James R. Kastner

Effect of operating conditions of thermochemical liquefaction on biocrude production from Spirulina platensis

This study investigated the optimum thermochemical liquefaction (TCL) operating conditions for producing biocrude from Spirulina platensis. TCL experiments were performed at various temperatures (200-380°C), holding times (0-120 min), and solids concentrations (10-50%). TCL conversion at 350°C, 60 min holding time and 20% solids concentration produced the highest biocrude yield of 39.9% representing 98.3% carbon conversion efficiency. Light fraction biocrude (B(1)) appeared at 300°C or higher temperatures and represented 50-63% of the total biocrude. Biocrude obtained at 350-380°C had similar fuel properties to that of petroleum crude with energy density of 34.7-39.9 MJ kg(-1) compared to 42.9 MJ kg(-1) for petroleum crude. Biocrude from conversion at 300°C or above had 71-77% elemental carbon, and 0.6-11.6% elemental oxygen and viscosities in the range 40-68 cP. GC/MS of biocrude reported higher hydrocarbons (C(16)-C(17)), phenolics, carboxylic acids, esters, aldehydes, amines, and amides.

Wet Scrubber Analysis of Volatile Organic Compound Removal in the Rendering Industry

Abstract The promulgation of odor control rules, increasing public concerns, and U.S. Environmental Protection Agency (EPA) air regulations in nonattainment zones necessitates the remediation of a wide range of volatile organic compounds (VOCs) generated by the rendering industry. Currently, wet scrubbers with oxidizing chemicals are used to treat VOCs; however, little information is available on scrubber efficiency for many of the VOCs generated within the rendering process. Portable gas chromatography/mass spectrometry (GC/MS) units were used to rapidly identify key VOCs on-site in process streams at two poultry byproduct rendering plants. On-site analysis was found to be important, given the significant reduction in peak areas if samples were held for 24 hr before analysis. Major compounds consistently identified in the emissions from the plant included dimethyl disulfide, methanethiol, octane, hexanal, 2-methylbutanal, and 3-methylbutanal. The two branched aldehydes, 2-methylbutanal and 3-methylbutanal, were by far the most consistent, appearing in every sample and typically the largest fraction of the VOC mixture. A chlorinated hydrocarbon, methanesulfonyl chloride, was identified in the outlet of a high-intensity wet scrubber, and several VOCs and chlorinated compounds were identified in the scrubbing solution, but not on a consistent basis. Total VOC concentrations in noncondensable gas streams ranged from 4 to 91 ppmv. At the two plants, the odor-causing compound methanethiol ranged from 25 to 33% and 9.6% of the total VOCs (v/v). In one plant, wet scrubber analysis using chlorine dioxide (ClO2) as the oxidizing agent indicated that close to 100% of the methanethiol was removed from the gas phase, but removal efficiencies ranged from 20 to 80% for the aldehydes and hydrocarbons and from 23 to 64% for total VOCs. In the second plant, conversion efficiencies were much lower in a packed-bed wet scrubber, with a measurable removal of only dimethyl sulfide (20–100%).

Production of aromatic green gasoline additives via catalytic pyrolysis of acidulated peanut oil soap stock.

Catalytic pyrolysis was used to generate gasoline-compatible fuel from peanut oil soap stock (PSS), a high free fatty acid feedstock, using a fixed-bed reactor at temperatures between 450 and 550°C with a zeolite catalyst (HZSM-5). PSS fed at 81 gh(-1) along with 100 mL min(-1) inert gas was passed across a 15 g catalyst bed (WHSV=5.4h(-1), gas phase residence time=34s). Results indicate that fuel properties of PSS including viscosity, heating value, and O:C ratio were improved significantly. For PSS processed at 500°C, viscosity was reduced from 59.6 to 0.9 mm(2)s(-1), heating value was increased from 35.8 to 39.3 MJL(-1), and the O:C ratio was reduced from 0.07 to 0.02. Aromatic gasoline components (e.g., BTEX), were formed in concentrations as high as 94% (v/v) in catalytically-cracked PSS with yields ranging from 22% to 35% (v/v of PSS feed).

Pyrolysis conditions and ozone oxidation effects on ammonia adsorption in biomass generated chars.

