Bio Mass
Bio Mass
Bio Mass
Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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consumption of 500 to 600 kg of steam per tonne of cane has been reduced to 400 kg/t and even
380 kg/t, but due to the investment needed in process equipment, the reduction in steam
consumption has not advanced as much as it could be technically achieved (around 280 kg/t).
Bagasse has been the main biomass fuel used by this industry. Exceptionally, additional fossil fuel
has been employed to extend the generation period, such as coal in Mauritius. Some studies have
been made to use natural gas as supplementary fuel, with no project implemented so far (the high
cost of the fuel needs bigger plants to gain scale and efficiency).
Integration of the sugarcane factory with other processes or industry, consuming heat, power
and electricity is an important way of increasing global energy efficiency and improving economics.
Mills incorporating vinasse concentration or integrated to a sugar refinery or even mill process
integrated to soybean biodiesel production are examples of this optimisation.
Though not common, sporadic niche application for sugarcane biomass has been carried on.
One example is the use of bagasse for the pulp and paper industry in the nominated Ritter Process
and implemented at Ledesma Mill in Argentina. Bagasse fibrous material is separated and treated
with a lactic acid solution before storage and processing for paper production.
The use of trash for energy generation
The increase in energy generation and export of electricity by the mill can be made in three
ways: i) increasing energy generation efficiency, ii) reducing energy consumption and
iii) increasing the amount of fuel. Recently trash has emerged as an important biomass alternative to
increase the fuel amount. Two important trash collecting routes have been considered: baling and
partial cleaning. For the first one, trash in the field is left to dry and then is baled, bales loaded onto
trucks (Figure 1) and transported to the mill where some of the mineral impurities are removed and
trash is shredded and fed to boilers.
In the second route, harvester cleaning fan speed is reduced, letting more vegetal impurities
go with the cane to the factory. Cane reaching the factory has the trash and mineral impurities
separated by a dry cleaning system (Figure 2), with trash shredded before being sent to boilers.
Both routes have been implemented in a few mills in Brazil, with advantages and
disadvantages for each one. Typical amounts of recovered trash are in the range of 30 to 50% of the
available trash in the field. The definition of the amount of trash to be recovered depends on
agronomic and economic factors. Electricity export increases of 70% can be achieved if recovering
50% of the field available trash in unburned areas, using 67 bar/490 C boilers.
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Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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The optimisation and the commercial deployment of the trash technologies are still in its
initial phase, depending in many cases on specific country policies, energy transmission structure
and market prices.
Table 1 highlights the substantially larger amount of electricity export that can be generated
using higher pressure steam and power cogeneration technologies, already well-established
commercially, assuming the use of the bagasse and the additional 50% of the available trash.
Table 1Sugarcane potential for electricity export at a typical Brazilian mill today.
Export electricity potential bagasse
and 50% of the trash
(kWh/t cane)
Technology
22 bar, 300 C
10
67 bar, 490 C
63
108
74
126
The biomass considered is the bagasse from sugarcane with an average of 11% fibre content
in the stalk and 7% (in weight) of vegetal impurities in the cane load and process steam
consumption around 480 kg of steam/t cane.
Boosting biomass conversion to electric power
Other technologies for biomass electric power generation have been considered, especially
gasification-based power generation, including gasifier-engine, gasifier-gas turbine, and gasifierfuel cell systems. In the 1980s and 1990s there was significant research and development on power
generation from biomass gasifier gas turbine/steam turbine combined cycles and biomass gasifier
internal-combustion engine systems, leading to the construction and successful technical operation
of some pilot and demonstration plants around the world. Different technological alternatives have
been developed and tested, such as atmospheric and pressurised gasification, air and oxygen blown
gasification, fluidised and circulating bed, entrained flow, and so on.
The integrated gasification combined cycle (IGCC) also called biomass integrated
gasification with gas turbine (BIG-GT) has been considered the indicated technology for energy
generation at the mill site (Figure 3).
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Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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GAS TURBINE
G
GASIFIER
HIGH
PRESSURE
HOT GASES
AIR
STEAM
TURBINE
G
BIOMASS
DRYING
SYSTEM
GASES
CONDENSATE
HRSG
2,5 bar
PROCESS
Nevertheless, there has been no commercial-scale demo plant that could prove its economic
competitiveness in the production of electricity. Analysis of several commercial and pilot-scale
projects, some of them built and even commissioned such as the ARBRE project in the UK and the
VARNAMO project (Sydkraft, 2001) in Sweden (Figure 4), indicated that the failure to achieve
commercial success was mainly due to economic factors. Other factors, such as technology risk,
institutional arrangements and secure biomass supply played their role as additional barriers.
Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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Nevertheless, specific electricity export above 200 kWh/t of cane (with 50% of trash) and
electric efficiencies above 40% to the fuel energy, almost twice that of the Rankine cycle, still
attracts developers and environment specialists to the gasification technology, keeping the theme in
everyones agenda as a promise for the future. On the other hand, investments above US$ 2000/kW
installed and price of US$ 70/MW exported electricity (Larson and Carpentieri, 2008), with the use
of 50% of the bagasse and 50% of the trash for gasification, are still a barrier hindering the
implementation of the new technology. In fact, biomass can be co-gasified with coal, which can
offer some valuable synergies, especially in the reduction of GHG (Green House Gases) emissions,
what is already being commercially made at some electricity-generating facilities such as the
Buggenum facility in the Netherlands (Pastoors, 2006), and several co-gasification projects are
under development in Europe and in the U.S.
New alternatives Conversion of biomass to liquid fuels and chemicals
For the production of liquid fuels and chemicals, there are a variety of possible conversion
routes (Figure 5). Second-generation ethanol or butanol could be made via biochemical processing,
while other second-generation fuels including methanol, Fischer-Tropsch liquids (FTL), dimethyl
ether (DME) and green diesel could be made via thermochemical processing. Unrefined fuels such
as pyrolysis oils are also produced thermochemically.
Hassuani, S.J.
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MTG) or gasoline and diesel (via the MOGD process methanol to olefins to gasoline and
distillate), ethanol, and mixed alcohols (MOH). After gasification, contaminants in the gas are
removed, followed by adjustments to the composition of the gas, using gas reforming (CH4 + H2O
CO + 3H2), water-gas shift (CO + H2O CO2+ H2) reactions and carbon dioxide (CO2)
removal, preparing the gas for further downstream processing of the final products (Figure 6).
Major components of the clean and concentrated syngas are carbon monoxide (CO) and hydrogen
(H2) that react when passed over a catalyst to produce liquid fuel. The design of the catalyst
determines what biofuel is produced.
Fig. 6Illustration of process steps for thermochemical biofuels production (Larson, 2008),
A second option for converting syngas to liquid fuel and one that has received less attention
is represented by the dashed lines in Figure 6, where specially-designed micro-organisms ferment
the syngas to ethanol or butanol. Despite considerable research, development, and pilot-scale
demonstration work conducted by a few companies, commercial-scale projects are still needed to
demonstrate viability.
Many second-generation thermochemical fuels are fuels that are already being made
commercially from fossil fuels using processing steps that in some cases are identical to those that
would be used for biofuel production (Figure 5). These fuels include methanol, refined FischerTropsch liquids (FTL), dimethyl ether (DME) and diesel. Figure 7 indicates some of the possible
bioproducts that can be obtained from biomass through gasification to substitute the fossil ones.
Hassuani, S.J.
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Candidate diesel fuel substitutes are FT diesel or DME. While the future markets for these
are far larger than the production potential of the sugarcane industry (as with electricity), there are
challenges with both fuels that presently make them less attractive than electricity. FT diesel cannot
be made without a significant co-product of naphtha (or naphtha upgraded to gasoline), and the
economics of the diesel production depend on reasonable prices received for the co-product.
Chemical markets for naphtha are relatively small compared to fuel markets, so gasoline
would need to be the end co-product. DME is an excellent diesel engine fuel, but vehicle fuel
storage and delivery systems must be modified to enable DME use. This discourages the
consideration of DME production for vehicles.
The use of DME as a Liquefied Petroleum Gas (LPG) replacement requires no infrastructure
or end use equipment modifications for blends of up to about 25% DME in LPG. However, the
potential of the sugarcane industry for producing DME should be compared to the expected demand
for LPG to verify the economic feasibility, since in most cases the conversion of a small amount of
sugarcane biomass will be able to meet DME blending limitations. Similar consideration applies to
nitrogen fertiliser production from sugarcane biomass.
Most of the equipment components needed in a system for producing syngas for biofuel
production is commercially available today. However, two areas needing further engineering
development and demonstration are the feeding of biomass into large-scale pressurised gasifiers and
the clean-up of the raw gas produced by the gasifier. The relatively low bulk density of biomass
makes it challenging to feed into a pressurised gasifier efficiently and cost-effectively (Wilen and
Rautalin, 1993).
Development is also needed in the area of syngas clean-up (especially tar removal or
destruction) because tolerance to contaminants of downstream processes is low. Tars have been the
most problematic of syngas contaminants and have been the focus of much attention. Methods for
removal (or conversion to light permanent gases) are known, but still inefficient and/or relatively
costly. The technologies involved in the conversion of syngas by catalytic synthesis are fully
commercial today in some cases FT, DME, MTG while others are not yet commercially
demonstrated, but are under active development (e.g., mixed alcohols, syngas fermentation
technologies).
