Global NEST Journal

ISSN:

Print ISSN: 1790-7632

Electronic ISSN: 2241-777X

Issue 2

Volume number:

14

Publication year:

2012

Publication month:

June

Issue on Clean Energy and Sustainability

Articles

Comparative behaviour of agricultural biomass residues during termochemical processing

Rincon S. And Gomez A., Pages:111-117

DOI:

https://doi.org/10.30955/gnj.000866

Paper Topic:

General

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Abstract

A study of the pyrolysis and gasification of biomass residues such as oil palm shells and fibers,
coffee shells, sugarcane bagasse and beech wood is presented. All of them are abundant
agroindustrial biomass residues in Latin American countries.
The characterization of the raw materials and products includes proximate analysis (water, ash and
volatile matter contents) and ultimate analysis. Pyrolysis and gasification experiments are carried out
in a thermobalance and in a pilot scale rotary kiln reactor. Both facilities are equipped with evolved
gas analysis.
Pyrolysis experiments were carried out using nitrogen as carrier gas by heating up to a temperature
of 950 °C. Gasification is performed using water vapour as reaction agent in a concentration of 70 %
H2O in nitrogen. The gasification temperature is set to 850 °C.
All wastes show similar behavior during pyrolysis in the thermobalance with the main mass loss at
temperatures below 550 °C. The solid fraction varied from 18 % for sugarcane bagasse to 27 % for
oil palm shells and the gas fraction from 18 % for oil palm shells to 22 % for sugarcane bagasse.
The main evolved gases are CO2 (9 – 12%), CO (3.5 – 7.5 %) and CH4 (1.6 – 3 %). H2 was also
found but in a very small fraction (0.5 – 0.7 %) (all fractions are referred to the initial dry mass). The
heating value of the pyrolysis products from the experiments in the thermobalance of the different
wastes presented small variations with a mean value of 6.5 MJ kg-1 for the evolved gas, 20 MJ kg-1
for the tar and 19 MJ kg-1 for the solid residual.
The presence of secondary reactions in the rotary kiln affects considerably the amount of gas and
tar in the products. The higher heating value of the evolved gases varies between 17 and19 MJ kg-1.
The obtained results allow a possible further technological use of these materials as a cheap
renewable energy source in countries where these materials can be found.

Bioethanol production from thermochemically pre-treated olive mill solid residues using the yeast Pachysolen tannophylus

Senkevich S., Ntaikou I. and Lyberatos G., Pages:118-124

DOI:

https://doi.org/10.30955/gnj.000861

Paper Topic:

General

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Abstract

Olive oil mill solid residue (OMSR) is the solid waste generated during olive oil production process in
three-phase olive mills. It consists of the remaining pulp of olive processing after the extraction of oil,
as well as the cracked seeds of the olive fruits, containing thus mainly lignocellulose and residual oil.
The commonly used practice for OMSR management is combustion, after having extracted the
residual oil by secondary extraction using organic solvents. Other proposed ways of OMSR
management are their exploitation as substrate for edible fungi production and compost, and as
feedstock for biofuels generation such as methane and bioethanol. In the latter case, the complex
carbohydrates (cellulose and hemicellulose) of the lignocellulose of OMSR have to be degraded
towards their simple sugars and further fermented via microorganisms.
The purpose of the present study was to investigate the effect of thermochemical pre-treatment of
OMSR, on the final ethanol yield from the yeast Pachysolen tannophilus. Nine different types of
OMSR-based substrates were tested i.e. raw OMSR, hydrolysates generated from pretreated OMSR
with NaOH (0.5 %, 1.5 % w/v) and H2SO4 (0.5 %, 1.5 % v/v), and pretreated OMSR with NaOH (0.5 %,
1.5 % w/v) and H2SO4 (0.5 %, 1.5 % v/v) whole biomass. It was shown that in all cases pretreatment
enhanced the consumption of carbohydrates as well as ethanol final yields.

