Multi-response optimization of bio-oil production from catalytic solar pyrolysis of Spirulina platensis

In this work, the solar catalytic pyrolysis of Spirulina platensis microalgae using hydrotalcite as a catalyst was studied to improve the yield and quality of the bio-oil obtained from the algae. The effects of biomass loading, reaction time, and catalyst percentage on the product distribution and bio-oil composition were evaluated. The desirability function was used to identify the pyrolysis conditions that maximize the bio-oil yield and its hydrocarbon content. The experimental results indicated that the catalytic pyrolysis of Spirulina platensis produced considerable solid product content, and high liquid yields were reached in some tests favored by the catalyst presence. The hydrotalcite contributed to increasing the hydrocarbon formation in the bio-oil at lower reaction times, demonstrating the great performance of this catalyst for microalgae pyrolysis. At the optimal conditions, a bio-oil yield of 35.94% with 21.71% hydrocarbon content was achieved.     

Distributed production of hydrogen by auto-thermal reforming of fast pyrolysis bio-oil

We demonstrated an auto-thermal reforming process for producing hydrogen from biomass pyrolysis liquids. Using a noble metal catalyst (0.5% Pt/Al₂O₃ from BASF) at a methane-equivalent space velocity of around 2000 h⁻¹, a reformer temperature of 800 °C–850 °C, a steam-to-carbon ratio of 2.8–4.0, and an oxygen-to-carbon ratio of 0.9–1.1, we produced 9–11 g of hydrogen per 100 g of fast pyrolysis bio-oil, which corresponds to 70%–83% of the stoichiometric potential. The elemental composition of bio-oil and the bio-oil carbon-to-gas conversion, which ranged from 70% to 89%, had the most significant impact on the yield of hydrogen. Because of incomplete volatility the remaining 11%–30% of bio-oil carbon formed deposits in the evaporator. Assuming the same process efficiency as that in the laboratory unit, the cost of hydrogen production in a 1500 kg/day plant was estimated at $4.26/kg with the feedstock, fast pyrolysis bio-oil, contributing 56.3% of the production cost.     

Economic tradeoff between biochar and bio-oil production via pyrolysis

This paper examines some of the economic tradeoffs in the joint production of biochar and bio-oil from cellulosic biomass. The pyrolysis process can be performed at different final temperatures, and with different heating rates. While most carbonization technologies operating at low heating rates (large biomass particles) result in higher yields of charcoal, fast pyrolysis (which processes small biomass particles) is the preferred technology to produce bio-oils. Varying operational and design parameters can change the relative quantity and quality of biochar and bio-oil produced for a given feedstock. These changes in quantity and quality of both products affect the potential revenue from their production and sale. We estimate quadratic production functions for biochar and bio-oil. The results are then used to calculate a product transformation curve that characterizes the yields of bio-oil and biochar that can be produced for a given amount of feedstock, movement along the curve corresponds to changes in temperatures, and it can be used to infer optimal pyrolysis temperature settings for a given ratio of biochar and bio-oil prices.     

Oxidative pyrolysis of kraft lignin in a bubbling fluidized bed reactor with air

Fast pyrolysis of kraft lignin with partial (air) oxidation was studied in a bubbling fluidized bed reactor at reaction temperatures of 773 and 823 K. The bio-oil vapors were fractionated using a series of three condensers maintained at desired temperatures, providing a dry bio-oil with less than 1% water and over 96% of the total bio-oil energy.Oxygen feed was varied to study its effect on yield, composition, and energy recovery in the gas, char and oil products. The addition of oxygen to the pyrolysis process increased the production of gases such as CO and CO₂. It also changed the dry bio-oil properties, reducing its heating value, increasing its oxygen content, reducing its average molecular weight and tar concentration, while increasing its phenolics concentration. The lower reaction temperature of 773 K was preferred for both dry bio-oil yield and quality.Autothermal operation of the pyrolysis process was achieved with an oxygen feed of 72 or 54 g per kg of biomass at the reaction temperatures of 773 and 823 K, respectively. Autothermal operation reduced both yield and total energy content of the dry bio-oil, with relative reductions of 24 and 20% for the yield, 28 and 23% for the energy content, at 773 and 823 K.     

