Subcritical Water Hydrolysis of Microalgal Biomass for Protein and Pyrolytic Bio-oil Recovery

Microalgae are a promising source of protein and biofuels. This study involved the extraction of soluble proteins from raw microalgae using subcritical water hydrolysis followed by pyrolysis of the resulting spent microalgal biomass for bio-oil production. The extraction process produced solubilized protein in amounts up to 10 wt% of the dry biomass. The effects of hydrolysis temperature (150–220 °C), process time (90–180 min), and initial pH (2–12) on the chemical compositions and reactivity of the spent biomass as biofuel intermediates were investigated. It was found that when the temperature and time increased, the protein and carbohydrate fractions of the spent biomass were reduced, while their lipid fraction increased. A low initial pH led to lower protein content in the spent biomass. Compared with the raw microalgae, the spent biomass gave a higher yield of pyrolytic bio-oil that contained much less of the N-containing compounds and higher amounts of long-chain fatty acids (C₁₆) and C₁₄–C₂₀ long-chain hydrocarbons. In addition, enhanced energy recovery and a reduction in the energy consumption of the pyrolysis process were the other benefits acquired from the protein extraction. Therefore, subcritical water hydrolysis was considered to be an effective process to recover solubilized proteins, enhance the properties of the spent biomass, improve the energy balance of the subsequent pyrolysis process, and raise the quality of the bio-oil.     

Impact of Harvest Time and Cultivar on Conversion of Switchgrass to Bio-oils Via Fast Pyrolysis

The study of the effects of harvest time on switchgrass (Panicum virgatum L.) biomass and bioenergy production reported herein encompasses a large study evaluating the harvest of six switchgrass cultivars grown at three northern US locations over 3 years, harvested at upland peak crop (anthesis), post-frost, and post-winter. Delaying harvest of switchgrass until after frost and until after winter has resulted in decreased yields of switchgrass and reduced amounts of minerals in the biomass. This report examines how changes in biomass composition as a result of varying harvest time and other factors affect the distribution of products formed via fast pyrolysis. A subset (50) of the population (n = 864) was analyzed for fast pyrolysis and catalytic pyrolysis (zeolite catalyst) product yields using a pyrolysis-GC/MS system. The subset was used to build calibrations that were successful in predicting the pyrolysis product yield using near-infrared reflectance spectroscopy (NIRS), and partial least squares predictive models were applied to the entire sample set. The pyrolysis product yield was significantly affected by the field trial location, year of harvest, cultivar, and harvest time. Delaying harvest time of the switchgrass crop led to greater production of deoxygenated aromatics improving the efficiency of the catalytic fast pyrolysis and bio-oil quality. The changes in the pyrolysis product yield were related to biomass compositional changes, and key relationships between cell wall polymers, potassium concentration in the biomass, and pyrolysis products were identified. The findings show that the loss of minerals in the biomass as harvest time is delayed combined with the greater proportion in cellulose and lignin in the biomass has significant positive influences on conversion through fast pyrolysis.     

Effect of Pyrolysis Temperature on Chemical and Surface Properties of Biochar of Rapeseed (Brassica napus L.)

The biochar is an important carbon-rich product that is generated from biomass sources through pyrolysis. Biochar (charcoal) can be both used directly as a potential source of solid biofuels and as soil amendments for barren lands. The aim of this study was investigate influence of pyrolysis temperature on the physicochemical properties and structure of biochar. The biochars were produced by pyrolysis of rapeseed (Brassica napus L.) using a fixed-bed reactor at different pyrolysis temperatures (400–700°C). The produced biochars were characterized by proximate and elemental analysis, Brunauer–Emmett–Teller (BET) surface area, particle size distributions, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy. The results showed that both chemical and surface properties of the biochars were significantly affected by the pyrolysis temperature. Aromatic hydrocarbons, hydroxyl and carbonyl compounds were the majority components of the biochar. The biochar obtained at 700°C had a high fixed carbon content (66.16%) as well as a high heating value, and therefore it could be used as solid fuel, precursor in the activated carbons manufacture (specific surface area until 25.38 m² g^?1), or to obtain category-A briquettes.     

