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The aim of this paper is to develop a novel method for the retrofit of Heat Exchanger Networks based on Bridge Retrofit analysis. The method identifies Retrofit Bridges that correspond to energy saving modifications using two new proposed tools: The Heat Surplus-Deficit Table and the Modified Energy Transfer Diagram. These tools both allow the identification and quantification of Retrofit Bridges. These tools have been developed following conventional Pinch Analysis tools such as the Composite Curve and Grand Composite Curve. The connection between the conventional Heat Exchanger Network synthesis tools and the proposed retrofit tools is established to improve understanding of the method and relate it to what is currently used in both literature and industry. The method is demonstrated with a simple illustrative example and a more detail paper mill case study. The paper mill incorporates a paper machine and paper recycling plant and is co-located with a Kraft pulp mill in New Zealand. Results from the retrofit method suggest a retrofit design that will achieve an annualised profit of NZD 570,000/y (USD 414,000/y) with a payback of 2.4 y.

The economic feasibility of producing ammonia through the gasification of three different feedstocks produced in pulp and paper mills is investigated in this paper. The first case uses black liquor, the main by-product of the kraft pulping process, as the feedstock, and in the other two cases pulp sludge (PS) and waste sludge (WS) are co-gasified with black liquor. For all three cases, a process model in which mass and energy balances were calculated was developed. The model results were used to estimate the equipment size and estimate costs. Techno-economic models were developed and ammonia production costs were calculated. A case study for Alberta, a western Canadian province, was conducted. The results indicated that for a 10% discount rate (or internal rate of return [IRR]), ammonia production in all three cases is cost competitive with current ammonia prices. The cost of production (COP) of ammonia for all three cases ranges from 743 to 748 $/t. Sensitivity and uncertainty analyses were conducted on the estimated COP, and the results show that the COP is the most sensitive to the capital cost, discount rate, electricity price and plant lifetime.

The integration of different conversion technologies can strongly contribute to the biomass potential exploitation. To this aim, the use of intermediate pyrolysis biochar is analyzed in this paper as an alternative co-substrate in anaerobic digestion. The specie Ampelodesmos mauritanicus has been specifically chosen in this case for its capacity to tolerate, accumulate and, in some cases, degrade organic and inorganic pollutants. The biochar, produced under intermediate pyrolysis conditions at 450 °C, 500 °C and 550 °C, has been here considered for a biomethane potential assessment. The intermediate pyrolysis process improves the herbaceous bioavailability and promotes the microbial activity by reducing the digestion lag phase. Three reactors, namely B450, B500 and B550, have been considered in this study. Acclimatized cow manure from food wastes digestion has been used as inoculum with 5 g of biochar. The reactors have been continuously monitored for 15 days keeping the temperature fixed at 37 °C. Excluding the inoculum contribution, an accumulated methane production of 465–540.4 ml CH4/g-VS has been measured with an LHV evaluated in the range 25.8–26.9 MJ/kg. The modified Gompertz equation has been then used to describe the influence of biochar production temperature on methane conversion. A lag phase of 1.8, 2.2 and 3.8 days respectively for B450, B500 and B550, has been estimated showing an inverse proportionality to the biochar production temperature. The biomass to biogas energy conversion analysis reveals a reduction in the efficiency with the biochar production temperature increase. This fact is attributed to the steep reduction in volatile solids occurring by increasing the pyrolysis process severity. As a whole, the paper present a novel approach to possibly combine phytoremediation and production of renewable energy by using Ampelodesmos mauritanicus.

Black soldier fly larvae containing high lipids had been considered an novel sustainable feedstock for lipid extraction to biofuels. The insect lipid was extracted with microwave assisted solvent extraction method. The energy consumption of this way was analyzed to determine the feasibility of the lipid extraction process. The comparison of the effects of different extraction conditions (dehydration methods, water content, extraction temperature, extraction time, equipment power, and solute-solvent ratio) on the energy consumption of lipid extraction from the energy insect was investigated systematically. The dewatering of the insect biomass was the most energy consuming step via a dry extraction method in this paper, constituting about 40–80% of the total energy consumption demand. Within the ranges of extraction factors values compared in this analysis, the microwave radiation powder and lipid extraction temperature had a pronounced effect on the total energy consumption in the ranges of investigated parameter. At last, the lipid extraction yield-dependent evolution of energy consumption for different extraction conditions was also investigated. Anyway, the economic and environmental aspects of lipid extraction from the energy insect needed to be further improved for its large scale implementation in the future.

This paper present the results of a batch study on thermal-acid pre-treated sugarcane bagasse (SB) and food waste (FW) as the substrate with waste activated sludge (WAS) as inoculum. Experiments were conducted in six different batch reactors under ambient condition. Each batch reactor was fed with varied substrate ratio (mixture of SB+FW) maintaining inoculum constant (225 mL) to investigate the highest methane generation. The thermal acid pre-treated sugarcane bagasse (SB) with food waste at mixture ratio (SB: FW∼ 35:65) had resulted the maximum biogas production of 7338 mL followed by (SB: FW ∼ 50:50) - 6747 mL and (SB: FW ∼ 100:0) - 4040 mL. The maximum reduction in Total Solids (TS) concentration was achieved 57% at mixture ratio of [SB: FW ∼ 65:35] followed by 44%from [SB: FW ∼ 85:15] and 41% from [SB: FW∼100:0]. Thermal acid pre-treated sugarcane bagasse produced 81% higher biogas generation at mixture ratio of [SB: FW ∼ 100:0], 63% at [SB: FW ∼ 50:50] and 22% at [SB: FW ∼ 35:65] and results obtained for biogas generation were modelled using Gompertz and logistic model and fitted well.

