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The production of cellulosic ethanol has been gaining attention in the industry sector because of the high availability of lignocellulosic biomass from agricultural and forestry activities. Pinus patula is one of the most typical softwood species in Colombia. The aim of this work is to evaluate the production of ethanol using Pinus patula as raw material using dilute acid pretreatment and enzymatic hydrolysis to produce sugars able to be used as substrate for the strain Saccharomyces cerevisiae. Three fermentation configurations were selected to evaluate the performance of the microorganism: configurations 1 and 2 used glucose in a percentage of 80%w/v and 70%w/v, respectively, as substrate to establish the adaptation requirements of the microorganism. The configuration 3 considered the use of concentrated P. patula hydrolysate. An experimental yield of 0.364 ± 0.009 g ethanol/g sugar (73% of the theoretical) was obtained. Additionally, the economic and energetic comparison between the biochemical (ethanol production through fermentation) and thermochemical (synthesis gas through gasification) pathways to produce bioenergy was performed through simulation approaches. As main results, a higher ethanol production cost (1.53 USD/L) was obtained in comparison to the market price (0.77 USD/L) and a low energy efficiency (20%). Different alternatives such as waste integration and energy incentives must be considered in order to produce ethanol in a feasible way.
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Waste and Biomass Valorization
Fermentative Production ofEthanol Using Pinus patula asRaw
Material: Economic andEnergy Assessment
CarlosA.García‑Velásquez1· EstefannyCarmona‑Garcia1· AshleySthefaníaCaballero1· JuanC.Solarte‑Toro1 ·
JimmyA.Martínez‑Ruano1,2· CarlosA.Cardona1
Received: 6 February 2018 / Accepted: 24 October 2018
© Springer Nature B.V. 2018
The production of cellulosic ethanol has been gaining attention in the industry sector because of the high availability of
lignocellulosic biomass from agricultural and forestry activities. Pinus patula is one of the most typical softwood species in
Colombia. The aim of this work is to evaluate the production of ethanol using Pinus patula as raw material using dilute acid
pretreatment and enzymatic hydrolysis to produce sugars able to be used as substrate for the strain Saccharomyces cerevisiae.
Three fermentation configurations were selected to evaluate the performance of the microorganism: configurations 1 and 2
used glucose in a percentage of 80%w/v and 70%w/v, respectively, as substrate to establish the adaptation requirements of
the microorganism. The configuration 3 considered the use of concentrated P. patula hydrolysate. An experimental yield of
0.364 ± 0.009g ethanol/g sugar (73% of the theoretical) was obtained. Additionally, the economic and energetic comparison
between the biochemical (ethanol production through fermentation) and thermochemical (synthesis gas through gasification)
pathways to produce bioenergy was performed through simulation approaches. As main results, a higher ethanol production
cost (1.53USD/L) was obtained in comparison to the market price (0.77USD/L) and a low energy efficiency (20%). Different
alternatives such as waste integration and energy incentives must be considered in order to produce ethanol in a feasible way.
Keywords Ethanolic fermentation· Energy and economic assessment· Biochemical versus thermochemical routes
State ofNovelty
Pinus patula is a softwood that is highly available in Colom-
bia and other countries. Nevertheless, the application of this
raw material has been limited to furniture making and direct
energy production through combustion. The high cellulose
and hemicellulose content of P. patula as well as its process-
ing residues (having the same composition) evidences the
possibility to obtain different added-value products through
different platforms (i.e. sugar extraction and gasification).
Therefore, this work presents a technical, economic and
energetic assessment of the ethanol production using P. pat-
ula as raw material in order to determine the main technical
concerns (experimental procedure), economic bottlenecks
(processing costs) and energy constraints (valorization of
Pinus patula (PP) is one of the types of softwood with high
production in Colombia because of its fast growth and high
crop yield among the forest plantations [1]. Pinus patula has
a high content of cellulose and hemicellulose, between 40
and 50% on dry basis [2]. However, one of the disadvantages
of most softwoods is the high lignin content (approximately,
25% on dry basis) that hinders the application of this type
of raw material to obtain bio-based materials. Consequently,
the use of softwood as feedstock for the direct production
of energy (thermochemical route) is very common due to
the easy treatment requirements [3]. Thermochemical routes
Electronic supplementary material The online version of this
article (https :// 9-018-0494-4) contains
supplementary material, which is available to authorized users.
* Carlos A. Cardona
1 Instituto de Biotecnología y Agroindustria, Departamento
de Ingeniería Química, Universidad Nacional de Colombia
Sede Manizales, Cra. 27 No. 64-60, Manizales, Colombia
2 School ofBiochemical Engineering, Pontificia Universidad
Catolica de Valparaíso, Av. Brasil, 2085Valparaíso, Chile
Waste and Biomass Valorization
1 3
involve different processes such as pyrolysis, combustion,
and gasification in order to produce different species that
can be used as platform for different products such as elec-
tricity, steam and liquid fuels through the Fischer–Tropsch
process [4]. On the other hand, the growing interest in the
production of cellulosic ethanol is related to the advances
in different pretreatment methods (chemical, enzymatic and
physical) that allow the production of fermentable sugars,
which are considered a promising substrate for microorgan-
isms to produce different added-value products, such as
ethanol [57]. The most studied application of softwood in
fermentative processes is the production of ethanol on labo-
ratory [8, 9] and commercial scales [10] due to the content
of cellulose, hemicellulose and lignin. In fact, softwoods
contain around 43–45% cellulose, 20–23% hemicellulose
and 25–28% lignin. Theoretically, around 410L of ethanol
can be produced per metric ton of dry raw material using
only the hexose fraction and 455L if all carbohydrates are
considered [8].
In this context, Söderström et al. [11] investi-
gated the effect of the two-step steam pretreatment of
SO2-impregnated softwood (Picea abies.) on the ethanol
yield at different severities. Additionally, the effectiveness
of the developed pretreatment was assessed by both enzy-
matic hydrolysis of the solids and simultaneous sacchari-
fication and fermentation (SSF) of the whole slurry. From
the enzymatic hydrolysis, an overall sugar yield of 80% was
reached. In the SSF configuration, an overall ethanol yield of
69% was achieved. Hoyer etal. [9] studied the production of
ethanol using spruce as raw material. Based on the content
of fermentable sugars in the fermenter, a theoretical yield
of 81% was reached using a water-insoluble solids (WIS)
content of 12% and SSF. Furthermore, Cellunolix® plant
located in Kajaan (Finland) produces 10million L of ethanol
per year on an industrial scale using sawdust and recycled
wood as raw material [12].