Production of pyrolytic liquids from industrial sewage sludges in an induction-heating reactor

With the application of induction-heating, the pyrolytic experiments have been carried out for three sewage sludges from the food processing factories in an externally heated fixed-bed reactor. The thermochemical characteristics of sludge samples were first analyzed. The results indicated that the calorific value had about 15 MJ/kg on an average, suggesting that it had a potential for biomass energy source. However, its nitrogen concentration was relatively high. From the thermogravimetric analysis (TGA) curves, it showed that the pyrolysis reaction can be almost finished in the temperature range of 450-750 degrees C. The yields of resulting liquid and char products from the pyrolysis of sewage sludge were discussed for examining the effects of pyrolysis temperature (500-800 degrees C), heating rate (200-500 degrees C/min), and holding time (1-8 min). Overall, the variation of yield was not so significant in the experimental conditions for three sewage sludges. All results of the resulting liquid products analyzed by elemental analyzer, pH meter, Karl-Fischer moisture titrator and bomb calorimeter were in consistence with those analyses by FTIR spectroscopy. Furthermore, the pyrolysis liquid products contained large amounts of water (>73% by weight) mostly derived from the bound water in the biosludge feedstocks and the condensation reactions during the pyrolysis reaction, and fewer contents of oxygenated hydrocarbons composing of carbonyl and nitrogen-containing groups, resulting in low pH and low calorific values.     

Fast pyrolysis of palm kernel cake in a closed-tubular reactor: product compositions and kinetic model

In this study, fast pyrolysis of palm kernel cake (PKC) was carried out in a closed-tubular reactor over a temperature range of 550 to 750 °C with various retention times. The pyrolyzing gas products mainly included CO, CO₂, and light hydrocarbons; it is noted that no hydrogen was detected in the product. In order to investigate the reaction pathway, the kinetic lump model of Liden was applied to verify and calculate all rate constants. The results obtained at different temperatures indicated that the rate constant increased with pyrolysis temperature. Furthermore, the experimental results were in good agreement with the proposed mechanism.     

Production of hydrocarbon fuels from biomass using catalytic pyrolysis under helium and hydrogen environments

This study is focused on hydrocarbon production through changing carrier gas and using zeolite catalysts during pyrolysis. A large reduction in high molecular weight, oxygenated compounds was noticed when the carrier gas was changed from helium to hydrogen during pyrolysis. A catalytic pyrolysis was conducted using two different methods based on how the biomass and catalysts were contacted together. For both methods, there was no significant change in the carbon yield with the change in pyrolysis environment. However, the mixing-method produced higher aromatic hydrocarbons than the bed-method. In addition, two methods were also tested using two ratios of biomass to catalyst. Nonetheless, there was no significant increase in hydrocarbon yield as the catalyst loading was increased from two to five times of biomass in the catalyst-bed method. In contrast to this, a significant increase was noticed for the catalytic-mixing method when the biomass to catalyst loading was increased from 1:4 to 1:9.     

A detailed one-dimensional model of combustion of a woody biomass particle

A detailed one-dimensional model for combustion of a single biomass particle is presented. It accounts for particle heating up, pyrolysis, char gasification and oxidation and gas phase reactions within and in the vicinity of the particle. The biomass pyrolysis is assumed to take place through three competing reactions yielding char, light gas and tar. The model is validated using different sets of experiments reported in the literature. Special emphasis is placed on examination of the effects of pyrolysis kinetic constants and gas phase reactions on the combustion process which have not been thoroughly discussed in previous works. It is shown that depending on the process condition and reactor temperature, correct selection of the pyrolysis kinetic data is a necessary step for simulation of biomass particle conversion. The computer program developed for the purpose of this study enables one to get a deeper insight into the biomass particle combustion process.     

