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The objective of this work is to study the addition of n-pentanol with the Calophyllum Inophyllum biodiesel to evaluate the performance, emission and combustion characteristics. Five different fuel blends are prepared by varying the n-pentanol fraction (10%, 20%, 30%, 40% and 50%) on volume basis with biodiesel. The prepared samples are tested in single cylinder constant speed CI engine. The addition of n-pentanol with biodiesel improves the thermal efficiency of the fuel blend up to 30% as compared to pure biodiesel. Among all fuel samples, B90P10 blend has shown higher brake thermal efficiency as 27% which is slightly lower than BTE of diesel fuel. The brake specific fuel consumption of biodiesel-pentanol blends are increased from 4.2% to 27.3% when compared to diesel fuel (D100). However, addition of n-pentanol more than 40% shows a negative effect in terms of performance and combustion. It is noted that biodiesel and n-pentanol blends have shown 15–43% and 33–50% reduction in hydrocarbon and carbon monoxide emissions compared to diesel. Further, the oxides of nitrogen and smoke emissions are found to be lesser for n-pentanol blends while comparing to the pure biodiesel. Among all blends, B90P10 is found to have better performance and emission characteristics.

Non-edible Jatropha seed used for biodiesel production has increased due to its high-oil contents in kernel and potential to reduce greenhouse gas emission. High demand for biodiesel generates a large volume of waste. In this study, de-oiled Jatropha seed kernel was torrefied at 200 °C, 250 °C and 300 °C, holding time of 15, 30, 45 and 60 min and particle sizes of 0.5–1.0 and 1.0–2.0 mm to produce solid fuel. Torrefaction performance was highly affected by torrefaction temperature compared with holding time. The enhancement factor of HHV increased up to 1.243 after torrefaction at 300 °C and 60 min with particle size of 0.5–1.0 mm. The large particle size reduces the diffusion rate of torrefaction vapour through internal pores, thereby producing high solid yield and low enhancement in HHV. The analysis of torrefaction severity index shows that HHV increase is highly dependent on the weight loss, thereby directly decreasing the total energy in biochar. Scanning electron microscopy image clearly illustrated that the microparticles on the surface were destroyed to increase the porous structure of the biochar with increasing torrefaction temperature. Severe torrefaction with particle size of 0.5–1.0 mm was an effective approach to increase the energy content of biochar.

Rapid depletion of fossil fuel and CO2 mitigation are two major challenges in the modern society. CO2 gasification of carbon-neutral biomass could be an attractive technology to cope up these two emerging problems. Replacing conventional gasifying agent air with CO2 could reduce the fraction of undesired N2 in the gas products because CO2 behaves as inert gasifying agent under low temperature and could be converted to CO at high temperature range. However, most researches on CO2 gasification are limited at the lab-scale level due to the endothermic feature of Boudouard reaction. In this work, a feasibility study of small-scale autothermal gasification using 15% CO2 and 85% air was conducted and compared with traditional air gasification. Prior to that, a lab-scale study of gasification behaviors, under N2, air and CO2 agents, were performed. It was found that using CO2 as gasification oxidant could produce comparable energy (6.67 kJ/g feedstock) to air gasification (7.45 kJ/g feedstock) at equivalent condition (800 °C, 40 min). The pH of biochar obtained under CO2 condition at 800 °C was measured to be 10.63 while the pH of biochar derived by air gasification at the same temperature could reach 12.32. In addition, a small-scale gasification experiment with 15% CO2 addition was successfully conducted in a downdraft autothermal reactor. The results showed CO production was greatly enhanced while CH4 generation was suppressed owing to Boudouard reaction and CO2 dry reforming. Cold gas efficiency and carbon conversion efficiency were both enhanced by 5.8% and 6%, respectively, with CO2 addition. Meanwhile, particulate matters (PM) emitted from both air gasification and 15% CO2 gasification experiments were measured. It was found that under the same equivalence ratio (ER), 75.4% less particle number concentration was emitted during 15% CO2 gasification compared to air gasification.

Biogas production of three-phase olive mill solid waste (3POMSW) was studied in lab-scale continuously stirred tank reactors (CSTR) at organic loading rates of 1.5–2.0 g VS L−1 d−1 and temperatures of 35 and 55 °C. To acclimate microorganisms to 3POMSW the start-up phase was performed under thermophilic and mesophilic conditions for 40 days. In order to improve the biogas yield, the enzyme MethaPlus® was added and its effect was investigated. Results indicate that thermophilic processing has a higher biogas yield by 8% compared to mesophilic conditions, but there was no significant difference in methane yield. Under thermophilic conditions, addition of the enzyme to 3POMSW resulted in a significant increase in methane yield by 10%. Under mesophilic conditions, the enzyme did not have a significant effect on biogas yield or reactor performance. The quality of biogas for all experiments was sufficient. Long-term experimentation indicated the beginning of reactor failure.

This work is a study of tribo-corrosion and engine characteristics of Aegle Marmelos Correa biodiesel and its diesel blends. The tribology results revealed that B50 showed the lowest steady-state coefficient of friction (SSCOF) amongst all the other blends. SSCOF of B100 is 23.27% more than B50. Similarly, SSCOF of B90, B60, B20, B10, and diesel are 19%, 8%, 17.23%, 31.9% and 40.11% greater than the SSCOF of B50 respectively. Wear scar diameter (WSD) results also showed that B50, B60, B90, and B100 have lower WSD of around 0.6 mm. Diesel showed the highest WSD of 0.8 mm. Flash temperature parameter (FTP) is inversely related to WSD, and thus B50, B60, B90, and B100 exhibited higher FTP of around 80. On evaluating the corrosion characteristics, B50 exhibited lesser corrosion inducing capability compared to all the other blends. Experimental investigation of the engine showed that B100 yielded lesser thermal efficiency and higher specific fuel consumption than diesel. The CO, HC, NO, and smoke emissions were minimum for B100 when compared to diesel. Finally, all the results revealed that B100 is the ideal blend that can perform efficiently and be a sustainable energy source for diesel engines.

The effects of microwave (MW) final temperature (80 and 160 °C) and holding time (1 and 30 minutes) were evaluated by ten anaerobic digesters (AD). MW was applied to dewatered secondary sludge with total solids of 10.5 ± 0.5% (by weight) to minimize energy input. Mixed sludge was digested under thermophilic and mesophilic conditions at sludge retention times (SRTs) of 20, 12, and 6 days. MW final temperature had significantly higher effect on solubilization than holding time. At MW of 80/160 °C, longer holding times further enhanced solubilization but increased volatile fatty acid accumulation at thermophilic SRT of 6 days. While all mesophilic digesters met the Class B requirement in terms of pathogens removal, all thermophilic digesters produced Class A biosolids. MW-ADs were able to tolerate 15–20% higher loading rates compared to controls. Up to 21% higher organics removals were achieved by MW. MW at 160 °C generated the highest amount of extra heat that could be used within/outside of plant. However energy recovered from the enhanced methane production was not sufficient to cover the electrical energy consumed by MW. Therefore, a custom-designed electromagnetic heating unit based on dielectric properties of sludge is needed to minimize energy input and maximize energy recovery for full-scale applications.

