Open access peer-reviewed chapter

Advances in the Pyrolysis Process and the Generation of Bioenergy

Written By

Vittor Rodrigues Santos Alves

Submitted: August 8th, 2021Reviewed: August 19th, 2021Published: December 3rd, 2021

DOI: 10.5772/intechopen.99993

Chapter metrics overview

114 Chapter Downloads

View Full Metrics

Abstract

The reduction of environmental impacts caused by emissions of greenhouse gases has become an internationalized goal. In this context the development of technologies capable of producing energy from clean or renewable sources has gained broad prominence, among them the fast pyrolysis is a type of thermochemical process capable of converting biomass and agroindustrial waste into a liquid product called bio-oil that has a wide range of applications in the bioenergy scenario. For this type of technology to be consolidated as an alternative source of renewable energy, economic, political and environmental incentives are necessary, as well as research development to improve the conversion processes, such as reactor types, logistics in obtaining and pre-treating potential biomass, improvement and conversion routes for bio-oil obtained in renewable biofuels or chemicals with higher added value. This chapter covers the fundamentals of thermal conversion of biomass into bio-oil and the most studied processes to convert bio-oil into a product with better properties, such as deoxygenation and energy densification.

Keywords

  • biomass
  • fast pyrolysis
  • bio-oil
  • bioenergy
  • environmental

1. Introduction

The demand for clean energy sources and the accompanying reduction in greenhouse gas emissions have gained increasing emphasis on environmental policy agendas around the world. One of the current portraits of these discussions was in 2021, when the Climate Summit was promoted, in which the political leaders of each nation set social, technological and political goals for the coming years in order to mimic the agents causing natural and climate changes. Among the most discussed measures, mainly by countries in the northern hemisphere, is the attack on the consumption of fossil fuels such as diesel, gasoline and mineral coal.

Biomass, urban and agricultural waste have great potential to be converted into products with added energy value. Although there are several routes for converting biomass into fuels (biological, thermal and physical–chemical), most of them, as biological, are highly selective, offering little variability of the final product. In thermal processing there is the possibility of producing a range of complex products such as chemicals, advanced biofuels and integrated electrical energy. Although the production of charcoal, through the carbonization process, is an old and well-known process, it was during the oil crisis in the 1970s that research was directed towards obtaining renewable fuels from lignocellulosic materials, where fast pyrolysis stood out. In this process, the carbonaceous material is subjected to moderate temperatures (in the range of 500°C) at high heating rates and in the absence of oxygen, thus, the release of organic vapors and gases occurs at low resistance times in the reactor, in addition to the formation of a char fraction [1, 2].

The biomass pyrolysis process in general can be understood as a thermal fractionation of the lignocellulosic complex into three predominant fractions: char, gases and liquids (condensable vapors). The greater or lesser yield of each of these fractions is adjusted according to the input parameters and adjustment of process variables such as temperature, reactor type, biomass composition, biomass physical properties and so on. In the fast pyrolysis process, all these parameters are conditioned in such a way as to provide low residence times in the vapor phase reactor. When being condensed, these vapors form a liquid phase composed of a variety of organic compounds called bio-oil.

Bio-oil has a wide range of applications. Due to its varied composition (alcohols, organic acids, sugars, phenolic aromatics, etc.) it can be used to obtain chemical species through refining and extraction, raw material for obtaining advanced biofuels, in addition to liquid biofuels for processes of direct burning of biomass is not possible. In addition, as it is a liquid product, its handling and transportation are facilitated in relation to solid biomass. Finally, bio-oil can have its quality improved by modifications directly in the pyrolysis process such as downstream upgrading processes.

Thus, this work presents an overview of the fast pyrolysis of biomass for bio-oil production, the properties of bio-oil and its general application, showing the main processes (reactors) developed and new trends for the improvement of the pyrolysis process aiming to obtain more efficient bioenergy sources.

Advertisement

2. Fast pyrolysis: general aspects

Thermochemical processes have by their nature the conversion of raw materials into products that have greater added energy value. These processes occur having heat as the agent of transformation, either by release or demand of the process. Figure 1 shows a summary of the main endothermic processes [3, 4, 5, 6, 7, 8, 9].

Figure 1.

Diagram showing the main characteristics of the most conventional thermochemical processes.

During the fast pyrolysis process, the lignocellulosic structure of the biomass is degraded and converted mostly under specific reaction conditions, generating a main product called bio-oil. Table 1 shows an overview summary of the main physical–chemical properties of a typical bio-oil compared to a heavy fuel oil.

PropertyHeavy oil fuelBiomass feedstock
Mahogany waste woodOak/mapleBirchPine wood
Elemental analysis (dry basis), % wtC83–8650.244.045.7
H11–146.66.97.0
N<1<0.40.2<0.1<0.1
O<0.142.649.047.0
S<4<0.06<0.010.000.02
Ash0.030.150.010.0040.03
Moisture, % wt0.121.422.018.917.0
pH5.642.52.52.4
Density, kg/L0.940.951.181.251.24
HHV, MJ/kg4429.5217.016.5a17.2a
Viscosity (40°C), cSt5.5–244.650b28b28b
Solids (char), % wt0.0450.060.03
Distillation residue, % wt<1not distillable
Flash point, °C68.0556295
Pour point, °C−1813.5−25−24−19
Ref.[10, 11, 12, 13][14][15][16, 17][16, 17]

Table 1.

Main properties of bio-oil from different feedstock compared to heavy fuel oil.

as LHV.


at 50°C.


In order to quantitatively obtain organic products in the form of bio-oil in an expressive way, it is necessary to maintain some parameters and variables in an essential way during fast pyrolysis.

  • High heating rates of the particle, for this it is necessary that the feed is in reduced particle size and moisture [18, 19].

  • Good temperature control, allowing the process to occur in temperature ranges close to 500°C [18, 19].

  • Low residence times of the vapor phase (below 2 s) as well as a fast cooling of these [18, 20].

By carefully following these parameters, it is possible to obtain bio-oil yields of up to 75% on a dry basis depending on the technology (reactor type) employed and the nature of the material. Moreover, depending on its composition and the way it is collected, the bio-oil can form two phases, a lighter one with a higher presence of water and a heavier one with a higher concentration of organic fraction.

