Chryseobacterium, Flavobacterium, Dyadobacter and Pseudomonadaceae which are known bioremediators of hydrocarbons. We hypothesise that a recorded short-term reduction in the soluble As concentration due to biochar amendment allowed native soil microbial communities to overcome As-related stress. We propose that increased microbiological activity (dehydrogenase activity) due to biochar amendment was responsible for enhanced degradation of organochlorines in the soil. Biochar therefore partially overcame the co-contaminant effect of As, allowing for enhanced natural attenuation of organochlorines in soil.

Esterification of glycerol over a solid acid biochar catalyst derived from waste biomass

N. Lingaiah, Mahammad Rafi J., Rajashekar A, Srinivas M, BVSK Rao and Prasad B N R. (2015). “Esterification of glycerol over a solid acid biochar catalyst derived from waste biomass.” RSC Advances online ahead of print. DOI: 10.1039/C5RA06613A

Abstract: Karanja seed shells were subjected to pyrolysis in inert atmosphere at different temperatures to prepare biochar. The biochar was characterized by X-ray diffraction, FT-infra red, Laser Raman, thermo gravimetric analysis, CHNS-elemental analysis, BET surface area and temperature programmed desorption of ammonia. These biochar carbon catalysts were used as catalysts without any functionalization/treatment for the esterification of glycerol with acetic acid. Carbonization at 400 oC led to the formation of biochar with more number of strong acidic sites. High temperature carbonization amorphous carbon composed of aromatic carbon sheets oriented in a considerably random fashion. The biochar obtained at 400 oC exhibited highest glycerol esterification activity. The catalytic activity of the biochar was explained based on its properties derived from different characterization methods. The biochar catalyst can be reusable with consistent activity.

Biochar and Activated Carbon for Enhanced Trace Organic Contaminant Retention in Stormwater Infiltration Systems

Bridget Anne Ulrich, Eugenia Im, David Werner, and Christopher P. Higgins (2015). “Biochar and Activated Carbon for Enhanced Trace Organic Contaminant Retention in Stormwater Infiltration Systems.” Environmental Science & Technology, Just Accepted Manuscript. DOI: 10.1021/acs.est.5b00376.

Abstract: To assess the effectiveness of biochar and activated carbon (AC) for enhanced trace organic contaminant (TOrC) retention in stormwater infiltration systems, an approach combining forward-prediction modelling and laboratory verification experiments was employed. Batch and column tests were conducted using representative TOrCs and synthetic stormwater. Based on batch screening tests, two commercially available biochars (BN-biochar and MCG-biochar) and an AC were investigated. The AC exhibited the strongest sorption, followed by MCG-biochar and BN-biochar. Langmuir isotherms provided better fits to equilibrium data than Freundlich isotherms. Due to superior sorption kinetics, 0.2 wt% MCG-biochar in saturated sand columns retained TOrCs more effectively than 1.0 wt% BN-biochar. A forward-prediction intraparticle diffusion model based on the Langmuir isotherm adequately predicted column results when calibrated using only batch parameters, as indicated by a Monte Carlo uncertainty analysis. Case study simulations estimated that an infiltration basin amended with F300-AC or MCG-biochar could obtain sorption-retarded breakthrough times for atrazine of 54 years or 5.8 years, respectively, at a 1 in/hr infiltration rate. These results indicate that biochars or ACs with superior sorption capacity and kinetics can enhance TOrC retention in infiltration systems, and performance under various conditions can be predicted using results from batch tests.

Recent biochar research articles

Liang, Yuan; Cao, Xinde; Zhao, Ling; Xu, Xiaoyun; Harris, Willie (2014). “Phosphorus Release from Dairy Manure, the Manure-Derived Biochar, and Their Amended Soil: Effects of Phosphorus Nature and Soil Property.” Journal of Environmental Quality 43:1504–1509. DOI: 10.2134/jeq2014.01.0021