An experimental study was conducted in a port-fuel injection (PFI) spark-ignition (SI) engine fueled with acetone-butanol-ethanol (ABE) and gasoline. 30 vol% ABE blends with different component ratios (A:B:E = 3:6:1, 6:3:1, and 5:14:1), referred to as ABE(3:6:1)30, ABE(6:3:1)30, and ABE(5:14:1)30, were used as test fuels. Additionally, 30 vol% ethanol and 30% vol.% butanol blended with 70 vol% gasoline, referred to as E30 and B30, respectively, were also used as test fuels. Both the regulated emissions, which include unburned hydrocarbons (UHC), carbon monoxide (CO), and nitrogen oxide (NOx), and unregulated emissions, including acetaldehyde, 1,3-butadiene, benzene, toluene, ethylbenzene, and xylene (BTEX), were investigated under various conditions. The experiments were conducted at an engine speed of 1200 rpm and at engine loads of 3, 4, 5, and 6 bar brake mean effective pressure (BMEP) under various equivalence ratios (φ = 0.83–1.25). The results indicated that ABE(6:3:1)30 had the lowest UHC and CO emissions, with ABE(3:6:1)30 having slightly higher NOx emissions. As for unregulated emissions, B30 showed the highest acetaldehyde emission and ABE(6:3:1)30 had the lowest among all the fuel blends. ABE(3:6:1)30 and ABE(6:3:1)30 showed a reduction in 1,3-butadiene emission. Regarding the BTEX emissions, an overall reduction was observed for all the fuel blends, with ABE(3:6:1)30 having shown the lowest BTEX emissions among all the test fuels. The results indicate that ABE could be used as a promising alternative fuel in SI engines, owing to the reduction in emissions.

The increasing cost of fossil fuels as well as increasing environmental pollution has attracted research in alternative fuels and additives for improving the performance and reducing emissions of diesel engines without costly engine modifications. In the present article, an exhaustive analysis of the performance and emissions of oxygenated ternary fuel blends is done through modeling and experimental investigation to determine the optimal blending ratio of additives for reduced emissions. The Nitromethane-n-butanol–diesel blend is termed as bio-oxygenated fuel. Baseline data were generated by using diesel and a blend of 20% (v/v) n-butanol with diesel (B20). Ternary blends of Nitromethane (NM) and B20 containing 1–3% NM by volume were prepared and experiments were conducted. It was observed that 1% of Nitromethane by volume (NM1B20) gives best results for emission reduction. The overall effect of this ternary blend was reduction in smoke and nitrogen oxides (NOx) by 61.85% and 8.07%, respectively, as compared to diesel. Moreover, the performance of ternary blend was also found to be better than the base fuels. It was thus concluded that Nitromethane-n-butanol–diesel blends can be highly effective alternatives in reducing emissions in diesel engines with a little improvement in the overall performance characteristics.

The present work encompasses combustion, performance, and emission parameters of experimental investigations of a single cylinder, four stroke, water cooled, direct injection (DI), naturally aspirated compression ignition (CI) engine with a rated power output of 3.7 kW at constant engine speed (1500 rpm) using diesel and different blends of microalgae spirulina. The microalgae spirulina blend of ratio with diesel (BYY) where YY indicates blending percentage (0%, 20%, 40%, 60%, 80%, and 100% volume basis with diesel respectively) with different engine loading condition (25%, 50%, 75% and 100%) were compared with diesel at CR17.5:1. The output illustrates that the most optimum value is B20% when compared with diesel. The result depicts firstly that there is a reduction in brake thermal efficiency by 0.98%, exhaust gas temperature by 1.7%, hydrocarbon (HC) by 16.3%, carbon monoxide (CO) by 3.6%, NOX emission by of 6.8%, and smoke emission by 12.35% respectively. Secondly, there is an increase in specific fuel consumption by up to 5.2% and CO2 emission by 2.8% for spirulina blend ratio (B20%) as compared to diesel (B0%) at full load condition engine with constant engine speed.

One prevailing issue for assessing the performance of hydrothermal liquefaction is understanding the role of the extraction solvent used for product separation. This study evaluated the extraction agent's impact on the hydrothermal liquefaction products and energy efficiency. Three representative solvents (acetone, dichloromethane, and toluene) were chosen with three representative high-carbohydrate, protein, and ash content feedstocks (Chlorella sp., Nannochloropsis sp., and Enteromorpha pr., respectively). Extraction of the oil using dichloromethane led to the highest biocrude oil yield (dry biomass) for Chlorella sp. (48.8%), toluene for Nannochloropsis sp. (23.3%), and acetone for Enteromorpha pr. (9.8%). The solvent selection led to a maximum variation of 20.4% for all oil yields. Dichloromethane produced high energy recovery values (maximum: 67.1%) and low energy consumption ratios (minimum: 0.06) regardless of the feedstock chemical composition. Dichloromethane also led to consistently high net energy values and high fossil energy ratios amongst all feedstocks. We speculate that the solvent polarity, chemical structure, hydrogen bonding, and dipole-dipole interactions influenced output parameters by the selective isolation and extraction of the chemical compounds in the biocrude oil. This study suggested that the extraction solvent selection should be carefully considered and normalized for the reporting of hydrothermal liquefaction yields and energy efficiency values.

The combustion behaviors of three oil sludge samples and their corresponding semicoke prepared from a laboratory-scale pyrolysis/gasification reactor were investigated using a thermogravimetric-differential scanning calorimeter-mass spectrum (TG-DSC-MS) system over the temperature range of 313-1173 K under atmospheric pressure. The obtained results revealed that the combustion process can be divided into five stages, and the interval temperature and mass loss of each stage were given. To explain the combustion characteristics of the oil sludges and semicokes during ignition and subsequent burning in detail, a series of combustion characteristic parameters and the derived comprehensive indexes were determined based on the DTG and DSC results. Both the Starink method and Friedman method were employed to conduct combustion kinetics analysis, and the distribution and mean value of the activation energy were obtained. The emissions of the main combustion products, incomplete combustion products, gaseous pollutants, and oxidizing agent during the combustion process were detected by mass spectrometry. Finally, the product yield from the previous pyrolysis/gasification experiments and the data extracted from the former sections were used to conduct a PCA. The synthetical evaluation results indicated that the comprehensive thermochemical treatment scheme might be a more effective choice for the treatment and recovery of oil sludge.

Mineral carbonation of blast furnace slag (BFS) has been proposed as a comprehensive method for carbon capture and storage and utilization of the industrial solid waste. However, the challenge for this technology to be applied practically is how to reduce the cost of process. A completely wet process combining a CO2-mineralization cell for CO2 capture and membrane electrolysis for recovery of carbonated mother liquor is proposed to simultaneously fix CO2 and produce multiple value-added products. In this process, Ca, Mg, Al, and Si are extracted from BFS with an NH4HSO4 solution prepared from H2SO4 and (NH4)2SO4 with extraction ratios of 97.3%, 98.8%, 96.4%, and 94.3% under optimized conditions, respectively. The extracted Al and Si are then recovered as NH4Al(SO4)2·12H2O (99.59 wt%) and SiO2 (97.70 wt%) with 93% and 98.1% yield, respectively. The CaSO4-rich leaching residue and MgSO4-rich leachate after complete depletion of the residual Al and Si are successively carbonated with an NH4HCO3 solution obtained from a CO2-mineralization cell with total CO2 capacity up to 361 kg-CO2 per tonne BFS. The preliminary economic evaluation shows that the present carbonation route is a cost-efficient method to comprehensively utilize BFS and reduce CO2 emissions.

