Open access peer-reviewed chapter

Review Chapter: Waste to Energy through Pyrolysis and Gasification in Brazil and Mexico

By José Antonio Mayoral Chavando, Valter Silva, Danielle Regina Da Silva Guerra, Daniela Eusébio, João Sousa Cardoso and Luís A.C. Tarelho

Submitted: November 22nd 2020Reviewed: May 13th 2021Published: June 8th 2021

DOI: 10.5772/intechopen.98383

Downloaded: 70

Abstract

Millions of tons of forest residues, agricultural residues, and municipal solid waste are generated in Latin America (LATAM) each year. Regularly, municipal solid waste is diverted to landfills or dumpsites. Meanwhile, forest and agricultural residues end up decomposing in the open air or burnt, releasing greenhouse gases. Those residues can be transformed into a set of energy vectors and organic/chemical products through thermochemical conversion processes, such as pyrolysis and gasification. This book chapter provides information on current examples of gasification on large scale in the world, which typically operate at 700°C, atmospheric pressure, and in a fluidized bed reactor. The produced gas is used for heat and energy generation. Whereas pyrolysis at a large scale operates around 500°C, atmospheric pressure, and in an inert atmosphere, using a fluidized bed reactor. The produced combustible liquid is used for heat and energy generation. The decision of using any of these technologies will depend on the nature and availability of residues, energy carries, techno-socio-economic aspects, and the local interest. In this regard, the particular situation of Brazil and Mexico is analyzed to implement these technologies. Its implementation could reduce the utilization of fossil fuels, generate extra income for small farmers or regions, and reduce the problem derived from the accumulation of residues. However, it is concluded that it is more convenient to use decentralized gasification and pyrolysis stations than full-scale processes, which could be an intermediate step to a large-scale process. The capabilities of numerical models to describe these processes are also provided to assess the potential composition of a gas produced from some biomass species available in these countries.

Keywords

  • Gasification
  • Pyrolysis
  • biomass
  • MSW
  • RDF

1. Introduction

LATAM has a rising renewable energy market, where more than a quarter of its primary energy is generated from renewable sources, twice the world average [1]. Across the continent, hydropower plays a pivotal role in the energy sector. However, LATAM has also access to biomass resources, which may enable the production of bioenergy, providing the opportunity to exploit a domestic, low carbon, and sustainable energy source, strengthening the renewable energy sector, and generating profits in rural areas. Table 1 shows the renewable power capacity, considering the maximum net generating capacity of power plants and other installations that use renewable energy sources to produce electricity in LATAM. This information is also available for the European Union (EU), and the world to highlight where LATAM is in terms of renewable energy. It is interesting to notice Brazil’s share of renewable energy production in LATAM is ∼55%, from which ∼78% comes from hydropower and ∼10% from bioenergy. In contrast with the EU, whose hydropower represents ∼36%, and bioenergy ∼18%. On the other hand, Mexico’s renewable energy in LATAM share is 6%.

RegionTotal Renewable energyHydropowerWind EnergySolar EnergyGeothermal EnergyBioenergy
Cap.(MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018Cap. (MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018
BR141,933495,945109,092388,97115,36448,489248539870014,99254,498
MX25,64854,77012,67132,526659112,87744401363936 o537510102628
VE16,59825,27816,52125,1837188560000
CO12,37558,43311,92756,66118439014003401715
AR12,77642,50111,31439,9571609141344110840 o2142981846
CL11,48838,515667923,3671620358826485218005026128
PY882259,912881059,21100000022701
PE664033,483571530,731372150232679700186452
EC527921,224507920,6782180283800152428
UY377214,2341538655715214732258415004252529
BO103629677362612275912012700154169
CAM*15,69147,658814729,1601942583822182625722396926636066
Lat262,058894,920198,229715,61429,15678,70913,05914,6981698955820,74477,160
EU497,2671,052,187156,412379,820191,277377,494132,500128,358916676541,179188,053
W**2,532,8666,586,1241,307,9944,267,085622,4081,262,914584,842562,03313,90988,408124,026522,552

Table 1.

Renewable Energy in LATAM [2].

In refers to central America and the Caribbean area.


World.


Note: Numbers followed by the letter “o” are figures that have been obtained from official sources such as national statistical offices, government departments, regulators, and power companies. The letter “u” follows figures that have been obtained from unofficial sources, such as industry associations and news articles. The letter “e” follows figures that have been estimated by IRENA from a variety of different data sources. All figures from the IRENA questionnaire are presented without any indicator.

Renewable energy production in Brazil accounts for ∼82.63% [3]. Brazil relies on hydroelectricity for 65% of its electricity, and it plans to expand the ∼6% share for biomass and wind energy [4]. While renewable energy production in Mexico is around 16.92% [3]. Without a doubt, Mexico has lagged in the development of renewable energy, comparing with other LATAM countries.

Although LATAM has been a remarkable positive development in renewable energies, the energy demand is increasing at the time, similarly to the impacts of climate change derived from the overconsumption of fossil fuels. Thus, it makes sense today more than ever to take advantage of LATAM’s potential for producing bioenergy. Table 2 shows the production and capacity of the different solid biofuels and renewable waste to produce bioenergy, where bagasse is the main solid biofuel source to produce bioenergy. Brazil is a key player having a 70% share of the total bioenergy production from solid biofuels and renewable waste, occupying first place in LATAM. Regarding renewable municipal waste as a source to produce bioenergy, Martinique is the only one that utilizes them. This situation can be seen as a wise and potential solution to deal with the problems that municipal solid waste (MSW) in landfills and open dumps areas bring out. Therefore, it could be produced a refuse-derived fuel (RDF) to produce bioenergy through gasification or pyrolysis as some developed countries are already doing it at a large-scale, adding value to a material that has no other valorization option and is disposed of in landfills.

RegionTotal Solid Biofuels and Renewable WasteRenewable Municipal Solid WasteBagasseOther Solid Biofuels
Cap.(MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018Cap.(MW) 2019Prod. (GWh) 2018
BR14,67053,3640011,462 o35,435 o319517,928
MX811236800791 e177021598
VE00000000
CO336171100336 e171100
AR25417010056 o3511981350
CL442605900004426059
PY207000020 e70000
PE1754020017540200
EC14438200144 o382 o00
UY42324820010 e184132464
BO14916800149 o168 o00
CAM*262059376232509559910315
Latam**20,04475,27462315,59646,536427928,714
EU26,051122,078466422,96915531821,22898,680
W***101,426426,83014,51862,14819,07055,35567,702309,214

Table 2.

Solid Biofuels and Renewable Waste [2].

In refers to central America and the Caribbean area.


World.


From Martinique.


Note: Numbers followed by the letter “o” are figures that have been obtained from official sources such as national statistical offices, government departments, regulators, and power companies. The letter “u” follows figures that have been obtained from unofficial sources, such as industry associations and news articles. The letter “e” follows figures that have been estimated by IRENA from a variety of different data sources. All figures from the IRENA questionnaire are presented without any indicator.

Other materials that need better valorization are the biomass residues from agricultural and forestry activities (agroforestry residues) since they are sometimes burnt in the field, causing a range of health issues and significantly raise pollution levels [5]. Similar to Municipal Solid Waste (MSW), agroforestry residues can turn into alternative products. For example, briquettes and pellets made from those residues can partially replace coal in thermal power plants.

Together, RDF and agroforestry residues can be used to generate a set of energy vectors and organic products in LATAM, implementing pyrolysis and gasification at a large-scale, like some countries in the world are already doing. Those products can be used in distinct applications to partially replace fossil fuels. This strategy can add value to the solid waste management sector and the agriculture sector. In this regard, Section 2 presents how some companies in the world utilize pyrolysis and gasification on a large-scale, and Section 3 shows the feedstock availability in Brazil and Mexico, as well as a brief analysis of the current situation in bioenergy in these countries. Section 4 shows an Experimental and Numerical Analysis of two important biomasses in Brazil and Mexico (Wood and coffee husk). Section 5 analyzes the viability of these technologies in Brazil and Mexico. Finally, the conclusion will present, highlighting the main remarks.

