Microwave pyrolysis of distillers dried grain with solubles (DDGS) for biofuel production

Microwave pyrolysis of distillers dried grain with solubles (DDGS) was investigated to determine the effects of pyrolytic conditions on the yields of bio-oil, syngas, and biochar. Pyrolysis process variables included reaction temperature, time, and power input. Microwave pyrolysis of DDGS was analyzed using response surface methodology to find out the effect of process variables on the biofuel (bio-oil and syngas) conversion yield and establish prediction models. Bio-oil recovery was in the range of 26.5-50.3 wt.% of the biomass. Biochar yields were 23.5-62.2% depending on the pyrolysis conditions. The energy content of DDGS bio-oils was 28 MJ/kg obtained at the 650 °C and 8 min, which was about 66.7% of the heating value of gasoline. GC/MS analysis indicated that the biooil contained a series of important and useful chemical compounds: aliphatic and aromatic hydrocarbons. At least 13% of DDGS bio-oil was the same hydrocarbon compounds found in regular unleaded gasoline.     

Olive bagasse (Olea europea L.) pyrolysis

Olive bagasse (Olea europea L.) was pyrolysed in a fixed-bed reactor. The effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rates on the yields of the products were investigated. Pyrolysis runs were performed using pyrolysis temperatures between 350 and 550 degrees C with heating rates of 10 and 50 degrees C min(-1). The particle size and sweep gas flow rate varied in the ranges 0.224-1.8mm and 50-200 cm3 min(-1), respectively. The bio-oil obtained at 500 degrees C was analysed and at this temperature the liquid product yield was the maximum. The various characteristics of bio-oil obtained under these conditions were identified on the basis of standard test methods. The empirical formula of the bio-oil with heating value of 31.8 MJ kg(-1) was established as CH(1.65)O(0.25)N(0.03). The chemical characterization showed that the bio-oil obtained from olive bagasse may be potentially valuable as a fuel and chemical feedstock.     

Influence of pyrolysis condition on switchgrass bio-oil yield and physicochemical properties

The poor and inconsistent physicochemical properties of bio-oil are inhibiting its industrialized production. We investigated the variability in properties of switchgrass bio-oil produced at three pyrolysis temperatures (T = 450, 500, and 550 °C) and three feedstock moisture contents (MC = 5%, 10%, and 15%) in a 3 × 3 factorial experiment in order to exploit opportunities to improve bio-oil properties through optimization of pyrolysis parameters. Results showed that even with the single type of feedstock and pyrolysis system, the two main factors and their interaction caused large variations in bio-oil yield and most of the measured physicochemical properties. Following improvements of bio-oil properties could be individually achieved by selecting an optimal pyrolysis condition (shown in parenthesis) comparing with the worst case: increase of bio-oil yield by more than twofold (MC = 10%, T = 450 °C), increase of pH by 20.4% from 2.74 to 3.3 (MC = 10%, T = 550 °C), increase of higher heating value by 18.1% from 16.6 to 19.6 MJ/kg (MC = 10%, T = 450 °C), decrease of density by 5.9% from 1.18 to 1.11 g/cm³ (MC = 5%, T = 550 °C), decrease of water content by 36% from 31.4 to 20.1 wt.% (MC = 5%, T = 450 °C), decrease of viscosity by 40% from 28.2 to 17 centistokes (MC = 5%, T = 550 °C), decrease of solid content by 57% from 2.86 to 1.23 wt.% (MC = 15%, T = 550 °C), and decrease of ash content by 41.9% from 0.62 to 0.36 wt.% (MC = 15%, T = 550 °C). There is no single, clear-cut optimal condition that can satisfy the criteria for a bio-oil product with all the desired properties. Trade-offs should be balanced according to the usage of the end-products.     

Bio-oil from hydro-liquefaction of Dunaliella salina over Ni/REHY catalyst

The hydro-liquefaction of Dunaliella salina over solid acid catalyst was examined under moderate conditions (200 °C, 2.0 MPa, 60 min). The significant increment of bio-oil yield was obtained over Ni/REHY catalyst, increasing about 20% compared without modified REHY. H₂-temperature-programmed desorption (H₂-TPD) and X-ray powder diffraction (XRD) demonstrated that Ni/REHY as bifunctional catalyst played roles in hydrogenation and cracking, and further achieved the deoxygenation and desulfurization of D. salina under hydrogen gas. The oxygen and sulfur contents of bio-oils decreased relative to D. salina, and the higher heating value (HHV) significantly increased to 30.11 MJ/kg. From gas chromatography/mass spectrometry (GC/MS), the dominant compounds of the bio-oils were found to be esters, glycerins. The qualities of bio-oils were greatly improved. Hydro-liquefaction was beneficial to the exploration of bio-oils from microalgae.     