On the other hand, the thermochemical pathway com-
prises the direct conversion of the raw material into inter-
mediate products (i.e. synthesis gas and bio-oil) that can
be used as platform for the production of energy (heat and/
or electricity). The most important thermochemical pro-
cesses that have been used to evaluate the energy potential
of softwood are pyrolysis, combustion, and gasification.
Pyrolysis includes the conversion of biomass into char,
gas and a liquid composed of a mixture of hundreds of
oxygenated organic compounds, which is known as bio-oil
[1315]. Combustion involves three phenomena: evapora-
tion of the water, volatilization at 200°C and combustion
at 500°C [16, 17]. Instead, gasification converts biomass
into a gaseous mixture (i.e., hydrogen, methane, carbon
monoxide and carbon dioxide), small quantities of char
and condensable compounds [1820]. The use of softwood
for one of these pathways will depend on different factors
such as environmental friendliness, energy efficiency and
economic profitability. In this paper, the main goal of the
production of energy using P. patula will be the economic
and energetic comparison of two technological routes
(biochemical and thermochemical). Different authors
have evaluated the economic performance of the ethanol
and electricity production using softwood[21]. Moncada
etal. [2] performed the techno-economic analysis of the
ethanol production using P. patula as raw material, obtain-
ing a production cost of 1.08USD/L. Furthermore, other
authors have evaluated the production cost of electricity
through gasification (5USD/kWh) and direct combustion
(7.2USD/kWh) using as raw material softwood [22].
The aim of this work is to evaluate the potential use of
P. patula for the production of ethanol using two different
approaches: experiments and simulation. First, a series of
experiments were carried out involving dilute acid pre-
treatment followed by an enzymatic saccharification. Then,
C6-sugar fermentation was carried out using the strain Sac-
charomyses cerevisiae to obtain ethanol. Additionally, the
simulation of the ethanol production was performed using
the software Aspen Plus v9.0. Subsequently, the economic
assessment of the fermentative production of ethanol was
evaluated at different process scales. Finally, the energy
comparison between the biochemical and thermochemi-
cal pathways for energy production using P. patula as
raw material was performed based on the energy poten-
tial of the produced ethanol and the electricity generation
through gasification.
Materials andMethods
In this section, two procedures are presented aiming to
evaluate the production of ethanol using P. patula as raw
material. The characterization of the raw material, the
pretreatment (i.e. dilute acid hydrolysis and enzymatic
saccharification) and the ethanol production (i.e. fermen-
tation) are categorized in “Experimental Procedure” sec-
tion. The main purpose of this section is to summarize the
methods, protocols, and conditions used in each one of the
experimental procedures. On the other hand, the simula-
tion process (“Simulation Procedure” section) involves the
use of the obtained results from the experimental assays
as well as the reported data in the literature for ethanolic
fermentation of softwood as input for the economic and
energy assessment of the biochemical route for ethanol
production. Additionally, the gasification of P. patula was
simulated in order to compare the ethanol fermentation
from the energetic point of view.
Waste and Biomass Valorization
1 3
Experimental Procedure
Raw Material
Pinus patula (PP) was collected from a farm located
in the central western region of Colombia (5°0358N
75°2905W) and dried at room temperature (18–23°C).
The wood was milled with an upper vibratory disk mill
(Retsch SR 200) and sieved to a particle diameter of 400µm.
The chemical characterization of P. patula was taken from a
previous work García etal. [23].
Reagents For the pretreatment of P. patula, sulfuric acid
96% (MERCK) and distillate water were used. In the
enzymatic hydrolysis, cellulases (Celluclast® 1.5 L),
multienzyme complex (Viscozyme® L), citric acid (Dis-
proalquimicos) and sodium citrate (CARLO ERBA) for
the buffer solution, and sodium azide solution 2% were
used. Freeze-dried Saccharomyces cerevisiae strain, d(+)-
glucose (MERCK), ammonium sulfate (Panreac), potas-
sium dihydrogen phosphate (MERCK), magnesium sulfate
(MERCK), calcium chloride (Panreac) and distillate water
were used in the fermentation. For the determination of sug-
ars, 3,5-dinitrosalicylic acid (MERCK), sodium hydroxide
(MERCK), potassium sodium tartrate (Panreac) and distil-
late water were employed.
Dilute‑Acid Pretreatment ofP. patula The raw material was
mixed with a dilute solution of sulfuric acid (2%v/v) in a
solid to liquid (S/L) ratio of 1:10. The procedure was carried
out in an autoclave at 121°C and 15 psig during 90 min,
which are typical operation conditions that ensures a high
hemicellulose solubilization and low inhibitors production
[24]. After the acid pretreatment, a vacuum filtration was
performed aiming to separate the solid and liquid fraction
(i.e., hydrolysate). The solid fraction was washed using tap
water until reach a pH near to 4.8, which is the pH condi-
tion of the enzymatic hydrolysis. This fraction was not dried
to avoid re-crystallization of amorphous cellulose and to
ensure a high sugars yield from this process [25]. Instead,
the liquid fraction from the dilute acid pretreatment was
cooled to room temperature and stored until sugars analysis.
Enzymatic Saccharification Enzymatic hydrolysis was car-
ried out following the protocol NREL/TP-510-42629 [26]
with a commercial cellulase (Celluclast® 1.5L) and multi-
enzyme complex (Viscozyme® L). The enzymatic hydroly-
sis was carried out using 30g of the solid fraction from the
dilute acid pretreatment. For this, it was used an enzyme
dosage of 64 filter paper units (FPU) per g of cellulose and
60 p-nitrophenyl-β-glucoside units (pNPGU) per g of cellu-
lose for Celluclast 1.5L and Viscozyme L, respectively. The
reaction volume was 2L, the pH was adjusted using a 0.1M
citrate buffer solution (pH 4.8–5.0). Finally, a 2%v/v sodium
azide solution was added to prevent the growth of organ-
isms during the saccharification. The operative conditions
for the enzymatic hydrolysis process were 72h at 50°C and
100rpm. Afterward, the liquid C6-rich hydrolysate was sep-
arated by vacuum filtration. Then, this hydrolysate was used
as substrate for the fermentation process.
Ethanolic Fermentation Freeze-dried S. cerevisiae was
used for the production of ethanol. The microorganism was
able to intake C6 sugars from the saccharification process.
Different fermentative configurations (three mediums) were
prepared in 200 mL Erlenmeyer flasks (100mL working
volume): sugar concentration of 15g/L (80% glucose and
20% hydrolysate), sugar concentration of 10g/L (70% glu-
cose and 30% hydrolysate) and total (100%) hydrolysate.