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2. Large-scale pyrolysis and gasification process

Pyrolysis and gasification are thermochemical conversion processes like combustion, where biomass is broken down into smaller hydrocarbon chains by applying heat and chemical interactions. Unlike combustion that only produces heat, pyrolysis and gasification produce components that can be turned into higher-value commercial products, for example, transportation fuels, chemicals, and fertilizers [6]. Below is a brief description of each technology.

  • Combustion: it burns biomass directly with excess oxygen at 800 to 1000°C. It generates heat to be transformed into mechanical power and produce electricity. It is already a well-known commercial technology and broadly accessible at domestic and industrial scales [7].

  • Gasification: it transforms biomass into a combustible gas mixture throughout partial biomass oxidation. It operates normally at temperatures from 700 to 900°C [7].

  • Pyrolysis: it is the thermal destruction of biomass in the absence of air/oxygen. Pyrolysis of biomass starts at 350 to 500°C and can go to 700 °C, producing bio-oil, gases, and char [7].

These three technologies have not only different operating conditions but also different products, as is described in Figure 1.

Figure 1.

Biomass thermal conversion adapted from [8,9].

The oldest thermochemical conversion process to produce energy is certainly biomass combustion. Besides, it is the most dominant process in the thermochemical conversion field. However, pyrolysis and gasification are two promising technologies since their products can be transformed into multiple energy vectors and some chemicals. In fact, some companies already commercialize these technologies on a large-scale to produce power and heat mainly. The following section presents some of those companies and their general process to transform different kinds of biomass into power and heat.

2.1 Large-scale fast pyrolysis

The main objective of fast pyrolysis is to produce bio-oil, which can be utilized as a replacement for fossil fuels in energy production, and transport. Bio-oil is a complex mixture of organic fuels containing some water and a small amount of fine carbon [10]. It aims to mobilize biomass into the energy sectors (heat, power, and transport). It is more manageable to transport and handle, and more cost-effective than solid wood-based fuels or biomass, to be successfully commercialized, its characteristics should follow the ASTM D7544–09 and EN16900/2017 standards. Table 3 presents the main physical and chemical requirements for bio-oils produced from biomass [12].

PropertyUnitTest MethodRequirement
LHVMJ/kgASTM D24015 minimums
Solid contentMass %ASTM D75442.5 maximum
Water contentMass %ASTM E20230 maximums
AciditypHASTM E704.1
Kinematic viscositycSt (40 °C)ASTM D445125 maximums
Densitykg/dm3 (20 °C)ASTM 40521.1–1.3
SulfurMass %ASTM 42940.05
Ash contentMass %ASTM 4820.25

Table 3.

Main physical and chemical requirements for bio-oils produced from biomass [11].

Bio-oil production on a large-scale involves multiple processes, working together to set up a functional bio-oil refinery. The heart of bio-oil production is in the fast pyrolysis process, where pre-treated biomass is converted into bio-oil. Pre-treated biomass has basically (1) appropriate particle size (<5 mm) and (2) proper moisture content (<10% w) [13]. Then it is fed into the reactor (approximately 500°C), causing the biomass to become a gas. This process occurs in nearly oxygen-free conditions to prevent combustion. The resulting gas enters a cyclone, where carbon and other solids are mechanically separated from the gas flow. Then, the gas passes through a condenser system, where it cools down and condenses into bio-oil, then it is filtered. Finally, non-condensable gases are used to produce heat [13].

According to The Green Fuel Nordic company, Bio-oil can be used as a replacement for fossil fuels in the energy production, and transport sector [11]. Furthermore, bio-oil can be transformed into high value-added products like chemical compounds, food ingredients, cosmetics compounds, etc. Table 4 presents large-scale fast pyrolysis examples in different countries, where the produced bio-oil is used to produce transport fuels, electricity, and heat or to be refined, as appropriate in each case.

CountryREFCompany/entityTechnology/InformationProductBiomassFor ProducingFeed rate/ProductionStatus
SE[14]Pyrocell-SetraBTG-BTL
Rotating cone
Bio-oilSawdustTransportation fuels40,000d ton/year of biomassConstruction
Start:2021
FI[15, 16]Green Fuel NordicBTG-BTL
Rotating cone
Bio-oilWoodElectricity and heat24,000 ton/y of bio-oilOperational
2020
CA[17]EnsynEnsyn Fluid bed/riserBiocrudeWoodHeat & refinery65,000d ton/y of biomassOperational
NL[18]Twence / Twence / EMPYROBTG-BTL
Rotating cone
Bio-oilWoodElectricity
450 GWh
-Operational
USA[19]Ensyn and Renova Capitacirculating fluidized bed reactorBio-oilWood residuesTo refinery76 ML/yTo Start-up
USA[20]Biogas EnergyAblative reactorBio-oilWood and agricultural residuesIntermediate fuels500 kg /h of biomassOperational
IE[21]Kerry Group PLCRTP (Ensyn)BiocrudeWood residuesFood ingredients30–40 tons/d of biomassOperational
DE[22]KITTwin-screw mixing reactorBiosyncrudeWheat StrawIntermediate fuel500 kg/hr. of biomassOperational
FI[23] [24]Fortum - ValmentFluid bed (VTT)Bio-oilWood residuesElectricity and heat50,000 ton/y bio-oilOperational
BZ[25]Ensyn, Suzano S.Acirculating fluidizedBio-oilEucalyptus forest residues83 ML/yDetailed engineering
underway
CH[26]Shanxi Yingjiliang Biomass Companycirculating fluidized bed reactorBio-oilRice Husk2–6 MLOperational
IN[27]MASH EnergyBio-oilWaste materials

Table 4.

Large-scale Fast Pyrolysis Examples.

d: dry.

A successful example of a bio-oil refinery is Green Fuel Nordic company, whose business model is based on utilizing pyrolysis technology to produce an advanced bio-oil. Then this bio-oil is commercialized and send to its customers like the Savon Voima heating plant to produce heat [16]. Another successful and profitable example is Fortum company, which is a Finnish company that invested €30 million in its bio-oil plant in Joensuu, receiving about €8 million in government investment subsidies for new technology demonstration [13]. This company signed a contract to supply bio-oil produced in Joensuu to Savon Voima, which uses bio-oil to replace the use of heavy and light fuel oil in its district heat production in Iisalmi [13]. In December 2019, Fortum signed an agreement to sell its district heating business in Joensuu Finland to Savon Voima Oyj. The contract concluded in January 2020, registering a tax-exempt capital gain of €430 million in the City Solutions segment’s first-quarter 2020 results [28].

The integrated Coal handling plant (CHP) in Joensuu was constructed in 2012 and began full operation in 2015, producing heat, electricity, and 50,000 tons of bio-oil (maximum planned capacity per year). The process consists of a fluidized bed boiler that supplies heat for the pyrolysis reactor and burns the coke, biochar, and non-condensed gases produced during the pyrolysis process to produce electricity and heat (See Figure 2). In such a way, high efficiency can be reached for the pyrolyzed fuel production process. Additionally, when a fluidized bed boiler is integrated, pyrolysis is a cost-efficient way of producing bio-oil to replace fossil oils.

Figure 2.

Large-Scale Fast Pyrolysis Process (Valmet) adapted from [13].

It is also interesting to notice that Brazil has already taken a leading role in LATAM with the partnership 50/50 between Ensyn and Suzano to produce 2 million gallons/year of Ensyn biocrude. The project is located at Suzano’s pulp facilities at Aracruz city, in the State of Espirito Santo, Brazil. The company derivated from this partnership (NYSE: SUZ) is now the world’s largest eucalyptus pulp company in America Latina [25].