Production and characterization of pyrolysis liquids from sunflower-pressed bagasse

Pyrolysis experiments on sunflower (Helianthus annus L.)-pressed bagasse were performed in a fixed-bed tubular reactor. The effects of nitrogen flow rate and final pyrolysis temperature on the pyrolysis product yields and chemical compositions were investigated. The maximum bio-oil yield of 52.10 wt.% was obtained in a nitrogen atmosphere with flow rate of 50 ml min(-1) and at a pyrolysis temperature of 550 degrees C with a heating rate of 5 degrees C s(-1). The chemical characterization results showed that the oil obtained from sunflower-pressed bagasse may be a potentially valuable source as fuel or chemical feedstocks.     

Pyrolysis of safflower (Charthamus tinctorius L.) seed press cake: part 1. The effects of pyrolysis parameters on the product yields

Safflower (Charthamus tinctorius L.) seed press cake was pyrolysed in a fixed-bed reactor. The effects of pyrolysis temperature, heating rate and sweep gas flow rates on the yields of the products were investigated. Pyrolysis runs were performed using pyrolysis temperatures between 400 and 600 °C with heating rates of 10, 30 and 50 °C min⁻¹. The obtained bio-char, gas and bio-oil yields ranged between 25 and 34 wt%, 19 and 25 wt%, and 28 and 36 wt%, respectively, at different pyrolysis conditions. The highest liquid yield was obtained at 500 °C pyrolysis temperature with a heating rate of 50 °C min⁻¹ under the sweep gas of N₂ with a flow rate of 100 cm³ min⁻¹. Employing the higher heating rate of 50 °C min⁻¹ results in maximum bio-oil yield, probably due to the decrease in mass transfer limitations. According to the results obtained under the conditions of this study, the effects of pyrolysis temperature and sweep gas flow rate are more significant than the effect of heating rate on the yields.     

The effects of different catalysts on the pyrolysis of industrial wastes (olive and hazelnut bagasse)

Pyrolysis of olive and hazelnut bagasse biomass samples with two selected catalysts, namely activated alumina and sodium feldspar, have been conducted in a fixed-bed reactor. Experiments were carried out under certain pyrolysis conditions in a fixed-bed Heinze reactor. The catalyst was mixed with feedstock in different percentages. The effects of catalysts and their ratio (10%, 20%, 30% and 40% w/w) on the pyrolysis product yields were investigated and the results were compared with the results of experiments performed without catalyst under the same conditions. The maximum bio-oil yields for the bio-oils obtained from pyrolysis of olive bagasse were found as 37.07% and 36.67% on using activated alumina and sodium feldspar as catalysts, respectively, while these values were 27.64% and 31.68%, respectively, for the bio-oils from hazelnut bagasse. The oxygen contents of the bio-oils were also markedly reduced while the yield of bio-oil was reduced by the use of catalysts. The pyrolysis oils were examined using some spectroscopic and chromatographic analysis techniques. The results were compared with the petroleum fractions and the possibility of being a potential source of bio-oils was investigated.     

Fast pyrolysis of soybean cake: product yields and compositions

This study was an investigation of the role of important parameters influencing pyrolysis yields from soybean cake. Experiments were carried out at temperatures ranging from 400 to 700 degrees C, for various nitrogen flow rates, heating rates and particle sizes. The maximum liquid yield was 42.83% at a pyrolysis temperature of 550 degrees C with a sweeping gas rate of 200 cm3 min(-1) and heating rate of 700 degrees C min(-1) for a soybean cake sample having 0.425 < D(p) < 0.85 mm particle size. The various characteristics of liquid product were identified. Thus, the aliphatic sub-fraction of the bio-oil was analysed by GC-MS and further structural analyses of bio-oil and aromatic and polar sub-fractions were conducted using FT-IR and 1H-NMR. The H/C ratios and the structural analysis of the fractions obtained from the biocrudes showed that the fractions were quite similar to currently utilised transport fuels.     

