• Energy Research

We evaluated the thermochemical properties and suitability of a variety of lignocellulosic biomass residues in Pakistan for energy production. Proximate, ultimate and calorific value analyses were performed to know the energy perspective, whereas thermogravimetric analysis was used to study the decomposition behavior of biomass samples under pyrolysis conditions. The moisture content, volatile matter, fixed carbon and ash content in the biomass samples were found within the range of 4.38–5.69%, 63.25–80.53%, 7.97–23.13%, and 7.12–14.35%, respectively. The range of carbon, hydrogen, and oxygen content was reported as 35.83–47.23%, 5.2–6.56%, and 45.6–58.55%, respectively. Lower values of sulfur and nitrogen content amongst the samples indicated that the biomass was environmentally friendly in terms of energy production. The heating value of the biomass was reported in the range of 15.20–18.44 MJ/kg. Fourier transform infrared spectroscopy showed the existence of hydroxyl, aldehydes, ketones, aromatic compounds, carbonyl compounds, ether, and halogen groups. Orange leaf biomass indicated a greater potential in producing bio-oil, whereas the horticulture biomass and mango leaves may have greater potential for biochar.

Abstract Pakistan’s current energy portfolio is problematic due to a lack of proper management and implementation of appropriate energy policies. This densely populated country has a high energy demand that rises yearly and is expected to increase three-fold by 2050. However, fossil fuel resources are continuously depleting by global overuse while negatively impacting the environment through increasing greenhouse gas emissions. This study reviewed the potential for agricultural residues to be used as renewable energy sources for bioenergy production in Pakistan to address the energy-related challenges that would also help in addressing the economic and environmental concerns. First, a comparison was made between the current energy situation, potential renewable energy scenarios, and global trends. Second, greenhouse gas (i.e., CO2) emissions in Pakistan were summarised and compared with other regions. Third, the thermochemical properties of different agricultural residues were reviewed along with varying the options of processing to produce renewable energy such as thermochemical conversion approaches (combustion, pyrolysis, gasification, and liquefaction) and biochemical conversion options (anaerobic digestion, and fermentation). Pakistan being an agricultural-based economy, produces vast quantities of agricultural residue biomass, which is mostly underutilized as animal feed, conventional fuel substitutes, left to rot in fields or burnt to get rid, resulting in the vast emissions of greenhouse gases causing severe environmental pollution and smog formation. A considerable share of Pakistan’s national energy demand can be fulfilled if these feedstocks are adequately managed and exploited through the energy sector and converted into large-scale bioenergy.

Raney nickel is extensively used as a catalyst in the hydrogenation of vegetable oils. However, it deactivates over time and is known as a spent nickel catalyst, which is potentially hazardous to the environment. By contrasting different approaches, a straightforward and original strategy for regenerating spent nickel catalyst was developed by comparing various methods. The fresh, spent nickel catalyst, and treated catalyst samples were characterized using X-ray diffraction, Fourier transform infrared, atomic absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and color scheme analyses. The results showed that the catalyst deactivation was primarily due to oil deposition over the active sites, agglomeration of catalyst, and entrainment of nickel during hydrogenation. Using n-hexane as the solvent with a spent nickel catalyst-to-solvent ratio of 1:12 (g/mL), a 65 °C temperature, and a two-hour extraction time, ultrasonication-assisted solvent extraction of spent nickel catalyst proved to be the most effective and efficient process for regeneration.

In the recent era, hydrogen has gained immense consideration as a clean-energy carrier. Its storage is, however, still the main hurdle in the implementation of a hydrogen-based clean economy. Liquid organic hydrogen carriers (LOHCs) are a potential option for hydrogen storage in ambient conditions, and can contribute to the clean-fuel concept in the future. In the present work, a parametric and simulation study was carried out for the storage and release of hydrogen for the methylcyclohexane toluene system. In particular, the methylcyclohexane dehydrogenation reaction is investigated over six potential catalysts for the temperature range of 300–450 °C and a pressure range of 1–3 bar to select the best catalyst under optimum operating conditions. Moreover, the effects of hydrogen addition in the feed mixture, and byproduct yield, are also studied as functions of operating conditions. The best catalyst selected for the process is 1 wt. % Pt/γ-Al2O3. The optimum operating conditions selected for the dehydrogenation process are 360 °C and 1.8 bar. Hydrogen addition in the feed reduces the percentage of methylcyclohexane conversion but is required to enhance the catalyst’s stability. Aspen HYSYS v. 9.0 (AspenTech, Lahore, Pakistan) has been used to carry out the simulation study.