These success cases seem to support the pyrolysis of biomass as a wise way to reduce the use of fossil fuels, adding value to biomass and contributing to mitigate the impact of greenhouse gases without losing sight of profitability. Applying technologies might make sense to countries with a bast biomass availability. However, as in any process, it is necessary to evaluate the performance of the process to look for continuous improvements. The following section contains some of these performance parameters.

2.1.1 Pyrolysis performance

Pyrolysis is a thermochemical cracking process in which organic material is transformed into a carbon-rich solid and volatile matter (gas and liquids) by heating in the absence of oxygen as Eqs. (1)-(4) describe [29].

BiomassChar+Ash+Moisture+VolatileC0CO2CH4C2H4H2OE1
BiomassMolecule2RInitiationE2
RnOj+RnjPropagationE3
2RProductsTerminationE4

Eq. (1) is the general pyrolysis reaction. The other reactions represent the thermal cracking process, where Rnis a free radical with a chain length n. Ojis an alkene from olefins with a chain length j [29].

Pyrolysis temperature ranges from 350 to 600°C and it plays a critical role in the cracking process since, at higher temperatures, molecules move violently, which causes the breaking of shorter chains from the main C-C chain. Therefore, shorter hydrocarbon products are favored as in fast pyrolysis or gasification. While biochar is boosted under low temperatures and large residence times as in slow pyrolysis [29].

General measures of performance are often quoted as measures of how effective a given pyrolysis scheme may be. These parameters can be oriented to a mass balance and an energy balance.

2.1.1.1 Product yields

Some parameters can affect the product yield of pyrolysis, such as temperature, particle size, heating rate, etc. If the desired product is liquid, then producing more liquids will indicate a more effective process. While, if the desired product is solid, then producing more solids will indicate a more effective process. Eqs. (5)-(8) describe the pyrolysis yield calculations.

mF=msolid+mgas+mliquidE5
Ysolid=msolidmF100E6
Ygas=mgasmF100E7
Yliquid=mliquidmF100E8

where mFrepresents the feedstock mass, msolidis the solid mass, mgasis the gas mass, mliquidis the liquid mass, mFis the feedstock mass, Ysolidis the solid yield, Ygasis the gas yield, and Yliquidis the liquid yield.

2.1.1.2 Lower heating value (LHV)

The lower heating value of the products is determined by the contribution of each of the compounds contained in a specific phase. This parameter is important because it indicates the amount of energy contained in the products. The LHV of the gas, liquid, and solid yield is calculated as the following equations describe.

LHVgas=yigasmiLHVimgasE9
LHVliquid=yiliquidmiLHVimliquidE10
LHVsolid=yisolidmiLHVimsolidE11

where yigasis the mass fraction of the component “i” in the gas, yiliquidis the mass fraction of the component “i” in the liquid, yisolidis the Mass fraction of the component “i” in the solid, miis the mass of the component “i”, msolidis the solid mass, mgasis the gas mass, mliquidis the liquid mass, LHViis the LHV of the component “i”, LHVgasis the LHV of the gas, LHVliquidis the LHV of the liquid and LHVsolidis the LHV of the solid.

2.2 Large-scale gasification

Similar to pyrolysis on large-scale, gasification on a large-scale involves other processes working together. The main product of gasification is combustible gas. But unlike pyrolysis, the main product is not stored and then transported to be used somewhere else but used in the same facilities where it was produced. Even so, gasification offers great benefits, namely reducing CO2 emissions for replacing fossil fuels and avoiding their extraction. Another benefit is that gasification can use materials that currently have no other valorization option but to be disposed of in landfills. Waste gasification provides much better electrical efficiency compared with the direct combustion of waste [30].

A perfect successful gasification example is its integration with an existed coal-fired plant in Vaskiluodon Voima Oy, Vaasa, Finland. This integration of gasification into the coal-fired facilities had several advantages, such as the investment cost was kept to about one-third of a similar-sized new biomass plant, it was also kept the full original coal capacity, and the use of coal was cut off by 40% by using local biomasses like wood, peat, and straw [31]. The Plant generates 230 MW electricity and 170 MW district heating.

Another example is ThyssenKrupp, whose main product is syngas, which can be used in multiple processes. While its byproducts are slags, ash, and sulfur components. These byproducts can be employed in road building, cement industry, or recovered [32]. The typical gas composition is CO + H2 > 85 (vol.%), CO2 2–4 (vol.%), and CH4 0.1 (vol.%) [32].

More examples of large-scale gasification in the world are provided in Table 5, where one can notice several examples are using materials like MSW, plastics, and solid recovered fuels (SRF). The resulting gas is being used to produce heat and electricity.

CountryREFCompany/entityTechnology/InformationBiomassFor ProducingFeed rate/Production (ton/day)Status
USA[33]Energy Products of Idaho*Bubbling bed1040
DE[34]HTW-Plant Berrenrath / GermanyThyssenKrupp Fluidized-BedHigh-ash coalmethanol25 ton/hShut down
1986–1997
FI[35]Kemira OyThyssenKruppPeatNH330 ton/h PeatShut down
1988–1991
FI[36] [37]NSE Biofuels Oy Ltd.Sumitomo heavy industries ltd
CFB
Wood residuesHeat
12 MWth
Start-up 2009
FI[38]Corenso United Ltd.Sumitomo heavy industries ltdPlastic Waste50 MWthStart-up 2000
BE[39]ElectrabeSumitomo heavy industries ltdWood residuesHeat
50 MWth
Start-up 2002
JP[40]HTW-PreconThyssenKruppMSW48 ton/dayStart-up 1999
FI[41]Lahti Energia Oy,Valmet
CFB
SRF160 MW250,000 ton/yStart-up 2012
FI[31]Vaskiluodon Voima OyValmet
CFB
Wood, peat, and straw230 MW electricity
170 MW heating
Start-up 2012
FI[42]RENUGASANDRITZ Carbona Bubbling Fluidized Bed (BFB)Wood pellets, or chip100–150 ton/dayStart-up 2013
SE[43]GoBiGasValmet
CFB
Wood residues20 MWStart-up 2013
ID[44]OKI Pulp & PaperValmet
CFB
Bark and wood residues110 MW X2Start-up 2017
USA[45] [46]Taylor Biomass EnergyDual bedMSW300–400 ton/day2021
UK[47] [48]Amec Foster WheelerVESTA patented technologyCoal, biomass, waste250,000 Nm3/h of Sin gas

Table 5.

Large-Scale Gasification Examples.

It was bought by Outotec.


ThyssenKrupp facilities have a feed dust system, so the biomass must be smaller than 0.1 mm. Then, biomass is gasified using oxygen and steam as gasification agents. The operational temperature is higher than the ash melting temperature to remove ash as slag. While the pressure is around 40 bar. The technology has multiple, horizontally arranged burners to provide heat to the gasifier and produce steam in a drum boiler (see Figure 3) [32].

Figure 3.

Large Scale Gasification Process (Thyssenkrup PRENFLO), adapted from [32].

On the other hand, Figure 4 presents the Valmet equipment that has a screw feeder system, so it allows biomass with higher particle size, it also has a cyclone, which separates solids from the gas. After the cyclone, the gas goes through a gas cleaning system, delivering a clean gas, which enables the production of high pressure and temperature steam for the turbine without risk of boiler corrosion. In Lahti, the electrical efficiency is over 30% (540°C and 120 bar). Furthermore, this plant operates with RDF (250,000 ton/y) and wood, producing 2 x 80 MW hot gas cleaning [50]. VASKILUODON VOIMA OY (formerly Fortum) produces 230 MW electricity and 170 MW district heating, by integrating the gasification capability with the original coal-fired plant. The biomass gasification plant contributes 140 MW and a woodchip dryer. The gas produced in the gasifier and coal enters a circulating fluidized bed boiler, where hot water is transformed into steam, that goes to high-pressure superheaters and then continues to the high-pressure turbine (HPT). From HPT, the steam returns to the boiler’s preheaters and ends in the intermediate-pressure turbine (IPT). Here the steam is divided into different streams (1) district heat exchangers, (2) storage water tank to preheat it, and (3) the low-pressure turbine (LPT), where steam rotates the turbine’s rotor, and a generator produces electricity for the electrical network. Finally, the gas resulting from the combustion goes to the flue-gas desulphurization, the cleaning process creates gypsum.