Biological biomass conversion to liquid biofuels and chemicals
Second-generation biochemically-produced alcohol fuels are often referred to as cellulosic
ethanol and cellulosic biobutanol. The basic steps for producing these include pre-treatment,
saccharification, fermentation, and distillation.
Pre-treatment is done to separate the main biomass constituents: cellulose, hemicellulose
and lignin, so that the complex carbohydrate molecules constituting the cellulose and hemicellulose
can be broken down into simple sugars by enzyme-catalysed or acid-catalysed hydrolysis (water
addition). Acid hydrolysis for ethanol production was already practised commercially in the 1930s,
but due to high capital and operating costs was uncompetitive. Some companies are now once again
promoting acid hydrolysis processes.
Cellulose is composed of long chains of glucose (6-carbon) sugar molecules which structure
is difficult to separate into simple sugars, but once separated, the sugar molecules are easily
fermented to ethanol using well-known micro-organisms, and some micro-organisms for
fermentation to butanol are known. Hemicellulose consists of polymers of 5-carbon sugars and is
relatively easily broken down into its constituent sugars such as xylose and pentose. However,
fermentation of 5-carbon sugars is more challenging than that of 6-carbon sugars. Some recently
developed micro-organisms are able to ferment 5-carbon sugars to ethanol and others to butanol
(Jeffries, 2006; Aden et al., 2002). Lignin consists of phenols, which for practical purposes are not
fermentable. However, lignin can be recovered and utilised as a fuel to provide process heat and
electricity at an alcohol production facility or used as a raw material to other products.
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Hassuani, S.J.
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A variety of different process designs have been proposed for production of second
generation ethanol. One relatively well-defined approach for ethanol production is the use of
separate hydrolysis (or saccharification) and fermentation steps. Other concepts include one that
combines the hydrolysis and fermentation steps in a single reactor (simultaneous saccharification
and fermentation) (Aden et al., 2002), and one that additionally integrates the enzyme production
(from biomass) with the saccharification and fermentation steps (consolidated bioprocessing or
CBP) (Zhang and Lynd, 2005). Less work has been done on butanol. There are only a few operating
commercial demonstration plants for cellulosic ethanol production in the world today, such the one
owned by Iogen (www.iogen.ca) in Canada, and the one of Inbicon (Langhans, 2012) in Denmark.
Presently, expected yield potential for the enzymatic-hydrolysis processes is about 270 litres
of ethanol per tonne of dry biomass, but some researchers believe that the potential can reach
400 litres, with adequate financial support for research, pilot and commercial scale projects.
The biological technology has been supported by some governments and research
institutions. Development and demonstration efforts presently include (Houghton et al., 2006):
Development of biomass with lower lignin content and structure that facilitates
access to carbohydrate molecules.
Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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Advantages of the biomass derived ethanol include avoiding impact on food-price and
indirect land use change due to biofuels production. There is a strong worldwide push for the
substitution of transportation fossil fuels by biofuels, but presently the international market for
bioethanol is still uncertain. Tariffs on imported ethanol in several countries, the need of a
distribution network and modifications in the car engines are barriers to overcome. In the technical
and economic aspects of the biological conversion, aside from fermentation of C6 sugars to ethanol,
commercially-viable conversion rates (including fermentation of C5 sugars) are yet to be
demonstrated, although many significant efforts are underway to overcome this drawback.
Anaerobic digestion, a biological processing technology to produce gas used in gas engines
and turbines, that has been used in some countries, has historically not been of interest due to the
size of fermentation reactors, considering the amount and characteristics of the feedstock (vinasse,
bagasse and sugarcane trash) and the process characteristics (long retention time). The production
of chemicals, such as butanol, acetic acid, succinic acid, xylitol, and others are more valuable
products recently under consideration to be produced from biomass, which normally face the
limitation of a small market potential.
Gasification is considered by several researchers as an important thermochemical
conversion technology that should be introduced in the sugarcane sector because of the tremendous
flexibility it offers for new revenue streams (electricity, liquid fuels, chemicals, etc.). Gasificationbased technologies offer some intrinsic advantages over biochemical systems for power generation
and for production of liquid fuels, synthetic natural gas, nitrogen fertilisers and other synthesised
products.