Advertisement

3. Bio oil properties and its applications

In general, biomass is composed essentially of three organic components: cellulose, hemicellulose and lignin. Besides these there is also an inorganic fraction (ash) and the water associated with the structure of the material in the form of moisture. The composition of these fractions is an important reference in the quality of bio-oil to be obtained. Table 2 shows a general summary of the lignocellulosic composition of various biomasses.

BiomassComposition, % wtRef.
CelluloseHemicelluloseLigninOther
Softwood4124287[9, 20]
Oakwood34.518.628
Birchwood35.725.119.3
Hardwood3935207
Leaves15–2080–850
Olive husk2423–2448–49
Miscanthus244417
Sugarcane bagasse19–2432–4823–32
Willow plant501925
Rice straw30251233
Wheat Straw40281715
Nut shell25–3025–3530–40
Walnut shell25–2622–2352–53
Corncob50.53115

Table 2.

Lignocellulosic composition of various biomasses.

During the pyrolysis process these three polymers decompose at virtually the same time, however each has different thermal decomposition kinetics [21], which can lead not only to different yields of bio-oil and its sub products (biochar and gas) but also generate a variation in the distribution of organic functions that make up the bio-oil [22].

Due to the different physicochemical properties of cellulose, hemicellulose and lignin, they tend to produce different products. While cellulose tends to contribute to higher bio-oil yields, higher lignin concentration contributes more significantly to biochar formation [20, 23, 24]. The organic composition of bio-oil is extremely variable and presents several classes of organic composts. Figure 2 shows a deviation map of these organic functions that typically compose the pyrolysis bio-oil in relation to the thermal reactivity of cellulose, hemicellulose and lignin [25].

Figure 2.

Thermal decomposition of lignocellulosic compounds and their products (adapted from [25]).

In addition, the inorganic fraction of biomass (ash) can also influence the characteristics of bio-oil. Some studies show that biomasses with alkali rich ash, such as potassium (K), and phosphorus can exhibit catalytic properties and alter the distribution of organic compounds present in bio-oil [26]. A number of other characteristics of bio-oil can be described to assess its quality, such as appearance, typically characterized by a dark brown or reddish color; odor, which is characteristic of acidic flavors and can even cause airway and visual irritation upon prolonged exposure; and miscibility, which is a complex factor as it is not miscible with petroleum fuels due to the large presence of polar and oxygenated compounds, and is not water soluble as excessive addition can lead to the formation of two liquid phases [19, 20].

Due to its varied composition, a number of applications have been attributed to bio-oil. Figure 3 illustrates some of the main applications.

Figure 3.

Bio-oil applications.

The pyrolysis bio-oil presents compounds in high concentrations such as phenols, guaiacs, acetic acid among others and with the advancement of separation techniques, such as liquid–liquid extraction, with the addition of solvents (hexane, chloroform etc.) has allowed the recovery of fractions with high concentrations of these compounds that have high added value for the industry, production phenolic resins, organic acids among others [27, 28, 29, 30]. In addition, the greatest potential for use of bio-oil is in its use for the production of biofuels, being necessary, firstly, the application of upgrading steps to improve its properties.

Bio-oil can also be used in combustion or co-combustion systems with other fuel oils to obtain heat in industrial processes. However, the applications of bio-oil in these combustion systems are traditional for combustion of heavy or mineral oils due to their physical–chemical characteristics completely different and their instability that can impact on essential parameters for a quality combustion of oil as the quality of atomization, ignition, tendency to coke formation, vaporization rate of drops, clogging among others. However, having a good understanding of the properties of the bio-oil used and the ratio some benefits are reported in co-combustion operations such as the reduction of SO2 and thermal NOx emissions [27, 28, 29, 30].

Advertisement

4. Reactors to fast pyrolysis

The design of a fast pyrolysis process has at its core the reactor where the appropriate heat and mass transfer conditions will be provided for the thermochemical processing of the material. In general, a fast pyrolysis process consists of a biomass fitting unit (1) to fit the required particle size and moisture conditions, the pyrolysis reactor (2) where the bio-oil (vapors) and by-products (biochar and non-condensable gases) are formed, cyclone(s) and/or particulate removal systems (3), condensation unit and bio-oil collection (4) and finally a thermal energy conversion and integration system in the system (5) as illustrated in Figure 4.

Figure 4.

General system to biomass fast pyrolysis.

The pyrolysis is an endothermic process, as the goal of fast pyrolysis is to obtain higher yields in liquids, the other by-products (biochar and gas) can be used as fuels in the thermal energy generation unit providing the necessary entapia, to perform the pyrolysis reactions. Fast pyrolysis reactors in general can be separated into those that use a gaseous agent for heat transfer in the reactor and those that do not use gas as a fluid, and most of them are already in commercial scale. A Table 3 mostra um resumo dos principais reatores utilizados nos processos de pirólise dus prncipais características e seu status comercialização.

Reactor typeMain featuresLimitationsReferences
Circulating fluidized bedEasy scale-up.
Efficient heat and mass transfer.
Flexibility in system design.
Low solid phase residence time (similar to gases) leading to higher coal yields.
Complex hydrodynamics.
[1, 31, 32, 33, 34, 35, 36, 37, 38, 39]
Bubbling fluidized bedGood heat and mass transfer, easy control, operational simplicity.
High bio-oil yields.
High pre-treatment accuracy of biomass, requiring low particle sizes
Rotating coneIt uses centrifugal force to move the particles.
Uses little carrier gas.
Yields in bio-oil in the range of 60–70%.
A more complex in-grid system is required with cone pyrolysis reactor, riser for transport and recycle of the sand particles, fluidized bed combustion chamber.
Auger or screwThe process takes place during mechanical conveying.
The heat carrier can be the walls or ceramic/sand particles.
Suitable for heterogeneous biomass/waste or waste that is difficult to transport and handle.
Longer residence time of the vapors.
Lower bio-oil yield compared to fluid bed reactors.
AblativeHeat transfer is via reactor part contact, allowing the use of larger diameter parts and without the need for carrier gas.Limitation in the scale-up mainly concerning the reactor surface.
Spouted bedVery high heat and mass transfer coefficients.
Short residence times.
High liquid yields (up to 70%).
Complex scale-up accompanied by high pressure drop.

Table 3.

Description of the main fast pyrolysis reactors and their characteristics.