Figure 4.

Pioneer of Biofuel Plants, Producer of Combined Heat and Power adapted from [49].

The gasification process is a potential solution to deal with problems linked to MSW, plastics, and other residues, producing energy vectors at the same time. This could be a massive opportunity for LATAM countries that are dealing with exorbitant amounts of waste. Similar to pyrolysis, the gasification performance can be evaluated for a continuous improvement process.

2.2.1 Gasification performance

Gasification is a partial oxidation process in which organic material is transformed mainly into gases through heterogeneous (Eqs. (12)-(16)) and homogeneous reactions(Eqs. (17)-(21)), as the following reactions describe.

C+O2CO2E12
C+CO22COE13
C+CO22COE14
C+H2OCO+H2E15
C+2H2CH4E16
CO+0.5O2CO2E17
H2+0.5O2H2OE18
CH4+2O2CO2+2H2OE19
C2H4+O22CO+2H2E20
CH4+2H2OCO+3H2E21

The temperature in the gasification ranges between 600 and 700°C and plays an important role in the product yields and gas composition [51]. Besides, the product yields and LHV of the products exist another parameter to evaluate the performance of the gasification process like Cold Gas Efficiency (CGE) and Gas Efficiency (Ygas).

2.2.1.1 Cold gas efficiency (CGE)

Cold gas efficiency is the output energy by input energy [52], and it can be described mathematically with the following equation:

CGE=LHVgasmgasLHVFmF100%E22

where CGEis the cold gas efficiency, LHVFis the lower heating value of the feed stream, LHVgasis the lower heating value of the gas mixture, mgasis the mass of the gas mixture, and mFis the mass of the feed stream.

2.2.1.2 Gas efficiency (ygas)

Y gas can be also described as the ratio of the produced gas volume by the feedstock mass as the following equation expresses:

ygas=VgasmFE23

where mFis the mass of the feed stream and Vgasthe volume of the gas mixture.

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3. Biomass availability in Brazil and Mexico and potential analysis

Biomass is a renewable organic material that serves as a sustainable source of energy to produce electricity or other forms of power. Some of the drivers to utilize it are lowering fossil-fuel utilization, decreasing greenhouse gas (GHG) emissions, and promote economic development and agricultural development. The following sections briefly describe the potential of Brazil and Mexico for bioenergy production using agroforestry residues and MSW.

3.1 Brazil

Brazil has an electrical matrix of predominantly renewable origin with an emphasis on the water source. Renewable sources account for 82.9% of the domestic supply of electricity in Brazil, which is the result of the sum of the amounts referring to domestic production plus imports distributed as 64.9% hydro, 8.6% wind, 8.4% biomass, and 1% solar [49]. The energy production from fossil fuels accounted for 17.1% of the national total, which 2.0% oil products, 2.5% nuclear, 9.3% natural gas, and 3.3% charcoal. This distribution represents the structure of the domestic supply of electricity in Brazil in 2019 [53].

The energy needed to move the economy of a region in a period, Internal Energy Supply in 2019, was 294 million toe (tons of oil equivalent) or Mtoe. Looking specifically the renewable sources, they increased by 2.8% in 2019 compared to 2018, that was supported by a strong increase in the production of sugarcane products with 5.5% in ethanol, adding the increase of wind, solar, and biodiesel with 4.4% [54], as shown in Table 6.

The choice for the energy matrix also relates to the system costs and regional conditions. For agro-industrial regions, biomass can be a viable raw material to produce clean and renewable energy, at the same time is a form to minimize the environmental impacts of agro-industrial production. In the Brazilian energy matrix, the types of biomass most used are from sugar cane and its products, firewood, black liquor, and rice husks. Considering the energy matrix in Brazil, a general view of the installed potency is shown in Table 7, the installed capacity of electricity generation by source in MW, and the evolution from 2015 to 2019 [53].

3.1.1 Forestry residues

Brazil is a forest country with hectares (59% of its territory) of natural and planted nearly 500 million forests [55], representing the second largest forest area in the world with 502,082.1 (1000 ha) [55], only surpassed by Russia [56]. The distribution area is 57.31% in natural forests and 1.16% in planted ones [56].

Brazil has around 10 million hectares of forest plantations, mainly with species of Eucalyptus and Pinus genera, which represent 96% of the total area. Forest plantations amount to 1.2% of Brazil’s area, and 2.0% of the total forest areas. The composition of forest plantations in 2018 was 7,401,334 ha of Eucalyptus, 2,030,419 ha of Pinus, and 407,933 ha of other species [56] including rubber, acacia, teak, and parica.

The industrial sector of forest plantations is based on the cultivation of trees for industrial purposes, generating a variety of products numbering nearly five thousand, including lumber, pulp, paper, flooring, wood panels, and charcoal [57]. Figure 5 presents the area of planted trees in 2019, by state and by genus (in millions) [57].

Figure 5.

Area of Planted Trees in Brazil in 2019, by state and by genus (in millions) [56].

According to the Food and Agriculture Organization of the United Nations, FAO, in 2019 the generated wood residues in Brazil were 19,140,000 m3 [58]. Concerning the management of industrial and forest waste, the Brazilian planted tree sector has adopted sustainable practices to dispose of various types of domestic and urban waste generated during its production processes.

As shown in Table 8, in 2019 most of the waste from factories and forest companies was directed toward energy generation, approximately 67%. In the second place, 12% of waste was directed to other industrial sectors for reuse as a raw material. Of the total waste generated before consumption, 7.4% was kept in the field to protect and enrich the soil, 4.2% was sent to landfills, and 3.4% was recycled [57].

DescriptionProduction (ktoe)Increase or retraction %Production (%)
2018201920182019
Non-renewable157,972158,3950.354.553.9
Petroleum and derivatives99,627101,0511.434.434.4
Natural gas35,90535,909012.412.2
Mineral coal and derivatives16,41815,480−5.75.75.3
Uranium (u3o8) and derivatives4174417401.41.4
Other non-renewablea18481780−3.70.60.6
Renewable131,898135,6422.845.546.1
Hydraulics and electricity36,46036,364−0.312.612.4
Firewood and charcoal25,51125,7250.88.88.7
Sugar cane derivatives50,09052,8415.517.318
Other renewablesb19,83720,7124.46.87
TOTAL289,870294,0361.4100100
of which fossils153,798154,2210.353.1

Table 6.

Internal Energy Supply (OIE) [54].

Blast furnace, melt shop, and sulfur gas.


Black liquor, biodiesel, wind, solar, rice husk, biogas, wood waste, charcoal gas, and elephant grass.