Ammonia adsorbents were generated via pyrolysis of biomass (peanut hulls and palm oil shells) over a range of temperatures and compared to a commercially available activated carbon (AC) and solid biomass residuals (wood and poultry litter fly ash). Dynamic ammonia adsorption studies (i.e., breakthrough curves) were performed using these adsorbents at 23 degrees C from 6 to 17 ppmv NH(3). Of the biomass chars, palm oil char generated at 500 degrees C had the highest NH(3) adsorption capacity (0.70 mg/g, 6 ppmv, 10% relative humidity (RH)), was similar to the AC, and contrasted to the other adsorbents (including the AC), the NH(3) adsorption capacity significantly increased if the relative humidity was increased (4 mg/g, 7 ppmv, 73% RH). Room temperature ozone treatment of the chars and activated carbon significantly increased the NH(3) adsorption capacity (10% RH); resultant adsorption capacity, q (mg/g) increased by approximately 2, 6, and 10 times for palm oil char, peanut hull char (pyrolysis only), and activated carbon, respectively. However, water vapor (73% RH at 23 degrees C) significantly reduced NH(3) adsorption capacity in the steam and ozone treated biomass, yet had no effect on the palm shell char generated at 500 degrees C. These results indicate the feasibility of using a low temperature (and thus low energy input) pyrolysis and activation process for the generation of NH(3) adsorbents from biomass residuals.

Glucose repression of xylitol production in Candida tropicalis mixed-sugar fermentations

Glucose repressed xylose utilization inCandida tropicalis pre-grown on xylose until glucose reached approximately 0–5 g l−1. In fermentations consisting of xylose (93 g l−1) and glucose (47 g l−1), xylitol was produced with a yield of 0.65 g g−1 and a specific rate of 0.09 g g−1 h−1, and high concentrations of ethanol were also produced (25 g l−1). If the initial glucose was decreased to 8 g l−1, the xylitol yield (0.79 g g−1) and specific rate (0.24 g g−1 h−1) increased with little ethanol formation (<5 g l−1). To minimize glucose repression, batch fermentations were performed using an aerobic, glucose growth phase followed by xylitol production. Xylitol was produced under O2 limited and anaerobic conditions, but the specific production rate was higher under O2 limited conditions (0.1–0.4 vs. 0.03 g g−1 h−1). On-line analysis of the respiratory quotient defined the time of xylose reductase induction.

Effect of pH and Temperature on the Kinetics of Odor Oxidation Using Chlorine Dioxide

Abstract Increasing public concerns over odors and air regulations in nonattainment zones necessitate the remediation of a wide range of volatile organic compounds (VOCs) generated in the poultry-rendering industry. Currently, wet scrubbers using oxidizing chemicals such as chlorine dioxide (ClO2) are utilized to treat VOCs. However, little information is available on the kinetics of ClO2 reaction with rendering air pollutants, limiting wet scrubber design and optimization. Kinetic analysis indicated that ClO2 does not react with hexanal and 2-methylbutanal regardless of pH and temperature and implied that alde-hyde removal occurs primarily via mass transfer. Contrary to the aldehydes, ethanethiol or ethyl mercaptan (a model compound for methanethiol or methyl mercaptan) and dimethyl disulfide (DMDS) rapidly reacted with ClO2. The overall reaction was found to be second and third order for ethanethiol and DMDS, respectively. Moreover, an increase in pH from 3.6 to 5.1 exponentially increased the reaction rate of ethanethiol (e.g., k 2 = 25– 4200 L/mol/sec from pH 3.6 to 5.1) and significantly increased the reaction rate of DMDS if increased to pH 9 (k 3 = 1.4 × 106 L2/mol2/sec). Thus, a small increase in pH could significantly improve wet scrubber operations for removal of odor-causing compounds. However, an increase in pH did not improve aldehyde removal. The results explain why aldehyde removal efficiencies are much lower than methanethiol and DMDS in wet scrub-bers using ClO2.

Continuous catalytic upgrading of fast pyrolysis oil using iron oxides in red mud

A catalyst composed primarily of magnetite was prepared from red mud, via H2 reduction at 300 °C, which significantly increased the surface area. Ammonia and CO2 temperature programmed desorption indicated both acid and base active sites. Continuous reaction studies conducted with individual compounds, mixtures of model compounds, and water extracted fast pyrolysis oil indicated that acetone was the primary product from acetic acid, and acetone and 2-butanone from acetol. Levoglucosan went down the same pathway, since it formed acetic acid, formic acid, and acetol. Total conversion and yields approached 100% and 22 mol% ketones at 400 °C and a W/F of 6 h for a model mixture and 15–20 mol% ketones at W/F 1.4–4 h and 400–425 °C using water extracted oil. Space time yields approached 60 g ketones per L-cat per h for the model mixture and 120 g per L-cat per h for a commercial oil. The catalyst simultaneously reduced acidity, allowed recovery of carbon, and generated upgradable intermediates from the aqueous fraction of fast pyrolysis oil in a “continuous” process.