Advertisement

5. Pyrolysis and bio-oil improvement strategies

Bio-oil obtained from lignocellulosic feedstock with fast pyrolysis has many disadvantages in front of fossil fuels such as high water content, presence of small particles of coal and alkaline ash, acidity, low calorific value and thermal stability that make it difficult to application of bio-oil in the power system such as engines [40]. The currently technological research shows that there are basically three ways to improve the performance of the fast pyrolysis and the quality of the obtained bio-oil. The Figure 5 shows these deferments strategies.

Figure 5.

Different processes and strategies to improve the fast pyrolysis of bio-oil quality.

5.1 Pre-treatment

Several authors have already reported the effect of physical treatments (i.e. treatments that do not alter the chemical composition or chemical structure of biomass) of biomass on pyrolysis processes. The most relevant one reported is the biomass grinding aiming at its particle size reduction, which has a positive impact on all fast pyrolysis reactors, providing an increase in the bio-oil yield [41].

The washing (or leaching) it’s a process used to remove or modified inorganic compounds of the biomass or modified the lignocellulosic complex. The H2O washing it’s a simple and low cost process able to remove mainly alkalis (K, Ca), Cl and S [42, 43]. The Acid washing it’s a more complete but expensive kind of washing with (organic or inorganic) acid diluted, this process its able to remove near all components (alkalis, halogens, heavy metals etc) found in biomass ashes promoting the complete demineralization [42, 44]. In addition to these effects, the acid treatment of biomass (washing and acid infusion) can lead to the formation of bio-oil rich in sugars [45, 46]. Studies have pointed out [46] showed that there is considerable enrichment in sugars, especially levoglusan (up to 55% of cellulose) during the acid infusion of corn stover. These results were mainly attributed to the catalysis of the decomposition of the cellulose structure.

Another process considered a pre-treatment of biomass for fast pyrolysis is Dry Torrefaction. This process is like mild pyrolysis; occurring in the range of 200–280°C and in an inert atmosphere, it promotes a thermal pre-degradation of lignocellulosic polymers, generating a biomass with the potential to produce a bio-oil with better quality [47, 48]. In parallel, the Wet Torrefaction (WT) process can also qualitatively improve the biomass properties for the fast pyrolysis process. It occurs in aqueous phase and ambient to moderate pressures, with water at high temperatures it removes alkalis, carbonates and halogens. Research shows that bio-oil produced from biomass pre-treated with WT produced bio-oil with less phenols, ketones, furans and richer in sugar, especially levoglucosan. However, in addition to energy consumption, this process generates a biomass with high water content [46, 49, 50, 51, 52].

The process of acid treatment and torrefaction of biomass can be combined to improve the performance of fast pyrolysis both quantitatively (higher bio-oil yield) and qualitatively (bio-oil with better properties) as shown in Figure 6. Studies showed that the coupling of acid washed with acetic acid (1% wt) and dry torrefied (270°C) in the pretreatment of P. radiataallowed achieving 57.8% of bio-oil yield and improving the quality of bio-oil with low H2O and organic acids content [54].

Figure 6.

A combination of acid treatment and dry torrefaction to improve the fast pyrolysis process performance (adapted from [53]).

5.2 In situ upgrading

Other strategy to improve the properties of the bio-oil obtained by pyrolysis process is the modification in situ, i.e., inside the own reactor by change of the variables and the parameters. Two strategies that have gained prominence and show good results in obtaining a bio-oil with good qualities are hydrogenation and catalytic pyrolysis, and the hybrid process with both.

The addition of H2 as a pyrolysis gas agent in the absence of catalysts promotes hydrogenation reactions mainly with the volatiles released and may have various effects such as increased formation of less oxygenated species, greater selectivity in phenolic compounds among others. For example, the effect of adding hydrogen in the carrier gas (up to 15% vol) in the pyrolysis of food waste in a dawndraft reactor promoted the formation of a bio-oil more selective in aromatic, phenolic compounds while reducing the amount of heterocycline nitrogenous species such as (quinoline) [55]. Other biomasses, such as poplar wood showed the same behavior upon pyrolysis in H2 atmosphere (6% vol) compared to pure N2 atmosphere obtaining higher yield and selectivity in phenolic species [56]. Another important effect of the addition of H2 in the pyrolysis process is that, regardless of the presence of catalysts, it can promote the production of bio-oil with higher H/C ratio which is highly beneficial for the use of bio-oil as liquid fuel [57].

Recycling the pyrolysis gas to the reactor as a reactive atmosphere is a potential alternative, although its effect is not yet clear. When fast pyrolysis of biomass takes place under a N2 atmosphere, the main gaseous products of pyrolysis are CO, CO2, H2, CH4 and low levels of light hydrocarbons, therefore, when this gas is recycled to the reactor, it can promote a reactive atmosphere and not more inert. Studies in fluidized bed reactors, in the temperature range of 430–500°C, show that the increase in gas recycling rates can lead to a decrease in the production of organic liquids, but some biomasses, such as oak and switch grass, show good results. Deoxygenation effect and HHV increase in your bio-oil with gas recycling rates of up to 80%. However, other biomasses, such as Pennycress Presscakeand pine wood, had no effect on the yield and composition of bio-oil with the pyrolysis gas recycled in the reactor [58, 59].

Among all the in situ alternatives to improve the obtainment of higher quality bio-oil, catalytic pyrolysis stands out as the most promising. The process basically consists of the insertion of a solid catalyst in the pyrolysis reactor capable of acting in the set of pyrolysis reactions, promoting the formation of bio-oil with better properties and selectivity in the components of interest of interest. Several authors have already published works testing different catalysts, in different process configurations, attesting to diverse improvements in obtaining bio-oil. Among these improvements in the use of catalysts in the fast pyrolysis process, it is worth mentioning: [60].

  • The use of some catalysts can provide lower temperature operation. Considering that the pyrolysis process is endothermic, this would lead to a reduction in energy costs [61, 62].

  • Reduction of bio-oil acidity and possible corrosion problems due to less formation of acidic compounds.

  • High degree of deoxygenation, increased H/C ratio and associated energy densification [63].

  • Considerable increase in the selectivity of bio-oil products, reducing the molecular weight range of the hydrocarbons obtained (C5–C12) [64].

  • Depending on the catalyst(s) selected, there may be a significant increase in aromatic compounds (up to 50%), giving greater stability to the bio-oil and providing a potential use as a fuel [60, 65].