Optimization of a free-fall reactor for the production of fast pyrolysis bio-oil

A central composite design of experiments was performed to optimize a free-fall reactor for the production of bio-oil from red oak biomass. The effects of four experimental variables including heater set-point temperature, biomass particle size, sweep gas flow rate and biomass feed rate were studied. Heater set-point temperature ranged from 450 to 650 °C, average biomass particle size from 200 to 600 μm, sweep gas flow rate from 1 to 5 sL/min and biomass feed rate from 1 to 2 kg/h. Optimal operating conditions yielding over 70 wt.% bio-oil were identified at a heater set-point temperature of 575 °C, while feeding red oak biomass sized less than 300 μm at 2 kg/h into the 0.021 m diameter, 1.8 m tall reactor. Sweep gas flow rate did not have significant effect on bio-oil yield over the range tested.     

Microwave-assisted pyrolysis of microalgae for biofuel production

The pyrolysis of Chlorella sp. was carried out in a microwave oven with char as microwave reception enhancer. The results indicated that the maximum bio-oil yield of 28.6% was achieved under the microwave power of 750 W. The bio-oil properties were characterized with elemental, GC-MS, GPC, FTIR, and thermogravimetric analysis. The algal bio-oil had a density of 0.98 kg/L, a viscosity of 61.2 cSt, and a higher heating value (HHV) of 30.7 MJ/kg. The GC-MS results showed that the bio-oils were mainly composed of aliphatic hydrocarbons, aromatic hydrocarbons, phenols, long chain fatty acids and nitrogenated compounds, among which aliphatic and aromatic hydrocarbons (account for 22.18% of the total GC-MS spectrum area) are highly desirable compounds as those in crude oil, gasoline and diesel. The results in this study indicate that fast growing algae are a promising source of feedstock for advanced renewable fuel production via microwave-assisted pyrolysis (MAP).     

Characterization of Bio-oil and Bio-char from Pyrolysis of Palm Oil Wastes

The residues from the palm oil industry are the main contributors to biomass waste in Malaysia, and these wastes require extra attention with respect to handling. The biomass waste is a renewable resource that can potentially be used to produce absorbents, fuels, and chemical feedstocks through the pyrolysis process. In this study, the wastes of palm shell, empty fruit bunches, and mesocarp fiber were characterized and then pyrolyzed in a fixed-bed reactor under the following conditions: a temperature of 500 °C, a nitrogen flow rate of 2 L/min and reaction time of 60 min. After pyrolysis, characterization of the products with an emphasis on the bio-oil and the bio-char was performed using various approaches (including Karl Fischer water-content tests, FTIR, SEM, TGA and CNH/O analyses). The results showed that the pyrolysis of palm oil wastes yielded more bio-oil than bio-char or non-condensable gases. The results also indicated that all of the bio-oils were acidic and contained high levels of oxygen. The bio-oils heating values were low and varied from 10.49 MJ/kg to 14.78 MJ/kg. The heating values of the bio-chars (20–30 MJ/kg) were higher than those of the bio-oils. Among the biomasses studied in this work, palm shell contained the highest level of lignin and showed the highest levels of bio-char yield and fixed and elemental carbon in the raw and bio-char form.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

Characteristic Studies on the Pyrolysis Products from Hydrolyzed Canadian Lignocellulosic Feedstocks