For liquid fuels production, while biological processes have historically been favoured
because of the familiarity of traditional ethanol processes, thermochemical processing offers
(i)
more flexibility in the variety of feedstock (and variations within a given feedstock,
(ii)
lower performance sensitivity to variations in process conditions such as temperature
or feedstock contamination levels, and
(iii) a diversity of fuel and chemical end-products. No new fundamental research
breakthroughs are needed.
Some engineering development work is still needed (such as feeding of sugarcane bagasse
and trash into pressurised gasifiers), but the primary requirement preceding deployment of
gasification-based conversion is system demonstration at the commercial scale. The challenge of
getting to technically workable systems that are also economically viable should not be
underestimated.
Most and not to say all mentioned technologies are not yet commercial, and no certain bet
can be made on which ones will prevail. The economic competiveness of the green products vis a
vis the petrochemical ones is still a great challenge. Despite technical success, the deployment of
any technology will strongly rely on a learning curve, which maturation depends on adequate
regulatory and economic conditions favouring research, demonstration of the technology and the
installation of a set of first plants.
Presently this scenario is favouring the biological process, especially in the United States,
where huge resources have been provided for research and demonstration of the cellulosic ethanol
(called advanced ethanol) technology, added to a regulatory mandate setting advantages for its
commercialisation. Nevertheless, delays in the technical success of the process can change this
scenario.
The electric engine is another technological route competing with liquid fuel engine for the
huge car market. Strong research and investments have been made, especially focusing on reducing
battery weight and increasing mileage, with significant involvement of the auto industry. Hybrid
and electric cars are already a technical success, and the deployment of this technology has already
started, and its impact on the fuel market should not be underestimated.
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Gasification-based power could, in the future, supply significant increase in the amount of
sugarcane electricity and cellulosic ethanol can greatly increase the ethanol production. Other
products and technologies will come up, but the process has not been as fast as one would expect,
due to the already mentioned challenges. In this dynamic scenario of new technologies and
products, delay in technology reaching commercial competitiveness increases the risk of market
changes, and increases uncertainty in technology deployment success. In most countries, electricity
continues to be the safe choice in the near and medium future, with a market large enough to readily
absorb all electricity generated from sugarcane biomass. Electricity generation is a familiar process
to the sugarcane industry, and marketing channels are already well established in most countries.
High pressure boilers, use of trash as additional fuel, reduction of process steam consumption are
commercial technologies not fully utilised yet, that if implemented can increase the competitiveness
of electricity even more.
REFERENCES
Aden, A., Ruth, M., Ibsen, K. et al. (2002). Lignocellulosic biomass to ethanol process design and
economics utilising concurrent dilute acid prehydrolysis and enzymatic hydrolysis for corn
stover. NREL/TP-510 32438, National Renewable Energy Laboratory, Golden, CO.
Hassuani, S., Leal, M.L.R.V. and Macedo, I.C. (2005). Biomass Power Generation, Sugarcane
Bagasse and Trash. Programa das Naes Unidas para o Desenvolvimento and Centro de
Tecnologia Canavieira, Piracicaba, Brazil.
Houghton, J., Seatherwas, S. and Ferrell, J. (2006). Breaking the biological barriers to cellulosic
ethanol: a joint research agenda. United States Department of Energy.
Jeffries, T.W. (2006). Engineering yeasts for xylose metabolism. Current Opinion Biotechnology,
17(3): 320326.
Langhans, B. (2012). Instrumentation & Control experience at a cellulosic ethanol plant. Proc. Int.
Soc. Sugar Cane Technol. Coproducts Workshop, Bangkok, Thailand.
Larson, E.D. and Carpentieri, E. (2008). Biomass-Energy Technologies: Perspectives for Brazils
Sugarcane Industry. Confidential report carried on for CTC.
Larson, E.D. (2008). Biofuel production technologies: status, prospects and implications for trade
and development. United Nations.
Pastoors, H. (2006). The Willem Alexander Centrale. Powerpoint presentation, Haelen, the
Netherlands, 11 July.
Sydkraft, A.B. (2001). Vrnamo Demonstration Plant. A demonstration plant for biofuel-fired
combined heat and power generation based on pressurised gasification. Berlings Skogs,
Trelleborg.
Wilen, C. and Rautalin, A. (1993). Handling and feeding of biomass to pressurised reactors: safety
engineering. Bioresource Technology, 46: 7785.
Zhang, Y. and Lynd, L.R. (2005). Cellulose utilisation by clostridium thermocellum:
bioenergetics and hydrolysis product assimilation. Proceedings of the National Academy of
Science, 102: 72317325.