Despite promising experimental results, the fast pyrolysis process using catalysts still needs to overcome some obstacles to reach the industrial level. The basis for these challenges is the development of catalytic reactors capable of supporting the pyrolysis atmosphere without expressive rates of catalyst deactivation, expanding the selection of desired products in bio-oil, in addition to efficient developments in the recovery and regeneration of catalysts [41, 60]. Table 4 below shows a set of works on catalytic pyrolysis of biomass at different scales, the characteristics of the catalysts used as well as the yield in bio-oil.

FeedstockProcess parametersCatalystYieldDeoxygenationRef.
Loblolly pineCirculating fluidized bed
36 kgbiom/h
520°C
γ-Al2O313–6–24.2% wt O[66]
Forest pine woodchipsAuger reactor
450°C
2 kgbiom/h
CaO
CaO.MgO
48–50%24.2–25.4% wt O[67]
Pine woodAuger reactor
500°C
0,2 kgbiom//h
ZSM-5 based acidic catalys50,3%[68]
Pine woodBubbling fluidized bed reactorSspray-dried 40% ZSM-545.5–50.0%[69]
Microalgae (Enteromorpha prolifera) + HDPE plasticsFixed bed reator
550°C
EP:plastic:catalyst ratio 1:1:2
HZSM-571.4%13.5% wt O[70]
MiscanthusConical spouted reactor
400–600°C
1–5 catalyst/biomass
ZSM-537.5% [500°C]1,7% of phenols and 5,5% wt other oxygenates [500°C][71]
Waste tires + pistachio seedsFixed bed
500°C
5% wt catalyst
Ni-Mo/Al2O363%5.3% wt (oxygen)[72]
LingninFixed bed reactor
450°C
K2CO329%O/C=1,40[73]
L. japonica + polypropyleneFixed bed reactor
500°C
Al-SBA-1550,32%~ 10% of oxygenate compounds[74]
Pine woodFluidized bed reactorH-MOR-2017,6% (free water)[75]

Table 4.

Some research about catalytic pyrolysis.

5.3 Ex situupgrading

Ex situprocesses are carried out outside the pyrolysis reactor, ie outside the main reaction zone. Esses processos podem ser de natureza física ou físico-química, promovendo alguma melhoria na qualidade do bio-óleo bruto gerado na pirólise. Dentre esses, pode se citar: [76, 77, 78].

  • Physical methods

    • Solvend adition

    • Emulsification

    • Hot vapor filtration

  • Chemical

    • Catalytic hydrodeoxygenation (HDO)

    • Steam reforming

    • Esterification

    • Supercritical fluids

Although there are several strategies to improve the quality of bio-oil, the most studied processes, aiming at the industrial potential, are hot vapor filtration (HVF), catalytic hydrodeoxygenation (HDO) and steam reforming.

HVF is one of the most common and simple able to improve some properties of bio-oil. It consists of passing the pyrolysis vapors through a filtering medium, even at higher temperatures. This method, in addition to being more efficient than traditional cyclones for removing small particles of coal and ash, can add better properties to the condensed bio-oil later on [48, 79].

Some types of filter (fixed bed glass wool, ceramic candles) and biomass raw material (sugarcane, rice and cassava waste) for pyrolysis were tested in the configuration: reactor + hot filter. In short, the addition of the filter introduces a longer residence time of the bio-oil organic vapor at high temperatures, promotes cracking reactions of organic molecules and causing a loss in bio-oil yield (around to 5%), increase in yield of the gas in addition to the higher content of H2O in the bio-oil. But the condensed bio-oil tends to present a series of improvements such as: practically free of char and ash, less viscous. There may also be a certain deoxygenation of the bio-oil (decrease in the O/C molar ratio) but this effect is not fully understood, depending on the type of hot filter, biomass and operating conditions of the pyrolysis [79, 80, 81].

Another upgrading process, of the great highlighted is the hydrodeoxygenation (HDO) of the bio-oil. The HDO it’s a particular case of hydrotreatment process, where the bio-oil is its reacted with H2 under specific conditions of temperature, pressure, catalystic, and fluidynamis (Figure 7). In this way, the organic compounds of the bio-oil are submitted to a set of reactions, mainly hydrogenation and hydrodeoxygenation, providing an improvement in properties, forming less oxygenated and more stable compounds.

Figure 7.

Schematic of the catalytic hydrodeoxygenation process, its variables and products.

Good control of the variables and parameters is essential to obtain a bio-oil with a high degree of deoxygenation and with lower H2 consumption. The process occurs in the range 200–450°C and higher temperatures, in general, increase the degree of deoxygenation but at the expense of a decrease in the yield of improved bio-oil due to higher gas production. The partial pressure of H2 is a variable of great relevance in the process and a minimum value of around 80 bar is required for good solubilization of the bio-oil, increased catalytic activity and minimization of adverse effects such as repolymerization of the bio-oil forming unwanted solid products [82, 83].

Finally the selection of the catalyst, jutanly with the support, is fundamental. The first catalysts tested in this process were CoMo/γ-Al2O3 and NiMo/γ-Al2O3 due to their use in oil refineries for nitrogen and sulfur removal processes. About these a number of sulfide, noble metal, and transition catalysts have been studied, each presenting different advantages with respect to higher catalytic activity, selectivity, and deactivation rates upon the presence of inorganic elements such as sulfur and ash present in the bio-oil [83]. The catalytic hydrodeoxygenation becomes a promising alternative for obtaining a bio-oil of higher quality and opening the possibility for the production of biofuels from it.

The steam reforming process emerges as another alternative of great potential for the valorization of lignocellulosic currents and hydrogen production. H2 is a gaseous fuel with high added value due to its energy density and its combustion is free of carbon emissions. In this process, bio-oil, as well as fossil fuels, react with H2O vapor at temperatures in the range of 700–1000°C, in the presence of a catalyst (usually nickel-based) offering as main product the H2-rich syngas, along with CO2 [76, 77, 78]. The main advantage of this process is the simultaneous production of high value-added fuel (H2), and it allows the assimilation of CCSU (Carbon Capture Storage and Utilization) technologies. But one of the major disadvantages is the high energy demand to carry out the process.

The overall balance of this process can be given by Eq (1): [77, 78].