Plants in operation20152016201720182019
UHE / Hydro86.36691.49994.66298.287102.999
PCH / Hydro4.8864.9415.0205.1575.291
CGH / Hydro398484594695768
EOL / Wind7.63310.12412.28314.39015.378
SOL / Solar21249351.7982.473
TermoTotal39.56441.27541.53740.52341.219
Biomass13.25714.14714.50514.79014.978
Bagasse10.57310.97911.15811.36811.438
Others2.6843.1683.3473.4223.540
Biogas84119135140186
Elephant Grass3266323232
Charcoal5154434348
Rice Peels4545454553
Charcoal Gas112115114128128
Black-Liquor1.9232.3332.5432.5562.544
Vegetal Oil274444
Wood Residue409432431474544
Fossil24.96125.55025.45324.12724.642
Steam Coal3.3893.3893.3242.8583.228
Refinery Gas316316316320320
Natural Gas12.42812.96512.98013.35913.385
Fuel Oil3.1974.0204.0563.3633.316
Diesel Oil5.6324.8254.7374.1864.353
Viscous Oil
Others135414140
Industrial Effluent1.3461.5781.5791.6061.599
Gaseous Effluent216017617217266
Sulfur7171717179
Blast Furnace Gas216422422417512
Process Gas674654658721715
Steel Gas225255255225226
Unknown sources92
Nuclear1.9901.9901.9901.9901.990
Total140.858150.338157.112162.840170.118

Table 7.

Installed Capacity of Electricity Generation by Source [53].

Includes TAR.


Includes heat of the process (Table in MW).


Waste generated during the production process% of tons by type of waste, by destinationFinal destination
Bark, branches, leaves, lime sludge, boiler ash, others7.4%kept in the fields to protect and fertilize the soil, composted
Drags and grits, sludge, ash, metal scrap, plastic, cardboard, etc.3.4%recycling
Bark, branches, leaves, woodchips, sawdust, black liquor66.6%energy generation
Sawdust, paper scraps, lime sludge, and boiler ash0.7%reused as raw materials by companies in the planted tree sector
Sawdust, paper scraps, lime sludge, and boiler ash11.7%reused as raw materials by other industrial sectors
Paper scraps, lime sludge, non-hazardous wastes, others4.2%sent to landfills
Bark, sawdust, sludge/filtrate from water treatment plants, knots, and rejects from fiber lines0.7%sold or shipped to various companies
Various types of waste already described above and other non-specified5.3%other destinations, including co-processing

Table 8.

Solid Waste Generated by Type, According to Final Destination, in % of Total Waste [57].

3.1.2 Agricultural residues

Agricultural occupation in Brazil is estimated at 65.91 million hectares, equivalent to 7.8% of the national territory [59], the numbers show that Brazil uses 7.57% of its territory for crops. This area also corresponds to only 3.41% of the cultivated area worldwide.

Agroindustry waste generation in Brazil is spread off in all the country states from North to South regions, is from various crops, varies with seasonality, and represents a huge amount. The availability of the main selected products from agricultural residues, animal waste, and its respective analyses as to generation potential was determined [60]. The main selected products are analyzed from the point of view of Brazil’s economy and about the necessary conditions for the rural producer to keep up with sustainable growth. Table 9 presents the most common and produced agricultural residues [60].

FeedstockAbbreviationGenerating potential index -GPa (tons/total residues - tons/total wasteb)
Sugar caneSC0.22 t TR/SC
SoybeanSO2.05 t TR/SO
Maize (corn)MI1.42 t TR/MI
Rice (straw)RI1.49 t TR/RI
Cotton (Perennial)CO2.95 t TR/CO
Orange - 100OG0.50 t TR/OG
Wheat −70WH1.42 t TR/WH
Cassava - 100CA0.20 t TR/CA
TobaccoTO0.75 t TR/TO

Table 9.

Estimates of generating potential index (GP) for agricultural residues and animal waste in Brazil [60].

Generating potential index GP (Tons/culture).


GP Index abbreviation: TR= Total Residue: TW= Total waste.


Brazil stands out as a major biomass generator, the mass supply of biomass in 2005 was 558 million tons, with a projected growth to 1402 million tons in 2030 [53]. Table 10 shows the evolution of mass supply per agricultural residue, agro-industrial, and forestry residues.

Residue20052010201520202030
Total55873189810581402
Agricultural Residues4786337689041196
Soybean185251302359482
Maize (corn)176251304361485
Rice (straw)5759626669
sugar cane6073100119160
Agro industrial waste8098130154207
Bagasse sugar cane587097115154
Rice (Husk)22333
Black Liquor1317212534
Wood68101216
Energy Forests1330314346
Super plus Wood1330314346

Table 10.

Mass supply of biomass by agro-industrial agricultural waste and forestry (millions of tons) [61].

Biomass availability is a key aspect of bioenergy. The total bioenergy supply in 2019 was 93.9 Mtoe (1824 thousand bop/day), corresponding to 31.9% of the Brazilian energy matrix. Sugarcane products as bagasse and ethanol with 52.8 Mtoe, accounted for 56.3% of bioenergy and 18% of the matrix. Firewood, with 25.7 Mtoe, accounted for 27.4% of bioenergy and 8.7% of the matrix.

Other bioenergy (black liquor, biogas, wood residues, residues from agribusiness, and biodiesel), with 15.3 Mtoe, accounted for 16.3% of bioenergy and 5.2% of the matrix [49]. Tables 11 and 12 show the energy supply and consumption by sugarcane products: sugarcane bagasse as input for electricity generation and sugarcane juice for alcohol production [50].

Flow20152016201720182019
Production162.6168.6165.6157.8162.2
Total consumption162.6168.6165.6157.8162.2
Transformation*28.028.728.928.529.3
Final consumption134.6139.9136.8129.3132.9
Final energy Consumption134.6139.9136.8129.3132.9
Energy sector61.857.556.067.171.1
Industrial72.882.480.862.161.9
Chemical0.00.00.00.00.0
Foods and beverages72.782.380.662.061.7
Paper and pulp128.0141.0146.0157.0147.0
Others0.00.00.00.00.0

Table 11.

Sugar Cane Bagasse [53].

Input for alcohol production (Table in 103 ton).


Flow20152016201720182019
Production209.3183.7179.9243.1260.5
Total Consumption209.3183.7179.9243.1260.5
Transformation*209.3183.7179.9243.1260.5

Table 12.

Sugar Cane Juice [53].

Input for alcohol production (Table in 103 ton).


3.1.3 Municipal solid waste residues

Between 2010 and 2019, the generation of MSW in Brazil registered a considerable increase, going from 67 million to 79 million tons per year (in 2020). In Brazil, most of the collected MSW goes to disposal in landfills, having registered an increase of 10 million tons in a decade, going from 33 million tons per year to 43 million tons. On the other hand, the amount of waste that goes to inadequate units (dumps and controlled landfills) has also grown, from 25 million tons per year to just over 29 million tons per year [62].

It should be noted, in Figure 6, that the organic fraction remains the main component of MSW, with 45.3%. Dry recyclable waste, on the other hand, adds up to 35% being mainly composed of plastics (16.8%), paper and cardboard (10.4%), in addition to glass (2.7%), metals (2.3%), and multilayer packaging (1.4%) [58]. The tailings, in turn, correspond to 14.1% of the total and mainly contemplate the sanitary materials. As for the other fractions, we have textile waste, leather, and rubber, with 5.6%, and other waste, also with 1.4%, which contemplate various materials theoretically reverse logistics objects [62].

Figure 6.

Gravimetry of MSW in Brazil [62].

The national gravimetry, in Figure 6, was estimated based on the weighted average of the total generation of MSW by income bracket of the municipalities and their respective gravimetry, considering the population and generation per capita.

It is possible to estimate the economic development of a country by analyzing the physical composition of its MSW. In general, the greater the income of a country the higher the consumption and, therefore, the amount of waste generated [63]. The physical compositions of MSW from towns in different regions of Brazil are shown in Table 13 [63].

RegionsNortha (%)North-eastb (%)Mid-westc (%)South-eastd (%)Southe (%)Brazilf (%)
MSW
Organic matter54.6857.0054.0252.0057.2751.4
Recyclables27.4610.3129.7241.7026.8731.9
Metal1.091.743.641.661.462.9
Paper and cardboard10.873.77.4815.3911.6213.1
Plastic14.673.8616.7321.1511.2313.5
Glass0.831.011.873.502.562.4
Others17.8632.6916.266.3015.8616.7
Total100100100100100100

Table 13.