In this study, the utilization of textile fibres as energy feedstock in the form of biochar was investigated depending on the fibre type. The biochars were produced from waste natural and synthetic fibres and its blends. For this purpose, different types of textile fibres (cotton, viscose, polyester, acrylic) and their blends (cotton/polyester, acrylic/wool, acrylic/polyester, acrylic/viscose) were torrefied at temperatures between 300 and 400 degrees C. The effects of torrefaction temperature and fibre type on biochar yield and biochar properties (fuel properties, morphological and structural properties and combustion characteristics) were investigated. The results showed that the temperature had a significant effect on biochar yield whereas the fibre type was the only significant factor on energy densification ratio and biochar properties. The torrefaction of tested fibres and blends resulted in an energy-intensive solid fuel, having a negligible amount of ash and sulphur. Although torrefied acrylic based textile fibres had similar H/C and O/C ratios to bituminous coal, it was concluded that high nitrogen contents will limit their usage as fuel. Overally, this study showed that torrefaction of cotton and cotton/polyester textile wastes is a promising process for the production of a solid fuel, which can be used as a substitute fuel in coal/waste co-firing systems. (C) 2018 Elsevier Ltd. All rights reserved.

Air gasification of waste polyethylene (PE) was conducted using active carbon as a tar removal agent in a new type of three-stage gasifier. The main focus was on the in-situ regeneration of active carbon, which was conducted simply with air treatment, which was mainly performed with variations of treatment time and air flow rate. In the experiments, active carbon was found to be very effective in hydrogen production and tar removal. The maximum hydrogen content of the producer gas obtained with active carbon was approximately 27 vol%, while the producer gas was free of tar. Active carbon, treated with air for 10 min, while stopping feeding, had a surface area of 937 m2/g (83% recovery rate). A 4 h of gasification performed with a dolomite guard bed and a mesh type distributor produced a gas having H2 and heavier tar than toluene contents of 28 and 0 vol%, respectively. The regeneration study suggested that a severe coke formation could be diminished, when methods such as frequent air regeneration with short treatment time, the use of other regeneration agents, such as CO2 or H2O and/or the selection of a proper distributor would be applied.

Anaerobic membrane bioreactor (AnMBR) was employed as a secondary treatment unit for anaerobically treated wastewater from a full-scale digester of a fish canning factory. A lab-scale hollow fiber membrane AnMBR was operated at various intermittent liquid circulation (ILC) levels using granular activated carbon (GAC) as a moving media within the reactor, at a hydraulic retention time of 8 h. The experiment was aimed to investigate the effect of ILC with ON/OFF time-interval ratios of 15/15, 30/15, 45/15 (minute/minute) versus continuous circulation. Results showed that all reactors achieved chemical oxygen demand (COD) removal above 84% while nitrogen removals of only 31.5–41.5% were attained without biological nitrification/denitrification. The overall membrane fouling rate, a change of transmembrane pressure over time, was effectively controlled in higher ILC conditions, i.e., 21.6, 10.5, 7.2 and 3.6 mbar/day at 15/15, 30/15, 45/15 ILC and continuous liquid circulation, respectively. Analyses of resistance revealed that a larger contribution by cake layer formation was found at higher ILC which was related to its morphology by SEM. Finally, the energy requirement and COD removal efficiency were compared against the activated sludge process currently used at the canning factory. The analysis suggests a sizable energy saving with the anaerobic membrane process.

In the present study, a diesel-like fuel was produced from crude oil sludge with the method of catalytic pyrolysis. The initial liquid that was derived from the direct pyrolysis has considerably high sulfur content. Therefore it was subjected to two stage novel desulfurization methods. At the first stage the pyrolysis reactions were applied with perlite, CaO, Ca(OH)2 and zeolite catalysts. The sulfur content was reduced by 52.63% with using 10% perlite as the novel catalyst. As the second stage, in the acidic desulfurization reactions, the sulfur content of this liquid was reduced by 82.31% which means that the cumulative sulfur reduction was by 91.32%. At the end of both stages, low-sulfur diesel-like fuel (LSDLF) has 0.132% sulfur amount, highly similar to that of diesel fuel (DF) 0.1%. It was determined that the density and viscosity values of the LSDLF were close to those of DF, but its cetane number and heating values were slightly lower along with little higher sulfur content. The pure diesel-like fuel LSDLF100, its blend the LSDLF50 and the DF were tested in a single-cylinder and direct injection diesel engine. The engine performance characteristics and exhaust emission values obtained from these tests were comparatively examined. It was concluded that the obtained fuels can be used in diesel engines without any engine operations problems such as injector sticking, difficult start, overabundance noise, black smoke exhaust or any engine modifications.

In lieu of the fact that modern-day research is saddled with the responsibility of replacing/supplementing fossil fuels with biodiesel for use in diesel engines, the challenge still remains the need to improve the properties of biofuels towards stimulating high engine compatibility and performance. Despite the advances made in improving biofuels such as those sourced from Juliflora with additives, none seems to have addressed the potentials that underly the use of hybrid nano-particles as property-improvers of Juliflora-biofuel for use in diesel engines. This then led to the need to harness the potential use of hybrid CeO2:CuO, MnO2:Al2O3, ZnO:TiO2, and TiO2:Al2O3 in different ratios as a means of determining the best combination for improved fuel properties, high engine performance and reduced emissions. The nanoparticles were produced via sol-gel method and ultrasonicated with the biofuel before being characterized using scanning electron microscopy/atomic force microscopy. Based on the engine-test results, the brake thermal efficiency (BTE) increased from 1.11 to 2.21% for the biodiesel mixed with nanoparticles. Furthermore, the Nitrogen oxide (NOx), hydrocarbon (HC) and carbon monoxide (CO) emissions for the admixed biofuels decreased by 16.29–23.76%, 14.07–17.32% and 5.51–8.27% respectively compared to conventional diesel, thus reducing environmental pollution.

In this study, effectiveness of a thermo-catalytic waste and biomass gasification unit consisting of a pyrolysis stage and a splitted product gasification stage (PSPG) was verified considering: increase of gas lower heating value (LHV), reduction of gas tar content (GTC), increase of cold gas efficiency (CGE) and carbon conversion efficiency (CCE). The unit consisted of three reactors: an auger pyrolysis reactor (PR), fixed-bed char gasification reactor (CHGR) and fixed-bed secondary catalytic reactor (SCR). A low-cost natural clay-based catalyst and a natural zeolite were used in the secondary catalytic reactor. Tar content in syngas and tar yield were significantly affected by the air split ratio. Splitting air between SCR and CHGR reduced the syngas tar content and gasification tar yield. Suitable equivalence ratio and air split ratio in the studied region were 0.1595 and 0.325, respectively. At these ratios, the highest LHV/GTC value was achieved (2.01), CGE was 62.33%, CCE 80.90%, and feed conversion was 94.15%. Tar concentration in syngas was 3.64 g.Nm−3 and tar yield was 5.21 g kg−1. The lower heating value of syngas was 7.34 MJ.Nm−3. To find overall optimal process conditions, higher equivalence and air split ratios will have to be studied.