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Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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Rsum
PENDANT LONGTEMPS, L'INDUSTRIE de la canne sucre a mis l'accent uniquement sur le jus de
canne, son extraction et sa conversion en sucre. La bagasse tait alors considre comme un rsidu
et brle de faon inefficace pour gnrer de la vapeur et de lnergie. Au cours des dernires
dcennies, la bagasse a progressivement commenc tre convertie en nergie de manire plus
efficace, fournissant toute l'nergie ncessaire l'industrie sucrire (travail mcanique, vapeur et
lectricit) et, dans certains cas, un excdent significatif dlectricit a t export sur le rseau
publique, devenant ainsi une autre source importante de revenus. Cela a motiv plusieurs tudes sur
des systmes plus avancs de gnration d'nergie pour augmenter cette export. Plus rcemment, les
technologies dites de 2ime et 3ime gnration sont mises en avant avec de nombreuses options,
promettant de convertir la biomasse en produits plus haute valeur ajoute tels que des
biocarburants, des produits chimiques, de lengrais, des granuls, etc.. Malheureusement, les
attentes et opportunits non satisfaites sont en train de monter. De plus, ces technologies sont en
concurrence pour la mme biomasse, et cela doit tre considr. L'industrie a commenc se
demander sur quelle voie aller , la stratgie et les investissements judicieux. La prsente tude
fournit un large scnario sur les disponibilits de la biomasse et son emploi, avec une vue prcise
sur les principaux procds et produits qui pourraient avoir un rle important sur l'avenir de la
biomasse dans l'industrie de la canne sucre.
REVISION DE LA SITUACIN ACTUAL
DEL EMPLEO DE LA BIOMASA
S.J. HASSUANI
CTC Centro de Tecnologia Canavieira S.A.
Piracicaba SP Brazil
suleiman@ctc.com.br
PALABRAS CLAVE: Biomasa, Bioenerga,
Biocombustibles, Bioqumicos,
Caa de Azcar.
Resumen
LA INDUSTRIA DE LA CAA de azcar se enfoc por largo tiempo solamente en el jugo de caa, su
extraccin y su conversin en azcar. El bagazo era considerado un residuo y se le quemaba
ineficientemente para generar vapor y potencia. En las ltimas dcadas se comenz a convertir el
bagazo en una forma ms eficiente, suministrando todas las necesidades energticas de la industria
(potencia, vapor, electricidad) y, en algunos casos, cantidades significativas de electricidad han sido
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Hassuani, S.J.
Proc. Int. Soc. Sugar Cane Technol., Vol. 28, 2013
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exportadas a la red, convirtindose en otra fuente importante de ingresos. Lo anterior motiv varios
estudios de sistemas mas avanzados de generacin de energa para incrementar la exportacin a la
red. En aos mas recientes, han aparecido en escena tecnologas denominadas de 2 y 3 generacin
con muchas opciones, prometiendo convertir biomasa en productos mas valorados tales como
biocombustibles, qumicos, fertilizantes, pellets, etc. Las expectativas insatisfechas y las
oportunidades estn creciendo. Por otro lado, estas tecnologas compiten por la misma biomasa y
esto tiene que ser considerado. La industria ha planteado la pregunta que direccin tomar, en
estrategia y enfoque de inversin. El presente trabajo plantea un escenario amplio para la
disponibilidad de biomasa y su empleo, concentrndose en los principales procesos y productos que
podran tener un papel importante en el futuro de la biomasa en la industria de la caa de azcar.
Resumo
DURANTE MUITO TEMPO, indstria de cana focou-se somente no caldo de cana, em sua extrao e
converso em acar. O bagao era considerado um resduo e queimado de sem eficincia para
gerar vapor e energia. Nas ltimas dcadas, o bagao comeou aos poucos a ser convertido em
energia de maneira mais eficiente, atendendo a todas as necessidades energticas da indstria de
acar e, em alguns casos, excedentes de eletricidade tem sido exportados e se tornado importante
fonte de receitas. Esse fato motivou vrios estudos de sistemas mais avanados de gerao de
energia para aumentar as exportaes de eletricidade. Nos ltimos anos, tecnologias denominadas
segunda e terceira gerao dominaram a cena com muitas opes, prometendo converter biomassa
em produtos mais valiosos, como biocombustveis, qumicos, fertilizantes, pellets, etc. Ainda h
muitas expectativas e oportunidades no exploradas. Por outro lado, essas tecnologias esto
competindo com a mesma biomassa, e isso deve ser considerado. A indstria comeou a questionar
qual o caminho tomar em termos de estratgias e investimentos. Este estudo apresenta um cenrio
amplo da disponibilidade de biomassa e seu emprego, com uma viso ntima dos principais
processos e produtos que poderiam ter um papel importante no futuro da biomassa na indstria da
cana-de-acar.
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