Lignocellulosic feedstocks are utilized for the production of fuel ethanol and butanol through dilute acid/enzymatic hydrolysis and fermentation. Hydrolysis residue, a major by-product of biomass hydrolysis, is rich in recalcitrant carbon as majority of cellulosic and hemicellulosic components are released during pretreatment. With the intention of their effective utilization, hydrolysis residues from forestry (pinewood), energy crop system (timothy grass), and agriculture (wheat straw) were pyrolysed in a fixed-bed reactor at 600 °C with slow heating rate of 5 °C/min for 4 h. In order to understand the product (biochar, bio-oil, and gases) properties and advocate their energy and environmental values, chemical characterizations such as carbon–hydrogen–nitrogen–sulfur analysis, inductively coupled plasma-mass spectrometry, pH, electrical conductivity, scanning electron microscopy, porosity analysis, thermogravimetric analysis, X-ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, nuclear magnetic resonance (NMR) and gas chromatography–mass spectrometry (GC-MS) were employed. The yield of biochar, bio-oil and gases was 38.9–41.7, 18.6–22.3, and 24.9–28.8 wt%, respectively. The high pH and electrical conductivity of biochars with substantial amounts of Na, Mg, K, and Ca indicated their alkaline and saline nature, which would necessitate proper agronomical soil applications. Variable intensities of C–C, C–H, C–O, O–H, and C–N functional groups were detected in the FTIR spectra of residues, biochars, and bio-oils. Raman spectroscopy showed the development of graphite (1,580–1,610 cm^?1) and defect (1,325–1,380 cm^?1) carbon structures in biochars. ¹H NMR of bio-oils indicated aromatics, olefinics, and aliphatics, whereas ¹³C NMR indicated carbonyls, aromatics, carbohydrates, alkyls, methoxy, and hydroxy carbon. GC studies of pyrolysis gases identified chiefly H₂ and CO with traces of CH₄, CO₂, and C₂+ components.     

Preparation of carbon black from rice husk by hydrolysis, carbonization and pyrolysis

Carbon black is a form of amorphous carbon that is produced by incomplete combustion of petroleum- or some plant-derived materials and has a number of industrial uses. A process consisting of hydrolysis, carbonization and pyrolysis of rice husk was developed. Under optimal hydrolysis conditions (72 wt.% sulfuric acid, 50 °C, 10 min), a hydrolysis ratio of 52.72% was achieved. After carbonization of the hydrolysis solution by water bath, the solid carbon was further pyrolyzed. As the pyrolysis temperature was increased from 400 to 800 °C, the carbon content increased from 83.41% to 94.66%, the number of O-H, C-H, CO, and CC surface functional groups decreased, and based on Brunauer-Emmett-Teller (BET) results, the specific surface area and pore volume of carbon black increased from 389 to 1034 m²/g and from 0.258 to 0.487 cm³/g, respectively. X-ray diffraction pattern (XRD) and Raman spectroscopy analyses of samples pyrolyzed at 400-800 °C showed a localized graphitic structure. It is possible that the hydrolysis/carbonization/pyrolysis process developed in this study could also be applicable to the preparation of carbon black from other types of biomass.     

Gelation of high-methoxy pectin by enzymic de-esterification in the presence of calcium ions: a preliminary evaluation

Cohesive gels have been obtained by de-esterification of 1.0 wt % high-methoxy citrus pectin (degree of esterification ≈ 68%) in the presence of Ca²⁺ cations, using a commercial preparation (NovoShape) of fungal methyl esterase cloned from Aspergillus aculeatus. A convenient rate of network formation (gelation within ∼30 min) was achieved at an enzyme concentration of 0.2 PEU/g pectin. At a Ca²⁺-concentration of 40 mM and incubation temperature of 20 °C, severe syneresis (>7% of sample mass) was observed, but release of fluid decreased with decreasing concentration of Ca²⁺ and increasing temperature of incubation, becoming undetectable for 10 mM Ca²⁺ at 30 °C. Under these conditions, progressive development of solid-like character (storage modulus, G′) was observed during 160 min of enzymic de-esterification, and the mechanical spectrum recorded at the end of the incubation period had the form typical of a biopolymer gel. On subsequent heating to 70 °C, dissociation of the gel network (sigmoidal reduction in G′ and G″) was observed. At or above the midpoint temperature of this melting process (∼50 °C), there was no indication of gel formation on enzymic de-esterification (at 50 or 60 °C). At lower temperatures (20, 30 and 40 °C), the rate of gelation (assessed visually) showed no systematic increase as the incubation temperature was increased towards the temperature-optimum of the enzyme (∼50 °C). This unexpected behaviour is attributed to competition between faster de-esterification and slower formation of Ca²⁺-induced ‘egg-box’ junctions.     