Microalgal biomass produced from the inexpensive nutrient medium is a potential raw source for manufacturing different essential products covering a broad spectrum of applications. In this study, six separate microalgal strains were isolated from lake freshwater and screened based on their growth and biomass productivity in 10% raw dairy wastewater (DWW). Statistically optimized growth parameters of microalga using CCD-RSM were light intensity 65 μE m−2s−1, pH 7, temperature 35 °C and agitation 150 rpm with maximum dry biomass yield 16.35 ± 0.34 g/L in ultrasonic pre-treated DWW (UPDWW) (75%, v/v). The physicochemical properties of 75% UPDWW were observed pre- and post-algal cultivation and found 94.8% COD removal, indicating the strain's potential phycoremediation. At optimal conditions, hydrolysate of C. sorokiniana NITTS3 biomass yielded 13.67 g/L of bioethanol using selected yeast. The findings of this investigation suggest that C. sorokiniana NITTS3 isolated from freshwater could effectively be used for phycoremediation of DWW with concomitant biomass production as an appropriate feedstock for bioethanol production.

In this work, the concept of biomass direct (air) gasification was demonstrated in a pilot-scale bubbling fluidized bed and the influence of in-situ application of low-cost catalytic materials on the produced gas characteristics and gasifier performance was analyzed. Three different low-cost catalysts were tested: bottom bed ashes resulting from combustion of residual forest biomass derived from eucalyptus, char particles resulting from wood pellets direct (air) gasification, and synthetic fayalite (Fe2SiO4). Without using catalysts, the produced gas composition was 7.7–16.9%v CO, 3.2–8.3%v H2, 0.5–3.4%v CH4 and 9.5–14.6%v CO2, with 2.4–4.3 MJ/Nm3 lower heating value, specific dry gas production between 1.0 and 1.8 Nm3 dry gas/kg biomass (dry basis), cold gas efficiency between 13.7 and 30.5% and carbon conversion efficiency between 30.7 and 50.9%. With the use of catalysts, the produced gas composition was 14.2–37.6%v CO, 9.5–14.7%v H2, 2.6–3.5%v CH4 and 3.6–14.8%v CO2, with 3.9–6.3 MJ/Nm3 lower heating value, specific dry gas production between 1.4 and 2.0 Nm3 dry gas/kg biomass (dry basis), cold gas efficiency between 38.1 and 66.3% and carbon conversion efficiency between 56.8 and 86.6%. The highest increase in H2 concentration (352% increase) was observed on experiments using wood pellets char as catalyst while the highest increase in CO (305% increase), lower heating value (123% increase), specific dry gas production (62% increase), cold gas efficiency (262% increase) and carbon conversion efficiency (174% increase), was observed on experiments using synthetic Fe2SiO4 as catalyst.

In the present study, artificial neural network (ANN) method was applied for predicting osmotic pretreatment based on the energy and exergy analyses in microwave drying of orange slices. For this purpose, the oranges were cut into slices with a thickness of 4 mm and treated with salt (NaCl) and distilled water solution (7% by weight) for 30, 60, and 90 min as osmosis pre-treatment. Then, they were dried in three replicates using a microwave dryer and at three powers of 90, 360, and 900 W. The statistical analysis results showed that the osmosis time is significant for the energy efficiency and exergy efficiency and specific exergy loss at 1% level. The highest energy and exergy efficiency was observed at 900 W and in the osmosis time of 90 min. The highest energy and exergy efficiency was observed at 42.1% and 31.08%, respectively. The maximum exergy loss was seen at 360 W and osmosis time of 60 min. The osmosis time did not affect the specific energy loss. The microwave power was statistically significant for all the parameters (energy and exergy) such that with increasing the microwave power, the energy and exergy efficiency increased, while the specific exergy and energy loss decreased. Overall, with increasing osmosis time and microwave power, the energy and exergy levels of the microwave dryer increased. The maximum coefficient of determination (R2) in a network containing 6 neurons in the hidden layer was 0.999 for energy efficiency, R2 = 0.871 for specific energy loss, R2 = 0.999 for specific exergy loss, and R2 = 0.972 for exergy efficiency. This amount was seen in a network containing 4 neurons in the hidden layer.

By determining the methane production, volatile fatty acids (VFA) and ammonia nitrogen content of deer manure anaerobic fermentation system we explored the effects of adding biogas slurry on biogas production for the anaerobic fermentation of deer manure. The initial mushroom slag amount that was added was 35 g, total solid content was 6%, and temperature was 35 °C. One set of experiments was not added to the biogas slurry during the experiment, and for the other three groups, the amounts of biogas slurry that were originally added to the fermentation mixture were 10%, 30% and 50%. The results showed that the addition of biogas slurry during the fermentation of raw materials improved biogas total production and CH4 total production and also produced CH4 in advance. The total amounts of biogas and CH4 produced were the largest when the amount of biogas slurry added to the fermented mixture was 30%. Upon increasing the amount of biogas slurry, the trend of the VFA content in the fermented material first increased, then decreased and finally increased again. The content of VFA was the smallest when 30% biogas slurry was added to the fermented mixture because this was the most favorable condition for CH4 production.

In this research a hybrid thermochemical and biochemical approach is proposed to produce biocarbon, biomethane and biofertilizer from corn residue using the concept of resource recovery from biowaste. In this approach, corn residue is first pretreated in hydrothermal carbonization process to produce solid biocarbon. Hydrothermal process water, a co-product of hydrothermal carbonization process underwent fast anaerobic digestion to produce biomethane and biofertilizer. Effects of operating conditions (process temperature and residence time) on both biocarbon and hydrothermal process water contents were studied. Four selected hydrothermal temperatures of 200 °C, 220 °C, 240 °C and 260 °C and their three corresponding residence times of 10 min, 20 min and 30 min were considered. Among these 12 hydrothermal processes, 240 °C for 30 min process produced hybrid bioenergy of 14.26 MJkg−1 of raw corn residue with an overall energy yield of 78.65%. Biocarbon produced at 240 °C for 30 min and 260 °C for 10–30 min were comparable to pulverized coal used in power plants, which contained high heating values of 23.01 MJkg−1 to 24.70 MJkg−1. All anaerobic digestion digestate are nutrient enriched and useable as liquid fertilizer.

