• Energy Research

Characteristics of the char produced in the co-pyrolysis of used rubber and larch sawdust were studied in the conversion of low-valued pyrolysis char into value-added activated carbon using two-step co-pyrolysis, namely pyrolysis and activation processes. The physicochemical characteristics of the chars were examined by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM). The results revealed that after the two-step co-pyrolysis, the upgraded carbon had BET surface areas ranging from 600 m2 g−1 to 900 m2 g−1, which were higher than the requirements for activated carbon (American Water Works Association B600 standard). Additionally, as the sawdust/rubber ratio increased, the BET value increased accordingly. A possible reaction mechanism is proposed based on the experimental results during the activation process.

Abstract Peanut shells (i.e., an abundant industrial by-product) were subjected to an innovative hydrothermal pretreatment approach using high-pressure CO2 to enhance their enzymatic hydrolysis conversion into glucose. This pretreatment led to a reduction in hemicellulose content in the pretreated peanut shells from 12.4% to as low as 1.8%, which facilitated subsequent conversion into glucose by enzymatic hydrolysis. This pretreatment approach was assessed within a 170–200 °C temperature range and a 20–60 bar CO2 pressure range, after which the results of these conditions were compared to those of conventional hot water pretreatment. Treatment at 190 °C and a 60-bar CO2 pressure was determined to be optimal, resulting in the highest glucose yield (80.7%) from subsequent enzymatic hydrolysis. Acidic conditions resulting from CO2-derived carbonic acid significantly reduced the hemicellulose content of the peanut shells and weakened the interaction between cellulose, hemicellulose, and lignin, improving enzyme accessibility to the cellulose. Furthermore, high-pressure CO2 increased the pore size and porosity of the resulting pretreated peanut shells, improving their enzyme adsorption capacities, as confirmed by cellulase adsorption and mercury intrusion porosimetry tests. The dual effect from high-pressure CO2 led to significant hemicellulose reduction and improved adsorption of enzymes on the cellulose, which in turn increased glucose yield from the subsequent enzymatic hydrolysis of pretreated peanut shells. Alcoholic fermentation of the hydrolyzed glucose resulted in a 12.4% increase in bio-ethanol production compared to a glucose control, thus highlighting the potential of pre-treated peanut shells as a glucose precursor used in biofuel industry.

Different CO2 concentration such as 0.03, 5, 10 and 15% and low-cost urea repletion/starvation in Chlorella vulgaris on growth, total and non-polar lipid content and fatty acid composition was studied. Chlorella vulgaris grown at 0.03% CO2 apparently revealed inferior biomass yield 0.55 g/L on 14th day compared to CO2 supplemented cells. In the case of CO2 supply, 15% CO2 has unveiled higher biomass yield at about 1.83 g/L on day 12 whereas biomass yield for 5 and 10% CO2 supplemented cells was 1.61 and 1.73 g/L, respectively on 12th day of cultivation. The biomass productivity (g) per liter per day was 32 mg in control condition whereas it was 125, 134 and 144 mg/L/d in 5, 10 and 15% CO2 supplied cells, respectively. Lipid content of the strain grown at control, 5, 10 and 15% CO2 was 21.2, 22.1, 23.4 and 24.6%, respectively and however, without CO2 addition in low-cost urea repleted and urea depleted medium grown cells revealed 21.2 and 24.2%, respectively. Interestingly, strain grown at 15% CO2 supply in urea deplete medium yielded 28.7% lipid and contribution of non-polar lipids in total lipids is 69.7%. Further, the fatty acid composition of the strain grown in 15% CO2 supply in urea depleted medium showed C16:0, C16:1, C18:1 and C18:3 in the level of 30.12, 9.98, 23.43, and 11.97%, respectively compared to control and urea amended condition.

A continuous increase in the amount of greenhouse gases (GHGs) is causing serious threats to the environment and life on the earth, and CO2 is one of the major candidates. Reducing the excess CO2 by converting into industrial products could be beneficial for the environment and also boost up industrial growth. In particular, the conversion of CO2 into methanol is very beneficial as it is cheaper to produce from biomass, less inflammable, and advantageous to many industries. Application of various plants, algae, and microbial enzymes to recycle the CO2 and using these enzymes separately along with CO2-phillic materials and chemicals can be a sustainable solution to reduce the global carbon footprint. Materials such as MOFs, porphyrins, and nanomaterials are also used widely for CO2 absorption and conversion into methanol. Thus, a combination of enzymes and materials which convert the CO2 into methanol could energize the CO2 utilization. The CO2 to methanol conversion utilizes carbon better than the conventional syngas and the reaction yields fewer by-products. The methanol produced can further be utilized as a clean-burning fuel, in pharmaceuticals, automobiles and as a general solvent in various industries etc. This makes methanol an ideal fuel in comparison to the conventional petroleum-based ones and it is advantageous for a safer and cleaner environment. In this review article, various aspects of the circular economy with the present scenario of environmental crisis will also be considered for large-scale sustainable biorefinery of methanol production from atmospheric CO2.