CnHmOk+2nkH2OnCO2+2n+m2kH2E1

Where the coefficient expresses the maximum possible H2 yield per mole of carbon fed. The steam reforming of bio-oil can be performed mainly in fixed bed, fluidized bed or staged bed reactors. The process can be carried out using a wide range of catalysts (Dolomite, Ru, Ni, Co, Rh) and supports (Al2O3, ZrO2, MgAl2O4, etc.) but Ni based catalysts are the most active but also have the highest deactivation rates due to coke formation. However, changes in the processes, mainly concerning the Vapor/Carbon ratio, besides the temperature and the catalytic support, can minimize the impact of the decay of the catalytic activity by coke formation in the steam reforming process [84, 85].

Advertisement

6. Conclusions

The process of fast pyrolysis is an alternative of great potential for the conversion of biomass and waste into renewable fuels and chemicals of high added value contributing to the reduction of emissions of greenhouse gases, with potential for application and integration in biorefinery projects. Technically some technologies such as fluid bed and rotating cone reactors are emerging for commercial applications and the main product generated, bio-oil, has a variable and complex composition requiring stages of improvement and stabilization. In this sense, several studies point out routes to improve the quality of bio-oil obtained from the pre-treatment of biomass (such as washing and torrefaction), in situ improvements and downstream processes such as HDO and steam reforming capable of converting bio-oil into a stream with higher added value.