The mediums were supplemented with minerals: 1.5 g/L
, 1 g/L
, 0.3 g/L
and 0.05g/L
. Experiments were carried out at 32°C and 150rpm
in an incubator (BINDER Incubator BD056) with a shaker.
Analytical Quantification The amount of sugar in the sam-
ple was determined using the dinitrosalicylic acid (DNS)
method, where the absorbance was measured at a wave-
length of 540nm according to the procedure proposed by
Miller [27]. The biomass concentration (g/L) was deter-
mined by dry weight of yeast. The concentration of ethanol
was determined using a GC-2014 (Shimadzu) gas chroma-
tograph equipped with a flame ionization detector (FID) and
a capillary column Stabilwax. The operating conditions of
the gas chromatograph were: injection volume 10µL, injec-
tor temperature 220°C, detector temperature 270°C, nitro-
gen as carrier gas with a flow in the column of 0.5mL/min
and running time of 21.75min.
Simulation Procedure
The production of ethanol using P. patula as raw material
was simulated based on the results from the experimen-
tal section and complemented with data reported in the
literature. For this purpose, the dilute acid pretreatment,
enzymatic saccharification and ethanolic fermentation
were conceptually designed using main simulation tools as
software Aspen Plus V9.0 (Aspen Technology, Inc, USA),
which allows calculating the mass and energy balances of
the process scheme. The behavior of the pretreatment, sac-
charification and fermentation were described based on data
reported in the literature from different authors (see, “Eth-
anolic Fermentation” section) [28, 29]. Then, the kinetic
models of these stages were modeled using the computa-
tional tool Matlab (MathWorks, USA). The properties of
Waste and Biomass Valorization
1 3
missing components in the Aspen Plus Database were taken
from external databases, especially the work developed by
Wooley and Putsche [30]. The selection of the thermody-
namic method was based on previous works [31], where
the Non-Random Two Liquid (NRTL) model was used to
describe the behavior of the liquid phase. For calculations,
a mass flow rate of 3300 ton/day of P. patula (wet basis)
and a moisture content of 40% were used in the simulation
The results from the simulation procedure were used as
starting point for the economic and energetic analysis. In
the economic analysis, the contribution of the total capital
costs and the operating costs (variable and fixed) to the total
production cost of the process was assessed. Furthermore,
the ethanol production cost from the evaluated process was
compared with other studies that deal with the production of
ethanol using different pretreatment configurations and raw
materials [32, 33]. Since most forest materials (hardwood
and softwood) are commonly used for the direct produc-
tion of energy through thermochemical processes (i.e. com-
bustion and gasification), the energy analysis was focused
on the potential energy used from P. patula for bioenergy
production through a biochemical pathway (fermentation)
and its comparison with a common thermochemical route
(i.e. gasification). Therefore, the gasification of P. patula
was also simulated but only for the energy comparison. The
energy efficiency of both processes was calculated based
on the relation between the energy content of the products
(ethanol and synthesis gas) and the energy content of the
feedstock [3]. A detailed description of the economic and
energy assessment is presented in “Economic Assessment
and “Energy Analysis” section, respectively.
Ethanolic Fermentation
Pinus patula is initially chipped and dried in order to achieve
the particle size and moisture content required for the fer-
mentation (see, “Ethanolic Fermentation” section). Subse-
quently, the physical treated raw material is submitted to a
two-step hydrolysis process in order to achieve the extraction
of sugars from the lignocellulosic matrix. In the first stage,
the hemicellulose fraction is hydrolyzed with dilute sulfuric
acid (2% by weight) at a temperature of 121°C. This stage
was modeled using the kinetic model and the parameters
reported by Rafiqul etal. [34] (see, Supplementary material
TableS1). Moreover, the kinetic model was solved using the
residence time specified in the experimental section (i.e.,
90min) aiming to obtain similar concentrations in compari-
son with those quantified in the experimental dilute acid pre-
treatment. Once the model was solved using the experimen-
tal conditions, the process was modeled in the Aspen Plus
V9.0 simulation software and the flowsheet was completed.
From this pretreatment, a non-converted solid fraction and
a rich-pentose liquor are obtained. This stream is separated
by filtration. The liquor is mainly composed of xylose and
glucose. Although, this stream was not considered for fer-
mentation since the strain S. cerevisiae used in this study
was not able to degrade xylose. The solid fraction, rich in
cellulose and lignin, is sent to an enzymatic saccharification
process at 50°C using cellulase as enzyme, which is able to
convert the cellulose to glucose for further use as substrate
in the ethanolic fermentation. The enzymatic hydrolysis
was modeled based on the experimental yields and using
the kinetic model and parameters reported by Khodaverdi
etal. [35] and Kadam etal. [36] (see, Supplementary mate-
rial TableS2). As in the case of the dilute acid pretreatment,
the experimental conditions applied to the enzymatic sac-
charification were used as input data in the kinetic model.
In fact, the cellulose, cellobiose and glucose concentration
profiles were calculated up to a residence time of 72h. Once
the final yields of the saccharification process were obtained,
these results were used to simulate the enzymatic hydroly-
sis in the Aspen Plus V9.0 software employing a RYield
model. Then, the fermentation process is simulated using
the S. cerevisiae as microorganism at 32°C. The yields of
the ethanolic fermentation were taken from the results of the
experimental procedure previously described in “Gasifica-
tion” section. Afterward, the cell biomass is separated from
the culture broth through a centrifuge. The culture broth
with an ethanol concentration of 7–10wt% is taken to the
separation stage that consists of two distillation columns and
molecular sieves. In the first column, ethanol is concentrated
nearly to 50–55% by weight[37]. This distillation column is
designed with 20 trays, a reflux ratio of 1.5 and a distillate-
to-feed ratio of 0.03. In the second column, the liquor is con-
centrated until the azeotropic point (96wt%) using a 20-tray
column with a reflux ratio of 1.5 and a distillate-to-feed ratio
of 0.3. Subsequently, the azeotropic mixture is sent to the
dehydration zone with molecular sieves to obtain ethanol at
99.7wt% [38]. The process scheme for the ethanol produc-
tion from P. patula is presented in Fig.1.