Physical composition of MSW from towns in different regions of Brazil [63].

Prefeitura Municipal de Araguaína (2013).


Contrato Prefeitura Municipal de Cubatí (2013).


Prefeitura de Paranaíba (2014).


Prefeitura da Cidade do Rio de Janeiro (2015).


Prefeitura de Porto Alegre (2013).


Ministério do Meio Ambiente (2012).


The National Solid Waste Policy (NSWP) was established by Federal Law n. 12,305 in August 2010, and it can be a milestone for waste management in Brazil [64]. The goals of this law are the reduction, reuse, recycling, treatment, and appropriate disposal of MSW, including energy recovery systems, to avoid damage to the environment and public health. This law prohibits the open dump disposal of MSW, and it is stipulated that all states and cities must have closed their open dumps by 2014. Nevertheless, the situation about MSW in Brazil has changed very little since the introduction of the NSWP [63].

3.1.4 Brazilian politics related to the bioenergy sector

In Brazil, the bioenergy sector is promoted by programs instituted by the federal government. In 2002 the Brazilian government launched the Incentive Program for Alternative Sources of Electric Energy (PROINFA), of the Ministry of Mines and Energy in response to the scarcity of energy in the country, in search of renewable sources [63].

As part of the incentive to biodiesel, the National Biodiesel Production and Use Program (PNPB) was launched in 2004 [65]. The PNPB’s strategy is to make feasible the production and use of biodiesel in the country, with a focus on competitiveness, the quality of the biofuel produced, the guarantee of security of its supply, the diversification of raw materials, the social inclusion of family farmers and in strengthening the regional potential for the production of raw materials [66].

RenovaBio is the new National Biofuel Policy, instituted by Law 13,576/ 2017 [67], whose objective is to expand the production of biofuels in Brazil, based on predictability, environmental, economic, and social sustainability, and compatible with the growth of the market. Based on this expansion, the aim is to make an important contribution by biofuels in reducing greenhouse gas emissions in the country. The program will seek its performance based on four strategic axes: discussing the role of biofuels in the energy matrix; development based on environmental, economic, and financial sustainability; marketing rules and attention to new biofuels [68].

Regarding MSW and its destination to the bioenergy sector, in 2020, an association of four important sectorial entities - ABCP (portland cement), Abetre (waste and effluent treatment), Abiogás (production and use of biogas), and Abrelpe (public cleaning) - launched the FBRER (Brazil Front for Energy Recovery of Waste), which aims to boost energy capture from waste deposited in landfills. The signing of the Cooperation Agreement for Energy Recovery of Waste was signed by the entities and the Ministry of the Environment of the federal government [69].

The cooperation agreement will seek to coordinate efforts to remove regulatory barriers that hinder the more intense use of waste. Besides, it intends to make feasible projects for the energy recovery of solid waste and promote its integration into the clean and renewable energy market [69].

3.1.5 Limitations for implementing pyrolysis and gasification of biomass in Brazil

In Brazil, one of the challenges faced by biomass gasification projects is that the facilities are constructed and operated in the laboratory, and on a small scale, it was not possible managed to show viability on a large scale. The lack of gasification plants in operation leads to the unreliability of the business, which alienates investors.

Another factor observed is the comparison between the technologies used to reduce MSW. Considering gasification, pyrolysis, and incineration, it is observed that for the gasification process, solid waste generally needs to have humidity lower than 30%, an average granulometry of 50 mm, and an average calorific value of 3500 kcal/kg [70], the solid waste must be prepared as fuels derived from municipal waste. Such treatment of waste to transform it into a good fuel requires an increase in the costs of production.

Likewise, in the pyrolysis process, waste also needs to be pre-treated. This pre-treatment raises the costs of the MSW energy plant. The pyrolysis process produces gases, oils, and solid waste (metals, oxides, and inert material), which need to be of high quality to identify markets for their absorption. Given these characteristics of gasification and pyrolysis process, energy reuse projects for solid waste end up using incineration technology.

There are several challenges for Brazil to achieve high levels of sustainability in the management of MSW as waste to energy through gasification or pyrolysis technologies. The biggest of these is related to the sale of energy that will be generated by plants using MSW, as it is the largest revenue of this enterprise since this market is not yet regulated.

3.2 México

In contrast with Brazil, around 88.70% of the energy production in Mexico comes from fossil fuels, 3.17% charcoal, 1.16% Nuclear, and 6.97% renewable (3.79% biomass, 1.62% geothermal, hydropower 1.42%, solar and wind 0.14%). Regarding energy contribution to power generation, 78% comes from fossil fuels, 2.8% nuclear, biomass 9.30%, hydropower 3.70%, and 6% from others. As one may infer, energy production in Mexico relies mostly on fossil fuels [71]. Therefore, the potential of other resources such as biomass is not being exploited, preventing the strengthening of the agricultural sector and the reduction of GHG.

Mexico occupies 3rd place in LATAM and the Caribbean in terms of cropland area, after Brazil and Argentina. The cultivated area in 2007 was 21.7 million ha, producing 270 million tons. The residuals from these crops are currently used for animal feed and bedding, mulch, and burning to produce energy and compost. In fact, in 2012 bioenergy has an operational capacity of 645 MW installed, of which 598 MW are from bagasse and the rest from biogas. However, in 2019, it is registered that Mexico increased its capacity of bagasse to 791 MW, which means 32% more, or a 4.28% increase per year [71]. Although the production of energy from biomass has increased, the full potential is not being exploited. The following section presents the biomass availability in Mexico.

3.2.1 Forestry residues

Mexico has 138 million hectares of forest, equivalent to 70% of the national territory. The forests and jungles are an important part of these lands and cover 64.9 million hectares, of which it is estimated that 15 million hectares have the potential for commercial use. The available forest biomass is distributed in different areas of the country. However, the greatest potential is in the mountain ranges of and the Yucatan peninsula [72].

Forest biomass contributes 8% of primary energy demand, being used in residential firewood and small industries. However, it can be considered as an alternative source for renewable energy generation and provide multiple benefits [72].

Forest management, extraction, and industrialization activities generate a significant amount of residual forest biomass annually. Some studies have been carried out on the use of forest residues in the production of bioenergy, and the results indicate that Mexico generates around 703,323.6 (1,774,994.0 m3r, cubic meters of unbarked round timber) tons of dry base biomass, which come from forest residues of mainly pine, and oak. [72].

According to the production of forest biomass, 598,858.1 tons correspond to pine and 104,465.5 tons to oak. In terms of energy, this forest biomass represents a renewable energy resource of 12,827.8 TJ of which 11,425.4 TJ corresponds to pine and 1402.4 TJ to oak. [72]. In Mexico, the main industry supply forest basins have been identified (Figure 7), where a remarkable amount of sawmill waste is concentrated, which can be used as feedstock for integrated energy generation systems (thermal and electrical) [72]. The fact of integrating forest residues into energy generation is an opportunity for community forest companies, ejidos, and communities, to generate income that comes from forest biomass that is now used for waste or that has a minimal economic recovery.

Figure 7.

Main Industrial supply forest basin in Mexico adapted from [72].

3.2.2 Agricultural residues

Several studies have pointed out and assessed the potential of biomass energy production in Mexico, considering three main categories: wood & forestry residues, crop, and agro residues, and MSW [72]. Some estimates range from 3035 to 4550 PJ/y, where wood forestry residues share is 27–54%, crop and agro residues 26, and 0.6% from MSW. Other estimates more conservative said 626 PJ/y and 2228 PJ/y.

Table 14 shows the main agricultural residues produced in Mexico, which considers the residue index (RI) of each crop. Maize primary residue has a 44% share of the main crop residues producing in Mexico. While sorghum primary residue is 31%. As forestry residues, the use of agro residues is an opportunity for agro communities and industries to generate income by a better valorization of residues.