This paper analyses the improved energy and environmental performance of the biomethanation of a mixture of sheep manure (20% by weight) and cheese whey (80% by weight) in a reactor of 2 L capacity containing 2 g of charcoal in the form of a fixed bed with respect to the same process but without the charcoal in the reactor (control experiment). The results show an increased methane production of 27.05% and a reduction of the H2S content in the biogas of 34.7%, over those obtained in the control experiment. These marked improvements of the biomethanation process are attributable to the content of highly electropositive metals such as K and Ca in the charcoal which, because chemical reactions, can increase the pH of the medium and thus favour the processes of methanogenesis and sulphate reduction. Charcoal would act as a bacteriological adherent promoting the biomethanation of the organic waste materials used in the study.

This paper addresses the techno-economic, energetic and environmental assessment of the indirect and direct production of bioenergy using Pinus patula (PP) as raw material. Ethanol and synthesis gas are evaluated as main products through biochemical (fermentation) and thermochemical (gasification) routes, respectively. The complete characterization of the raw material was performed aiming to determine the chemical, proximate and elemental composition of the PP that is used as starting point for the simulation procedure. Mass and energy balances were obtained from the simulation of both processes using the software Aspen Plus v9.0. Different economic criteria such as Net Present Value (NPV) and Payback Period (PBP) were used to determine the profitability of both processes. The overall energy efficiency was calculated considering the relation between the energy content of the products and the energy content of the inputs (raw materials and utilities). The environmental assessment involves an attributional life-cycle assessment (LCA) of different systems such as seedlings production, PP cultivation, harvesting and collection, and the evaluated processes using a cradle-to-gate approach. As a result, the production of ethanol evidenced a low production cost (0.549 USD/L), higher energy efficiency (45.1%) and higher CO2 emissions (0.17 kg per MJ EtOH) in comparison to the biomass gasification.

This paper presents the overall performance, emission and combustion characteristics of the engine, when fuelled with biodiesel blends of Calophyllum Inophyllum methyl ester as injected fuel and babul wood chip derived producer gas as inducted fuel at constant injection timing (230bTDC), injection pressure (230 bar) and speed (1500 rpm). To improve overall performance, combustion and reduced emission characteristics of the engine, the combustion chamber was varied with 5 different geometries. Experimental results revealed that Toroidal re-entrant combustion chamber had higher Exhaust Gas Temperature and Brake Thermal Efficiency by 20.75% and 6.37% than that of HCC, while Brake Specific Fuel Consumption was reduced by 4.49% at optimal loading condition. However, engine overall performance of TrCC was found to be comparable with Hemi-spherical chamber and other designed combustion chambers. Similarly, comparing exhaust emissions, Oxide of Nitrogen and Carbon dioxide were on its higher side by 19.90% and 27.20% than normal HCC. On the contrary, carbon monoxide, Hydrocarbon and Smoke opacity for TrCC were found to be 76.12%, 33.71% and 38.67% lower than HCC. From the above study, it is finally concluded that converted renewable fuels with TrCC might be utilized as an alternative fuel without any exhaust related problems.

This paper presents a comprehensive approach for improved efficiency of a once-through Benson type coal boiler in a coal-fired power plant. In the method, petrographic properties, ultimate analysis and proximate analysis of coal feedstock is firstly determined. In addition, operational parameters, like O2 concentration, coal mass flow, air/fuel ratio and load were varied to establish their impact on both SO2 concentration and NOx reduction. The coal samples are led by inertinite in the range of 34.4 – 47.8 vol% afterward total vitrinite content in the range of 20.3 – 24.4 vol%. Liptinite content occurs in minor proportions of 1.8 – 4.3 vol% range. The optimum conditions for simultaneous reduction of NOx emission and SOx are achieved when the O2 concentration is 3.58% and coal mass flow of 288 tonnes/hr. Reducing coal mass flow from 331 to 288 Tonnes/hr caused high SO2 concentration to reduce from 3862 mg/Nm3 to 2232 mg/Nm3. Moreover, NOx concentration reduced from 350 mg/Nm3 to 310 mg/Nm3 when the air/fuel ratio varied from the lean side to the rich side. The optimum air/fuel ratio of 7.24 resulted in NOx reduction. The highest boiler efficiency of 90.97% was achieved at full load and the O2 concentration of 3.58%.

Spent tea waste (STW) is an organic waste that is disposed in open land after preparation of tea. Generally, it is disposed in an open land which increases anthropogenic gases. Converting it into useful energy or value added product may reduce disposal problem and anthropogenic activity. In this study, STW was co-digested with cow manure (CM) for obtaining biogas by anaerobic digestion. For this purpose, STW was mixed with CM at different proportions, namely 50:50, 40:60, 30:70, 20:80, and 0:100 percentages on a mass basis, the samples were used in five different anaerobic digesters. The samples were kept in different anaerobic digesters for the study. The effect of important input parameters like pH, Carbon to Nitrogen (C/N) ratio, and digestion time on the biogas production were studied. Further, the collected biogas from the digesters were characterised to ensure the suitability for use as a renewable fuel. Furthermore, the digested slurry was also analysed for its use in agriculture sector. The results are presented in this paper.

The increase in prices and our dependence on fossil fuels coupled with concerns about harmful emissions have motivated researchers to look for renewable and alternative fuels that have clean combustion and which can be produced locally. The fumigation of ethanol in diesel engines has been recognized as an effective alternative to improve efficiency and to reduce emissions. In this paper, the effects of a compression ignition engine using B7 and hydrous ethanol by fumigation method has been investigated. Hydrous ethanol was injected in the engine intake manifold by a port fuel injector, representing ethanol energy ratios from 11.5% to 52.3%. The results indicated a maximum decrease about 69% in smoke index, reduction in exhaust gas temperatures and reduction in both CO and CO2 emissions. The lowest CO emission found was 0,11% and CO2 emissions were 4.6% by volume. A maximum increase of 26.2% in thermal efficiency and 22.9% in exergy efficiency was observed. Nevertheless, an increase in HC emissions and specific fuel consumption was noted, achieving the maximum values of 121 ppm and 270.2 g/kWh, respectively. The results were satisfactory, confirming the potential to use ethanol fumigation method to improve thermal and exergy efficiency and reduce harmful gases.