The simulation of the gasification was previously described
by García etal. [39]. The raw material is first conditioned
to the particle size and moisture content required for the
gasification. For this purpose, chipping and drying processes
are simulated in order to obtain a particle size between 0.5
and 1cm and a moisture content of 20%. Subsequently, the
chipped and dried raw material is submitted to a downdraft
gasifier where different chemical reactions (devolatilization,
combustion and reduction) take place. For simulation pur-
poses, the downdraft gasification is divided into two steps:
first, the devolatilization (pyrolysis) of the raw material is
carried out at 600°C in absence of air in order to obtain as
Waste and Biomass Valorization
1 3
main components carbon, hydrogen, oxygen, nitrogen, char
and ash. The elemental analysis (raw material characteriza-
tion) was used to determine the yields of carbon, hydrogen,
oxygen and nitrogen; whereas the char and ash content were
taken from the proximate analysis (raw material characteri-
zation). Then, the combustion and reduction are simulated
using the Free Gibbs Energy minimization method to predict
the composition of H2, CO2, CO, CH4, N2 in the synthesis
gas [40, 41]. Ash and particulate matter are separated from
the synthesis gas using a cyclone. This syngas can be used as
fuel for the production of electricity using gas engines. The
simulation of the engine was done based on the combustion
reaction between the syngas and air, but also considering the
electric efficiency of gas engines, which can vary between
40 and 45%.
Economic Assessment
The results of the mass and energy balances from the simula-
tion procedure were used as starting point for the economic
analysis. The total capital investment of the ethanolic fermen-
tation was calculated based on the data provided by the com-
plementary software Aspen Economic Analyzer v9.0 (Aspen
Technologies, Inc., USA), which performs the “mapping” (siz-
ing and costing) of the equipment. The operating costs were
divided into two types: fixed and variable. The fixed operat-
ing costs are those related to the operation of equipment in
the process such as labor, maintenance, fixed and general and
plant overhead costs. These costs were calculated based on the
estimation method reported by Peters and Timmerhaus [42].
Maintenance costs were estimated as the 6% of the total capital
investment [42]. The labor costs were determined based on
the number of employees-hour/day required for the operation
of a 3300 ton/day facility according to the data reported by
Peters and Timmerhaus [42]. Fixed charges were calculated
as the 3% of the total capital investment, whereas the plant
overhead and general costs were estimated as the 60% and
20% of the labor costs, respectively [42]. On the other hand,
the variable operating costs are those associated with the raw
material, reagents and utilities (heating and cooling) purchase
costs. The raw material and reagent costs were calculated
from the inflows of the process and the purchase prices (see,
Table1). The utility costs were calculated using the comple-
mentary software Aspen Energy Analyzer and data about the
market prices (see, Table1). This analysis was estimated in
US dollars for a 10-year period at an annual interest rate of
17% (typical for the Colombian economy), considering the
S. cerevisiae
Residual Solid Fraction
Pinus Patula
solid Water
Fig. 1 Scheme of the ethanol production from P. patula using S. cer-
evisiae as microorganism. Units (1) Acid Hydrolysis, (2) Filter, (3)
Detoxification, (4) Filter, (5) Dewatering, (6) Enzymatic Saccharifica-
tion, (7) Filter, (8) Dewatering, (9) Autoclave, (10) Ethanol Fermen-
tation, (11) Centrifuge, (12) Distillation column, (13) Rectification
column and (14) Ethanol dehydration. Repoduced with permission
from Referemce [31]
Table 1 Market prices of the raw material, utilities, and products
a Price of 1 ton of wood with a moisture content of 40% [43]. Update
b Price taken from Kemcore Supplier [44]. Updated 2018
c Price adapted from Colombian conditions. Update 2018
d Enzyme price calculated based on literature reports [45]
e Price taken from Federación Nacional de Biocombustibles [46].
Update 2018
f Price estimated using the correlations from [47]
Compound Value Unit
P. patula 60aUSD/ton
Sulfuric acid 275bUSD/ton
Process water 0.28fUSD/m3
Enzyme 110dUSD/ton EtOH
Ethanol 0.77eUSD/L
Electricity 0.016aUSD/MJ
Cooling water 0.07fUSD/m3
High-pressure steam 9.86cUSD/ton
Mid-pressure steam 8.18cUSD/ton
Low-pressure steam 7.56cUSD/ton
Waste and Biomass Valorization
1 3
straight-line depreciation method and an income tax of 25%.
Prices and economic data used in this analysis such as the costs
of the raw materials and utilities, income tax, labor salaries,
among others are summarized in Table1.
The results from the software Aspen Process Economic
Analyzer and the estimation method reported by Peters and
Timmerhaus [42] were used to determine the production cost
of 1L of ethanol using the dilute-acid hydrolysis coupled to
the ethanolic fermentation and P. patula as raw material. The
calculated production costs of the proposed process scheme
were compared to the reported data in the literature from dif-
ferent authors that have evaluated the production of ethanol
using different raw materials and pretreatments.
Energy Analysis
As mentioned in the methodology (“Materials and Meth-
ods” section), the energy comparison of the biochemical and
thermochemical pathways was carried out using ethanol and
syngas as energy carriers, respectively. The criteria selected
for this purpose was the energy efficiency of both processes,
which was calculated following the methodology proposed by
García etal. [3]. The energy efficiency was evaluated consid-
ering the gross energy content of the P. patula
the main products
of each pathway, as presented in
The energy content of the biomass was calculated based on
the mass flow (
) and the lower heating value (
) of the
P. patula reported by García etal. [23] (see, Eq.2).
In the same way, the energy content of the products was
calculated based on the mass flow rates and their respective
heating values (see, Eq.3, 4). The flow rates of ethanol and
syngas were obtained from the simulation procedure in the
software Aspen Plus. On the other hand, the heating values
were taken from different sources: the lower heating value
(LHV) of ethanol was 26.95MJ/kg [48], whereas the lower
heating value (LHV) of the synthesis gas was calculated
considering the mass composition and the heating content
of the main gaseous species in the synthesis gas (hydrogen,
methane and carbon monoxide). The LHV of the hydro-
gen, methane and carbon monoxide were 119.96, 50 and
10.11MJ/kg, respectively [48]. The calculated value for the
synthesis gas was 6.77MJ/kg.
Results andDiscussion
Dilute Acid Pretreatment andEnzymatic
Dilute-acid hydrolysis was used as the first stage for the pre-
treatment of the lignocellulosic biomass (P. patula) in order
to improve the efficiency of the enzymatic hydrolysis. The
quantification of the total reducing sugars was 25.37g/L,
which is higher than the results reported by Moncada etal.
[2] (20g/L) using P. patula bark. Additionally, Kim [49]
and Bösch etal. [50] reported yields of 39.3g of sugars per
100g of dry hemlock sawdust and 26.3g of sugars per 100g
of softwood spruce, respectively. The results obtained in this
work are acceptable in comparison to those reported in the
literature, despite the use of one-step dilute acid hydrolysis.