Two-stage steam gasification of waste biomass in fluidized bed at low temperature: parametric investigations and performance optimization

Steam gasification of waste biomass has been studied in a two-stage fluidized bed reactor, which has the primary pyrolysis fluidized bed using silica sand as bed material and the secondary reforming fixed bed with catalyst. The main objectives are parametric investigation and performance improvement especially at low temperature of around 600 °C using the wood chip and the pig manure compost as feedstock. Main operating variables studied are pyrolysis temperature, catalytic temperature, steam/biomass-C ratio, space velocity and different catalyst. Reaction temperatures and steam/C ratio have important role on the gasification process. About 60 vol.% H2 (dry and N2 free) and about 2.0 Nm3/kg biomass (dry and ash free basis) can be obtained under good conditions. Compared to Ni/Al2O3, Ni/BCC (Ni-loaded brown coal char) has a better ability and a hopeful prospect for the stability with coking resistance.     

Biomass Pyrolysis in an Argon/Hydrogen Plasma Reactor

This paper presents the experimental results of biomass pyrolysis in a laboratory argon/hydrogen plasma reactor. The samples tested were wood and rice husk. The gaseous product was found to contain mainly H₂, CO, C₂H₂ and CH₄. The conversion of carbon and oxygen from the biomass feed to gaseous product can reach up to 79 % and 72 %, respectively. The results indicate that plasma pyrolysis of biomass may be a useful way for gaseous fuel production.     

Productivity in the Barents Sea - Response to Recent Climate Variability

The temporal and spatial dynamics of primary and secondary biomass/production in the Barents Sea since the late 1990s are examined using remote sensing data, observations and a coupled physical-biological model. Field observations of mesozooplankton biomass, and chlorophyll a data from transects (different seasons) and large-scale surveys (autumn) were used for validation of the remote sensing products and modeling results. The validation showed that satellite data are well suited to study temporal and spatial dynamics of chlorophyll a in the Barents Sea and that the model is an essential tool for secondary production estimates. Temperature, open water area, chlorophyll a, and zooplankton biomass show large interannual variations in the Barents Sea. The climatic variability is strongest in the northern and eastern parts. The moderate increase in net primary production evident in this study is likely an ecosystem response to changes in climate during the same period. Increased open water area and duration of open water season, which are related to elevated temperatures, appear to be the key drivers of the changes in annual net primary production that has occurred in the northern and eastern areas of this ecosystem. The temporal and spatial variability in zooplankton biomass appears to be controlled largely by predation pressure. In the southeastern Barents Sea, statistically significant linkages were observed between chlorophyll a and zooplankton biomass, as well as between net primary production and fish biomass, indicating bottom-up trophic interactions in this region.     

Prevention of clogging in a biological trickle-bed reactor removing toluene from contaminated air

Removal of organic compounds like toluene from waste gases with a trickle-bed reactor can result in clogging of the reactor due to the formation of an excessive amount of biomass. We therefore limited the amount of nutrients available for growth, to prevent clogging of the reactor. As a consequence of this nutrient limitation a lower removal rate was observed. However, when a fungal culture was used to inoculate the reactor, the toluene removal rate under nutrient limiting conditions was higher. Over a period of 375 days, an average removal rate of 27 g C/(m(3) h) was obtained with the reactor inoculated with the fungal culture. From the carbon balance over the reactor and the nitrogen availability it was concluded that, under these nutrient-limited conditions, large amounts of carbohydrates are probably formed. We also studied the application of a NaOH wash to remove excess biomass, as a method to prevent clogging. Under these conditions an average toluene removal rate of 35 g C/(m(3) h) was obtained. After about 50 days there was no net increase in the biomass content of the reactor. The amount of biomass which was formed in the reactor equaled the amount removed by the NaOH wash. (c) 1996 John Wiley & Sons, Inc.     

Total recovery of resources and energy from rice straw using microwave-induced pyrolysis

This article presents the application of microwave-induced pyrolysis to total recovery of resources and energy from rice straw. The microwave power and particle size of feedstock were both key parameters affecting the performance of microwave-induced pyrolysis. Under 400-500W microwave power, the reduction of fixed carbon in the biomass was significant. From the experimental results of specific surface area, zeta potential, and Cu(2+) adsorption, the applications of solid residues in the water and wastewater treatment could be expected. The major compositions in gaseous product were H(2), CO(2), CO, CH(4) of 55, 17, 13, 10vol.%, respectively. The high H(2) content might imply that microwave-induced pyrolysis of biomass waste has the potential to produce the H(2)-rich fuel gas. Alkanes, polars, and low-ringed polycyclic aromatic hydrocarbons were three primary kinds of compounds in the liquid product.     