This paper investigates the performance and emission analyses of a turbo-charged diesel engine fuelled with pre-mixed and post-mixed hybrid biodiesel blends at varying load condition thereby maintaining injection timing, injection pressure and speed constant at 230bTDC, 220 bar and 1500 RPM. The experimental result depicted that post-mixed biodiesel blends (POBD 20) showed higher brake specific energy consumption and exhaust gas temperature by 4.6% and 2.02% than that of diesel while brake thermal efficiency was reduced by 5.68%. However, engine overall performance of post-mixed biodiesel blends (POBD 20) was found to be comparable with diesel and other prepared test fuel blends. Similarly, comparing exhaust emissions, oxides of nitrogen and carbon dioxide were on its higher side by 2.64% and 2.43% than normal diesel fuel. On the contrary, carbon monoxide, hydrocarbon and smoke opacity for POBD 20 were found to be 36.87%, 51.5% and 23.2% lower than conventional diesel fuel. From the above study, it is finally concluded that POBD 20 blend may be used as an alternative optional fuel that can substitute present diesel fuel without much engine modification and exhaust related problems.

The pyrolysis characteristics of sewage sludge, wheat straw and its mixture were studied by non-isotropic thermogravimetric analysis (TGA). In the temperature range of 400 K–950 K, 40 K/min, 45 K/min and 50 K/min heating rate were set respectively, in N2 atmosphere and CO2/N2 mixed atmosphere. According to the thermal analysis chart obtained from TGA, it was observed the vast majority of mass loss spread at the range of 450–800 K in all samples. The Co-pyrolysis kinetics of sewage sludge and wheat straw was described by a fourth-order DAEM model. It is proved that the model can well match the TG experimental data. The results obtained from the optimized parameters show that the activation of sewage sludge is lower than that of wheat straw, and the activity of the mixture gradually increased with the increase of wheat straw content. The presence of CO2 has a slight inhibitory effect on the pyrolysis of the mixture below 900 K compared to that in an N2 atmosphere, but with temperature increasing, CO2 will have a secondary reaction with biochar.

The co-gasification of coal and dried sewage sludge (DSS) was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor. In this study, the effect of the blending ratio of coal and DSS was investigated. Producer gases that were obtained from the tar-cracking reactor filled with active carbon contained high levels of hydrogen (maximum H2: 27.7 vol%) and low tar contents (minimum tar: 0 mg/Nm3). Upon gasification of the coal/DSS blends, the hydrogen content decreased and tar content increased with increasing DSS. Blends with coal/DSS ratios of 70/30 and 50/50 showed a synergetic effect on tar reduction, which could be attributed to the high ash content of the DSS. The gasification of the 70% DSS blend increased the condensed tar yield by only 0.1 wt%, compared to coal gasification. Lastly, a hot filter filled with Fe-impregnated active carbon was applied to completely remove tar from producer gas, which led to the production of a tar-free and hydrogen-rich gas (30 vol%). Furthermore, the Fe-impregnated active carbon reduced the H2S content to 229 ppmv. In summary, it was possible to produce a clean gas from coal and DSS blends in the UOS gasification process.

This study explored the optimization of pretreatment of pineapple peel for biogas generation. Pretreatments were carried out sulfuric acid and alkaline hydrogen peroxide prior to anaerobic digestion while the response surface methodology (RSM) was used for optimization of the pretreatment procedures. The physical, chemical, proximate and structural compositions of the peels were determined prior to and at the end of the pretreatment procedures. The dynamics of microorganisms in the reactors were also evaluated by rapid molecular methods while the Fourier Transform Infra-red (FTIR) spectroscopy was employed in the identification of the chemical changes as a result of pretreatments. The use of H2O2 pretreatment caused enormous lignin solubilization in the pineapple peel. In comparison, biogas production was 67% more in the alkaline pretreated pineapple peel than the biomass treated with acid and also 51% over the untreated samples. The total biogas volume produced from the acidic pretreated, alkaline pretreated, not sifted untreated and sifted untreated samples are 194.2 ± 3.0, 587.5 ± 5.2, 287.8 ± 2.1 and 245.4 ± 3.1 respectively. Thus, the alkaline pretreated experiment used lower retention time to achieve maximum gas production in this study. The use of alkaline H2O2 on lignocelluloses has remained unpopular prior to this study. However, its usage in this study yielded better result than all the conventional treatments in terms of lignin solubilization and improvement in methane yield. Economically, the use of H2O2 for pretreatment is adjudged feasible because the 1504 kWh t−1 TS thermal energy gain obtained from the biogas produced by the alkaline treated peel exceeded the 921 kWh t−1 TS used in the pretreatment. This gives a net thermal energy of 583 kWh t−1 TS. Whereas, the investment into acidic pretreatment of pineapple peel may not be economically justified because the total thermal energy gain of −200 kWh t−1 TS was far lower than the 1236 kWh t−1 TS thermal energy that was consumed during the pretreatment giving a net thermal energy of −1436 kWh t−1 TS. Therefore, the use of mild alkaline pretreatment is advocated in biogas generation from pineapple peel and also for biofertilizer production mostly in localities of mass production.