The solid fraction from the dilute acid hydrolysis was
used as input for the saccharification process. The highest
amount of reducing sugars in the liquid fraction from this
process was 20g of reducing sugars per 100g of dry feed
(3.02g/L). The results obtained in this work are in agree-
ment with those reported by other authors such as Söder-
ström etal. [11] (17g of sugars per 100g of Picea abies)
and Shinozaki etal. [51] (14g of reducing sugars per 100
f of ensiled rice straw). From the enzymatic saccharifica-
tion, a cellulose conversion of 67% (w/w) was achieved.
The enzymatic hydrolysate was used as carbon substrate
for the production of ethanol using S. cerevisiae as micro-
organism. The low concentration of reducing sugars in
the hydrolysate can be explained due to the high amount
of water used in the enzymatic hydrolysis. In this sense,
the hydrolysate was concentrated until a concentration of
Ethanolic Fermentation
The main objective of the experimental procedure was to
evaluate the potential use of P. patula for the production
of ethanol. For this purpose, the ability of the microor-
ganism to directly degrade the hydrolysate was evaluated.
Microorganisms can adapt to environmental perturbations,
such as changes in the osmotic pressure, temperature, and
depletion of nutrients [52]. Nevertheless, if the changes are
not progressive, the microorganism is submitted to stress,
which leads to a decrease in the cell growth or prolonged
lag phases. In order to reduce the stress of the microorgan-
ism, three fermentation configurations were proposed to
evaluate the effect of the substrate concentration and type
in the ethanol production (see, Table2).
Figure2 presents the consumption of total reducing
sugars during 69h of fermentation. As a result, a substrate
Waste and Biomass Valorization
1 3
consumption of 8.185, 7.996 and 6.295g/L was obtained
from the fermentation configurations 1, 2 and 3, respec-
tively. In the fermentation configuration 1, a relatively
high consumption of substrate was achieved; whereas the
final concentration of sugars in the configurations 2 and
3 were 50% of the initial concentration. It is important
to clarify that in the present study, inhibitors were not
quantified. However, previous studies have demonstrated
that lignocellulosic biomass (i.e. wood wastes) generates
hydrolysates that contain inhibitors such as furfural, HMF
and aromatic-lignin compounds that limit the microbial
growth, microorganism metabolism in the fermentation
and therefore, the consumption of the substrate [53]. In
this context, Qian etal. evaluated the dilute-acid hydroly-
sis of the softwood aiming to obtain a hydrolysate com-
posed of glucose and xylose, and its further fermentation
to ethanol by co-cultures [54]. In this study, two fermen-
tation configurations were studied: (i) detoxified hydro-
lysate by a combined method and (ii) hydrolysate without
detoxification. The use of the softwood hydrolysate with-
out detoxification evidenced the same behavior as the pre-
sent study, where 50% of the substrate was not consumed,
which indicates the possible presence of inhibitors in the
hydrolysate. Therefore, the hydrolysate should be detoxi-
fied in order to increase the substrate consumption and
ethanol production. However, the dilute-acid pretreatment
generates lower degradation products than the use of con-
centrated-acid pretreatments. Additionally, high hydrolysis
yields have been reported when pretreating lignocellulosic
materials with diluted H2SO4 [53]. Fermentation configu-
ration 3 showed a substrate consumption similar to con-
figuration 2, which was rich in glucose (15g/L). Conse-
quently, the microorganism does not require an adaptation
stage, so it is possible to use the microorganism in the
Additionally, Table2 presents the ethanol concen-
tration in each fermentation. An experimental yield of
0.364 ± 0.009g ethanol/g sugar (73% of the theoretical)
was obtained, which it is similar to the yields reported by
other authors Chacha [55] and Hawkins and Doran-Peterson
[56]. Nguyen etal. [57] used softwood chips through direct
impregnation with sulfuric acid and steam explosion as pre-
treatment to produce ethanol using S. cerevisiae. As a result,
ethanol yields between 74 and 89% of the theoretical were
obtained. Qian etal. [54] studied the fermentation of the
dilute-acid softwood hydrolysate to produce ethanol using
co-cultures of adapted S. cerevisiae and Escherichia coli.
The highest ethanol yield from the experimental procedure
was 0.45g/g total sugar. The low concentration of ethanol in
this work can be explained due to the use of substrates with
low sugar content, which suggests that the hydrolysate must
be concentrated to obtain a higher ethanol concentration.
Furthermore, fermentation 1 evidenced the lowest con-
centration of biomass (3.34g/L), as shown in Fig.3. While
Fermentation 2 (highest concentration of glucose) produced
a high concentration of biomass (4.51g/L) after 69h of fer-
mentation. The biomass concentration in the concentrated
hydrolysate showed an intermediate value between the two
Table 2 Fermentation
configurations for the ethanol
Description Total reducing sugars
Fermentation 1 Glucose (70%) + hydrolysate (30%) 10 3.678
Fermentation 2 Glucose (80%) + hydrolysate (20%) 15 5.563
Fermentation 3 Concentrated hydrolysate 13.5 4.790
Fig. 2 Substrate uptake in the
different fermentation configu-
Total reducing sugar(g/l)
Time (hour)
Waste and Biomass Valorization
1 3
previous experiments (3.7g/L). It should be noted that it is
very important to guarantee aseptic conditions (sterilization
of the medium and sampling) since the microorganism is
susceptible to external agents. This contamination can cause
reduction in the cell growth and undesirable products such as
lactic and acetic acid. In this work, these products were not
detected during the quantification of the samples.
Techno‑Eeconomic Analysis (TEA) oftheEthanolic
The total production costs of the ethanolic fermentation
were classified into four categories: raw material costs, util-
ity costs, fixed operating costs and total investment costs.
Figure4 presents the share distribution of these costs, evi-
dencing the effect of the raw material costs (63.4%) in the
total ethanol production cost. The utility costs account for
22.7% of the total production costs due to the high heating
requirements of the downstream processing of the fermenta-
tion broth. Besides, the purchase of equipment contributes
up to 12% of the total production costs. These results are in
agreement with the data reported by Mesa etal. [58] who
evaluated the production of ethanol through a dilute-acid
pretreatment using sugarcane straw as raw material. The
authors reported that the costs of raw materials (sugarcane
straw and enzymes) had the most significant impact on the
total production costs. The same behavior was evidenced in
this work as observed in Fig.5, where the share contribution
of the main raw materials costs is presented. In this case,
the P. patula and enzyme costs account for 59% of the raw
materials costs, whereas sulfuric acid accounts for 34%.
The moisture content of the P. patula has a significant
impact on the purchase price of this feedstock. According
to Forest Fuels [43], raw materials with high moisture con-
tent (40%) have a market price of 60 USD/ton, whereas raw
materials with low moisture (20%) content have a higher
market price 160 USD/ton.