Combustion characterization of producer gas from biomass gasification

Hernandez J.J., Barba J. and Aranda G. , Pages:125-132

DOI:

https://doi.org/10.30955/gnj.000859

Paper Topic:

General

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Abstract

In the present work, premixed flames from the combustion of producer gas have been analyzed.
Two different compositions have been tested, corresponding to air and steam gasification processes
(the latter leading to a better quality gas due to its higher CO and H2 concentration and its lower N2
content). The main objectives of the work have been the determination of the flame stability region
(placed between the flashback and the blowoff limits) for each producer gas composition, as well as
the study of the OH and CH radicals. The combustion experimental tests have been carried out by
using an atmospheric burner and a chemiluminescence camera.
The results obtained show that producer gas coming from biomass entrained-flow steam gasification
seems to be more adequate to be used in combustion systems, since it provides a larger flame
stability region, and its blowoff limit for a given relative producer gas/air ratio is higher (which enable
to obtained more power). From the study of CH and OH radicals, it can be deduced that it is possible
to reduce the nitrogen oxides emissions up to 18.6 and 15.2 % with producer gas from steam
gasification and air gasification respectively by using lean mixtures (while keeping the flame
stability).

Increase of biogas production through co-digestion of lipids and sewage sludge

Noutsopoulos C., Mamais D., Antoniou K. and Avramides C. , Pages:133-140

DOI:

https://doi.org/10.30955/gnj.000862

Paper Topic:

General

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Abstract

The aim of this study was to assess the feasibility of co-digesting lipids originated from domestic
wastewater along with sewage sludge. Three lab-scale single stage mesophilic anaerobic digesters
were operated under a constant hydraulic retention time (15 days). One system (C) was fed on a
daily basis with sewage sludge and served as the control system and its operation was compared
with two experimental systems (E1 and E2). Both experimental systems received mixtures of sludge
and lipids with different lipids content (20 % for system E1 and 60 % for system E2 on a VS basis),
whereas organic loadings were 2 KgVS m-3 d-1 and 3,5 KgVS m-3 d-1 for systems E1 and E2,
respectively.
According to the results it can be stated that the addition of lipids to sewage sludge up to 60 % on a
VS basis resulted in a significant increase of biogas production without producing any severe effects
on the properties of the digested sludge. More specifically biogas production of reactor E1 was 18 %
greater than that of reactor C, whereas biogas produced in reactor E2 was even greater (50 %
higher than that of reactor C). Finally it is interesting that during start-up a lag phase was recorded at
reactor E2 before biogas production initiated, which should be attributed to the time required for
growth of acetogenic bacteria capable to degrade LCFA.

Anaerobic treatment of sewage sludge and grease trap sludge in continuous co-digestion

Neczaj E., Bien J., Grosser A., Worwag G. and Kacprzak M., Pages:141-148

DOI:

https://doi.org/10.30955/gnj.000851

Paper Topic:

General

Issue:

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Abstract

In recent years many researchers show a high interest in co-digestion, simultaneous anaerobic
decomposition of a homogenous mixture of at least two biodegradable waste. Anaerobic codigestion
is reported to offer several benefits over digestion of separate materials, such as increased
cost-efficiency, increased biodegradation of the treated materials, as well as increased biogas
production. Most often sewage sludge is digested alone while co-digestion with other substrates
could be beneficial.
In this study, the feasibility of co-digestion sewage sludge and grease trap waste (GTW) from meatprocessing
plant was investigated in lab-scale reactor experiment. The research was made on the
sewage sludge coming from municipal wastewater treatment plant and grease trap waste coming
from meat industry company. Anaerobic co-digestion was studied in semi-continuous experiment at
37oC. Feeding of reactors was performed once a day with hydraulic retention time (HRT) of 10 days.
The grease trap waste accounted for 2, 4, 6, 8 and 10 % of the mixture on the volatile solids basis.
The mixtures were analyzed for the following parameters: total solids, volatile solids, pH, volatile
fatty acids and long chain fatty acids (LCFAs). The control of digestion process was made every day
on the basis of the measurement of the biogas production. What is more, there was determined the
volatile solid removal as well the biogas yield in order to assess the efficiency of co-digestion
process.
It was found that co-digestion of sewage sludge and grease trap waste improved both biogas
production and methane content. Grease trap waste addition of 10% of feed VS increased the
biogas production by 16 % as well as methane concentration (72 % of biogas) compared to the
period when reactor was feed only with sewage sludge. Moreover, the addition of GTW to the
anaerobic digestion of sewage sludge increased organic matter removal.
Although, the significant variations in LCFAs reduction, the biogas production and methane yield
increased with higher addition of GTW.
The results of the present laboratory study revealed that the use of GTW as a co-substrate is
considered to be interesting option for sewage sludge digestion due to increased methane
production. However, the feed should be planned carefully with stepwise increase to the desired
feed ratio in order to acclimatize the bacteria and to prevent reactor overloading.

