Issue 2 [June]( Issue on Clean Energy and Sustainability ) Comparative behaviour of agricultural biomass residues during termochemical processingRincon S. And Gomez A., Pages:111-117 DOI: https://doi.org/10.30955/gnj.000866Paper Topic: General Issue: Issue 2Get Full Paper AbstractA 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 tannophylusSenkevich S., Ntaikou I. and Lyberatos G., Pages:118-124 DOI: https://doi.org/10.30955/gnj.000861Paper Topic: General Issue: Issue 2Get Full Paper AbstractOlive 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 gasificationHernandez J.J., Barba J. and Aranda G. , Pages:125-132 DOI: https://doi.org/10.30955/gnj.000859Paper Topic: General Issue: Issue 2Get Full Paper AbstractIn 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 sludgeNoutsopoulos C., Mamais D., Antoniou K. and Avramides C. , Pages:133-140 DOI: https://doi.org/10.30955/gnj.000862Paper Topic: General Issue: Issue 2Get Full Paper AbstractThe 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-digestionNeczaj E., Bien J., Grosser A., Worwag G. and Kacprzak M., Pages:141-148 DOI: https://doi.org/10.30955/gnj.000851Paper Topic: General Issue: Issue 2Get Full Paper AbstractIn 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 productionVlassis T., Stamatelatou K., Antonopoulou G. and Lyberatos G., Pages:149-156 DOI: https://doi.org/10.30955/gnj.000864Paper Topic: General Issue: Issue 2Get Full Paper AbstractThis 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 cyclesEscudero M., Jimenez A., Lopez I. and Rodriguez J., Pages:157-165 DOI: https://doi.org/10.30955/gnj.000857Paper Topic: General Issue: Issue 2Get Full Paper AbstractAnalysis 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 catalystsBereketidou O., Charisiou N.D. and Goula M.A. , Pages:166-174 DOI: https://doi.org/10.30955/gnj.000854Paper Topic: General Issue: Issue 2Get Full Paper AbstractNitrogen 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 fuelsDodos G.S., Konstantakos T., Loginos S. and Zannikos F. , Pages:175-182 DOI: https://doi.org/10.30955/gnj.000856Paper Topic: General Issue: Issue 2Get Full Paper AbstractThe 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 ECKretzschmar J., Majer S. and Kroeger M. , Pages:183-191 DOI: https://doi.org/10.30955/gnj.000850Paper Topic: General Issue: Issue 2Get Full Paper AbstractBiofuels 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. Pages1 2 next › last »