Several authors have studied different methods to improve
the economic feasibility of the cellulosic ethanol production
by means of the on-site enzyme production. Liu etal. [45]
studied the influence of the enzyme cost on the cellulosic
ethanol production considering different scenarios where
the enzyme was commercially purchased or on-site pro-
duced. The authors concluded that the on-site enzyme pro-
duction can significantly reduce the enzyme cost, providing
Fig. 3 Biomass growth in the
ethanol fermentation
Cell concentration (g/l)
Time (hour)
Fig. 4 Share distribution of the total production costs of ethanol from
P. patula
Fig. 5 Share distribution of the raw material costs
Waste and Biomass Valorization
1 3
a promising option for the large-scale cellulosic ethanol
On the other hand, the high contribution to the total costs
of the sulfuric acid is related to the high liquid-to-solid ratio
used in the acid hydrolysis. From the experimental proce-
dure, a dilute sulfuric acid solution (2%v/v) in a liquid-to-
solid ratio of 1:10 was used. Considering the large process-
ing capacity of the evaluated process (3300 ton/day), the
required amount of sulfuric acid is too high and thus, it has
a great influence in the economic performance of the ethanol
production. Therefore, the amount of sulfuric acid used for
the pretreatment of P. patula should be reduced in order
to increase the profits of the process. One of the possibili-
ties is to reduce the concentration of sulfuric acid and the
liquid-to-solid ratio. However, these changes can affect the
sugar yields of the process and thus other variables must
be considered such as temperature and pretreatment time.
Parajó etal. [59] have evaluated these parameters in order to
determine the best conditions for the dilute acid hydrolysis
in order to use low amount of reagents and relative high
pretreatment times.
Based on the information provided by the economic
assessment, the production costs of 1L of ethanol were
calculated and compared with literature reports of differ-
ent raw materials that use the dilute-acid hydrolysis as pre-
treatment. Figure6 presents the comparison between the
ethanol production costs of the evaluated process, some
literature reports, and the market price. In this work, the
ethanol production cost was 1.53USD/L, which is higher
than the market price (0.77USD/L). However, the source
of the raw material has an important effect on the feasibility
of the ethanol production as evidenced by Daystar etal. [60]
who evaluated the ethanol production cost from different
raw materials (i.e. pine, eucalyptus, switchgrass and sweet
sorghum) using the dilute-acid pretreatment. When forest
biomass (pine) was used as raw material, the ethanol produc-
tion costs was 2.25USD/L, but if agricultural crops such as
sweet sorghum are used as feedstock, the ethanol production
cost drops to 0.5USD/L. Zhao etal. [61] studied the effect
of the dilute acid pretreatment in the ethanol production
using corn stover. As a result, an ethanol production cost of
1.6USD/L was obtained if no incentives were considered;
however, the ethanol cost can be reduced up to 1.24USD/L
if tax exemptions and Feed-in-tariff are considered.
Energetic Comparison ofBiochemical
andThermochemical Pathways forEnergy
Production Using P. patula
Table3 presents the results from the energy analysis of both
biochemical and thermochemical processes for bioenergy
production. It is evidenced that the energy yield of the etha-
nolic fermentation is lower than the gasification of P. patula.
As a result, the net energy efficiency of both processes was
20% and 42% for the ethanol and synthesis gas production,
respectively. The energy efficiency of the ethanolic fermen-
tation is lower than the data reported in the literature for
different raw materials [6264] since the valorization of the
xylose rich-liquor and the lignin was not considered in this
work. Additionally, the stillage from the first distillation col-
umn can be used as input for cogeneration systems, which
can reduce the heating requirements (steam) of the process
and thus, improve the overall energy efficiency. Despite the
high pretreatment requirements of P. patula for sugar extrac-
tion and the relatively low energy efficiency, the production
of ethanol through fermentation can promote the valoriza-
tion of the lignocellulosic matrix (cellulose, hemicellulose
and lignin) of this raw material to obtain different platforms
in comparison to the direct conversion to electricity. Elec-
tricity cannot be considered an added-value product due to
the low market price and the diversity of methods to produce
it, especially in Colombia where hydropower plants are used
to produce more than 60% of the electricity required in the
country [65]. On the other hand, the increment of the earth
temperature has increased the concern of using fossil fuels
as energy carriers due to the global warming. In this sense,
ethanol is gaining an important place as a future alternative
to fossil fuels, especially, in the automotive sector. In order
Fig. 6 Comparison of the ethanol production cost (USD/L) from dif-
ferent feedstocks
Table 3 Comparison of the energy potential of biochemical and ther-
mochemical pathways for energy production
a Calculation based on 3300 ton per day of P. patula
Biochemical pathway Thermo-
Process Fermentation Gasification
Main product Ethanol Synthesis gas
Energetic potential
Yield (MJ per kg PP)a3.91 7.68
Energy efficiency 22% 42%
Waste and Biomass Valorization
1 3
to fulfill the agreement in the COP21, blends between fossil
fuels and ethanol have been implemented aiming to reduce
the emissions from their combustion. This scenario provides
an opportunity not only to evaluate different technologies
to produce energy but also to consider other raw materials
that can be transformed into added-value products such as
It was evidenced that the P. patula hydrolysate can be used as
substrate for the production of ethanol. The microorganism
did not require a prior adaptation period to the hydrolysate.
Despite the low substrate consumption, an experimental
yield of 0.364 ± 0.009gethanol/g sugar (73% theoreti-
cal yield) was obtained. Nevertheless, it is highly recom-
mended to concentrate the hydrolysate due to the low solid
concentration in the enzymatic hydrolysis (15g/L). From
the simulation procedure, the costs associated with the raw
materials (P. patula, enzymes and sulfuric acid) have a sig-
nificant influence in the ethanol production costs and thus,
different scenarios should be analyzed in order to reduce the
ethanol production costs such as on-site enzyme production
and low sulfuric acid concentration. The calculated ethanol
production costs (1.55USD/L) were higher than the market
price (0.77USD/L); however, different alternatives can be
considered in the future aiming to improve the feasibility
of the ethanol production from forest biomass: integration
of waste streams and incentives for bioenergy production.
The lower energy efficiency (22%) of the biochemical route
in comparison to the thermochemical pathway endorse the
necessity to implement the previous alternatives in order to
consider the P. patula as a potential raw material to produce
added-value products such as ethanol.