References

  1. 1.Bridgwater, A. V. (2012). Review of fast pyrolysis of biomass and product upgrading. Biomass and Bioenergy, 38, 68-94. DOI:10.1016/j.biombioe.2011.01.048
  2. 2.Czernik, S., and Bridgwater, A. V. (2004). Overview of applications of biomass fast pyrolysis oil. Energy and Fuels, 18(2), 590-598. DOI:10.1021/ef034067u
  3. 3.Das Shreya, Mohanty Samanyita, Sahu Gayatri, Rana Mausami, and Pilli Kiran (2021). Biochar: A sustainable approach for improving soil health and environment. DOI:10.5772/intechopen.97136
  4. 4.Tekin, K., Karagöz, S., and Bektaş, S. (2014). A review of hydrothermal biomass processing. Renewable and Sustainable Energy Reviews, 40, 673-687. DOI:10.1016/j.rser.2014.07.216
  5. 5.Ribeiro, J.M.C., Godina, R., Matias, J.C.D.O., Nunes, L.J.R. Future perspectives of biomass torrefaction: Review of the current state-of-the-art and research development. Sustainability 2018, 10, 2323. DOI:10.3390/su10072323
  6. 6.Verma Anil, Shankar Ravi, and Mondal Prasenjit (2018). A review on pyrolysis of biomass and the impacts of operating conditions on product yield, quality, and upgradation. DOI:10.1007/978-981-13-1307-3_10
  7. 7.Kazawadi Deodatus, Ntalikwa Justin, and Kombe Godlisten (2021). A review of intermediate pyrolysis as a technology of biomass conversion for coproduction of biooil and adsorption biochar. Journal of Renewable Energy. 2021. DOI:10.1155/2021/5533780
  8. 8.Jahirul, M.I., Rasul Mohammad, Chowdhury Ashfaque, and Ashwath Nanjappa (2012). Biofuels production through biomass pyrolysis—A technological review. Energies. 5. 4952-5001.DOI:10.3390/en5124952
  9. 9.Molino, A., Larocca, V., Chianese, S., Musmarra, D. Biofuels production by biomass gasification: A review. Energies 2018, 11, 811. DOI:10.3390/en11040811
  10. 10.Uzun, B., Apaydın Varol, E., and Pütün, E. (2016). Pyrolysis: A sustainable way from biomass to biofuels and biochar. In: V. Bruckman, E. Apaydın Varol, B. Uzun, and J. Liu (Eds.), Biochar: A Regional Supply Chain Approach in View of Climate Change Mitigation (pp. 239-265). Cambridge: Cambridge University Press. DOI:10.1017/9781316337974.013
  11. 11.Oasmaa Anja, Elliott Douglas, and Müller, S. (2009). Quality control in fast pyrolysis bio-oil production and use. Environmental Progress and Sustainable Energy. 28. 404-409. DOI:10.1002/ep.10382
  12. 12.Zhou Xiaowei, Broadbelt, L.J., and Vinu Ravikrishnan (2016). Mechanistic understanding of thermochemical conversion of polymers and lignocellulosic biomass. DOI:10.1016/bs.ache.2016.09.002
  13. 13.Cheng Shouyun, Wei Lin, Zhao Xianhui, and Julson James (2016). Application, deactivation, and regeneration of heterogeneous catalysts in bio-oil upgrading. Catalysts. 6. 195. DOI:10.3390/catal6120195
  14. 14.Chukwuneke, J. L., Ewulonu, M. C., Chukwujike, I. C., and Okolie, P. C. (2019). Physico-chemical analysis of pyrolyzed bio-oil from swietenia macrophylla (mahogany) wood. Heliyon, 5(6), e01790. DOI:10.1016/j.heliyon.2019.e01790
  15. 15.Oasmaa, A., Peacocke, C., Gust, S., Meier, D., and McLellan, R. (2005). Norms and standards for pyrolysis liquids. End-user requirements and specifications. Energy and Fuels, 19(5), 2155-2163. DOI:10.1021/ef040094o
  16. 16.Ringer, M, Putsche, V, and Scahill, J. Large-scale pyrolysis oil production: A technology assessment and economic analysis. United States: N. p., 2006. Web. DOI:10.2172/894989
  17. 17.Elliott, D C. Analysis and comparison of biomass pyrolysis/gasification condensates: Final report. United States: N. p., 1986. Web. DOI:10.2172/7049810
  18. 18.Bridgewater Anthony. (2004). Biomass fast pyrolysis. Thermal Science. 8. 21-50. DOI:10.2298/TSCI0402021B
  19. 19.Bridgwater, A. (1999). Fast Pyrolysis of Biomass: A Handbook
  20. 20.Jahirul, M.I., Rasul Mohammad, Chowdhury Ashfaque, and Ashwath Nanjappa (2012). Biofuels production through biomass pyrolysis—A technological review. Energies. 5. 4952-5001. DOI:10.3390/en5124952
  21. 21.Yang, W., Ponzio, A., Lucas, C., Blasiak, W. Performance analysis of a fixed-bed biomass gasifier using high-temperature air. Fuel Proc. Technol. 2006, 87, 235-245. DOI:10.1016/j.fuproc.2005.08.004
  22. 22.Garcia-Nunez, J. A., Pelaez-Samaniego, M. R., Garcia-Perez, M. E., Fonts, I., Abrego, J., Westerhof, R. J. M., and Garcia-Perez, M. (2017). Historical developments of pyrolysis reactors: A review. Energy and Fuels, 31(6), 5751-5775. DOI:10.1021/acs.energyfuels.7b00641
  23. 23.Venderbosch Robbie, and Prins, W. (2010). Fast pyrolysis technology development. Biofuels, Bioproducts and Biorefining. 4. 178-208. DOI:10.1002/bbb.205
  24. 24.Chouhan Ashish, and Sarma Anil (2013). Critical analysis of process parameters for bio-oil production via pyrolysis of biomass: A review. Recent Patents on Engineering. 7. 98-114. DOI:10.2174/18722121113079990005
  25. 25.Arnold, S., Moss, K., Henkel, M., and Hausmann, R. (2017). Biotechnological perspectives of pyrolysis oil for a bio-based economy. Trends in Biotechnology, 35(10), 925-936. DOI:10.1016/j.tibtech.2017.06.003
  26. 26.Gómez, N., Banks, S. W., Nowakowski, D. J., Rosas, J. G., Cara, J., Sánchez, M. E., and Bridgwater, A. V. (2018). Effect of temperature on product performance of a high ash biomass during fast pyrolysis and its bio-oil storage evaluation. Fuel Processing Technology, 172, 97-105. DOI:10.1016/j.fuproc.2017.11.021
  27. 27.Shah, Z., CV, R., AC, M., and DS, R. (2017). Separation of phenol from bio-oil produced from pyrolysis of agricultural wastes. Modern Chemistry and Applications, 05(01). DOI:10.4172/2329-6798.1000199
  28. 28.Panwar, N.L., and Paul Arjun. (2020). An overview of recent development in bio-oil upgrading and separation techniques. Environmental Engineering Research. 26. DOI:10.4491/eer.2020.382
  29. 29.Lehto Jani, Oasmaa Anja, Solantausta Yrjö, Kytö Matti, and Chiaramonti David. (2018). Fuel oil quality and combustion of fast pyrolysis bio-oils. DOI:10.13140/RG.2.2.15925.99042
  30. 30.Hou Shuhn-Shyurng, Huang Wei-Cheng, Rizal Mokhammad, and Lin Ta-Hui. (2016). Co-firing of fast pyrolysis bio-oil and heavy fuel oil in a 300-kWth furnace. Applied Sciences. 6. 326. DOI:10.3390/app6110326
  31. 31.Freire José Teixeira, and Dermeval José Mazzini Sartori. 1992. Tópicos Especiais Em Secagem. São Carlos, SP: UFSCar
  32. 32.Alvarez, J., Lopez, G., Amutio, M., Bilbao, J., and Olazar, M. (2014). Bio-oil production from rice husk fast pyrolysis in a conical spouted bed reactor. Fuel, 128, 162-169. DOI:10.1016/j.fuel.2014.02.074