Manipulation of chemical species in bio-oil using in situ catalytic fast pyrolysis in both a bench-scale fluidized bed pyrolyzer and micropyrolyzer

In situ catalytic fast pyrolysis (CFP) of biomass was conducted with base or acid catalysts in a bench-scale fluidized bed pyrolyzer. Complete mass balances were performed, allowing for quantitatively investigating the catalytic impacts on the final bio-oil composition. Acidic catalysts exhibited relatively higher activities for decomposition of sugar and pyrolytic lignin, dehydration, decarbonylation, and coke formation, as relative to base catalysts. Carbon balances revealed that a significant amount of carbon in bio-oil was transformed to coke during CFP. Due to the decrease in the bio-oil yield during CFP, significantly less energy was recovered in CFP products than in control fast pyrolysis products. CFP was also performed in micropyrolyzer and the results were compared with those in the bench-scale reactor to determine the consistency across the experimental systems. Different from the bench-scale pyrolyzer, the basic catalyst more strongly influenced the micropyrolyzer products and the discrepancies suggest a more rapid deactivation of the basic catalyst.     

Improving the quality of fast pyrolysis bio-oil by reduced pressure distillation

In the present study, reduced pressure distillation was performed to obtain distilled bio-oil from fast pyrolysis bio-oil. The experiments were completed at temperature 80 °C with a residual pressure of 15 mmHg. The distilled bio-oil yields of 61 wt% from reduced pressure distillation of fast pyrolysis bio-oil were obtained. The oxygen contents of the distilled bio-oil is 9.2 wt% and the distilled bio-oil has lower content of oxygen than the fast pyrolysis bio-oil. For this reason, compared with the fast pyrolysis bio-oil, the distilled bio-oil has higher heating value, lower corrosivity and better stability. The heating value of distilled bio-oil is 34.2 MJ/kg, which is about 2 times of that of fast pyrolysis bio-oil. It is found that the distilled bio-oil stored at 60 °C results in a weight loss of about 0.3% for mild steel and the distilled bio-oil’s viscosity hardly increases during storage. These properties of distilled bio-oil make it more suitable for fuel oil use or as a source of chemicals than fast pyrolysis bio-oil.     

Bio-oil production from cotton stalk

Cotton stalk was fast pyrolyzed at temperatures between 480 °C and 530 °C in a fluidized bed, and the main product of bio-oil is obtained. The experimental result shows that the highest bio-oil yield of 55 wt% was obtained at 510 °C for cotton stalk. The chemical composition of the bio-oil acquired was analyzed by GC–MS, and its heat value, stability, miscibility and corrosion characteristics were determined. These results showed that the bio-oil obtained can be directly used as a fuel oil for combustion in a boiler or a furnace without any upgrading. Alternatively, the fuel can be refined to be used by vehicles. Furthermore, the energy performance of the pyrolysis process was analyzed. In the pyrolysis system used in our experiment, some improvements to former pyrolysis systems are done. Two screw feeders were used to prevent jamming the feeding system, and the condenser is equipped with some nozzles and a heat exchanger to cool quickly the cleaned hot gas into bio-oil.     

Optimum conditions for maximising pyrolysis liquids of oil palm empty fruit bunches

As production of palm oil is expanding, a more efficient use of oil palm biomass to obtain more energy from oil palm plantations is investigated. The work was carried out on a fluidised bed bench scale fast pyrolysis unit, with the objective of determining the important conditions and key variables which are required to maximise the liquid yield and its quality. The investigation on the impact of reactor temperature, varying residence time by changing the nitrogen flow rate and combined impact of ash content and particle size on the product yields is presented. The properties of the liquid product were analysed and compared with wood derived bio-oil and petroleum fuels. It was found that in all cases the liquid product separated into two phases presenting difficulties for fuel applications, which are critically discussed. Potential solutions are also proposed which include upgrading of the liquid for fuel applications and other useful applications.     

Selective pyrolysis of paper mill sludge by using pretreatment processes to enhance the quality of bio-oil and biochar products

Paper mill sludge (PMS) is a residual biomass that is generated at paper mills in large quantities. Currently, PMS is commonly disposed in landfills, which causes environmental issues through chemical leaching and greenhouse gas production. In this research, we are exploring the potential of fast pyrolysis process for converting PMS into useful bio-oil and biochar products. We demonstrate that by subjecting PMS to a combination of acid hydrolysis and torrefaction pre-treatment processes it is possible to alter the physicochemical properties and composition of the feedstock material. Fast pyrolysis of pretreated PMS produced bio-oil with significantly higher selectivity to levoglucosenone and significantly reduced the amount of ketone, aldehyde, and organic acid components. Pretreatment of PMS with combined 4% mass fraction phosphoric acid hydrolysis and 220 °C torrefaction processed prior to fast pyrolysis resulted in a 17 times increase of relative selectivity towards levoglucosenone in bio-oil product along with a reduction of acids, ketones, and aldehydes combined from 21 % to 11 %. Biochar, produced in higher yield, has characteristics that potentially make the solid byproduct ideal for soil amendment agent or sorbent material. This work reveals a promising process system to convert PMS waste into useful bio-based products. More in-depth research is required to gather more data information for assessing the economic and sustainability aspects of the process.     