Abstract This study investigated the potential of sawdust from the processing of Acacia wood for the furniture making industry to produce bio-oil and biochar in an auger pyrolysis reactor system. The necessary characterization to assess the suitability of feedstock and strategies the pyrolysis parameters was also carried out. The volatile matter, ash content, carbon content and the higher heating value of the sawdust feedstock were reported as 68.46 wt%, 1.13 wt%, 47.40 wt% and 19.33 MJ/kg, respectively, with very low nitrogen and sulfur content. The thermogravimetric (TGA and DTG) analysis of sawdust showed that the weight loss from biomass occurred in three main stages as a result of the removal of moisture and extractives, decomposition of hemicellulose, cellulose, and the lignin components. Based on the decomposition temperature window and peak conversion temperature the pyrolysis experiments were carried out in the range of 400–600 ℃ by maintaining the nitrogen flow rate, biomass feeding rate, rotation speed of the conveyer the residence time of materials and biomass particle size as 300 cm3/min, 180 g/h, 4.5 RPM, 5 min, and 0.5–1.0 mm, respectively. The yields of the non-condensable gases, biochar and bio-oil were reported in the ranges 16.70–38.47 wt%, 29.72–51.85 wt% and 29.40–45.10 wt%, respectively. The pyrolysis products were pragmatically analyzed to evaluate the influence on yield and their properties. The higher heating values of bio-oil produced were reported in the range 28.781–29.871 MJ/kg while the pH of bio-oil indicated the strongly acidic nature with values in the range of 2.9–3.4. Chemical compounds in bio-oils were categorized as phenols, nitrogen containing compounds, guaiacols, organic acids, ketones, anhydrous sugars, esters, and aldehydes. Biochar characterization showed an energy potential comparable to those of the low ranked coals with the higher heating values reported in the range of 25.01–25.99 MJ/kg. The surface morphological characteristics and Brunauer–Emmett–Teller (BET) analysis of the biochars indicated potential for other valued applications in the adsorption, environmental, catalyst, and agricultural context.

Biodiesel is a popular alternative useful fuel due to its low environmental impact. Herein, we developed new heterogeneous catalysts from waste-materials, rice husk and eggshells, and utilized for the biodiesel-making process. Apricot seeds are widely accessible around the world and are used as an oil feedstock to produce biodiesel, an ecologically beneficial fuel. Modified silica dioxide (obtained from rice husk) and calcium oxide (obtained from calcining eggshells) are used to make synthetic catalysts, with both materials being impregnated to increase their activity. Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy techniques utilized to evaluate the catalysts. Gas chromatography mass spectroscopy identified the components in biodiesel and raw apricot oil by retention duration and area peaks. The parametric research was performed to optimize the reaction conditions, the biodiesel synthesis is greatest at 55 to 65 °C, 90 min, 25 methanol to oil molar ratio, 3 wt.% catalyst loading, and 90% yield. The biodiesel’s fuel characteristics and industry standards (ASTM6751 & EN14214) proved that it might be a renewable fuel. Furthermore, it discovered that the catalyst could be reprocessed up to five times without losing substantial activity. This research suggests that waste-derived catalysts can be used to make commercial biodiesel.

Abstract This study examined the non-isothermal kinetics of the slow pyrolysis of Imperata Cylindrica (IC). Pyrolysis conditions were developed under the pure N2 flow and non-isothermal conditions at the heating rates of 2.5, 5, 10, and 17.5 K/min and over the temperature range of 303–1173 K. The IC pyrolysis profiles could be identified into three parallel reactions, each of which corresponded to pseudo-hemicelluloses (P-Hem), pseudo-cellulose (P-Cell), and pseudo-lignin (P-Lig) decomposition. A systematic kinetic study of the pyrolysis of IC via thermogravimetric analysis (TGA) deconvolution using Asymmetric Double Sigmoidal (Asym2sig), Friedman differential iso-conversional and combined kinetics of biomass pseudo-components was carried out. The kinetics parameters of pseudo components fitted well with the pyrolysis experimental data for all the heating rates. Differential master-plots showed that the reaction mechanisms for pseudo hemicellulose (P-Hem) and pseudo cellulose (P-Cell) were diffusional and order based, and high order based (3rd order) for the pseudo lignin (P-Lig). Mechanism of P-Hem, P-Cell and P-Lig could be further reconstructed to Sestak and Berggren model of f α = α - 0.9875 1 - α 1.325 - l n ⁡ ( 1 - α ) 0.0209 , f α = α 0.3313 1 - α 1.4731 - l n ⁡ ( 1 - α ) 0 . 0215 and f α = α - 2.9551 1 - α 2.7642 - l n ⁡ ( 1 - α ) 0.0074 , respectively. The combined kinetic reported the activation energies of pseudo-components were as 194.709 kJ/mol, 179.968 kJ/mol and 219.226 kJ/mol for P-Hem, P-Cell and P-Lig, respectively.

Biodiesel is regarded as an environmentally friendly alternative fuel. The current research synthesises novel heterogeneous catalysts derived from waste (lab glassware and eggshells) and utilised for biodiesel production. Beef fat, abundantly available worldwide, is used as an oil feedstock and then converted into biodiesel, an environmentally friendly fuel. The synthesised catalyst consists of precursor silica dioxide (treated waste glassware) and calcium oxide (calcined from eggshells) that have been modified by impregnating cerium oxide to increase activity. The catalyst is characterised to ensure its suitability for the reaction to produce methyl esters (biodiesel) from animal fat, and biodiesel production is then tested. Characterisation revealed the suitability of the catalyst for the intended application, followed by a comprehensive parametric study to optimise the reaction conditions, including process temperature, time, methanol to oil molar ratio, and catalyst loading. According to the parametric study, the optimal conditions are as follows; process temperature (70 °C), time (100 min.), methanol to oil molar ratio (11) and catalyst loading (3 wt%), where the optimum biodiesel yield was 95.29 wt%. Furthermore, the produced biodiesel is then characterised to report its fuel properties and compared to standards (ASTM6751 & EN14214) which revealed its suitability as a potential alternative fuel. The reusability of the catalyst is also determined. The results indicated that it could be reused up to five times without a noticeable decrease in its reactivity. Based on the results, it can be concluded that synthesised catalysts from such waste materials are a viable option for commercial biodiesel production.