The energy consumption of an ammonia process plays an important role in the industrial energy consumption. For an ammonia synthesis process using pure oxygen gasification, the energy consumption of cryogenic air separation occupies a large proportion. The purity of the oxygen product from the air separation unit is mostly 99.6% in an ammonia process with pure oxygen gasification. The energy consumption of air separation will decrease significantly, if the purity of the oxygen product is reduced properly, which will lead to the decrease of the energy consumption of the total ammonia process, as the nitrogen element is needed for ammonia synthesis. However, the operating costs of the subsequent units will increase because of the increase of the syngas flow rate. So, there is an optimal oxygen purity that can minimize the energy consumption of the whole ammonia synthesis process. According to temperature, purification technology can be divided into cold and hot technologies. In this work, two different process models for ammonia production from coal with different purification technologies are developed to determine the process energy consumption with different inlet oxygen purity. In the process of ammonia production from coal with cold purification, the reduction of oxygen purity leads to the increase of energy consumption of oxygen compressor, methanol regeneration and refrigeration, and the decrease of nitrogen compressor power consumption. In the process with hot purification, the reduction of oxygen purity leads to the increase of energy consumption of oxygen compressor, preheating and MDEA regeneration, and the decrease of nitrogen compressor power consumption. The relationships between the eight kinds of energy consumption and oxygen purity are linear. Combined with the relationship between oxygen purity and the energy consumption of the air separation unit, the optimal oxygen purity which minimizes the process energy consumption is obtained. In the ammonia production process with cold purification, the optimal oxygen purity is 95%, which can save 10.3% of the energy consumption of the air separation compared with the current process using the 99.6% purity oxygen. While in the ammonia production process with hot purification, the optimal oxygen purity is 96%, which can save 8.4% of the energy consumption of the air separation.

The practice of injecting a coal/biomass blend can alleviate the pressure on carbon emissions and energy of ironmaking blast furnaces (BFs). In this paper, corn stalks treated by hydrothermal carbonization (HTC) are used as raw materials to eliminate the harm of alkali metals in the ash. The overall performance of individual behavior of the hydrochar, coal, and their blends are analyzed over the raceway with special reference to gas flow, temperature, species, and combustion efficiency. The results show that the hydrochar with higher volatile content is faster to devolatilize, showing a higher CO2 content at the nozzle tip, and reaching a higher burnout in the raceway. The addition of hydrochar to coal can improve the overall flow and combustion performance of the blends. The simulated value is higher than the calculated value, indicating the synergistic effect has existed. When the proportion of the hydrochar is 75% in blends, the synergistic effect is most obvious. The model provides an effective tool for the design of coal/biomass blends.

This paper shows use of cow dung compost soil as a biocatalyst to optimize the urea fuel concentrations in the range of 0.1 g/ml to 0.5 g/ml in cow dung compost microbial fuel cells (CC-MFCs). The results indicate that the CC-MFC with the urea fuel concentration of 0.4 g/ml produces the maximum power. Moreover, the bacterial population plays a vital role in electricity generation. For constant cell operation and cell sustainability, it must be refuelled with the catalyst after every 12 h cycle and the max power density was generated 17.84mW/m2 by CC-MFC. This study confirms for the first time that cow dung compost directly works as a noval biocatalyst. Here primary focus is to generate power through soil processes using urea-rich wastewaters (urine) as fuel. CC-MFCs are inexpensive, non-toxic, leakage proof, low maintenance, less labour intensive, durable, stable, easily disposable, sustainable, and efficient. Moreover, these fuel cells can generate clean energy without biocatalyst deactivation. Research is going on fabrication and development of CC-MFC for application depend upon the type of urea rich urine wastewater used as fuel for power generation and cleaning the environment.

Different sludges such as municipal sewage sludge, paper/pulp mill sludge, and slaughterhouse sludge were collected and characterized for energy production. Bio-oils were produced from these sludges by supercritical liquefaction at 300 °C with methanol as the solvent. Carbon-rich and viscous bio-oils with yields about 20–30% were obtained. With methyl esters as the dominant component, these bio-oils were upgraded by blending or microemulsifying with biodiesel (fatty acid methyl esters). The optimum microemulsions were formed at biodiesel/bio-oil ratio of 10, with bio-oil content of more than 8% (which doubled that obtained by blending) and surfactant effectiveness of 0.5–0.6 g rhamnolipid/g bio-oil being obtained. The thermogravimetric studies show that the blending and microemulsifying processes led to the shift of decomposition range and rate to higher levels and the reduction of activation energy of the hybrid fuel systems. There may be synergies of enhancing the combustion or ignition of microemulsions when biodiesel and bio-oil were used in combination in diesel engines, overcoming the disadvantages of using either biodiesel (e.g., long ignition delay, etc.) or bio-oil (e.g., long ignition delay and viscosity, etc.) individually. Microemulsification may be a promising bio-oil upgrading technology.

The sugar industry is the second largest agro-industry in the world, with more than 80% of sugar produced from sugarcane. Sugar mills are energy-intensive and historically not designed to be energy efficient, even though they may be energy self-sufficient. This study presents a comprehensive exergy analysis of cane sugar production processes to identify inefficient components for improvement. The exergy analysis was based on rigorous mass and energy balances calculated from an Aspen Plus® simulation of a typical 250 ton per hour sugar mill, along with an appropriate exergy methodology. The exergy analysis of the cogeneration system, which has been found to be the principal sugar mill exergy destruction unit, is conducted separately and will be presented in a subsequent paper. The overall sugar mill irreversibility and functional exergy efficiency were 217.3 MJ per ton of cane crushed and 9.7%, respectively. The evaporation unit generated the highest irreversibility of 100 MJ/ton of cane, while crystallization unit had the lowest functional exergy efficiency of 9.6% and the highest potential for improvement of 47.0 MJ/ton of cane. The exergetic performance of the mill may be improved by adopting a single stage crystallization with an integrated biorefinery.

In this paper, we have produced bio diesel from papaya and watermelon seed oil by trans-esterification process using methanol and KOH (catalyst) and a new biodiesel i.e. WP is produced which is a mixture of papaya seed oil biodiesel and watermelon seed oil biodiesel in 1:1 ratio is prepared. The blends (B0, B20, B30, B40, and B100) of WP with diesel and watermelon 100% and papaya 100% are used for further testing. The performance, combustion and emission test were conducted on single cylinder 4-stroke diesel engine using different blends of these biodiesels and the results showed that B20 is superior blend among other biodiesel blends. Further the performance and combustion characteristics of B20 is very close to diesel while the emission characteristics of B20 is better than that of diesel as the emission of CO, HC and smoke is 27.27%, 23.8%, 8.3% less for B20 than diesel respectively. Thus we concluded that B20 is the most suitable blend of WP for substitute of diesel which will reduce diesel consumption by 20%.