Techno-economic performance analysis of bio-oil based Fischer-Tropsch and CHP synthesis platform

The techno-economic potential of the UK poplar wood and imported oil palm empty fruit bunch derived bio-oil integrated gasification and Fischer-Tropsch (BOIG-FT) systems for the generation of transportation fuels and combined heat and power (CHP) was investigated. The bio-oil was represented in terms of main chemical constituents, i.e. acetic acid, acetol and guaiacol. The compositional model of bio-oil was validated based on its performance through a gasification process. Given the availability of large scale gasification and FT technologies and logistic constraints in transporting biomass in large quantities, distributed bio-oil generations using biomass pyrolysis and centralised bio-oil processing in BOIG-FT system are technically more feasible. Heat integration heuristics and composite curve analysis were employed for once-through and full conversion configurations, and for a range of economies of scale, 1 MW, 675 MW and 1350 MW LHV of bio-oil. The economic competitiveness increases with increasing scale. A cost of production of FT liquids of 78.7 Euro/MWh was obtained based on 80.12 Euro/MWh of electricity, 75 Euro/t of bio-oil and 116.3 million Euro/y of annualised capital cost.     

Microwave assisted catalytic pyrolysis of bagasse to produce hydrogen

Using Ni/SiC as a catalyst, bagasse was microwave-assisted pyrolysis in a homemade quartz reactor. The results showed that with the continuous increase of Ni content, the experimental catalytic pyrolysis effect on bio-oil became more and more obvious, and the hydrogen yield gradually increased. When Ni content exceeded 8%, the hydrogen yield and bio-oil catalytic pyrolysis efficiency decreased, and the lowest bio-oil yield was 9.55% when Ni content was 15%, With the increase of power, the catalytic cracking efficiency and hydrogen yield of bio-oil increased, With the increase of catalyst dosage, the catalytic efficiency and the hydrogen yield increase gradually. When the catalyst quality exceeds 1/4 of the material, the growth rate of catalytic efficiency decreases, after alkali treatment, the variation law of hydrogen yield and bio-oil is consistent with that without alkali treatment. In contrast, more hydrogen can be produced after alkali treatment. Under the optimum conditions, the hydrogen yield was 35.85 g/kg biomass.     

Pyrolysis of Alternanthera philoxeroides (alligator weed): Effect of pyrolysis parameter on product yield and characterization of liquid product and bio char

In the present work, fast pyrolysis of Alternanthera philoxeroides was evaluated with a focus to study the chemical and physical characteristics of bio-oil produced and to determine its practicability as a transportation fuel. Pyrolysis of A.philoxeroides was conducted inside a semi batch quartz glass reactor to determine the effect of different operating conditions on the pyrolysis product yield. The thermal pyrolysis of A. philoxeroides were performed at a temperature range from 350 to 550 °C at a constant heating rate of 25 °C/min & under nitrogen atmosphere at a flow rate of 0.1 L/min, which yielded a total 40.10 wt.% of bio-oil at 450 °C. Later, some more sets of experiments were also performed to see the effect on pyrolysis product yield with change in operating conditions like varying heating rates (50 °C/min, 75 °C/min & 100 °C/min) and different flow rates of nitrogen (0.2, 0.3, 0.4 & 0.5 L/min). The yield of bio-oil during different heating rate (25, 50, 75 and 100 °C/min) was found to be more (43.15 wt.%) at a constant heating rate of 50 °C/min with 0.2 L/min N₂ gas flow rate and at a fixed pyrolysis temperature of 450 °C. The High Heating Value (HHV) value of bio-oil (8.88 MJ/kg) was very less due to presence of oxygen in the biomass. However, the high heating value of bio-char (20.41 MJ/kg) was more, and has the potential to be used as a solid fuel. The thermal degradation of A. philoxeroides was studied in TGA under inert atmosphere. The characterization of bio-oil was done by elemental analyser (CHNS/O analyser), FT-IR, & GC/MS. The char was characterized by elemental analyser (CHNS/O analysis), SEM, BET and FT-IR techniques. The chemical characterization showed that the bio-oil could be used as a transportation fuel if upgraded or blended with other fuels. The bio-oil can also be used as feedstock for different chemicals. The bio-char obtained from A. philoxeroides can be used for adsorption purposes because of its high surface area.     