Abstract The high polymer and low wood content of current transparent wood has limitation in the mechanical strength and hence obstruct green sustainable transition of the building industry. In this study, a novel method for manufacturing transparent wood was reported by minimizing the usage of polyethylene glycol using partial impregnation followed by a densification approach. The delignified wood was firstly partially impregnated by polyethylene glycol, and subsequently compressed to eliminate pores for the compressed transparent wood, providing the strong hydrogen bonds and dense structures for transparent wood. The wood content of the novel compressed transparent wood was dramatically increased to 64%, compared with the uncompressed transparent wood of 25%. Additionally, the obtained compressed transparent wood demonstrated satisfactory optical transmittance, suitable thermal energy storage, and superior mechanical strengths owing to the formation of densely packed microstructures. This novel, sustainable, and low-cost transparent wood was easy to be manufactured while having increased mechanical and energy-saving characteristics compared to those available in the existing market.

Abstract Owing to the greatest need and continuous requirement of the fossil fuel, the immediate search of alternate resources to the petroleum fuel is essential. This research deals with the production and utilization of waste cooking oil biodiesel and nanoparticles blends in the direct ignition engine. The nanoparticles added blends was then reinforced with hydrogen flow while conducting the tests. The fuel blends used for the tests were D100 (pure diesel), B10 (90% diesel + 10% biofuel), B20 (80% diesel + 20% biofuel), D100T10 (pure diesel with 100 ppm nanoparticles), B10TH (90% diesel + 10% biofuel with 100 ppm nanoparticles + 5 L/min of H2) and B20T10 (80% diesel + 20% biofuel with 100 ppm nanoparticles + 5 L/min of H2). While conducting the tests, the hydrogen flow was given at the constant mass flow rate of 10 L/min. The performance and emission measures were keenly calculated from the tests. All tests were conducted at different speeds from 1800 rpm to 2800 rpm. The performance parameters were improved by these nanoparticles and hydrogen together with the pure diesel and also with the biodiesel blends. For example, the power, torque and brake thermal efficiency were improved while the brake specific fuel consumption was decreased. The main objective of reducing the emission of CO, CO2 and other UHC was satisfied whereas the NO emission was slightly increased.

Abstract The aim of this work is to crack the used cooking oil in a fixed bed cracking unit using impregnated CaO/SBA-15 catalyst to yield liquid hydrocarbons with high % of biogasoline (BioG)fraction. Further, to investigate the capacity of the biogasoline fraction as well as the bio gasoline blends with fossil gasoline in increasing its efficiency. The porous morphology, pore distribution and surface area, elemental composition and phase formation of catalysts were analysed by Scanning electron Microscopy, Surface area analyser and X-ray diffraction techniques. All the synthesized materials were crystalline and least changes were observed with incorporation of CaO on SBA-15. The morphology of the materials were as expected without much agglomeration. SBA-15 exhibited fair surface area of around 1300 m2/g and discrete pores gas chromatography mass spectrometry (GC–MS). Among the catalysts, the composite material, CaO/SBA-15 (4 wt%) efficiently cracked 97% of used cooking oil into 70% liquid products and 69.7% of biogasoline which was confirmed using gas chromatography-mass spectrometry (GC–MS). BioG showed a good Calorific value of 10000 MJ/Kg which was comparable to that of petroleum fuel. Results of the engine test indicated that using biogasoline–gasoline blended fuels, torque output and fuel consumption of the engine increased when compared to gasoline; CO and SO2 emissions decreased largely due to the oxidation, CO2 emission increased because of the improved combustion and NOX emission from bio gasoline blends was low than gasoline.

Abstract There is an increasing environmental concern of using glass-fiber sheet molding compound (GF-SMC) in automobiles. Here, a zinc oxide (ZnO) blended natural fiber-reinforced biocomposite (NFRBC) was developed and evaluated to replace the commercial automotive GF-SMC (Meridian’s SLI 323IF) due to its superior properties and environmental friendliness. The NFRBC consists of kenaf (Hibiscus cannabinus) fibers blended with ZnO nanoparticles to obtain a fiber-mat preform used to manufacture the final NFRBC using a vacuum-assisted resin transfer molding process. Adding 12.4 % ZnO nanoparticles increased flexural strength (121 %), tensile strengths (38 %) and water resistance (76 %). The ZnO12.4 %-NFRBC had comparable mechanical properties as GF-SMC while the production consumed 9% less energy and reduced the environmental burden by 33 % from life-cycle assessment (LCA). Although the water-resistance of ZnO12.4 %-NFRBC was significantly improved, further adjustments are needed to fully meet the requirements for GF-SMC replacement.