Drying performance of a novel compressed air drying method using different liquid desiccants, including LiCl solution, LiBr solution and mixed solutions (LiCl/CaCl2), is compared by experiments. It is found that drying performance of LiCl solution is better than that of LiBr solution. Besides, drying performance of three mixed solutions (44%, 46% and 49%) selected is similar to that of 40% LiCl solution, verifying the feasibility of substituting single solution with much cheaper mixed solution. The water vapor pressure of mixed solutions and LiCl solution is same in experiments, therefore it can be selected as an indicative factor to evaluate substitute of LiCl solution. Moreover, the cost of the three mixed solutions is 18% cheaper than that of 40% LiCl solution at least, which shows significant economization in application. Finally, system performance of the compressed air drying system is analyzed. The dew point of outlet compressed air could reach −7.7 °C at operating pressure of 0.8 MPa, indicating the dryness can satisfy requirement of various industrial applications which used typical electricity-driven cooling-drying method. The solution temperature of regeneration could reach 70 °C, validating that it is feasible to use waste heat recycled from the air compressor to drive solution regeneration.

In this study, engine performance, exhaust emissions and combustion behaviors of a single-cylinder, four-stroke, direct-injection diesel engine running on biodiesel/diesel/1-butanol and biodiesel/diesel/n-pentanol fuel blends were investigated and compared with diesel fuel under different engine speeds and full load operating conditions. Test fuels were prepared with 5 and 10 vol% 1-butanol and n-pentanol. Engine test results indicated that brake powers and torques decreased as the amount of alcohol increased, while BSFC increased between 0.77% and 8.07%. Alcohol blended fuels acquired lower EGT and CO2, while observing higher O2 emission due to high oxygen content of alcohol compared to diesel fuel. Alcohol treated blends also diminished NOX by 0.56–2.65%, CO by 6.90–32.40%, and smoke by 10.47–44.43%. Moreover, n-pentanol blended fuels showed better performance and emission results than 1-butanol blends. Maximum in-cylinder pressure of higher alcohol blended fuels found between 94.55 and 95.82 bar at 371-372oCA for 1400 rpm, and between 78.19 and 82.19 bar at 375-376oCA for 2600 rpm. Alcohol addition into the blends increased maximum in-cylinder pressure up to 1.38% at low speed, whereas it decreased up to 3.75% at high speed. Furthermore, higher HRR values up to 8.5% were observed with the alcohol mixed fuels. Consequently, higher alcohols (n-pentanol and 1-butanol) can be utilized as alternative additives in biodiesel/diesel blends for diesel engines to improve emissions, although they adversely influence engine performance.

Three treatment technologies (mono-cultivation of microalgae, co-cultivation of microalgae with fungi or activated sludge) including two selected strains Chlorella vulgaris (C. vulgaris) and Scenedesmus obliquus (S. obliquus) were cultivated in the piggery wastewater (PWW) with different COD concentration of 800–2000 mg L−1. The effect of different COD concentration on pollutant removal of PWW, CO2 removal of raw biogas and the optimum strategy selection with light/dark ratio of 12 h:12 h was investigated. The results showed that co-cultivation of microalgae with activated sludge exhibited better performance than with fungi or mono-cultivation. The medium COD level of 1200 mg L−1 was proved to be the optimal dilution. The highest removal efficiencies of COD, TN, TP and CO2 were attained in co-cultivation of C. vulgaris with activated sludge mode under diluted COD of 1200 mg L−1, which were 79.86 ± 6.11%, 80.23 ± 6.31%, 89.37 ± 6.58% and 63.48 ± 4.27%, respectively, with the highest CH4 content of 83.24 ± 3.84%, and the heavy metal lower than the threshold of 0.6 mg L−1. The results confirmed the superiority of cultivation of microalgae with activated sludge in PWW for removal of nutrients, heavy metals and simultaneous biogas upgrading at reduced cost.

In this work, the effect of single and split injection strategy on combustion, performance and emissions characteristics of biodiesel was experimentally investigated on a common rail direct injection assisted diesel engine. In single injection strategy, Nozzle opening pressure and fuel injection timing was varied from 200 to 600 bar and 19°–27° CA bTDC respectively. Experimental results revealed that B100 had the maximum brake thermal efficiency of 35.74% at 500 bar and 25° CA bTDC. Engine exhaust emissions of unburned hydrocarbon and smoke were decreased, whereas nitric oxide emission increased in B100 fuel at higher nozzle opening pressure and advanced fuel injection timing. In split injection strategy, start of main injection timing and post injection timing was varied from 19° to 25° CA bTDC and −5° CA bTDC to 5° CA aTDC respectively. The results exhibited that the B100-90%-10% has the maximum brake thermal efficiency of 34.43%. Minimum unburned hydrocarbon and smoke emissions were obtained in B100-75%-25%. Maximum nitric oxide emission was obtained in B100-90%-10%. Thus, the experimental studies clearly states that advanced injection strategy reduces the exhaust emissions and improves the engine performance.

Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning system comprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reduction with zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol production allowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantage derived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

Anaerobic digestion (AD) is an effective way to improve the utilization of food waste (FW). Activated persulfate is a powerful oxidant. This research investigated the effect of activated persulfate on gas production from FW AD. Three activation methods including heating, lighting, and ultrasonication were used. The results showed that the addition of activated persulfate promoted gas production from FW AD. And the main biogas composition were CH4, CO2, and N2. The difference in SO42− concentration further verified the effect of activated methods on producing sulfate free radicals by heating, lighting and ultrasonication from persulfate. The activated persulfate enhanced gas production by improving the organic hydrolysis. Relatively, lighting and ultrasonication were better than heating in persulfate activation. At the same time, the accumulated gas volumes from ultrasonication (587 mL) and lighting (574 mL) were significantly higher than that in heating (478 mL). The environmental impact assessment and economic assessment suggests that the addition of activated persulfate in FW AD is beneficial because of the lower secondary pollution, lower cost and higher additional value.

To achieve reductions in CO2 emissions, replacing fossil fuels with biomass in thermal power generation is becoming increasingly prevalent. In general, the fuel nature and combustion characteristics of biomass are distinct from those of fossil fuels. Biomass is typically subjected to torrefaction to improve its grindability, hydrophobicity, and heating value (HV). However, the pretreatment process is accompanied by fuel property alteration and an energy penalty. This is strongly associated with the operating envelope and combustion stability of biochar cofiring with coal. Therefore, in this study, the Taguchi method was used to calculate the optimal torrefaction parameters for maximum energy yield and HV. Thermogravimetric and fuel characteristic analyses were performed to examine the pyrolysis features and combustion behavior of the studied fuels. In addition, a blend of 50% Miscanthus biochar and 50% Australia coal was produced and pressed into pellets. The pellets were placed into a free-drop furnace to observe their combustion behavior. The results demonstrated that the ignition temperature and burnout temperature of the blended fuels could be effectively reduced, and that their fuel conversion rates and combustion characteristic index could be enhanced. The results can be applied to coal cofiring in large-scale boilers in the future.