The co-combustion of raw and torrefied biomasses is recognised as environmental friendly energy conversion. Co-combustion of hard coal with raw biomass has been widely investigated in the literature. In contrast, co-combustion with torrefied biomass has been not particularly investigated. This paper shows the investigations of co-combustion of raw, torrefied biomass and biodegradable waste in bubbling fluidized bed combustor. Two kind of biomass sources (i.e. willow (Salix viminalis), olive oil residue) and waste wood from furniture manufacturing were analysed in terms of fuel feeding rate, CO, SO 2 and NO x emission and ash behavior. The part of a raw biomass was torrefied using a rotary kiln reactor. Hence, the combustion performance of raw and torrefied biomass was compared. The impact of torrefaction on the emission of CO, SO 2 and NO x depends on biomass type. In the case of willow the decrease of SO 2 emission was obtained when the raw biomass was substituted by the torrefied biomass. Additionally, ash fusibility from the raw and torrefied biomass was analysed. It was noticed that co-combustion of torrefied biomass caused increase of ash initial deformation temperature (IDT) comparing to co-combustion with a raw biomass.

Landfill leachate secreted from the compressed wastes in landfills over time is toxic to natural ecosystem and poses serious health issues for communities and surrounding environment. The dual role of microalgae for leachate remediation and biomass production make them one of the most sustainable renewable systems for leachate quality improvement. Ultra-membrane treated leachate from Istanbul municipal landfill was evaluated in three laboratory scale experimental sets for the growth of indigenous microalgal strains and ammonium nitrogen (NH 4 + -N) removal. Among all the dilutions of leachate 50% showed better microalgal growth curves, but significantly lesser than control nutrient media. NH 4 + -N removal was systematically decreasing with increasing leachate concentration. Highest removal efficiency (100%) was observed in 10% TL (∼50 mg/L NH 4 + -N). Overall quality of TL was improved in terms of NH 4 + -N removal which is considered as one of the most persistant pollutants pertaining to leachate toxicity. The issues discussed in the paper can be a focus point to further improve leachate quality.

The main aim of the paper is to analyze the effect of different pretreatment processes (HTC, torrefaction and slow pyrolysis) on the properties of Miscanthus giganteus. In this study, the HTC process was conducted in a Zipperclave Stirred Reactor under following parameters: temperature (180, 200 and 220 °C), pressure (

Using lignocellulosic biomass as an alternative resource for transportation fuel is an attractive prospect due to its abundance and low cost. Conventional pre-treatment methods such as steam explosion or ammonia fibre expansion need technologically complex equipment and high energy input, and they use toxic chemicals in order to achieve high glucose and ethanol yields. In this paper, the freezing pre-treatment of barley straw is investigated as a low energy input and cost-effective alternative pre-treatment method for second generation bioethanol production. In the freezing pre-treatment method, milled biomass mixed with water was frozen in temperatures as low as −18 °C for a certain period of time and was then thawed to room temperature (around 22 °C). The freezing cycles were repeated several times so that the effect of repeated freezing could be studied. In addition, field experiments were carried out by taking samples of barley straw which had been stored outside, both in bales and swathes during a period of time between September and March in two consecutive years (in winter 2014–2015 and 2015–2016). Freezing pre-treatment was followed by enzymatic hydrolysis and fermentation. Glucose and ethanol yields and, additionally, hydrolysis and fermentation efficiencies were used as indicators of pre-treatment efficiency. The highest hydrolysis efficiency figure was 19.42%, which was achieved in laboratory tests where the biomass was frozen and thawed a total of four times. The best result from a field test was 10.28% from straw which had been stored in a swathe and which has been gathered in March. Fermentation yields ranged up to 88.80 g per kilogramme of biomass. Field tests showed that in the bale the temperature never fell below freezing and therefore the pre-treatment was not effective. When in the swathe the straw does freeze through, but the winter in Estonia was too changeable for this method to work effectively.

The main objective of the research was to develop a method of biomass grindability determination (Biomass Grindability Index), which would allow for a clear classification of different types of solid biofuels in terms of their milling properties. The objective of the research included also the assessment of the possibility of adaptation of the existing coal grindability determination methods for evaluation of biomass milling. In the course of research, the biomass grindability determination method was modified to obtain the highest possible reliability of the developed index. The scope of laboratory tests being focused on influence of circumferential speed of test mill beaters, particle size distribution of sample, test time, mass and volume of sample. The results of laboratory and industrial tests have shown that the grindability index based on mean particle sizes of feed and product is unreliable. Grindability of different types of biomass, comminuted in beater mills, can be clearly determined by the index expressed as the ratio of energy consumption during the test to the amount of specified product size fraction. During the study laboratory test results obtained for proposed grindability index were compared to other grindability indices determined for utilized in research types of biomass.

In this work, the liquefaction of coal and biomass with direct liquefaction strategy was explored. The point of liquefaction is both to utilize a greater amount of the current coal and biomass assets all the more productively and to create an alternative liquid fuel to oil. Along these lines, the procedure parameters must be resolved to expand the liquefaction efficiency. In addition, it is proposed to do the liquefaction efficiency, particularly in the reactant conditions, to expand the measure of oil. Process parameters were controlled by utilizing Factorial Experimental Design technique in the liquefaction procedures. The solid/liquid ratio was changed as 1/2-1/4, the catalyst concentration was 2–6%, the temperature was 375–400 °C and the duration was 30–90 min. Starting nitrogen pressure was set at 30 bar, stirring speed was 400 rpm, coal/biomass proportion was settled at 1/1. Tetralin as a solvent and MoO3 as catalyst were utilized. Toward the finish of the liquefaction procedure, the total conversions were computed in view of the acquired non-reactive solid (char). As indicated by the outcomes obtained, the most total conversion (81.9%) was acquired at a solid/liquid proportion of 1/2, a catalyst concentration of 2%, a reaction time of 90 min and a reaction temperature of 400 °C. In light of total conversions and elective liquid fuel (oil) in the given conditions, the solid/liquid ratio should be taken as 1/2, the catalyst concentration is 2%, the reaction time is 30–90 min and the reaction temperature is 400 °C. The lowest reaction time found, in this study, is the innovative solution for reducing co-liquefaction cost preferred.