Upgrading of fast pyrolysis bio-oil to drop-in fuel over Ru catalysts

Catalyst plays a key role in the upgrading of fast pyrolysis bio-oil to advanced drop-in fuel, while the selectivity and deactivation of catalyst still remain the biggest challenge. In this study, three Ru catalysts with activated carbon, Al₂O₃ and ZSM-5 as supports were prepared and tested in bio-oil hydrotreating process. The physical properties and components of upgraded bio-oil were detected to identify the difference in catalytic performance of three catalysts. The results showed that furan, phenols and their derivatives in fast pyrolysis bio-oil could be hydrogenated to alkanes, alkenes and benzenes over Ru catalysts. The different components of oil phase over three catalysts may be resulted from the surface properties of three supports. Activated carbon supported Ru catalyst showed the best catalytic performance and was suggested to be the most promising catalyst for pyrolysis bio-oil upgrading.     

Utilization of lignin: A sustainable and eco-friendly approach

The use of renewable carbon sources as a substitute for fossil resources is an extensively essential and fascinating research area for addressing the current issues related to climate and future fuel requirements. The utilization of lignocellulosic biomasses as a source for renewable fuel/chemicals/mesoporous biochar derivative is gaining considerable attention due to the neutral carbon cycle. The cellulose and hemicellulose are highly utilized components of biomass, and on the other hand, lignin is a plentiful, under-utilized component of the lignocellulosic biomass in 2G ethanol and paper industry. Significant researchers have contributed towards lignin valorization, with a central goal of the production and upgradation of phenolic, unstable, acidic and oxygen-containing bio-oil to valuable chemicals or fuel grade hydrocarbons. This review is aimed to present the lignin valorization potential from pretreatment of biomass as an initial step to the final process, i.e., lignin bio-oil upgradation with mechanistic pathways. The review offers the source, structure, composition of various lignocellulosic biomasses, followed by a discussion of various pre-treatment techniques for biomass depolymerization. Different thermochemical approaches for bio-oil production from dry and wet biomasses are highlighted with emphasis on pyrolysis and liquefaction. The physical, chemical properties of lignin bio-oil and different upgradation methods for bio-oil as well as its model compounds are thoroughly discussed. It also addresses the related activity, selectivity, stability of numerous catalysts with reaction pathways and kinetics in a broad manner. The challenges and future research opportunities of lignin valorization are discussed in an attempt to place lignin as a feedstock for the generation of valuable chemical and fuel grade hydrocarbons.     

Tailoring Cu/Al2O3 catalysts for the catalytic pyrolysis of tomato waste

In this study, pyrolysis of tomato waste has been performed in fixed bed tubular reactor at 500 °C, both in absence and presence of Cu/Al₂O₃ catalyst. The influences of heating rate, catalyst preparation method and catalyst loading on bio-oil yields and properties were examined. According to pyrolysis experiments, the highest bio-oil yield was obtained as 30.31% with a heating rate of 100 °C/min, 5% Cu/Al₂O₃ catalyst loading ratio and co-precipitation method. Results showed that the catalysts have strong positive effect on bio-oil yields. Bio-oil quality obtained from fast catalytic pyrolysis was more favorable than that obtained from non-catalytic and slow catalytic pyrolysis.     

An overview of empty fruit bunch from oil palm as feedstock for bio-oil production

Empty fruit bunch (EFB) from oil palm is one of the potential biomass to produce biofuels like bio-oil due to its abundant supply and favorable physicochemical characteristics. Confirming the assertion, this paper presents an overview of EFB as a feedstock for bio-oil production. The fundamental characteristics of EFB in terms of proximate analysis, ultimate analysis and chemical composition, as well as the recent advances in EFB conversion processes for bio-oil production like pyrolysis and solvolysis are outlined and discussed. A comparison of properties in terms of proximate analysis, ultimate analysis and fuel properties between the bio-oil from EFB and petroleum fuel oil is included. The major challenges and future prospects towards the utilization of EFB as a useful resource for bio-oil production are also addressed.     