  33. 33.Fernandez-Akarregi, A. R., Makibar, J., Lopez, G., Amutio, M., and Olazar, M. (2013). Design and operation of a conical spouted bed reactor pilot plant (25kg/h) for biomass fast pyrolysis. Fuel Processing Technology, 112, 48-56. DOI:10.1016/j.fuproc.2013.02.022
  34. 34.Alvarez, J., Hooshdaran, B., Cortazar, M., Amutio, M., Lopez, G., Freire, F. B., Olazar, M. (2018). Valorization of citrus wastes by fast pyrolysis in a conical spouted bed reactor. Fuel, 224, 111-120. DOI:10.1016/j.fuel.2018.03.028
  35. 35.Orozco, S., Alvarez, J., Lopez, G., Artetxe, M., Bilbao, J., Olazar, M. Pyrolysis of plastic wastes in a fountain confined conical spouted bed reactor: Determination of stable operating conditions. Energy Convers. Manag. 2021, 229, 113768. DOI:10.1016/j.enconman.2020.113768
  36. 36.Sharifzadeh, M., Sadeqzadeh, M., Guo, M., Borhani, T. N., Murthy Konda, N. V. S. N., Garcia, M. C., Shah, N. (2019). The multi-scale challenges of biomass fast pyrolysis and bio-oil upgrading: Review of the state of art and future research directions. Progress in Energy and Combustion Science, 71, 1-80. DOI:10.1016/j.pecs.2018.10.006
  37. 37.Vamvuka, D. (2011). Bio-oil, solid and gaseous biofuels from biomass pyrolysis processes—An overview. International Journal of Energy Research, 35(10), 835-862. DOI:10.1002/er.1804
  38. 38.Yu X, Makkawi Y, Ocone R, Huard M, Briens C, Berruti F. A CFD study of biomass pyrolysis in a downer reactor equipped with a novel gas–solid separator—I: Hydrodynamic performance. Fuel Process Technol 2014; 126:366-382. DOI:10.1016/j.fuproc.2014.05.020
  39. 39.Perkins, G., Bhaskar, T., and Konarova, M. (2018). Process development status of fast pyrolysis technologies for the manufacture of renewable transport fuels from biomass. Renewable and Sustainable Energy Reviews, 90, 292-315. DOI:10.1016/j.rser.2018.03.048
  40. 40.Agblevor, F.A., Besler, S., 1996. Inorganic compounds in biomass feedstocks. 1. Effect on the quality of fast pyrolysis oils. Energy Fuels 10, 293-298. DOI:10.1021/ef950202u
  41. 41.Choi, H.S., Choi, Y.S., Park, H.C. Fast pyrolysis characteristics of lignocellulosic biomass with varying reaction conditions. Renew. Energy 2012, 42, 131-135. DOI:10.1016/j.renene.2011.08.049
  42. 42.Chang, S. H. (2019). Rice husk and its pretreatments for bio-oil production via fast pyrolysis: A review. BioEnergy Research. DOI:10.1007/s12155-019-10059-w
  43. 43.Deng L, Zhang T, Che D. (2013) Effect of water washing on fuel properties, pyrolysis and combustion characteristics, and ash fusibility of biomass. Fuel Process Technol 106:712-720. DOI:10.1016/J.FUPROC.2012.10.006
  44. 44.Ang TN, Ngoh GC, Chua ASM (2013) Comparative study of various pretreatment reagents on rice husk and structural changes assessment of the optimized pretreated rice husk. Bioresour Technol 135:116-119. DOI:10.1016/J.BIORTECH.2012.09.045
  45. 45.S. Oudenhoven, R.J.M. Westerhof, N. Aldenkamp, D.W.F. Brilman, S.R. Kersten, Demineralization of wood using wood-derived acid: Towards a selective pyrolysis process for fuel and chemicals production, J. Anal. Appl. Pyrol. 103 (2013) 112-118. DOI:10.1016/j.jaap.2012.10.002
  46. 46.Zhou Shuyu, Xue Yuan, Cai Junmeng, Cui Cunhao, Ni Ziang, and Zhou Zhongyue. (2021). An understanding for improved biomass pyrolysis: Toward a systematic comparison of different acid pretreatments. Chemical Engineering Journal. 411. 128513. 10.1016/j.cej.2021.128513
  47. 47.Mamvura, T.A., Danha, G. Biomass torrefaction as an emerging technology to aid in energy production. Heliyon 2020, 6, e03531. DOI:10.1016/j.heliyon.2020.e03531
  48. 48.Echresh Zadeh Zahra, Abdulkhani Ali, Aboelazayem Omar, Saha Basudeb (2020). Recent insights into lignocellulosic biomass pyrolysis: A critical review on pretreatment, characterization, and products upgrading. Processes. 8. 799. DOI:10.3390/pr8070799
  49. 49.S.R.G. Oudenhoven, C. Lievens, R.J.M. Westerhof, S.R.A. Kersten, Effect of temperature on the fast pyrolysis of organic-acid leached pinewood: The potential of low temperature pyrolysis, Biomass Bioenergy 89 (2016) 78-90. DOI:10.1016/j.biombioe.2015.12.019
  50. 50.S.R.G. Oudenhoven, R.J.M. Westerhof, S.R.A. Kersten, Fast pyrolysis of organic acid leached wood, straw, hay and bagasse: Improved oil and sugar yields, J. Anal. Appl. Pyrol. 116 (2015) 253-262. DOI:10.1016/j.jaap.2015.09.003
  51. 51.A. Zheng, Z. Zhao, S. Chang, Z. Huang, K. Zhao, G. Wei, F. He, H. Li, Comparison of the effect of wet and dry torrefaction on chemical structure and pyrolysis behavior of corncobs, Bioresour. Technol. 176 (2015) 15-22. DOI:10.1016/j.biortech.2014.10.157
  52. 52.S. Zhang, T. Chen, Y. Xiong, Q. Dong, Effects of wet torrefaction on the physicochemical properties and pyrolysis product properties of rice husk, Energy Convers. Manage. 141 (2017) 403-409. DOI:10.1016/j.enconman.2016.10.002
  53. 53.Srifa, A., Chaiwat, W., Pitakjakpipop, P., Anutrasakda, W., and Faungnawakij, K. (2019). Advances in bio-oil production and upgrading technologies. Sustainable Bioenergy, 167-198. DOI:10.1016/b978-0-12-817654-2.00006-x
  54. 54.Wigley, T., Yip, A. C. K., and Pang, S. (2017). A detailed product analysis of bio-oil from fast pyrolysis of demineralised and torrefied biomass. Journal of Analytical and Applied Pyrolysis, 123, 194-203. DOI:10.1016/j.jaap.2016.12.006
  55. 55.Xu, F., Ming, X., Jia, R., Zhao, M., Wang, B., Qiao, Y., and Tian, Y. (2020). Effects of operating parameters on products yield and volatiles composition during fast pyrolysis of food waste in the presence of hydrogen. Fuel Processing Technology, 210, 106558. DOI:10.1016/j.fuproc.2020.106558
  56. 56.Zhang, Z., Li, K., Ma, S., Cui, M., Lu, Q., and Yang, Y. (2019). Fast pyrolysis of biomass catalyzed by magnetic solid base catalyst in a hydrogen atmosphere for selective production of phenol. Industrial Crops and Products, 137, 495-500. DOI:10.1016/j.indcrop.2019.05.066
  57. 57.Wang, S., Persson, H., Yang, W., and Jönsson, P. G. (2018). Effect of H2 as pyrolytic agent on the product distribution during catalytic fast pyrolysis of biomass using zeolites. Energy and Fuels, 32(8), 8530-8536. DOI:10.1021/acs.energyfuels.8b01779
  58. 58.Mullen, C. A., Boateng, A. A., and Goldberg, N. M. (2013). Production of deoxygenated biomass fast pyrolysis oils via product gas recycling. Energy and Fuels, 27(7), 3867-3874. DOI:10.1021/ef400739u