Crop InformationPrimary ResidueSecondary Residue
CropCrop Production (kt/yr)C.V. (%)Residues Energy Potential (PJ/yr)ResidueResidue IndexProduction (kt/y)Available Material * (kt/y)HHV (MJ/kg)Energy Potential (PJ/y)ResidueResidue IndexRecovery FactorProduction (kt/yr)Available Material * (kt/yr)HHV (MJ/kg)Energy Potential (PJ/yr)
Sugarcane53,834.447.10124.19Tops & leaves0.147536.823014.7317.3152.18Bagasse0.140.507536.823768.4119.1172.01
Maize23,740.5312.97278.92Stover1.4133,474.1513,389.6617.18230.03Cob0.150.803561.082848.8617.1648.89
Sorghum6127.5617.85174.93Straw/stalk3.9023,897.489558.9918.30174.93
Wheat3622.619.6445.451.625868.632347.4519.3645.45
Coffee1186.382.04Pulp0.100.90118.64106.7719.102.04
Coffee1186.380.84Hull0.040.9047.4642.7119.590.84
Beans1079.8217.627.120.88950.24380.1018.747.12
Barley776.2125.4410.701.751358.37543.3518.4510.02Husk0.100.5077.6238.8117.500.68
Cotton631.6623.375.661.28808.52323.4117.505.66
Soybean268.0449.093.011.60428.86171.5517.523.01
Rice233.5314.432.671.61375.98150.3915.372.31Husk0.200.5046.7123.3515.360.36
Chickpea159.2232.861.961.70270.67108.2718.101.96
Safflower120.5642.242.112.28274.88109.9519.232.11
Oat96.7329.361.702.52243.7697.5017.481.70
Groundnut92.9112.391.922.12196.9778.7919.011.50Shells0.300.8027.8722.3018.730.42
Sesame45.1021.291.203.80171.3868.5517.471.20
Fava bean27.7230.690.261.4339.6415.8616.310.26
Tobacco12.9725.640.485.0064.8525.9418.520.48
Lentil6.1846.710.092.1012.985.1917.080.09
Sunflower7.836.680.163.0023.499.4017.500.16
Agave (tequila)1369.9523.523.98Leaves0.20273.99109.6017.501.92Bagasse0.120.80164.39131.5216.352.15
Agave (mescal)279.5926.710.88Leaves0.2055.9222.3718.840.42Bagasse0.120.8033.5526.8416.090.43
Total94,905.9670.34542.53127.81

Table 14.

Agricultural Residues in Mexico [73].

* Recovery factor 0.4.

3.2.3 Municipal solid waste residues

In Mexico, 102,895.00 tons of waste are generated daily, from which 83.93% are collected and 78.54% are disposed of in landfills or open-air dumps, recycling only 9.63% of the waste generated. That translates into an economic loss by diverting materials that are susceptible to rejoining the production system, reducing the demand and exploitation of new resources, unlike countries like Switzerland, the Netherlands, Germany, Belgium, Sweden, Austria, and Denmark, where the final disposal of waste is less than 5% in sanitary landfills [74].

Article 10 from the Mexican General Law for the Prevention and Comprehensive Management of Waste (LGPGIR) establishes municipalities oversee the integral management of MSW, which consists of the collection, transfer, treatment, and final disposal [75].

Municipalities encounter challenges that fall outside their technical and financial capacities due to the lack of trained personnel in acquiring or committing financial resources that give certainty to private sector investments. This situation is maybe because of the short time of the municipal administrations, which leads to the breaking of the learning curve, and therefore to a lack of continuity in actions and projects that guarantee integral management of urban solid waste [74]. Whatever the case, the reality is that MSW has become a big problem in Mexico, especially in big cities like Mexico City.

Mexico has 2203 areas (landfills or open-air dumps) for final MSW disposal. Figure 8 shows the average composition of MSW in Mexico.

Figure 8.

Mexican MSW Composition 2017 adapted from [76].

Food and garden waste and disposable diapers have a share of 48.98% of the total MSW in Mexico. While other MSW fractions like paper, paperboard, rags, and plastics represent around 25% of the total MSW in Mexico. Those fractions can be utilized to produce a refuse-derived fuel, which can be used as feedstock for gasification or pyrolysis processes, generating energy vectors and adding value to materials that did not have any other purpose than to be disposed of.

3.2.4 Mexican politics related to the bioenergy sector

The law for the promotion and development of bioenergetics published in 2008 aims to promote and develop bioenergetics to contribute to energy diversification and sustainable development as conditions that allow guaranteeing the development of the agricultural sector [77].

Another low that is related to the bioenergy sector is the Mexican General Law on Climate Change published in 2012 and modified in 2018, which sets the rights and responsibilities of state governments to climate change mitigation and adaptation. Since then, state governments have made progress in developing specific policy instruments, provided in both the Law and the National Climate Change Strategy. However, little clarity regarding the current level of progress of these state efforts exists at the national level. In this sense, seventeen policy instruments (laws, regulations, plans, programs, among others) of the 32 states of Mexico were set [78]. Four of them are related to MSW management, which is potential biomass to produce bioenergy.

3.2.5 Limitations for implementing pyrolysis and gasification of biomass in Mexico

Even though Mexico has a high potential for Renewable Energy Sources (RES) development, only a small amount of this energy has been utilized. This may be due to the following reasons:

  • The lack of an energy plan that evaluates the RES feasibility in short term.

  • Consume the cheapest energy source, usually fossil fuels, rather than sustainable and eco-friendly resources. This situation is preventing RES development.

  • Complex supply-chains and vulnerable to fossil carbon inputs mainly associated with feedstock transport.

  • Higher abatement CO2 costs compared to actions in other sectors. For liquid biofuels, the estimated cost ranges from 7 to 12 US$/tCO2e, while for biogas and upgraded wastewater treatment plants the cost is around 60 US$/tCO2e.

Whether forestry agricultural residues or municipal solid waste, it exists a great potential to produce energy vectors in Mexico. However, socio-political factors have delayed their use. To overcome such limitations is vital to have a national plan for renewable energy in Mexico by the explicit establishment of RES participation, considering financial schemes that help small renewable energy producers as it was established in the law for the promotion and development of bioenergetics published in 2008. Another noteworthy point is the palletization of agroforestry residues or MSW to produce fuel pellets, also known as RDF, which is a more uniform fuel than MSW regarding particle size and heating value, and it is easy to transport.

Another important factor is to know beforehand the composition and yields of each technology’s products, considering the available feedstocks in each country. Unfortunately, this would require major investments to produce experiential data. Knowing this information can help decision-makers to decide which agroforestry residue is a priority, the type of technology to employ, and the use of the products. Fortunately, mathematical models of these technologies can help predict with certainty this information. The following chapter describes a mathematical model used for the gasification of wood residues, an important residue in Brazil and Mexico.

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4. Experimental and numerical analysis

Mathematical models reduce efforts, investments, and time, promoting a better perception of the physical and chemical mechanisms immerse in complex technologies like pyrolysis and gasification [79]. Modeling approaches can be as complex as the available software allows. However, the approach can also be simple, effective, and with an excellent degree of certainty. For example, equilibrium models are reliable and uncomplex [79]. Nevertheless, they do not deal with essential parameters such as hydrodynamics, transport process, or reaction kinetics. In contrast with kinetic models that consider reactions’ kinetic, being much more accurate but computationally expensive [80].

Fortunately, the growth of computational power is leading to better software that is gradually replacing empirical or semi-empirical models for computational fluid dynamics. These models can provide relevant information on what is happening inside the reactor, which can lead to a better understanding of the technology as well as improvements in it. However, their extreme complexity means that these models are still in the development stage [81, 82].