Detailed model was proposed in this work for exergy analysis of a real biomass boiler. The model was based on an equilibrium model which uses Gibbs Energy minimization and energy balance to calculate the flue gas composition, the temperature of the furnace and the temperature of the flue gases along the boiler. The exergetic efficiency was calculated by the indirect method, and the exergy destruction in each component of the boiler and each material stream was evaluated. The Gibbs minimization model predicted successfully the complete combustion of the biomass and can be adapted to another thermochemical processes. The exergy analysis results showed that the furnace and the water walls have the higher exergy destruction, accounting for 47% and 30% of the total exergy destruction, respectively. In other parts of the boiler, the exergy destruction was higher in the water and steam flows than in the flue gases, and the results indicate that exergy destruction was higher in streams at lower temperatures. The global exergetic efficiency was 42.47%.

This investigation explored engine performance, combustion and exhaust emissions with a new series of fuels for compression ignition engine. Three blends were formulated using diesel, tea tree oil and diethylene glycol dimethyl ether (DGM). Low grade tea tree oil is considered as waste, which was used as fuel in this investigation. DGM was blended with tea tree oil and diesel as an additive for its high oxygen content and cetane number. Diesel was chosen for comparison purposes. The three blends examined in this study were, 70-30-0, 70-20-10 and 70-10-20 in ratios of diesel-tea tree oil-DGM. A six-cylinder, four-stroke, turbocharged diesel engine was used in this experiment. Four different loads of 25%, 50%, 75%, 100% and 1500 revolutions per minute (rpm) were selected for the experiments. Engine performance parameters like efficiency, power, mean effective pressure and specific fuel consumption were considered. In-cylinder pressure, the rate of heat release, peak and boost pressure were considered for combustion parameters. Carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM) and particulate number (PN) were considered for emission parameters. A maximum of 70% PM, 54% PN and 33% CO reductions were observed with three blends. However, 16% higher NOx emissions were observed with the blends.

This research presents the results of statistical significance tests for evaluating the main effect of water-diesel emulsion usage (containing 2%, 5%, 8% and 10% by vol.) and engine load on the engine performance and emission parameters. To exclude inevitable random errors of measurements, the mean values of measured data were compared using Duncan's multiple range tests (MRT). The decrease in heating value and increase in fuel density and viscosity were observed with increasing water content. Although the fuel pour point decreased with water presence, but it didn't depend to water percentage. The combustion of emulsions significantly decreased the engine power and torque at 1% probability level (P

The interest in water-diesel emulsion fuel (EM) is increased recently because of the significant reduction in emissions from diesel exhaust, especially NOx and PM. In this study, a diesel engine configured for experimental investigations was fueled by ultra-low sulfur diesel (ULSD) and a diesel-water emulsion (EM). Both fuels’ combustion characteristics were studied at a speed of 1500 rpm and using a load of 2.5 and 5 bars and variable injection timings. Regular and irregular pollutants were studied at the same conditions as well as at variable engine loads and speeds to better understanding for their formation conditions. As for the first time (in the case of an engine running with a water-diesel emulsion) irregular pollutants for EM emulsion were measured. The measured results indicated that the use of water-diesel emulsion reduced the heat released in the combustion chamber, which causes an increase in the brake specific fuel consumption and ignition delay. For the tested loads, the diffusion combustion duration for EM was decreased when the injection timing was retarded while the opposite was occurred for premixed combustion duration. The regulated NOx and Smoke Number were reduced when EM was used compared to ULSD while CO and HC levels were increased at low engine’s speed and loads. Besides, these concentrations are depending on injection timing (they were higher at restarted timing). The unregulated emissions measured (Formaldehyde, Acetaldehyde, Methane, Acetylene, Ethylene, and propylene, Ammonia, and Acetone) were increased with using EM, especially at no and low loads, indicating the high impact of the combustion chamber temperature on these pollutants formation.

Despite the advantages of bio-sourced lubricants, they are still far from replacing petroleum energy because of their poor cold flow properties and oxidation stability, so the recycling of waste lubricating oil with antioxidant vegetables extracts based energy resources remains a key management to avoid environmental pollution by millions of tons of degraded lubricating oils, and to contribute a good economic management of oil consumption which is being depleted. The regeneration of lubricating oils using vegetable oils is a method of trapping free radicals produced during lubricant degradation due to their tribological and physico-chemical property, including renewable character and biodegradability. This study aims to evaluate the effect of Chamaerops Humilis L. (EEG) and Amposta red onion (EET) antioxidants extracts on the regeneration of waste lubricating oils, using Electron Paramagnetic Resonance (EPR) and Fourier Transform Infrared spectroscopy (FTIR) techniques. These oily extracts have chosen because of their important composition of total Phenols in the form of Catechins and Gallic acid which offer them a very effective oxidation inhibition. The obtained results show that the oily naturel extract based on Chamaerops Humilis L has an oxidation inhibitor up to 82% and 60% for Amposta Red Onion extract.

Biodiesel appears as a replenishable and sustainable energy source and can be used a direct replacement to petro-diesel without any major transformations in ongoing diesel engines. This work concentrates on production of Calophyllum Inophyllum biodiesel (CIB) and preparing 10% blend (CIB10) sample to investigate the effects of varying the injection strategies and exhaust gas recirculation (EGR) in common-rail direct injection engine. The experimental results shows that 10% of pilot fuel and 90% main injection strategy (B10@P10-M90) is superior among all others injection strategies with respect to pure diesel. B10@P10-M90 fuel injection strategy produces the maximum efficiency of 35.8% and lowest fuel consumption of 0.25 kg/kWh compared to all the injection strategies. The carbon monoxide (CO) and hydrocarbon (HC) emissions are also found to be quite low compared to all the other test samples including pure diesel. However B10@P10-M90 results in higher average oxides of nitrogen (NOx) emission which is 18.9% higher in contrast to conventional diesel at full load condition. With the implementation of 10% and 20% EGR with B10@P10-M90, the average NOx emissions decreased by 14.4% and 27.6% respectively compared to B10@P10-M90 without any EGR without significant loss in the performance of the existing diesel engine.