The production of household wastes such as used frying oil (UFO) and plastic waste (PW) are increasing each year, thus representing potential feedstocks for conversion into an energy source. Microwave co-pyrolysis was investigated for its potential to transform a mixture of UFO and polyolefinic-based plastic waste into fuel product with desirable properties. The co-pyrolysis approach demonstrated positive synergistic effects in providing fast heating rate (up to 50 °C/min) and a lower reaction time (≤25 min), and generated up to 81 wt.% yield of liquid oil and 18 wt.% yield of pyrolysis gases for use as potential fuels. The liquid oil showed promising green properties comprising low oxygen content, free of nitrogen and sulphur and higher energy content (42–46 MJ/kg). The oil product also demonstrated improved stability and desirable fuel properties nearly similar to transport-grade diesel, thus indicating the great potential of microwave co-pyrolysis as an approach for transforming household wastes into value-added liquid fuel.

The irradiation of rumen fluid (RF) with laser source was hypothesized to enhance the anaerobic process and accelerate the manure digestion, which increases the biogas and methane production. The photobiostimulating effects of laser irradiation on biogas and methane production were investigated by irradiating the RF for 0.5, 1 and 2 h with 532 nm laser source compared with 1 h incandescent light, non-irradiated RF and the control. The highest significant values of the biogas and methane production were found to be 583 ml Biogas g−1 VS and 367.9 ml CH4 g−1 VS when RF was irradiated for 0.5 h with 532 nm laser source (p

In this study, valorisation of high acid value waste cooking oil into biodiesel has been investigated. Non-catalytic transesterification using supercritical methanol has been used for biodiesel production. Four controllable independent process variables have been considered for analysis including methanol to oil (M:O) molar ratio, temperature, pressure and time. Uncommon effects of process variables on the reaction responses, e.g. biodiesel and glycerol yields, have been observed and extensively discussed. Response surface methodology (RSM) via Central Composite Design (CCD) has been used to analyse the effect of the process variables and their interactions on the reaction responses. A quadratic model for each response has been developed representing the interrelationships between process variables and responses. Analysis of Variance (ANOVA) has been used to verify the significance effect of each process variable and their interactions on reaction responses. Optimal reaction conditions have been predicted using RSM for 98% and 2.05% of biodiesel and glycerol yields, respectively at 25:1 M:O molar ratio, 265oC temperature, 110 bar pressure and 20 minutes reaction time. The predicted optimal conditions have been validated experimentally resulting in 98.82% biodiesel yield, representing 0.83% relative error. The quality of the produced biodiesel showed excellent agreement with the European biodiesel standard (EN14214).

In this study, municipal solid waste was gasified with switchgrass, i.e., co-gasification, using a commercial-scale downdraft gasifier to produce power. The experiments were performed using a commercial-scale 100 kg/h downdraft gasifier at co-gasification ratios of 0, 20 and 40%. The hot and cold gas efficiencies, syngas compositions, heating value and yield, gasifier temperatures and tar content were measured and analyzed. The results indicate that co-gasification of up to 40% MSW performed satisfactorily. The heating values of syngas were 6.2, 6.5 and 6.7 MJ/Nm3 for co-gasification ratios of 0, 20 and 40%, respectively. The cold and hot gas efficiencies were 60.1, 51.1 and 60.0% and 65.0, 55.2 and 64.4% for co-gasification ratios of 0, 20 and 40%, respectively.

A physical means of dehumidification was used in this study to recover and reuse waste heat emitted from tumble dryers to increase drying efficiency and decrease power consumption. An experiment was conducted; waste heat from a dryer was dehumidified in a heat exchanger, and some heat was reclaimed to preheat external air. After the optimal mixture ratio of external and re-circulated air had been determined, that optimal air mixture was introduced into the dryer through the recirculation air ducts designed in this study. Experimental results showed that the improved dryer, operated at a 60% recirculation ratio produced the highest energy efficiency, resulting in 18% less power consumption than a standard dryer. In addition, this configuration produced the lowest specific moisture extraction rate (1.099) and the highest drying efficiency (60.6%). This efficiency was higher than that of the dryer (50%) and the proposed heat exchange system was thus more energy efficient than was the dryer. The theoretical mathematical model derived in this study matched experimental results. The average error values between the theoretical and experimental values for the drying efficiency and the specific moisture extraction rate were 0.7% and 0.6%; the largest error values were only 1.5% and 1.2%.

In this study, a novel attempt has been made to generate energy-efficient biomethane from marine macroalgae (Chaetomorpha antennina) by coupling thermochemical liquefaction with a disperser (thermo-chemo disperser (TCD) liquefaction). A temperature of (80 °C), pH 11 and disperser g-force of 1613 g were considered optimal parameters for effective solubilization and energy-efficient methane generation. This combinative liquefaction considerably reduced the treatment time and specific energy from 60 to 15 min and 6294 to 800 kJ/kg TS. The highest volatile fatty acids (VFA) accumulation of 890 mg/L was recorded in TCD compared to a thermo disperser (TD) (750 mg/L) and disperser (D) (322 mg/L) during anaerobic fermentation. TCD enhances the methane production potential of macroalgal biomass and a higher methane production of 215 mL/g VS was achieved for TCD compared to TD (149 mL/g VS) and D samples (100 mL/g VS), respectively. Cost analysis confirmed the field applicability of TCD liquefaction with a net profit of 90 USD/ton of marine macroalgae. A high energy ratio of 1.5 was achieved with the proposed mode of pretreatment (TCD) compared to TD (0.95) and D (0.28) pretreatment. Therefore, C. antennina is considered a suitable feedstock for methane generation.

Liquid Hot Water pretreatment (LHW) was evaluated on empty palm fruit bunch (EPFB) at 160–210 °C, residence time of 0–60 min and solid loadings of 5–25% wt. The effects of these conditions on ethanol yield and potential profit were determined. The “potential profit” was used as response variable to approach the economic feasibility because it helps to dismiss those experiments without economic sense, a task that the yield by itself is not capable. Ethanol yields between 109.6 and 172.1 L/ton dry fed biomass were obtained, the highest ethanol yield was obtained at conditions of 0 min, 5% of solids and 185 °C. Ethanol yield was favored at intermediate temperatures, low residence times and low solid loads. The potential profit was favored at intermediate temperature, lower residence times and high solid loads. The conditions for the optimal ethanol yield did not correspond to the conditions for the optimal potential profit. In fact, the experiment with the highest ethanol yield was not the one with the highest potential profit. Several other experimental conditions that led to moderate ethanol yields exhibited higher potential profits. These higher potential profits are mainly a consequence of higher ethanol concentrations obtained by working with high solid loading, which implies lower distillation costs. The best pretreatment conditions were 30 min, 15% solids and 185 °C because they led to the highest potential profit due to a synergetic effect of a high yield and a high concentration of ethanol.

A synergistic scheme of co-gasification of wet sewage sludge and torrefied biomass was proposed in order to get the hydrogen-rich syngas, which could avoid the dual energy input for drying of wet sewage sludge and steam generation. Co-gasification behavior of wet sewage sludge and torrefied biomass was evaluated by using a general non-stoichiometric thermodynamic equilibrium model developed based upon the Gibbs free energy minimization. The tenary plot of C H O system was used to evaluate the theoretical carbon formation performance at thermodynamic equilibrium state. The effects of mixing ratio and torrefaction severity on carbon conversion ratio, compositions of dry syngas, and H2 yield were also addressed. High mixing ratio of wet sewage sludge and high gasification temperature were required for the high carbon conversion ratio. The gasification temperature of 1100 K was a favorable level for the H2 yield and energy input. The optimal mixing ratio range of wet sewage sludge for low and middle temperatures torrefied biomass samples was between 30% and 40%, while that for high temperature ones was approximately 55%. This work could provide a feasible technical route and basic data for the resource and energy utilization of sewage sludge and biomass.