  59. 59.Pala, M., Marathe, P. S., Hu, X., Ronsse, F., Prins, W., Kersten, S. R. A., Westerhof, R. J. M. (2020). Recycling of product gas does not affect fast pyrolysis oil yield and composition. Journal of Analytical and Applied Pyrolysis, 104794. DOI:10.1016/j.jaap.2020.104794
  60. 60.Fadillah, G., Fatimah, I., Sahroni, I., Musawwa, M.M., Mahlia, T.M.I., Muraza, O. Recent progress in low-cost catalysts for pyrolysis of plastic waste to fuels. Catalysts 2021, 11, 837. DOI:10.3390/catal11070837
  61. 61.Mertinkat, J., et al., 1999. Cracking catalysts used as fluidized bed material in the Hamburg pyrolysis process. Journal of Analytical and Applied Pyrolysis 49 (1-2), 87-95. DOI:10.1016/S0165-2370(98)00103-X
  62. 62.Onu, P., et al., 1999. Thermal and catalytic decomposition of polyethylene and polypropylene. Journal of Analytical and Applied Pyrolysis 49 (1), 145e153. DOI:10.1016/S0165-2370(98)00109-0
  63. 63.French, R., Czernik, S., 2010. Catalytic pyrolysis of biomass for biofuels production. Fuel Processing Technology 91 (1), 25e32. DOI:10.1016/j.fuproc.2009.08.011
  64. 64.Muhammad, C., Onwudili, J.A., Williams, P.T., 2015b. Thermal degradation of real-world waste plastics and simulated mixed plastics in a two-stage pyrolysisecatalysis reactor for fuel production. Energy and Fuels 29 (4), 2601e2609. DOI:10.1021/ef502749h
  65. 65.Carlson, T.R., Vispute, T.P., Huber, G.W., 2008. Green gasoline by catalytic fast pyrolysis of solid biomass derived compounds. ChemSusChem 1 (5), 397e400. DOI:10.1002/cssc.200800018
  66. 66.Mante, O. D., Dayton, D. C., Carpenter, J. R., Wang, K., and Peters, J. E. (2018). Pilot-scale catalytic fast pyrolysis of loblolly pine over γ-Al2O3 catalyst. Fuel, 214, 569-579. DOI:10.1016/j.fuel.2017.11.073
  67. 67.Veses, A., Aznar, M., Martínez, I., Martínez, J. D., López, J. M., Navarro, M. V., García, T. (2014). Catalytic pyrolysis of wood biomass in an auger reactor using calcium-based catalysts. Bioresource Technology, 162, 250 258. DOI:10.1016/j.biortech.2014.03.146
  68. 68.Yildiz, G., Pronk, M., Djokic, M., van Geem, K. M., Ronsse, F., van Duren, R., and Prins, W. (2013). Validation of a new set-up for continuous catalytic fast pyrolysis of biomass coupled with vapour phase upgrading. Journal of Analytical and Applied Pyrolysis, 103, 343-351. DOI:10.1016/j.jaap.2013.02.001
  69. 69.Jae, J., Coolman, R., Mountziaris, T. J., and Huber, G. W. (2014). Catalytic fast pyrolysis of lignocellulosic biomass in a process development unit with continual catalyst addition and removal. Chemical Engineering Science, 108, 33-46. DOI:10.1016/j.ces.2013.12.023
  70. 70.Xu, S., Cao, B., Uzoejinwa, B. B., Odey, E. A., Wang, S., Shang, H., Nwakaire, J. N. (2020). Synergistic effects of catalytic co-pyrolysis of macroalgae with waste plastics. Process Safety and Environmental Protection. DOI:10.1016/j.psep.2020.02.001
  71. 71.Du, S., Sun, Y., Gamliel, D. P., Valla, J. A., and Bollas, G. M. (2014). Catalytic pyrolysis of miscanthus × giganteus in a spouted bed reactor. Bioresource Technology, 169, 188-197. DOI:10.1016/j.biortech.2014.06.104
  72. 72.Onay, Ö. (2014). The catalytic co-pyrolysis of waste tires and pistachio seeds. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 36(18), 2070-2077. DOI:10.1080/15567036.2013.791900
  73. 73.Rutkowski, P. (2011). Pyrolysis of cellulose, xylan and lignin with the K2CO3 and ZnCl2 addition for bio-oil production. Fuel Processing Technology, 92(3), 517-522. DOI:10.1016/j.fuproc.2010.11.006
  74. 74.Lee, H.W., Choi, S.J., Park, S.H. et al. Pyrolysis and co-pyrolysis of Laminaria japonica and polypropylene over mesoporous Al-SBA-15 catalyst. Nanoscale Res Lett 9, 376 (2014). doi:10.1186/1556-276X-9-376
  75. 75.Aho, A., Kumar, N., Eränen, K., Salmi, T., Hupa, M., and Murzin, D. Y. (2008). Catalytic pyrolysis of woody biomass in a fluidized bed reactor: Influence of the zeolite structure. Fuel, 87(12), 2493-2501. DOI:10.1016/j.fuel.2008.02.015
  76. 76.Attia, M., Farag, S., Chaouki, J. Upgrading of oils from biomass and waste: Catalytic hydrodeoxygenation. Catalysts 2020, 10, 1381. DOI:10.3390/catal10121381
  77. 77.Shan Ahamed, T., Anto, S., Mathimani, T., Brindhadevi, K., and Pugazhendhi, A. (2020). Upgrading of bio-oil from thermochemical conversion of various biomass – Mechanism, challenges and opportunities. Fuel, 119329. DOI:10.1016/j.fuel.2020.119329
  78. 78.Gollakota, A. R. K., Reddy, M., Subramanyam, M. D., and Kishore, N. (2016). A review on the upgradation techniques of pyrolysis oil. Renewable and Sustainable Energy Reviews, 58, 1543-1568. DOI:10.1016/j.rser.2015.12.180
  79. 79.Pattiya, A., and Suttibak, S. (2017). Fast pyrolysis of sugarcane residues in a fluidised bed reactor with a hot vapour filter. Journal of the Energy Institute, 90(1), 110-119. DOI:10.1016/j.joei.2015.10.001
  80. 80.Chen, T., Wu, C., Liu, R., Fei, W., and Liu, S. (2011). Effect of hot vapor filtration on the characterization of bio-oil from rice husks with fast pyrolysis in a fluidized-bed reactor. Bioresource Technology, 102(10), 6178-6185. DOI:10.1016/j.biortech.2011.02.023
  81. 81.Pattiya, A., and Suttibak, S. (2012). Production of bio-oil via fast pyrolysis of agricultural residues from cassava plantations in a fluidised-bed reactor with a hot vapour filtration unit. Journal of Analytical and Applied Pyrolysis, 95, 227-235. DOI:10.1016/j.jaap.2012.02.010
  82. 82.Tran N, Uemura Y, Chowdhury S, Ramli A. A review of bio-oil upgrading by catalytic hydrodeoxygenation. AMM 2014;625:255-258. DOI:10.4028/www.scientific.net/amm.625.255
  83. 83.Oyedun, A. O., Patel, M., Kumar, M., and Kumar, A. (2019). The upgrading of bio-oil via hydrodeoxygenation. Chemical Catalysts for Biomass Upgrading, 35-60. DOI:10.1002/9783527814794.ch2
  84. 84.Zhao, Z., Situmorang, Y. A., An, P., Chaihad, N., Wang, J., Hao, X., Guan, G. (2020). Hydrogen production from catalytic steam reforming of bio-oils: A critical review. Chemical Engineering and Technology. DOI:10.1002/ceat.201900487
  85. 85.Zhang, Y., Brown, T. R., Hu, G., and Brown, R. C. (2013). Techno-economic analysis of two bio-oil upgrading pathways. Chemical Engineering Journal, 225, 895-904. DOI:10.1016/j.cej.2013.01.030

Written By

Vittor Rodrigues Santos Alves

Submitted: August 8th, 2021Reviewed: August 19th, 2021Published: December 3rd, 2021