Anaerobic treatment of glycerol for methane and hydrogen production

Vlassis T., Stamatelatou K., Antonopoulou G. and Lyberatos G., Pages:149-156

DOI:

https://doi.org/10.30955/gnj.000864

Paper Topic:

General

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Abstract

This work focused on glycerol exploitation for biogas and hydrogen production. Anaerobic digestion
of pure glycerol was studied in a continuous stirred tank reactor (CSTR), operated under mesophilic
conditions (35oC) at various organic loading rates. The overall operation of the reactor showed that it
could not withstand organic loading rates above 0.25 g COD L-1 d-1, where the maximum biogas
(0.42 ± 0.05 L (g COD)-1) and methane (0.30 ± 0.04 L (g COD)-1) production were achieved.
Fermentative hydrogen production was carried out in batch reactors under mesophilic conditions
(35oC), using heat-pretreated anaerobic microbial culture as inoculum. The effects of initial
concentration of glycerol and initial pH value on hydrogen production were studied. The highest yield
obtained was 22.14 ± 0.46 mL H2 (g COD added)-1 for an initial pH of 6.5 and an initial glycerol
concentration of 8.3 g COD L-1. The main metabolic product was 1.3 propanediol (PDO), while
butyric and acetic acids as well as ethanol, at lower concentrations, were also determined.

Use of alternative fuels obtained from renewable sources in Brayton cycles

Escudero M., Jimenez A., Lopez I. and Rodriguez J., Pages:157-165

DOI:

https://doi.org/10.30955/gnj.000857

Paper Topic:

General

Issue:

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Abstract

Analysis and simulation of the behaviour of gas turbines for power generation using different nonconventional
fuels obtained from different renewable sources are presented. Three biomass-tobiofuel
processes are considered: anaerobic digestion of biomass (biogas), biomass gasification
(synthesis gas) and alcoholic fermentation of biomass and dehydration (bioethanol), each of them
with two different biomass substrates (energy crops and municipal solid waste) as input.
The gas turbine behaviour in a Brayton cycle is simulated both in an isolated operation and in
combined cycle. The differences in gas turbine performance when fired with the considered biofuels
compared to natural gas are studied from different points of view related with the current complex
energetic context: energetic and exergetic efficiency of the simple/combined cycle and CO2
emissions. Two different tools have been used for the simulations, each one with a different
approach: while PATITUG (own software) analyses the behaviour of a generic gas turbine allowing a
total variability of parameters, GT-PRO (commercial software) is more rigid, albeit more precise in
the prediction of real gas turbine behaviour. Different potentially interesting configurations and its
thermodynamic parameters have been simulated in order to obtain the optimal range for all of them
and its variation for each fuel.