The stable H2 production is the important link in the anaerobic biohythane fermentation. In order to address the key parameters for the stable H2 production in the recirculated temperature-phased anaerobic digestion (R-TPAD) system, a critical strategy was proposed to adjust the recirculation ratio (R). The adjusting strategy was examined on a lab-scale R-TPAD system. The R-TPAD system was started up and operated with R = 1. Another system without recirculation (R = 0) was also operated as the control system. By narrowing the probable range from 0

Palm oil mill effluent (POME) is a potential source for biohydrogen. A continuous stirred tank reactor was used to study the effects of mixing speeds of a Rushton turbine on the biohydrogen production. The initial organic loading rate and volatile solids of influent were 55 g of chemical oxygen demand per liter of influent per day and 30.28 g of volatile solids per liter of influent, respectively. The retention time was 24 h and the turbine speeds were 10, 50, 100, and 150 rpm. The corresponding hydrogen yields were 2,669, 2,868, 3,413, and 3479 mL per liter of influent. The total maximum hydrogen yield at 150 rpm was equivalent to 6958 mL per liter of POME. A speed of 100 rpm was recommended for the constant speed operation as it gave the highest net energy gain of 23.96 kJ LPOME-1. Five varying speed schemes were studied to determine the maximum net energy gain. The varying speed schedule should be 100 rpm for the first 8 h and 10 rpm for the rest 16 h, which increased the net energy gain by 11% in comparison to the 100 rpm constant mixing speed. Feasibility analysis revealed possibility in industrial application.

This work demonstrated the possibility of bioelectricity generation using microbial fuel cell technologies from sugarcane molasses by a bacterial strain isolated from molasses. The strain identified according to 16S rRNA as Brevibacillus borstelensis STRI1. Sugarcane molasses could be used as a substrate in MFC, because of its high sugar content. When the bacterial strain was used as biocatalyst and sugarcane molasses as a substrate in MFC. The voltage increased rapidly over time recording 990 ± 5 mV in open circuit voltage (OCV), and 453 ± 6 mV in closed circuit voltage (1000 Ω) after 10 days of operation. The power density (Pmax) determined from the polarization curve, and it was 188.5 mW/m2 with an initial concentration of sugarcane molasses 1 ml (1632 mg/L as COD). While the coulombic efficiencies (CEs) ranged from 59.8 to 28.03%, related to initial concentrations of 0.3 ± 0.05 to 2.0 ± 0.15 g/L. The COD removal was determined and it was 11.7% after 5 days and reached to 81.7% by the end of the operation (30 days). These results suggested that bioelectricity could be generated from sugarcane molasses by Brevibacillus borstelensis STRI1.

Limited fossil fuel reserves led to focus on alternatives fuels for combustion engines. Several studies reported optimal (20%) biodiesel blend for utility in compression ignition engine at constant compression ratio. Literature lacks on the study of palm-based biodiesel in blended form at varying engine compression ratios. In this study, an initiative was undertaken to study the effect of variable compression ratio (16:1, 17:1 and 18:1) on various engine characteristics by fuelling 20% palm biodiesel blending compression ignition engine. The ignition delay period decreased, whereas the peak cylinder pressure and brake thermal efficiency increased with increase in the engine compression ratio from 16:1 to 18:1. At 3.5 bar bmep, brake thermal efficiency values were observed to be 28.9, 30.8 and 33.8% at 16:1, 17:1 and 18:1 CRs, respectively in B20 fuel. Moreover, increasing compression ratio from 16:1 to 18:1, the average reduction in emissions of hydrocarbon, carbon monoxide and smoke opacity were observed to be 47.8, 41.0 and 35.7%, respectively whereas, oxides of nitrogen emissions increased by 41.1%. Thus, it is inferred that B20 fuel performed well at high engine compression ratio.

In this study the mixing quality of turbine impellers with blade angles of 30°, 45°, and 60° was studied on the anaerobic digestion efficiency using a new model based on mixing time, energy consumption, biogas compounds, and slurry characterizations. Study on the mixing process using a single indicator system based image processing technique showed a mixing for 5 and 10 min and pausing for 5 h. The results showed that (i) the impeller with blade angle of 30° and mixing time of 5 min consumed the least energy whereas produced the most CH4 amounts associated with more TS, T.VS, C, and N degradation, (ii) the impeller with blade angle of 60° produced the least CO amounts associated with more COD and BOD removal, and (iii) the suitable mixing time decreased the CO and H2S production. The results confirmed that the significant effects of the impeller blade angle and mixing time on biogas compounds were because of changing the slurry characterizations during the mixing process. Using the new model for efficiency evaluation, the impeller with blade angle of 30° in mixing time of 5 min had the highest efficiency among the researched cases documented its favorite for better digestion in higher efficiency.

Energy penalty of solvent regeneration in CO2 absorption process is a critical challenge. To avoid the energy consumption, novel ammonia absorption-microalgae hybrid CO2 capture process has been designed in this work. In the proposed process, the conventional desorption column is replaced by a microalgae cultivation system. As a result, the NH4HCO3 could be utilized as nutrient for microalgae growth and converted into biofuel or value-added ingredients. Meanwhile, the challenge of ammonia escape could be avoided via high purity ammonia recycling in the hybrid process. The experimental results indicated that the selected Chlorella sp. L166, L38 and UTEX1602 could be potential microalgae to be used in chemical-biological hybrid CO2 capture and utilization process with carbon fixation efficiency over 85%, and the yield of protein, lipid and polysaccharides was 164 ± 1 mg/L (L166), 710.6 ± 165.8 mg/L (UTEX1602) and 143.6 ± 28.8 mg/L (L38), respectively. The above results also indicated that the novel absorption-microalgae hybrid process could be a promising alternative to the conventional CO2 absorption technology.