Acknowledgements The authors express their acknowledgments to
the Centro de Bioinformática y Biología Computacional (BIOS) for
the financial support through the project entitled “Fortalecimiento
de CTEI en biotecnologia para el departamento de Caldas apoyado
por infraestructura computacional avanzada y trabajo colaborativo
(CALDAS BIOREGION)” Grant No. 08112013-0621. The authors
also express their gratitude to the Universidad Nacional de Colombia
Sede Manizales through the Projects entitled “Development of modu-
lar small-scale integrated biorefineries to produce an optimal range
of bioproducts from a variety of rural agricultural and agroindus-
trial residues/wastes with a minimum consumption of fossil energy—
SMIBIO” from ERANET LAC 2015 Grant No. 202010011331 and the
Project “Techno-economic and environmental evaluation of a biorefin-
ery using the residues from the Coffee Crop” Grant No. 202010014230.
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... The yield of CCS fermentation is 0.47 ± 0.03 g of ethanol per gram of glucose. García et al. (2018) reported several fermentation configurations using S. cerevisiae for analogous Pinus patula hydrolysates with some differences between them based on the substrate composition. For three different substrate compositions, experimental yields of 0.368, 0.371, and 0.355 g of ethanol per gram of glucose were obtained, after 69 h of fermentation (García-Velásquez et al. 2018). ...
... García et al. (2018) reported several fermentation configurations using S. cerevisiae for analogous Pinus patula hydrolysates with some differences between them based on the substrate composition. For three different substrate compositions, experimental yields of 0.368, 0.371, and 0.355 g of ethanol per gram of glucose were obtained, after 69 h of fermentation (García-Velásquez et al. 2018). When the obtained and reported results are compared, it is possible to conclude that the fermentation process carried out in this work presents better performance in terms of sugar consumption and ethanol yield. ...
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Energy-driven biorefineries can be designed considering biotechnological and thermochemical conversion pathways. Nevertheless, energy and environmental comparisons are necessary to establish the best way to upgrade lignocellulosic biomass and set the requirements of these processes in different scenarios. This paper aims to evaluate experimentally a biorefinery producing energy vectors using coffee-cut stems (CCS) as feedstock. The obtained yields were the basis for energy and environmental analysis, in two different biorefinery scenarios: (i) production of bioethanol and biogas and (ii) production of syngas and electricity. The energy results indicated that the overall energy efficiency calculated in the first scenario was only 9.15%. Meanwhile, the second biorefinery configuration based on thermochemical routes presented an energy efficiency value of 70.89%. This difference was attributed to the higher consumption of utilities in the biorefinery based on biotechnological routes. The environmental results showed that the impact category of climate change for the first biorefinery (i.e., 0.0193 kg CO2 eq./MJ) had a lower value than that of the second process (i.e., 0.2377 kg CO2 eq./MJ). Thus, the biorefinery based on the biotechnological route presented a better environmental performance. Additionally, the results for both biorefineries allowed concluding that the inclusion of by-products and co-products in the calculation of the environmental analysis can dramatically affect the results.
... CO2 generated from fossil resources, which are used in large quantities despite concerns about depletion, is one of the major causes of global warming [1]. Therefore, various studies have been conducted to form a sustainable energy recycling society with low environmental load using plant biomass [2][3][4]. Among plant biomass, woody biomass consisted of cellulose, hemicellulose, and lignin is the most abundant biomass on the earth, with less risk of depletion and less environmental impact, which could be a resource for the production of fuels and chemicals as an alternative fossil resources [5,6]. ...
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Steam treatment followed by milling treatment, an environmentally friendly method, was used and evaluated as a pretreatment of cedar for the preparation of cellulose nanofiber (CNF). The treated cedar was extracted with water followed by acetone and then received sodium chlorite (NaClO2) treatment, and separated into volatile component, water soluble component, acetone soluble component, NaClO2 soluble component, and NaClO2 insoluble component (a raw material of CNF preparation). The effects of steam pressures on the properties of treated cedar were examined from experimental data for the amounts of extracted components and the degree of polymerization. The properties of CNF obtained from cedar that was steam-treated at a steam pressure of 15 atm for a steaming time of 5 min and then milling-treated for 10 s were almost the same as those of commercial CNF (BiNFi-s). The reinforcing effect of CNF obtained in this treament condition was clarified, and the specific tensile strength and the specific Young’s modulus of PLA/CNF composite were 58.1 MPa/g/cm³ and 7.56 GPa/g/cm³ that corresponded to 1.6 and 3.1 times higher than those of PLA only, i.e. 33.0 MPa/g/cm³ and 2.44 GPa/g/cm³, respectively. Graphic Abstract
... With these data, an experimental yield of 0.476 ± 0.027 g of ethanol per g of glucose is obtained, which corresponds to 93.3% of theoretical yield (0.51 g ethanol per g glucose). García-Velásquez et al. (2018) reported several fermentation configurations using S. cerevisiae and P. patula hydrolyzate as microorganism and substrate, respectively. The difference between them is related to substrate composition (mixtures between hydrolysate and industrial glucose). ...
Lab and pilot-scale experiments during biorefineries design are mainly needed for modeling and validation purposes. This work presents experiments in a biorefinery based on Coffee Cut-Stems (CCS) to produce ethanol, electricity, and furfural. The biorefinery is proposed based on a flowsheet obtained in previous simulation work. Experimental and simulation results are compared in terms of productivities and conversions. As an overall result, the operating conditions for process stages involved in the CCS biorefinery are adjusted. The yields for the main products were obtained. In ethanol production, a yield of 0.476 ± 0.027 g ethanol per g of glucose is obtained. The dehydration reaction to furfural has a yield of 33.79 ± 0.42%, and the gasifier generates around 4.66kWh of electricity. In conclusion, the yields change significantly in comparison with the simulation results. The experimental work for the CCS biorefinery provided more accurate data for the proposed design.
The management of agricultural waste has become very important because the inappropriate disposal yields negative effects on the environment. The resources recovery from agricultural waste which converts waste into available resources can reduce the waste and new resource consumption. This review summarizes the 2018 researches of over three hundred scholar papers from several aspects: agricultural waste, and, waste chemical characterization, agricultural waste material, adsorption, waste energy, composting, waste biogas, agricultural waste management, and others. This article is protected by copyright. All rights reserved.