Several completely stirred tank reactors (CSTRs) connected in series for corn stover anaerobic digestion was devised to obtain more methane yield and increase conversion rates. Liquid fraction of the digestate (LFD) was recirculated from the second-stage reactor to first-stage reactors to reuse LFD and improve system performance. LFD recirculation didn’t inhibit methane production of serial digestion, and methane and biogas production were increased by 2.3% and 10.8%, respectively. Moreover, LFD recirculation increased pH and alkalinity concentration (AC) and decreased volatile fatty acids (VFAs) concentrations and the ratio of VFAs to AC, which means a significant increase in system stability of anaerobic digestion (AD). Ammonia concentrations gradually increased with LFD recirculation, but was far lower than the inhibition concentration. Microbial analysis indicated that the recirculation increased the richness, but decreased the diversity of both bacterial and archaeal community in the first and second stage of serial system. More specifically, LFD recirculation enriched the dominant bacterial phyla (Bacteroidetes and Firmicutes), but had little influence on the dominated archaeal genus (Methanobacterium). The results showed that the recirculation of LFD during serial AD was technically suitable by minimizing both discharge of LFD and possible pollution related with discharging LFD.

This study presents a real-time drying control system that was developed to control air drying of sawdust in a pneumatic conveying dryer to produce high-grade wood pellets in the range of the target moisture content (MC). The real-time drying control system was installed with moisture sensors to control the ON/OFF periods of the fuel (pellet) supply motor for the sawdust to generate the heat necessary to dry the sawdust to an optimum level of 15% moisture content for pelletizing. The results of the experiment and the simulation showed that the drying efficiency improved when a buffer was introduced instead of using a conventional system, and the average moisture content of the dried sawdust was measured to be about 12.4% in a pneumatic conveying dryer without buffer and about 14.7%–15.2% in the developed real-time drying control system. This study shows that the real-time drying control system could dry the sawdust to the targeted constant moisture content, and the buffer in the pneumatic conveying dryer could improve the drying efficiency according to an increase in the resident time of the sawdust.

In this paper, a kinetic model of biomass gasification for H2-rich syngas production is proposed using Aspen Plus process simulator. Having obtained the syngas composition, various parameters and characteristics of the biomass gasification can be determined; they include the gas yield, H2/CO, gas higher heating value (HHV), Carbon conversion efficiency (CCE) and cold gas efficiency (CGE). The gas yield and H2/CO increase as temperature increases from 750 °C to 900 °C. CCE and CGE were also found to increase with increasing temperature. Increasing equivalence ratio (ER) increases the gas yield and CCE due to the decreased concentration of chars in the products. Air induction also decreases the concentrations of combustible gases in the syngas, thereby decreases the HHV of the product gas. H2/CO shows a slight change with ER increasing from 0.1 to 0.4. The detailed analyses performed in the course of the present article reveals that the steam is a feasible gasification agent that can be utilized to generate a syngas with high H2 content. H2 increases from 16.75 vol% to 18.46 vol% with increasing S/B from 0.25 to 1.0. The gas HHV decreases with increasing S/B due to a slight decrease in CH4 content.

In order to explore the feasibility of suitable drying technology of tomato-paste, four solar drying methods were employed, namely (i) Basic Solar-drying Mode (SDM), (ii) Solar-Geothermal Drying (SGD), (iii) Convective Ventilated Solar Drying (CVD), and (iv) Combination of Ventilation and Geothermal Drying (VHD) and their effect on exergy efficiency, economic and quality attributes were investigated. Results showed that the drying time using different drying methods was 10, 9, 8, and 4.5 h for SDM, SGD, CVD, and VHD, respectively. Proposed model could better describe tomato paste drying behavior among eight tested mathematical models. Highest drying efficiency and specific energy consumption were observed for VHD method as 68.27% and 3.21 kWh/kg, respectively. Highest exergy efficiency was recorded for SGD and VHD as 54%. Payback period values were 0.28, 0.325, 0.3, and 0.169 years for SDM, SGD, CVD, and VHD, respectively. Color analysis revealed that CVD method was more suitable with the lowest total color change of 22.41 and highest brightness of the red color of 1.34. SGD method preserved 73.85% and 59.42% of phenol and flavonoid compounds, respectively, while VHD method preserve the highest flavonoid compounds as 82.24% compared to fresh sample. Geothermal energy combined with ventilation is recommended as a suitable drying method for tomato paste in terms of drying time, energy, exergy efficiency, economic, and quality attribute.

Harvesting of forest residual biomass contributes to regulating wildfires during hot and dry seasons. The collected biomass can be converted into liquid biofuel by pyrolysis. Simple pyrolysis procedures such as slow pyrolysis will allow to dimension and design of mobile pyrolysis units to avoid biomass transportation fees and guarantee efficient management of forest residues. Portuguese forest wastes, particularly biomass from maritime pinus and eucalyptus globulus, were characterized by thermogravimetry and pyrolyzed in a fixed bed reactor, at 698 K, using commercial alkali carbonates and zeolites, bauxite ores, and marble dust as catalysts. Pyrolysis data for mixed biomasses showed the existence of synergy effects. The catalytic pyrolysis experiments led to improved bio-oil quality for all the tested catalysts. The bio-oil produced from pyrolysis with sodium carbonate was the most volatile, since the maximum peak of the volatilization rate is at 390 K, while the bio-oils produced by the remaining catalysts have maximum volatilization at 410 K. Marble dust, a waste from ornamental stones industry, revealed excellent catalytic properties during biomass pyrolysis, allowing an improved bio-oil yield with a decrease in the oxygen-containing functional groups.

Torrefaction can upgrade the properties of biomass by reducing its oxygen content. In this study, the effects of torrefaction pretreatment on four different lignocellulosic biomass materials at three different temperatures (200 °C, 250 °C, and 300 °C) were studied using a Bosio EUP 6/1200 electric furnace. The results of proximate and ultimate analyses showed that the oxygen content is reduced with a higher torrefaction temperature, while the heating values increased, with 260 °C being the optimal temperature for the process. Among the torrefied products, oak waste wood (OWW, torrefied at 200 °C) had the highest solid yield, 93.2%, while the energy yield was 95.7%, fixed carbon (FC) content 11.8%, volatile matter (VM) content 80.9%, ash content 0.8%, and HHV 19.1 MJ/kg. The TGA/DTG experiments confirmed typical thermal properties for all lignocellulosic biomaterials, while the FTIR and XRD patterns for miscanthus and OWW indicate that the molecular chains of cellulose are broken (damaged) at temperatures higher than 300 °C. Porous ovals were observed at all temperatures in all biomass materials using SEM. SEM images showed that at higher temperatures the ovals started to crack, leading to materials with better grindability than the raw materials. Therefore, we conclude that solid biofuels with properties similar to coal can be produced with torrefaction.