Volatilisation of alkali and alkaline earth metallic species during the pyrolysis of biomass: differences between sugar cane bagasse and cane trash

Sugar cane bagasse and cane trash were pyrolysed in a novel quartz fluidised-bed/fixed-bed reactor. Quantification of the Na, K, Mg and Ca in chars revealed that pyrolysis temperature, heating rate, valence and biomass type were important factors influencing the volatilisation of these alkali and alkaline earth metallic (AAEM) species. Pyrolysis at a slow heating rate (approximately 10 K min(-1)) led to minimal (often <20%) volatilisation of AAEM species from these biomass samples. Fast heating rates (>1000 K s(-1)), encouraging volatile-char interactions with the current reactor configuration, resulted in the volatilisation of around 80% of Na, K, Mg and Ca from bagasse during pyrolysis at 900 degrees C. Similar behaviour was observed for monovalent Na and K with cane trash, but the volatilisation of Mg and Ca from cane trash was always restricted. The difference in Cl content between bagasse and cane trash was not sufficient to fully explain the difference in the volatilisation of Mg and Ca.     

In-situ upgrading of biomass pyrolysis vapors: catalyst screening on a fixed bed reactor

In-situ catalytic upgrading of biomass fast pyrolysis vapors was performed in a fixed bed bench-scale reactor at 500 °C, for catalyst screening purposes. The catalytic materials tested include a commercial equilibrium FCC catalyst (E-cat), various commercial ZSM-5 formulations, magnesium oxide and alumina materials with varying specific surface areas, nickel monoxide, zirconia/titania, tetragonal zirconia, titania and silica alumina. The bio-oil was characterized measuring its water content, the carbon-hydrogen-oxygen (by difference) content and the chemical composition of its organic fraction. Each catalytic material displayed different catalytic effects. High surface area alumina catalysts displayed the highest selectivity towards hydrocarbons, yielding however low organic liquid products. Zirconia/titania exhibited good selectivity towards desired compounds, yielding higher organic liquid product than the alumina catalysts. The ZSM-5 formulation with the highest surface area displayed the most balanced performance having a moderate selectivity towards hydrocarbons, reducing undesirable compounds and producing organic liquid products at acceptable yields.     

Modelling of pyrolysis of coal-biomass blends using thermogravimetric analysis

The primary objective of this work was to develop an appropriate model to explain the co-pyrolysis behaviour of lignite coal-biomass blends with different proportions using a thermogravimetric analyzer. A new parallel-series kinetic model was proposed to predict the pyrolysis behaviour of biomass over the entire pyrolysis regime, while a kinetic model similar to that of Anthony and Howard [Anthony, D.B., Howard, J.B., 1976. Coal devolatilization and hydrogasification. AIChE Journal 22(4), 625-656] was used for pyrolysis of coal. Analysis of mass loss history of blends showed an absence of synergistic effect between coal and biomass. Co-pyrolysis mass-loss profiles of the blends were predicted using the estimated kinetic parameters of coal and biomass. Excellent agreement was found between the predicted and the experimental results.     

Biosorption of sterols from tobacco waste extract using living and dead of newly isolated fungus Aspergillus fumigatus strain LSD-1

ABSTRACT

Sterols are verified to be able to produce polycyclic aromatic hydrocarbons during its pyrolysis. In this study, a kind of Aspergillus fumigatus (LSD-1) was isolated from cigar leaves, and the biosorption effects on the stigmasterol, β-sitosterol, campesterol, cholesterol, and ergosterol by using living and dead biomass of LSD-1 were investigated. The results showed that both living and dead biomass could efficiently remove these sterols in aqueous solution and tobacco waste extract (TWE). Interestingly, compared with the living biomass of LSD-1, the dead biomass of LSD-1 not only kept a high adsorption efficiency but also did not produce ergosterol. Overall, dead biomass of LSD-1 was a more suitable biosorbent to sterols in TWE. Furthermore, Brunner-Emmet-Teller (BET), Fourier transformed infrared spectrometer (FTIR) and scanning electron microscope (SEM) analysis were used to explore the biosorption process of living and dead biomass and their differences, suggesting that the biosorption of sterols was a physical process.     