The purpose of this work was to investigate the viability of a microalgae catalytic pyrolysis/hydrotreating plant to kerosene, diesel and gasoline using Aspen Plus. A series of 2000 dry tonne per day scenarios were simulated with the final goal of determine the price in USD per litre of the drop-in fuels produced and the economic feasibility of the technique at a large-scale. Different scenarios (mechanical, solar and thermal drying), microalgae (Nannochloropsis and Isochrysis) and catalysts (Li-LSX zeolite, Ni-Ce/Al2O3, Ni-Ce/ZrO2). For this work, a systematic design approach by Douglas was considered and the whole process was actualised with the Marshall and Swift Cost Index of 2016. The lowest minimum fuel selling price (1.418 $/L) was found for Isochrysis and Li-LSX-zeolite. Finally, the sensitivity analysis showed that the bio-oil yield was the most influent factor, leading to a variation of the fuel price between 1.158 $/L to 1.751 $/L assuming a 20% of variation. The techno-economic assessment and sensitivity analysis indicated that Isochrysis and Li-LSX-zeolites are promising for the production of drop-in fuels, but further research is required to further reduce the price of the feedstock production and drying to be competitive with lignocellulosic materials.

When using the novel N2 explosive decompression pre-treatment, its effect was investigated in relation to the biomass structure and chemical processes during the treatment process. The results that were gained from this testing were compared to those for the widely-used steam explosion pre-treatment method in order to be able to present the advantages in using each method. Both methods are economically and environmentally attractive since only the pressure and water or steam are used to break down the biomass structure. Two pre-treatment methods were used at different temperatures and samples from various process steps were analysed. The results were used to assess the pre-treatment effect and the chemical changes in the biomass and, finally, mass balances were compiled for the bioethanol process at different process steps. The results show that the highest glucose and ethanol yields were obtained by means of the steam explosion pre-treatment method at a temperature of 200 °C (24.29 g and 12.72 g for 100 g of biomass respectively), and at 175 °C (15.4 g and 9.0 g for 100 g of biomass respectively). At lower temperatures the nitrogen explosion treatment produced better yields.

The growing emphasis in alternative revenue streams, from the conversion of sugarcane bagasse into energy co-products has prompted a desire by the sugar factories to achieve higher levels of energy efficiency. This study presents a comprehensive overview of the parameters whose steady-state deviation leads to excess energy use in sugar mills. The effect of eight operating parameters on the defined energy indicators was investigated, using a MATLAB simulation of a 250-tonne per hour sugar mill. The captured energy trends were used to develop energy prediction models based on the parameters whose steady-state offsets resulted in excess energy use. High prediction accuracies of over 95% were obtained when the developed energy prediction models were validated for seasonal cane quality and evaporator heat transfer coefficient variations. Increased A-massecuite recycling had a more pronounced effect on the energy used per kilogramme of water in the evaporator unit as compared to the crystallisation unit. Of the eight parameters, elevated imbibition water use and A-massecuite recycling had a cumulative percentage effect of 79% on the overall steam used per tonne of cane and sugar produced. Hence increasing the syrup concentration, decreasing imbibition water use and massecuite recycling are preferred operational strategies for improved energy-efficiency in a sugar mill. Overall, this study strengthens the existing literature by illustrating an approach for developing suitable energy indicators for excess energy use monitoring in sugarcane mills.

Landfill Leachate is a heavily contaminated wastewater. MFCs (Microbial Fuel cells) are unique bioreactors, which utilize the catalytic activity of microbes for converting the chemical energy stored in organic-rich streams for bioelectricity production. MFCs represent an auspicious technology to treat landfill leachate and generate bioelectricity. Here, we evaluated the addition of ferrous sulfate as anodic coagulant as well as a media component to enhance the MFC performance. The Box-Behnken Design model of Response surface methodology (RSM) was found suitable for the determination of optimal conditions for the removal of chemical oxygen demand (COD). COD removal of 78.6% was achieved with coagulation alone at pH 8, reaction time of 90 min, and a coagulant dose of 3 g/L. Ferrous sulfate addition to MFC, significantly improved COD removal. 99.6% removal of total COD was achieved from 75% of landfill leachate, at a retention period of four days; whereas, with 100% leachate as anodic feed, 98.7% COD was removed on the third day. The volumetric power density of 6644.6 mW/m3 was achieved without any catalyst using flexible graphite sheets as electrodes. This study revealed that the integration of coagulation with MFC technology enhanced the treatment efficiency as well as power generation for landfill leachate.

Two sugarcane biofuels and mineral diesel fuel are tested under full load conditions, under the same values of performance and under the European Transient Cycle on an engine test bench, without any modifications to the ECU. The target is to compare engine performance and emissions. At full load, engine performance varies due to the variation in LHV. Under the same values of performance, the sugarcane biodiesel-LS9 provides the lowest THC emissions. The higher CN and exhaust gas recirculation of the sugarcane biodiesel-LS9 and the higher H/C ratio of the sugarcane diesel-farnesane compared to the diesel S50 provide a NOx reduction. Neither the increment in bsfc nor the increment of %EGR for the sugarcane biodiesel-LS9 deteriorate the combustion, so its CO emissions are lower. The sugarcane biodiesel-LS9 leads to the lowest NOx and PM specific emissions under transient operation, followed by the sugarcane diesel-farnesane. The THC and CO specific emissions are higher for the biofuels in comparison to the diesel S50. The main reason for these results is the impact of the properties of the biofuels on the ECU response However, both biofuels produce less harmful emissions at idle conditions, which supports their usage to reduce exhaust emissions in urban areas.