Gasification and pyrolysis processes involve multiple phases, which makes them very complex. Figure 9 summarize the validation of a model applied to two fluidized bed reactors with 250 kWth and the other 75 kWth, both operated by our research team. The relative deviation between the experimental and numerical syngas composition produced in the 250 kWth gasifier using forest residues and coffee husks is depicted in Figure 9a.

Figure 9.

(a) Relative deviation between the experimental and numerical syngas composition produced in the 250 kWth gasifier using forest residues and coffee husks (b) Experimental and numerical fluidization curves gathered at 8 and 18 cm height from the 75 kWth reactors (c) Model gas composition of wood (adapted from [83,84]).

Figure 9b displays the deviation between the experimental and the numerical fluidization curves performed at two different bed heights (8 and 18 cm) in the 75 kWth reactors. Overall, the numerical curves successfully forecasted the slope of the experimental curve with acceptable precision. The broader deviations arose at the lowest velocities. This is due to the movement of the solid before fluidization occurred. It can be also due to the inefficiency of the mathematical model since it considers a low entropy.

The mathematical model effectively predicted the acquired experimental data trends with acceptable accuracy for both equipment at different validation points and experimental conditions. It is worth acknowledging that this model has already been extensively validated and submitted to constant improvements in dealing with different biomass substrates and the heterogeneity of MSW at distinct operating conditions, gasifying agents, and reactor scales. In this example, the gas composition of wood gasification could contain an excellent number of combustible gases, namely H2, CO, CH4, and CO2 (see Figure 9c), which can be used to produce energy or heat in Brazil and Mexico.

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5. Feasibility

As it was discussed in Section 2, gasification and pyrolysis are already at full-scale, mostly in developed countries [85]. However, small-scale energy systems demonstrated to be more advantageous and cost-effective to install in certain regions since this model offers mobility and simplicity [86].

These models can provide energy to decentralized areas or rural households communities, particularly in developing countries like Brazil and Mexico, delivering alternative electric power solutions to communities where connection to the central grid is economically unfeasible. Furthermore, blending biomass residues with other wastes, such as MSW (RDF included), is praised as a clever strategy to lessen exploration costs, boost plant production efficiency, and avoid biomass exploration excess and consequent disequilibrium of ecosystems [87]. In fact, small-scale biomass gasification systems became attractive for off-grid functions due to their cost-effectiveness and high plant load factor.

Biomass-based systems afford an important asset particularly in rural areas since agricultural and timber residues are easily accessible. Furthermore, biomass exploration affords a helping hand towards wildfire hazards reduction, promoting forest biomass harvesting and cleaning in overgrown areas [88]. These units have already proved their suitability for power generation in small towns, being already widely used for rural electrification solutions. In fact, small towns require low electrical load demand. Thus, biomass gasification systems are more cost-competitive than solar PV or even grid electrification for rural areas that are off-grid [89].

These factors could point to the feasibility of energy production through biomass in Brazil and Mexico because of their large amounts of biomass and regions that are not connected to the grid. Besides, the used small stations could be the step towards large-scale production using, for example, MSW, which has become a big problem in large cities such as Brasilia and Mexico City.

The feasibility of financial indicators is resolved by measuring their flexibility and assessing the project performance response to stressful scenarios, appointing either a favorable or unfavorable evolution of several variables simultaneously, where some variables may be more uncertain than others. Some of the variables that can affect the feasibility of a gasification or pyrolysis project are: (1) the initial investment, (2) the return of investment, (3) future costs and benefits, (4) electricity sales price (5) electricity production, (6) biomass cost, (7) governmental policies, etc. In short, sensitivity analysis allows assessing the project’s risk by simulating several scenarios and forecasting their outcomes, assessing decision-making over uncertainty [90]. The World Bank Group has released a set of typical key financial benchmarks for success in biomass related energy projects, considering some financial indicators, namely Net Present Value (NPV) ought to be a positive value, International Rate of Return (IRR) above 10%, and a Payback Period (PBP) less than 10 years [91]. Some of these financial indicators might provide an idea of the benchmarks in the biomass to the energy sector. However, these financial indicators or models may not encompass all factors that can influence the success of a project. Some of these factors are the policy of a set country and its project-specific constraints. Yet, to the point, benchmarks allow standardizing decision-making by building trust within investors less willing to take risks.

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6. Conclusions

Latin American countries have one of the highest rates of urbanization in the world. Among the various problems caused by large urbanization, those that refer to mobility, safety, health, well-being, sanitation, and adequate management of MSW stand out. It is important to highlight that a waste energy recovery plant (WTE) is not exactly an energy generation undertaking, but essentially a sanitation agent whose energy input is a valuable by-product. This context is essential to demonstrate to the authorities the nature and essentiality of WTE plants, especially in terms of cost and benefit, when compared to other sources of power generation. Biomass and MSW have the potential to become a major source in LATAM’s primary energy sector, as presented in Section 3, with a survey of the availability of biomass and MSW found in Brazil and Mexico.

Implementing gasification and pyrolysis in these countries can offer benefits in terms of reducing the use of fossil fuels, reducing greenhouse gas emissions by preventing the extraction of virgin fossil fuels, and providing income diversification to farmers. However, the integration of these energy vectors on large scale should pass for a previous step, which is decentralized gasification and pyrolysis plants as was analyzed in the feasibility section. This is because many rural areas are not connected to the grid yet, in addition, the logistics of biomass is complicated in rural areas and involves an extra cost.

There is still a long way to go. However, the major urgency relies on real policy integration that enables a full converge of the different bioenergy actors. Therefore, catalyze the economic and environmental benefits that pyrolysis and gasification of biomass can provide.

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Acknowledgments

The authors would also like to express their gratitude to the Fundação para a Ciência e a Tecnologia (FCT) for the grant SFRH/BD/146155/2019, and the projects IF/01772/2014, FCT/CAPES 2018/2019, DMAIC-AGROGAS: 02/SAICT/2018. This work is also a result of the project “Apoio à Contratação de Recursos Humanos Altamente Qualificados” (Norte-06-3559-FSE-000045), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement.

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Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this chapter.

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Nomenclature

BR

Brazil

MX

Mexico

VE

Venezuela

CO

Colombia

AR

Argentina

CL

Chile

PY

Paraguay

PE

Peru

EC

Ecuador

UY

Uruguay

BO

Bolivia

CAM*

Central America

Lat

Latin America

EU

European Union

W**

World

SE

Sweden

FI

Finland

CA

Canada

NL

Netherlands

USA

The United States

IE

Ireland

DE

Germany

CH

Switzerland

IN

India

LATAM

Latin America

CHP

Coal handling plant

EU

European Union

GHG

greenhouse gas

MSW

municipal solid waste

RDF

refuse-derived fuel

RES

Renewable Energy Sources

CGE

cold gas efficiency

LHVF

lower heating value of the feed stream

LHVgas

LHV of the gas

LHVi

LHV of the component “i”

LHVliquid

LHV of the liquid

LHVsolid

LHV of the solid

mF

feedstock mass

mgas

gas mass

mi

mass of the component “i”

mliquid

liquid mass

msolid

solid mass

yigas

mass fraction of the component “i” in the gas

yiliquid

mass fraction of the component “i” in the liquid

yisolid

mass fraction of the component “i” in the solid

Ygas

gas yield

ygas

gas Efficiency

Yliquid

liquid yield

Ysolid

solid yield

VG

Gas Volume

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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José Antonio Mayoral Chavando, Valter Silva, Danielle Regina Da Silva Guerra, Daniela Eusébio, João Sousa Cardoso and Luís A.C. Tarelho (June 8th 2021). Review Chapter: Waste to Energy through Pyrolysis and Gasification in Brazil and Mexico, Gasification, Valter Silva and Celso Eduardo Tuna, IntechOpen, DOI: 10.5772/intechopen.98383. Available from:

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