Potential of biogas recirculation to enhance biomass accumulation on supporting media

Two lab-scale anaerobic hybrid reactors (AHR) were operated to investigate the effect of recirculated biogas on the development of biomass on supporting media during the start-up. The reactor comprised of two distinct zones; sludge bed on the bottom and packed bed using nylon fiber as the media on the upper half of the reactor. Both reactors were continuously fed with cassava starch wastewater. The organic loading rate (OLR) was increased from 0.3 to 5.5 g COD/L/day by gradually decreasing the hydraulic retention time (HRT) from 37 to 3.5 days in two months. The biogas at 2.6 L/L/day was recirculated merely in the first month of the operation in order to allow the attached biomass to grow according to the organic matters present in the reactor at the final stage of the start up. Chemical oxygen demand (COD) removal efficiency of over 80% was achieved throughout the study. The result demonstrated a better COD removal efficiency for the reactor with biogas recirculation, especially at low HRTs. The amounts of biomass accumulated on the media in both reactors were slightly different with 11.9 gVSS found on the one with biogas recirculation compared to 9.8 gVSS on the other. In addition, 16.3% increase of the sludge bed was achieved with biogas recirculation as opposed to 9% in the control one. The attached biomass activity test indicated a greater amount and more favorable ratio of the methanogenic bacterial group on the media with the recirculation correlating well to a relatively higher methane content in biogas. As a result, the recirculation of biogas has a potential of improving the characteristics of the AHR especially in terms of biomass accumulation.     

熔盐热裂解生物质制生物油

为探讨热裂解条件对熔盐中生物质热裂解制生物油的影响,在自行设计的反应器中,以摩尔比为7∶6的ZnCl2-KCl混合熔盐作为热裂解的热载体、催化剂和分散剂,考察了500 ℃时添加的金属盐和生物质原料的影响,并采用气相色谱-质谱仪 (GC-MS) 对生物油的主要组成进行了分析。结果表明：添加的金属盐显著影响热裂解产物得率,稀土金属盐显著提高生物油得率,降低生物油的含水率,添加摩尔分数为5.0％ LaCl3时生物油得率为32.0％,含水率为61.5％;水稻秸秆热裂解的生物油和焦炭得率较高,稻壳热裂解的气体得率较高;金属添加盐对生物油组成有较强的选择性,LiCl和FeCl2对生物质向小分子裂解具有较强的催化作用,而CrCl3、CaCl2和LaCl3对生物油二次裂解具有抑制作用。研究结果为熔盐热裂解生物质制生物油提供了参考。     

Lignin Pyrolysis Components and Upgrading—Technology Review

Biomass pyrolysis oil has been reported as a potential renewable biofuel precursor. Although several review articles focusing on lignocellulose pyrolysis can be found, the one that particularly focus on lignin pyrolysis is still not available in literature. Lignin is the second most abundant biomass component and the primary renewable aromatic resource in nature. The pyrolysis chemistry and mechanism of lignin are significantly different from pyrolysis of cellulose or entire biomass. Therefore, different from other review articles in the field, this review particularly focuses on the recent developments in lignin pyrolysis chemistry, mechanism, catalysts, and the upgrading of the bio-oil from lignin pyrolysis. Although bio-oil production from pyrolysis of biomass has been proven on commercial scale and is a very promising option for production of renewable chemicals and fuels, there are still several drawbacks that have not been solved. The components of biomass pyrolysis oils are very complicated and related to the properties of bio-oil. In this review article, the details about pyrolysis oil components particularly those from lignin pyrolysis processes will be discussed first. Due to the poor physical and chemical property, the lignin pyrolysis oil has to be upgraded before usage. The most common method of upgrading bio-oil is hydrotreating. Catalysts have been widely used in petroleum industry for pyrolysis bio-oil upgrading. In this review paper, the mechanism of the hydrodeoxygenation reaction between the model compounds and catalysts will be discussed and the effects of the reaction condition will be summarized.