Abstract: Land application of animal manure often risks excessive phosphorus (P) release into the surrounding water. The aim of this study was to convert the dairy manure into biochar, followed by their application into soil, and then to investigate P release from the manure and its derived biochar as well as from the manure- and biochar-amended soil. The results showed that P release was reduced when the manure was converted into biochar due to formation of less-soluble whitlockite [(Ca, Mg)3(PO4)2]. The cumulative P released from biochar over 240 h was 0.26 g kg−1, a 76% reduction of that from the manure (1.07 g kg−1). The kinetic release of P from the manure was determined by the fast desorption process and was better fitted to Elovich equation, whereas P release from biochar was initially controlled by the diffusion process and then by slow but steady dissolution of (Ca,Mg)3(PO4)2, following the parabolic diffusion and linear models, respectively. When the manure or biochar was incorporated into the soil, P release in the CaCl2 and simulated acid rain water extraction from biochar-amended soil was consistently lower than that from the manure-amended soil during 210-d incubation. The lower P release in the biochar-amended soil was determined by stable P form (Ca, Mg)3(PO4)2 in the biochar itself, but less from the soil property effect. Results indicated that initial high P release from manure can be mitigated by converting the manure into biochar.

Eykelbosh AJ, Johnson MS, Santos de Queiroz E, Dalmagro HJ, Guimarães Couto E (2014). Biochar from Sugarcane Filtercake Reduces Soil CO2 Emissions Relative to Raw Residue and Improves Water Retention and Nutrient Availability in a Highly-Weathered Tropical Soil. PLoS ONE 9(6): e98523. DOI: 10.1371/journal.pone.0098523

Abstract: In Brazil, the degradation of nutrient-poor Ferralsols limits productivity and drives agricultural expansion into pristine areas. However, returning agricultural residues to the soil in a stabilized form may offer opportunities for maintaining or improving soil quality, even under conditions that typically promote carbon loss. We examined the use of biochar made from filtercake (a byproduct of sugarcane processing) on the physicochemical properties of a cultivated tropical soil. Filtercake was pyrolyzed at 575°C for 3 h yielding a biochar with increased surface area and porosity compared to the raw filtercake. Filtercake biochar was primarily composed of aromatic carbon, with some residual cellulose and hemicellulose. In a three-week laboratory incubation, CO2 effluxes from a highly weathered Ferralsol soil amended with 5% biochar (dry weight, d.w.) were roughly four-fold higher than the soil-only control, but 23-fold lower than CO2 effluxes from soil amended with 5% (d.w.) raw filtercake. We also applied vinasse, a carbon-rich liquid waste from bioethanol production typically utilized as a fertilizer on sugarcane soils, to filtercake- and biochar-amended soils. Total CO2 efflux from the biochar-amended soil in response to vinasse application was only 5% of the efflux when vinasse was applied to soil amended with raw filtercake. Furthermore, mixtures of 5 or 10% biochar (d.w.) in this highly weathered tropical soil significantly increased water retention within the plant-available range and also improved nutrient availability. Accordingly, application of sugarcane filtercake as biochar, with or without vinasse application, may better satisfy soil management objectives than filtercake applied to soils in its raw form, and may help to build soil carbon stocks in sugarcane-cultivating regions.
Hao Sun, Catherine Elizabeth Brewer, Caroline A. Masiello, and Kyriacos Zygourakis (2015). “Nutrient Transport in Soils Amended with Biochar: A transient model with two stationary phases and intraparticle diffusion. Industrial & Engineering Chemistry Research Just Accepted Manuscript. DOI: 10.1021/ie503893t

Abstract: We present the development of a rate model that simulates nutrient transport in soils amended with biochar. The model considers two stationary adsorbent phases (biochar and soil), axial dispersion, interphase mass transfer and intraparticle diffusion. Langmuir isotherms govern the local equilibria between the solute diffusing in the liquid-filled pores and adsorbed on the pore surfaces of biochar and soil particles. We demonstrate that addition of biochar can effectively slow nutrient transport through the soil if the biochar/soil ratio and crucial biochar properties (like its adsorption capacity and affinity to the sorbate) are carefully matched to the soil properties (water velocity, soil type) and the amount of rainfall or irrigation. Simulations can also track the spatial and temporal evolution of nutrient concentration profiles, information that is essential for analyzing and interpreting experimental data. The new model can be a valuable tool for fine-tuning the production and use of biochar.