Catalytic ozonation of ammonia using biomass char and wood fly ash

Catalytic ozonation of gaseous ammonia was investigated at room temperature using wood fly ash (WFA) and biomass char as catalysts. WFA gave the best results, removing ammonia (11 ppmv NH(3), 45% conversion) at 23 degrees C at a residence time of 0.34 s, using 5 g of catalyst or ash at the lowest ozone concentration (62 ppmv). Assuming pseudo zero order kinetics in ozone, a power rate law of -r(NH3) = 7.2 x 10(-8) C(NH3)(0.25) (r, mol g(-1)s(-1), C(NH3)molL(-1)) was determined at 510 ppmv O(3) and 23 degrees C for WFA. Water vapor approximately doubled the oxidation rate using WFA and catalytic ozonation activity was not measured for the char without humidifying the air stream. Overall oxidation rates using the crude catalysts were lower than commercial catalysts, but the catalytic ozonation process operated at significantly lower temperatures (23 vs. 300 degrees C). Nitric oxide was not detected and the percentage of NO(2) formed from NH(3) oxidation ranged from 0.3% to 3% (v/v), with WFA resulting in the lowest NO(2) level (at low O(3) levels). However, we could not verify that N(2)O was not formed, so further research is needed to determine if N(2) is the primary end-product. Additional research is required to develop techniques to enhance the oxidation activity and industrial application of the crude, but potentially inexpensive catalysts.

Low-temperature catalytic oxidation of aldehyde mixtures using wood fly ash: kinetics, mechanism, and effect of ozone.

Poultry rendering emissions contain volatile organic compounds (VOCs) that are nuisance, odorous, and smog and particulate matter precursors. Present treatment options, such as wet scrubbers, do not eliminate a significant fraction of the VOCs emitted including, 2-methylbutanal (2-MB), 3-methylbutanal, and hexanal. This research investigated the low-temperature (25-160 degrees C) catalytic oxidation of 2-MB and hexanal vapors in a differential, plug flow reactor using wood fly ash (WFA) as a catalyst and oxygen and ozone as oxidants. The oxidation rates of 2-MB and hexanal ranged between 3.0 and 3.5 x 10(-9)mol g(-1)s(-1) at 25 degrees C and the activation energies were 2.2 and 1.9 kcal mol(-1), respectively. The catalytic activity of WFA was comparable to other commercially available metal and metal oxide catalysts. We theorize that WFA catalyzed a free radical reaction in which 2-butanone and CO(2) were formed as end products of 2-MB oxidation, while CO(2), pentanal, and butanal were formed as end products of hexanal oxidation. When tested as a binary mixture at 25 and 160 degrees C, no inhibition was observed. Additionally, when ozone was tested as an oxidant at 160 degrees C, 100% removal was achieved within a 2-s reaction time. These results may be used to design catalytic oxidation processes for VOC removal at poultry rendering facilities and potentially replace energy and water intensive air pollution treatment technologies currently in use.

Optimization of Protein Extraction from Spirulina platensis to Generate a Potential Co-Product and a Biofuel Feedstock with Reduced Nitrogen Content

The current work reports protein extraction from Spirulina platensis cyanobacterial biomass in order to simultaneously generate a potential co-product and a biofuel feedstock with reduced nitrogen content. S. platensis cells were subjected to cell disruption by high pressure homogenization and subsequent protein isolation by solubilisation at alkaline pH followed by precipitation at acidic pH. Response surface methodology (RSM) was used to optimize the process parameters - pH, extraction (solubilisation/precipitation) time and biomass concentration for obtaining maximum protein yield. The optimized process conditions were found to be pH 11.38, solubilisation time of 35 min and biomass concentration of 3.6 % (w/w) solids for the solubilisation step, and pH 4.01 and precipitation time of 60 min for the precipitation step. At the optimized conditions, a high protein yield of 60.7 % (w/w) was obtained. The protein isolate (co-product) had a higher protein content (80.6 % (w/w)), lower ash (1.9 % (w/w)) and mineral content and was enriched in essential amino acids, the nutritious γ-lenolenic acid and other high-value unsaturated fatty acids compared to the original biomass. The residual biomass obtained after protein extraction had lower nitrogen content and higher total non-protein content than the original biomass. The loss of about 50 % of the total lipids from this fraction did not impact its composition significantly owing to the low lipid content of S.platensis (8.03 %).