Potentiality of combined catalyst for high quality bio-oil production from catalytic pyrolysis of pinewood using an analytical Py-GC/MS and fixed bed reactor

The aim of this study was to investigate the potential of combined catalyst (ZSM-5 and CaO) for high quality bio-oil production from the catalytic pyrolysis of pinewood sawdust that was performed in Py-GC/MS and fixed bed reactor at 500 °C. In Py-GC/MS, the maximum yield of aromatic hydrocarbon was 36 wt% at biomass to combined catalyst ratio of 1:4 where the mass ratio of ZSM-5 to CaO in the combined catalyst was 4:1. An increasing trend of phenolic compounds was observed with an increasing amount of CaO, whereas the highest yield of phenolic compounds (31 wt%) was recorded at biomass to combined catalyst ratio of 1:4 (ZSM-5: CaO - 4:1). Large molecule compounds could be found to crack into small molecules over CaO and then undergo further reactions over zeolites. The water content, higher heating value, and acidity of bio-oil from the fixed bed reactor were 21%, 24.27 MJkg⁻¹, and 4.1, respectively, which indicates that the quality of obtained bio-oil meets the liquid biofuel standard ASTM D7544-12 for grade G biofuel. This research will provide a significant reference to produce a high-quality bio-oil from the catalytic pyrolysis of woody biomass over the combined catalyst at different mass ratios of biomass to catalyst.     

Characterization of bio-oils from the fast pyrolysis of white oak and sweetgum

Conversion of lignocellulosic biomass into bio-oil through fast pyrolysis process is considered one of the promising routes to supplement conventional fossil oil. Future bio-refineries require production large amounts of bio-oil from several biomass types. Characterization of the produced bio-oils is important to determine their suitability as bio-refinery feedstock. In this study, bio-oils were produced from white oak and sweetgum woods in an auger reactor at 450°C. The yields of char, liquid, and gas were calculated. The physical characterization of bio-oils was performed based on the investigation of different properties, such as pH, density, viscosity, water content, acid value, and molecular weight distribution of bio-oil components. The chemical compositions of the bio-oils were also investigated by gas chromatography/mass spectrometry and Fourier transform infra-red analyses. The physicochemical properties of the produced bio-oils were comparable to those obtained from similar woody biomass and the oils were suitable for fuel production.     

Liquefaction of palm kernel shell in sub- and supercritical water for bio-oil production

The heavy palm oil industry in Malaysia has generated various oil palm biomass residues. These residues can be converted into liquids (bio-oil) for replacing fossil-based fuels and chemicals. Studies on the conversion of these residues to bio-oil via pyrolysis technology are widely available in the literature. However, thermochemical liquefaction of oil palm biomass for bio-oil production is rarely studied and reported. In this study, palm kernel shell (PKS) was hydrothermally liquefied under subcritical and supercritical conditions to produce bio-oil. Effects of reaction temperature, pressure and biomass-to-water ratio on the characteristics of bio-oil were investigated. The bio-oils were analyzed for their chemical compositions (by GC–MS and FT-IR) and higher heating values (HHV). It was found that phenolic compounds were the main constituents of bio-oils derived from PKS for all reaction conditions investigated. Based on the chemical composition of the bio-oil, a general reaction pathway of hydrothermal liquefaction of PKS was postulated. The HHV of the bio-oils ranged from 10.5 to 16.1 MJ/kg, which were comparable to the findings reported in the literature.     

Pyrolysis of North-American grass species: Effect of feedstock composition and taxonomy on pyrolysis products

In the Midwest of the U.S., several members of the Poaceae family can be grown as bioenergy crops. Besides Miscanthus and switchgrass, which have been extensively studied, native Midwestern grasses such as big bluestem, coastal panicgrass, deertongue, indiangrass, sandreed and sideoats grama can be grown in monoculture or polyculture plantations. In addition to climate, soil fertility and water availability, the selection of bioenergy crops depends on the choice of conversion technology. One such technology, fast pyrolysis, is a thermochemical approach for converting biomass into a liquid product known as bio-oil, a hydrocarbon fuel intermediate. In this research, the eight aforementioned grass varieties were characterized by fiber and metal analyses as well as calorimetry and thermal gravimetry. Conversion by analytical pyrolysis showed that although variability exists, all eight grasses produced a similar spectrum of chemical compounds. Principal component analysis of pyrolysis-GC/MS data detected statistically significant differences amongst the grass varieties on the basis of six key chemical markers: glycolaldehyde, acetic acid, acetol, methyl glyoxal, 4-vinylphenol and levoglucosan. Though taxonomic classification was not found to affect product composition, correlation analysis verified that biomass composition and thermal properties might be responsible for the differences in pyrolysis products.