Simultaneous removal of NO and SO2 from combustion fuel gases using supported copper oxide catalysts

Bereketidou O., Charisiou N.D. and Goula M.A. , Pages:166-174

DOI:

https://doi.org/10.30955/gnj.000854

Paper Topic:

General

Issue:

Issue 2

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Abstract

Nitrogen oxide (NOx) and sulphur dioxide (SO2) emissions produced by the combustion of fuel in
stationary sources, such as power stations, industrial heaters or cogeneration plants, cause
significant environmental problems. Selective catalytic reduction (SCR) is a well established
process for the control of NOx emissions mainly due to its efficiency, selectivity and economics.
High removal efficiencies for both NOx and SO2 can be achieved with the use of copper oxide
catalysts, as they act as sorbents for the latter - forming copper sulfate - and catalyze the reduction
of the former - to N2, in the presence of NH3. An added advantage is that these catalysts are
relatively easy to be regenerated under reducing conditions.
This study examines the deactivation and regeneration procedures of copper oxide
catalysts/sorbents that are supported on Al2O3, SiO2, CeO2-Al2O3, in the presence of SO2 and
identifies the appropriate conditions for the simultaneous removal of NO and SO2. The results
obtained indicate that copper oxide supported on alumina, ceria-alumina and silica carriers, can be
used as effective catalysts for the simultaneous removal of NO and SO2. Furthermore, they can be
easily regenerated with a gas mixture of 1 % NH3/Ar at an optimum temperature of 673 K and they
retain their initial activity. Thus, the use of regenerative fixed bed catalytic reactor appears as one
of the most promising technologies however, further research focusing in new catalytic materials
performance is necessary.

Effects of microbiological contamination in the quality of biodiesel fuels

Dodos G.S., Konstantakos T., Loginos S. and Zannikos F. , Pages:175-182

DOI:

https://doi.org/10.30955/gnj.000856

Paper Topic:

General

Issue:

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Abstract

The introduction to the European Market of biodiesel blends along with the minimization of the
sulphur content in automotive diesel has rejuvenated the research interest on the microbial stability
of diesel fuel. Several microorganisms are able to metabolize hydrocarbons contained in
conventional fuels and particularly in diesel and jet stocks. With the advent of FAME (Fatty Acid
Methyl Esters) as a diesel fuel substitute there has been an increase in the number of samples
suspect of microbial contamination with confirmative results. The aim of this study was to investigate
the microbiological stability of FAME/diesel blends and consequently the impact of microbial
proliferation on their quality. A commercially available FAME was blended with Ultra-Low Sulphur
(ULSD) and Low Sulphur (LSD) conventional automotive diesel fuels in mixing ratios of 5, 10 and 20
% v/v. The resulting blends were contaminated with bottom-water of known viable microbial colonies
and were stored for a period of 16 weeks. During storage the microbiological growth was evaluated
by employing both semi-quantitative and quantitative methodologies. At the same time the
devolution of certain quality parameters, namely oxidation stability and acid number, which could be
influenced by microbial growth was examined. The overall results reveal the need to establish a
scheduled inspection plan adapted to the diesel fuel supply chain infrastructure aiming to control and
remedy efficiently the microbiological growth issues.
KEYWORDS:

International overview on waste to biofuel options with a focsu on waste potentials in Germany and funding incentives in the EC

Kretzschmar J., Majer S. and Kroeger M. , Pages:183-191

DOI:

https://doi.org/10.30955/gnj.000850

Paper Topic:

General

Issue:

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Abstract

Biofuels represent a possibility to reduce greenhouse gas (GHG) emissions within the transport
sector. In this context the sustainability of biofuels, especially so called 1st generation biofuels led to
controversial discussions in the past. Biofuels from waste and residues represent a well suited but
quantitative limited alternative due to their sustainability. At an international level, different
approaches for converting waste and residues into biofuels can be found. Developing countries in
general use classic transesterification of waste fats to produce biodiesel. Technically advanced
options such as pyrolysis, gasification, Fischer-Tropsch-Diesel, anaerobic fermentation and
distillation, as well as biogas production coupled with biomethane upgrading, are mostly found in
industrialized countries. Within this study, different waste to biofuel options are reviewed ranging
from small scale to industrial scale and take into account used raw materials, technological
application and (potential) GHG-reduction. Further the potential of several wastes and residues for
gasification processes and synthesis of biofuels in Germany is described. Biofuel from waste offers
promising funding incentives because of the “double counting” according to 2009/28/EC and the
switch in mandatory blending from an amount based quota to a GHG-based blending quota in 2015.

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