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Recently, hydrogen gas is becoming the most prominent alternative fuel due to its clean and environment-friendly nature. It only delivers water as a waste product during the operation instead of emitting harmful greenhouse gases. It has a high heating value (142 MJ/kg), over 2.75 times that of other hydrocarbon-based petroleum fuels. Presently, the primary method of producing hydrogen is the steam reforming of fossil fuels, which is not economical and environmentally harmful, and fossil fuels are on the deadline to finish. Hence, alternative methods of hydrogen production are the topic of current research. Biological methods of hydrogen production were found the best for producing green hydrogen because they utilize plentiful available renewable sources as feedstock. The dark fermentation technique is becoming more famous among all biological hydrogen generation methods because of its light autonomous nature and functional ability. It has the facility to convert any type of carbohydrate-rich organic substrates into bio-hydrogen, but pure carbohydrate substances are not economical on a commercial scale. Hence, carbohydrate-rich organic waste can be easily harnessed for bio-hydrogen generation. This method yields hydrogen gas and different high-volatility fatty acids, which could be used for industrial purposes after separation or as a precursor for the bio-methanation process for biogas production. This paper defines mechanism, microbiology, affecting factors, various integration methodologies, and potential and limitations related to the dark fermentation method. Graphical abstract
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This Intergovernmental Panel on Climate Change Special Report (IPCC-SRREN) assesses the potential role of renewable energy in the mitigation of climate change. It covers the six most important renewable energy sources – bioenergy, solar, geothermal, hydropower, ocean and wind energy – as well as their integration into present and future energy systems. It considers the environmental and social consequences associated with the deployment of these technologies and presents strategies to overcome technical as well as non-technical obstacles to their application and diffusion. SRREN brings a broad spectrum of technology-specific experts together with scientists studying energy systems as a whole. Prepared following strict IPCC procedures, it presents an impartial assessment of the current state of knowledge: it is policy relevant but not policy prescriptive. SRREN is an invaluable assessment of the potential role of renewable energy for the mitigation of climate change for policymakers, the private sector and academic researchers.
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Cost reduction on cellulase enzyme usage has been the central effort in the commercialization of fuel ethanol production from lignocellulose biomass. Therefore, establishing an accurate evaluation method on cellulase enzyme cost is crucially important to support the health development of the future biorefinery industry. Currently, the cellulase cost evaluation methods were complicated and various controversial or even conflict results were presented. To give a reliable evaluation on this important topic, a rigorous analysis based on the Aspen Plus flowsheet simulation in the commercial scale ethanol plant was proposed in this study. The minimum ethanol selling price (MESP) was used as the indicator to show the impacts of varying enzyme supply modes, enzyme prices, process parameters, as well as enzyme loading on the enzyme cost. The results reveal that the enzyme cost drives the cellulosic ethanol price below the minimum profit point when the enzyme is purchased from the current industrial enzyme market. An innovative production of cellulase enzyme such as on-site enzyme production should be explored and tested in the industrial scale to yield an economically sound enzyme supply for the future cellulosic ethanol production.
Forest residues are an important source of biomass. Among these, Coffee Cut-Stems (CCS) are an abundant wood waste in Colombia obtained from coffee crops renovation. However, only low quantities of these residues are used directly in combustion processes for heating and cooking in coffee farms where their energy efficiency is very low. In the present work, an energy and environmental assessment of two bioenergy production processes (ethanol fermentation and gasification) using CCS as raw material was performed. Biomass gasification seems to be the most promising thermochemical method for bioenergy production whereas, ethanol fermentation is a widely studied biochemical method to produce biofuels. Experimental runs of the CCS gasification were carried out and the synthesis gas composition was monitored. Prior to the fermentation process, a treatment of the CCS is required from which sugar content was determined and then, in the fermentation process, the ethanol yield was calculated. Both processes were simulated in order to obtain the mass and energy balance that are used to assess the energy efficiency and the potential environmental impact (PEI). Moderate high energy efficiency and low environmental impacts were obtained from the CCS gasification. In contrast, high environmental impacts in different categories and low energy efficiencies were calculated from the ethanolic fermentation. Biomass gasification seems to be the most promising technology for the use of Coffee Cut-Stems with high energy yields and low environmental issues.
Sugarcane straw is a lignocellulosic residue accumulated during the harvest of sugarcane and is a potential feedstock for second generation biofuel. This work covers the optimization of pretreatment step in the ethanol production using a complete factorial design (2³), where the analyzed factors were temperature, acid concentration and time in the Dilute Acid pretreatment. Desirability function was applied in this stage to maximize sugar yields and minimize inhibitor concentrations, resulting in overall sugars yield ∼60% and furfural concentration of 0.5 g/L. An enzymatic hydrolysis stage was done to increase sugar release. The fermentation stage was studied through three different configurations, such as Separate Hydrolysis and Fermentation (SHF), Simultaneous Saccharification and Fermentation (SSF) and Presaccharification and Simultaneous Saccharification and Fermentation (PSSF). The most promising alternative turned out to be PSSF due its higher ethanol concentration, with a value of 14.8 g/100 g dry weight (DW) biomass, equivalent to 187 L/tonne DW using C6-sugars. The economic analysis revealed that the integration between enzymatic hydrolysis and fermentation in the ethanol production affected the total capital cost. The cost of raw materials (sugarcane straw and enzymes) had the most significant impact on the total production cost and accounted between 35.66 and 25.88% of the total cost of the ethanol plant from sugarcane straw.
New efforts in the search of alternative clean and renewable energy to replace the current energy precursors have been assessed in order to reduce emissions to the environment. Lignocellulosic Biomass (LB) can be used to produce bioenergy due to its high energy potential and availability. Different ways are proposed for the transformation of these residues into high added-value products. Thermochemical and biochemical technologies are the most interest concepts focusing on the use of biomass as source for energy production at positive net balances. This study presents the techno-economic, energy and environmental assessment of five scenarios for the hydrogen production through gasification and dark fermentation based on the biorefinery and stand-alone concepts. The results demonstrated that the production of hydrogen based on the concept of a biorefinery can improve the profitability, energy efficiency and reduce the emissions of the processes compared to that based on the stand-alone way. The selection of ethanol and electricity as valuable co-products of the biorefinery in the hydrogen production process confirmed that the process scale and products diversity makes possible a flexible and suitable process to produce hydrogen and other energy carriers from Pinus Patula.
Lignocelluloses are widely investigated as renewable substrates to produce biofuels, e.g., ethanol, methane, hydrogen, and butanol, as well as chemicals such as citric acid, lactic acid, and xanthan gum. However, lignocelluloses have a recalcitrance structure to resist microbial and enzymatic attacks; therefore, many physical, thermal, chemical, and biological pretreatment methods have been developed to open up their structure. The efficiency of these pretreatments was studied using a variety of analytical methods that address their image, composition, crystallinity, degree of polymerization, enzyme adsorption/desorption, and accessibility. This paper presents a critical review of the first three categories of these methods as well as their constraints in various applications. The advantages, drawbacks, approaches, practical details, and some points that should be considered in the experimental methods to reach reliable and promising conclusions are also discussed.