Zhang Q-z, Dijkstra FA, Liu X-r, Wang Y-d, Huang J, et al. (2014) Effects of Biochar on Soil Microbial Biomass after Four Years of Consecutive Application in the North China Plain. PLoS ONE 9(7): e102062. DOI: 10.1371/journal.pone.0102062

Abstract: The long term effect of biochar application on soil microbial biomass is not well understood. We measured soil microbial biomass carbon (MBC) and nitrogen (MBN) in a field experiment during a winter wheat growing season after four consecutive years of no (CK), 4.5 (B4.5) and 9.0 t biochar ha−1 yr−1 (B9.0) applied. For comparison, a treatment with wheat straw residue incorporation (SR) was also included. Results showed that biochar application increased soil MBC significantly compared to the CK treatment, and that the effect size increased with biochar application rate. The B9.0 treatment showed the same effect on MBC as the SR treatment. Treatments effects on soil MBN were less strong than for MBC. The microbial biomass C:N ratio was significantly increased by biochar. Biochar might decrease the fraction of biomass N mineralized (KN), which would make the soil MBN for biochar treatments underestimated, and microbial biomass C:N ratios overestimated. Seasonal fluctuation in MBC was less for biochar amended soils than for CK and SR treatments, suggesting that biochar induced a less extreme environment for microorganisms throughout the season. There was a significant positive correlation between MBC and soil water content (SWC), but there was no significant correlation between MBC and soil temperature. Biochar amendments may therefore reduce temporal variability in environmental conditions for microbial growth in this system thereby reducing temporal fluctuations in C and N dynamics.

Keith Jones, Girish Ramakrishnan, Minori Uchimiya, and Alexander Orlov (2015). “New Applications of X-ray Tomography in Pyrolysis of Biomass: Biochar Imaging.” Energy & Fuels Just Accepted Manuscript. DOI: 10.1021/ef5027604.

Abstract: We report on the first ever use of non-destructive micrometer-scale synchrotron-computed microtomography (CMT) for biochar material characterization as a function of pyrolysis temperature. This innovative approach demonstrated an increase in micron-sized marcropore fraction of the Cotton Hull (CH) sample, resulting in up to 29% sample porosity. We have also found that initial porosity development occurred at low temperatures (below 350°C) of pyrolysis, consistent with chemical composition of CH. This innovative technique can be highly complementary to traditional BET measurements, considering that Barrett-Joyner-Halenda (BJH) analysis of pore size distribution cannot detect these macropores. Such information can be of substantial relevance to environmental applications, given that water retention by biochars added to soils is controlled by macropore characteristic among the other factors. Complementing our data with SEM, EDX and XRF characterization techniques allowed us to develop a better understanding of evolution of biochar properties during its production, such presence of metals and initial morphological features of biochar before pyrolysis. These results have significant implications for using biochar as a soil additive and for clarifying the mechanisms of biofuel production by pyrolysis.

New biochar publication from ISTC

Sorption of Polycyclic Aromatic Hydrocarbons (PAHs) to Biochar and Estimates of PAH Bioavailability

Biochars were produced by slow pyrolysis of corn stover under a nitrogen atmosphere at 450°, 550°, and 750°C. The chars were subjected to artificial aging, i.e., repeatedly freezing and thawing or incubating moist char at 60° and 110°C. A total of 12 materials was produced and characterized. The total polycyclic aromatic hydrocarbon (PAH) contents of 450° and 550° chars were 1.4 and 0.2 mg kg-1, respectively. Extraction and analysis of PAHs in the 750° char was performed, however the quality control associated with this assay indicated that PAHs could not be quantitatively extracted from this material by standard methods. Sorption and mild extraction experiments were performed. Mild extraction with 2- hydroxypropyl-β-cyclodextrin (HPCD), mimics bioaccessibility. Pyrene was used as a probe compound. The sorption data were well described by Freundlich isotherms. Pyrene sorption was strong for all chars, with the amount sorbed at 1μg L-1 dissolved pyrene ranging from 10 to the 6th to over 10 to the 7th μ g kg-1. The pyrene content of the chars was too low to be detected in the HPCD extracts, so the chars were spiked with pyrene and allowed to equilibrate before extraction. Only 10 to 15% of added pyrene was HPCD-extractable from the 450° char and 1 to 5% from the 550° and 750° chars. Aging had small but measureable effects on both sorption and HPCD extraction of pyrene.