A walk-in type solar greenhouse dryer supplemented with solar air heating system has been developed with an objective of sustainable development. One of its novel features is the use of an evacuated tube solar air heating system with the greenhouse dryer to achieve required drying temperature for different products in north India plains. This dryer was tested in laboratory in both batch and semi-continuous mode for turmeric (Curcuma longa). The open sun drying was used as control. The thermal efficiency of the dryer for batch and semi-continuous drying obtained are 18.5% and 22.5% respectively. Drying time in comparison to open sun drying has been found to be 55% approximately. The quality of dried turmeric obtained using this dryer is superior to open sun drying in terms of polishing loss, curcumic content, volatile oil content and colour. Its energy payback period and cost payback period were estimated as 2.95 and 1.10 years, respectively, which is very low as compared to its life of 20 years. In the entire lifetime, the CO2 mitigation was found to be 209.21 tons, which proves its suitability.

Biomass-derived biochar emerges as a potential green bio-coal candidate for power generation. Microwave-assisted pyrolysis has been proven to be an efficient and economical technique for biomass conversion into biochar. The process can be further improved by utilising susceptor. This research focuses on producing biochar from microwave pyrolysis of empty fruit bunch (EFB) in an alumina susceptor. EFB pellet (PEFB) and EFB short fibre (FEFB) were pyrolysed in a 14L bench scale microwave pyrolyser at temperatures between 200 and 400 °C. The pyrolyser performance (biochar yield, energy efficiency) and biochar properties (proximate analyses, ultimate analyses, calorific value and ash content) were analysed. The results showed that temperature of 300 °C demonstrated the optimised conditions for biochar production. FEFB produced 5.2% higher biochar yield and exhibited better biochar properties compared to PEFB. FEFB-derived biochar (FEFBC) overall characteristics were better than PEFB-derived biochar (PEFBC), with higher heating value (25.19 MJ/kg), fixed carbon (64.52%), volatile matter (13.38%) and carbon content (59.83%). However, FEFBC has high tendency of forming slagging and fouling in the combustor as the ash indexes was >0.34 kg/GJ and RB/A > 1.75.

Biomass structure and reactivity of torrefied products are a matter of great concern to explore the fuel properties, pyrolysis characteristics, and microcosmic appearance, and life cycle assessment (LCA) is of great importance to evaluate the environmental impact of the torrefaction process. This study investigates the properties and microstructure of torrefied rice straw, including fuel properties, pyrolysis kinetics, crystallinity, surface functional group changes, and microscopic appearance. Results show that a good linear distribution appears between the comprehensive pyrolysis index (CPI) and atomic H/C ratio, and CPI and crystallinity index (CrI). Fourier transform infrared spectra depict dehydration, decarboxylation, and decarbonylation occur during the torrefaction process. The scanning electron microscope images illustrated the surface characteristics are closely related to the release of volatiles during the torrefaction process. The solid 13C NMR spectra of raw and torrefied rice straw reflect that the aromaticity will improve with increasing the torrefaction severity. For LCA analysis, the environmental impact of the torrefaction process shows a positive correlation with torrefaction temperature, and the global warming potential is in the range of 0.1469–0.2707 kg CO2 emission. This study is meaningful for the evaluation of fuel properties and torrefaction performance as well as microstructure and reactivity of torrefied rice straw.

Three solid acid-catalyzed (SAC) processes for biodiesel production from residual oil and fats (ROFs) with HWSi/Al2O3 as catalyst were designed and optimized using Aspen Plus: simultaneous esterification, transesterification, and methanol separation based on catalytic distillation (CD) (process A) and catalytic absorption (CA) (process B), where CA has not yet been investigated in these conditions; and hydro-esterification industrial process using CD (process C1). For the first time, processes A, B and C based on SAC route were optimized and compared regarding to techno-economic and environmental aspects. Processes A and B were the most economically and eco-friendly options. Compared to process B, process A was the best option due to simpler flowsheet. Process A2 presented 25.6, 60.1, 4.6, 8.6, 52.6 and 62.8% lower capital, utilities ( C u t i l ), operation, total annualized ( T A C ), waste treatment ( C w a s t e ) and CO2 emission costs than process C1. A global optimization developed for process A saved 430 k$/year on T A C . After a heat integration, process B presented 4.9 and 10.8% lower C u t i l and C w a s t e than process A. Process A was also designed for FFA levels of 5–25 wt%, where the biodiesel break-even price remained competitive (0.48–0.75 $/kg) with diesel price.

Derived from bio-drying of municipal organic wastes (MOWs), biodried products (BPs) are normally accepted as carbon-neutral and renewable energy sources. In this study, torrefaction at different temperatures was conducted for BPs to upgrade their properties as fuels. The results indicated that high temperatures promoted formation of gases and liquids during BPs torrefaction. Among the gaseous products, the CO2 content was significantly higher than those of CO and H2. In the liquid products, including H2O, benzenes and phenols were two typical components, which coincided with organics devolatilization and lignocellulose depolymerization. Furthermore, the fuel properties of torrefied BPs were upgraded with higher fixed carbon contents (21.95%–29.25%) and heating values (15.15–17.98 MJ/kg) due to the elimination of oxygen-containing volatiles. During combustion of torrefied BPs, the devolatilization of organics was diminished, but the decomposition of lignocellulose was enhanced. Moreover, torrefaction promoted the char combustion with lower activation energy values (151.69–207.76 vs. 160.20–215.56 kJ/mol). In addition, torrefaction reduced the emissions of C O/C–O compounds and enhanced the release of CO2, CO and H2O during combustion. However, severe torrefaction decreased energy yields and the potentials of BPs for energy recovery as fuels. Moderate torrefaction (approximately 250 °C) was suggested to be more beneficial for upgrading BPs.

A new approach using torrefied spent coffee grounds (TSCG) as a bioadsorbent is presented for marine oil spill recovery. The adsorbent after diesel adsorption is referred to as “oilchar”. The torrefaction of spent coffee grounds (SCG) is performed at 200, 250, and 300 °C where the solid yields are 95%, 80%, and 62%, respectively. The specific surface area, hydrophobicity, thermal stability, diesel adsorption capacity of SCG increases with increasing torrefaction temperature. SCG torrefied at 300 °C (300-TSCG) can intensify its specific surface area, contact angle, crystallinity, diesel adsorption capacity by factors of 7.6 folds, 10.3%, 35%, and 1.47 times, respectively. The diesel adsorption capacity of 300-TSCG is 1.36 times that of commercial activated carbon. The higher heating value of 300-TSCG is 30.32 MJ kg−1, accounting for a 45.1% improvement compared with that of untorrefied SCG. After adsorbing diesel, the HHV of the oilchar from 300-TSCG is 1.23 times that of SCG-oilchar, while the ignition temperature of 300-TSCG decreases from 301 to 157 °C. Overall, TSCG is a promising material to adsorb spilled diesel oil for environmental protection, and the resultant oilchar is a potential alternative fuel for thermal power plants and steel mills, thereby achieving waste reuse and circular economy.