Intraspecific tolerance of Metarhizium anisopliae conidia to the upper thermal limits of summer with a description of a quantitative assay system

Conidial tolerance to the upper thermal limits of summer is important for fungal biocontrol agents, whose conidia are formulated into mycoinsecticides for field application. To develop an efficient assay system, aerial conidia of eight Metarhizium anisopliae, four M. anisopliae var. anisopliae, and six M. anisopliae var. acridum isolates with different host and geographic origins were wet-stressed for ≤180 min at 48 °C or incubated for 14 d colony growths at 10-35 °C. The survival ratios (relative to unstressed conidia) of each isolate, examined at 15-min intervals, fit a logistic equation (r² ≥ 0.975), yielding median lethal times (LT₅₀s) of 14.3-150.3 min for the 18 isolates stressed at 48 °C. Seven grasshopper isolates from Africa had a mean LT₅₀ of 110 (73-150) min, but could not grow at 10 or 15 °C. The mean LT₅₀ of five non-grasshopper isolates capable of growing at 10-35 °C was 16 (10-26) min only. Three isolates with typically low (type I), medium (type II), and high (type III) levels of tolerance to 48 °C were further assayed for ≤4-d tolerance of their conidia to the wet stress at 38, 40, 42, or 45 °C. The resultant LT₅₀s decreased to 20, 53 and 167 min at 48 °C from 507, 1612, and 8256 min at 38 °C for types I, II and III, respectively. For the distinguished types, the logarithms of the LT₅₀s were significantly correlated to the temperatures of 38-48 °C with an inverse linearity (r² ≥ 0.88). The method developed to assay quantitatively fungal thermotolerance would be useful for screening of fungal candidates for improved pest control in summer.     

Process optimization of an auger pyrolyzer with heat carrier using response surface methodology

A 1 kg/h auger reactor utilizing mechanical mixing of steel shot heat carrier was used to pyrolyze red oak wood biomass. Response surface methodology was employed using a circumscribed central composite design of experiments to optimize the system. Factors investigated were: heat carrier inlet temperature and mass flow rate, rotational speed of screws in the reactor, and volumetric flow rate of sweep gas. Conditions for maximum bio-oil and minimum char yields were high flow rate of sweep gas (3.5 standard L/min), high heat carrier temperature (∼600 °C), high auger speeds (63 RPM) and high heat carrier mass flow rates (18 kg/h). Regression models for bio-oil and char yields are described including identification of a novel interaction effect between heat carrier mass flow rate and auger speed. Results suggest that auger reactors, which are rarely described in literature, are well suited for bio-oil production. The reactor achieved liquid yields greater than 73 wt.%.     

Effect of hot-water extraction on alkaline pulping of bagasse

The effect of hot-water extraction on alkaline pulping was investigated. The properties of black liquor and pulp strength of bagasse were analyzed. The extraction was conducted at 160 °C for 30 min where 13.2% of the mass was dissolved in the extraction liquor. Untreated bagasse and extracted bagasse were digested by soda and soda-AQ processes at 17% and 15.5% (with 0.1% AQ) alkali charge (NaOH). Cooking temperatures were 160 °C and 155 °C respectively. The pulp from extracted bagasse had a lower Kappa number and a higher viscosity compared to the pulp from the untreated bagasse. The black liquor from pulping extracted bagasse had a lower solid content, a lower viscosity and a lower silica content, but a higher heating value than that from pulping of untreated bagasse. Hot-water extraction resulted in a significant decrease in bleaching chemical consumption and the formation of chlorinated organics. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index, bulk, opacity and pulp freeness were found to be higher when hot-water extraction was applied.     

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 (B₁) 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 (C₁₆-C₁₇), phenolics, carboxylic acids, esters, aldehydes, amines, and amides.     

Pyrolytic characteristics of biomass acid hydrolysis residue rich in lignin

Pyrolytic characteristics of acid hydrolysis residue (AHR) of corncob and pinewood (CAHR, WAHR) were investigated using a thermo-gravimetric analyzer (TGA) and a self-designed pyrolysis apparatus. Gasification reactivity of CAHR char was then examined using TGA and X-ray diffractometer. Result of TGA showed that thermal degradation curves of AHR descended smoothly along with temperature increasing from 150 °C to 850 °C, while a “sharp mass loss stage” for original biomass feedstock (OBF) was observed. Char yield from AHR (42.64-30.35 wt.%) was found to be much greater than that from OBF (26.4-19.15 wt.%). In addition, gasification reactivity of CAHR char was lower than that of corncob char, and there was big difference in micro-crystallite structure. It was also found that CAHR char reactivity decreased with pyrolysis temperature, but increased with pyrolysis heating rate and gasification temperature at 850-950 °C. Furthermore, CAHR char reactivity performed better under steam atmosphere than under CO₂ atmosphere.