• Energy Research

Large amount of food and agricultural residues are discharged as municipal wastes. These biogenic waste possess high sugar content and are being dumped into landfills or incinerated, creating severe environmental challenges. Anaerobic co-digestion (AcD) of food waste and agricultural residues provides a sustainable valorisation route for biogas production. Biochar addition promotes the microbial activity, electrical conductivity, and molar interactions in the anaerobic digester. The present review presents an overview of the influence of biochar on the product yield during AcD. An overview of different classification of food waste and agricultural residues is presented. In addition, studies related to the application of biochar to enhance AcD were critically reviewed as well as the future outlook. The conducted studies revealed that the addition of biochar to AcD process can mitigate the buffering capacity and toxic process inhibitors faced in AcD, and ultimately enhance biogas yields, shortening the lag-phase and biodegrading running time. Biochar has a unique surface functional groups that can be modified by functionalization or by adjusting the pyrolysis temperature for optimal efficiency of specific co-substrate combinations of feedstocks. In AcD process, engineered biochar can be directed to specifically adsorb precise indirect (limonene) or direct (NH3, CO2) inhibitors for optimal process efficiency and methane production based on active surface functional groups, alkalinity of the material and hydrophobicity. Hence, biochar enhanced with the right pore sizing and pH can offset AcD limitations and improve process efficiency. The presented review provide an in- depth understand on the influence of biochar on product yield during AcD process.

Large amount of food and agricultural residues are discharged as municipal wastes. These biogenic waste possess high sugar content and are being dumped into landfills or incinerated, creating severe environmental challenges. Anaerobic co-digestion (AcD) of food waste and agricultural residues provides a sustainable valorisation route for biogas production. Biochar addition promotes the microbial activity, electrical conductivity, and molar interactions in the anaerobic digester. The present review presents an overview of the influence of biochar on the product yield during AcD. An overview of different classification of food waste and agricultural residues is presented. In addition, studies related to the application of biochar to enhance AcD were critically reviewed as well as the future outlook. The conducted studies revealed that the addition of biochar to AcD process can mitigate the buffering capacity and toxic process inhibitors faced in AcD, and ultimately enhance biogas yields, shortening the lag-phase and biodegrading running time. Biochar has a unique surface functional groups that can be modified by functionalization or by adjusting the pyrolysis temperature for optimal efficiency of specific co-substrate combinations of feedstocks. In AcD process, engineered biochar can be directed to specifically adsorb precise indirect (limonene) or direct (NH3, CO2) inhibitors for optimal process efficiency and methane production based on active surface functional groups, alkalinity of the material and hydrophobicity. Hence, biochar enhanced with the right pore sizing and pH can offset AcD limitations and improve process efficiency. The presented review provide an in- depth understand on the influence of biochar on product yield during AcD process.

Abstract Biodiesel synthesis requires both feedstock diversification and sustainable heterogeneous catalyst precursors to impact its viability. This study is focused on the development of a heterogeneous catalyst from moringa leaves as a sustainable precursor for biodiesel production. The catalyst was prepared by facile calcination at 500 °C for 2 h and used directly in transesterification reaction with oil and methanol to synthesize biodiesel. The catalyst structural properties, surface morphology, and mineral constituents were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrometry of X-rays (EDS). The results show that inorganic carbonate minerals of dolomite, calcite, and (K2Ca(CO3)2) were obtained after calcination and these minerals promoted the transesterification reaction. Hence, under reaction conditions of 6:1 methanol/oil molar ratio, 120 min, 65 °C, and 6 wt% catalyst dosage, 86.7% FAME yield was observed. Consequently, the investigation of the ASTM standard for quality assessment indicates that the synthesized biodiesel meets the specification for commercial biodiesel. The catalyst could be reused in three cycles of the experiment.

Abstract Biodiesel synthesis requires both feedstock diversification and sustainable heterogeneous catalyst precursors to impact its viability. This study is focused on the development of a heterogeneous catalyst from moringa leaves as a sustainable precursor for biodiesel production. The catalyst was prepared by facile calcination at 500 °C for 2 h and used directly in transesterification reaction with oil and methanol to synthesize biodiesel. The catalyst structural properties, surface morphology, and mineral constituents were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectrometry of X-rays (EDS). The results show that inorganic carbonate minerals of dolomite, calcite, and (K2Ca(CO3)2) were obtained after calcination and these minerals promoted the transesterification reaction. Hence, under reaction conditions of 6:1 methanol/oil molar ratio, 120 min, 65 °C, and 6 wt% catalyst dosage, 86.7% FAME yield was observed. Consequently, the investigation of the ASTM standard for quality assessment indicates that the synthesized biodiesel meets the specification for commercial biodiesel. The catalyst could be reused in three cycles of the experiment.

Abstract Biodiesel (BD) is an alternative energy source to conventional diesel derived from fossil materials, which are unsustainable and non-renewable and contribute to global warming. BD production via transesterification with methanol leads to the synthesis of glycerol; this process accounts for 10% (w/w) of the total BD produced worldwide. The increasing demand for environmentally harmless BD has created a glycerol glut, which must be utilized to increase BD profitability. Glycerol is a stable and multifunctional compound used as a building block in fine chemical synthesis. Acetylation and carboxylation pathways have been studied to utilize and/or upgrade glycerol into fine chemicals. The use of catalysts, especially heterogeneous catalysts, remains the green approach for tailoring carboxylation and acetylation routes to achieve the desired products, namely, glycerol carbonate and glycerol acetyl esters, respectively. However, side-product formation, poorly structured channels of some catalysts, and catalyst deactivation or reusability hinder the effective utilization of heterogeneous catalysts and must be further studied. Moreover, introduction of variations to optimize reaction-influencing parameters is a potential green method that must be explored.

Abstract Biodiesel (BD) is an alternative energy source to conventional diesel derived from fossil materials, which are unsustainable and non-renewable and contribute to global warming. BD production via transesterification with methanol leads to the synthesis of glycerol; this process accounts for 10% (w/w) of the total BD produced worldwide. The increasing demand for environmentally harmless BD has created a glycerol glut, which must be utilized to increase BD profitability. Glycerol is a stable and multifunctional compound used as a building block in fine chemical synthesis. Acetylation and carboxylation pathways have been studied to utilize and/or upgrade glycerol into fine chemicals. The use of catalysts, especially heterogeneous catalysts, remains the green approach for tailoring carboxylation and acetylation routes to achieve the desired products, namely, glycerol carbonate and glycerol acetyl esters, respectively. However, side-product formation, poorly structured channels of some catalysts, and catalyst deactivation or reusability hinder the effective utilization of heterogeneous catalysts and must be further studied. Moreover, introduction of variations to optimize reaction-influencing parameters is a potential green method that must be explored.

We report, the catalytic application of sulphonated cellulose based solid carbon catalyst for conversion of oleic acid to methyl oleate-biodiesel production under microwave irradiation. Oleic acid, being one of the most widely found fatty acids in plant oils and animal fats; it was utilized as a model substrate to produce biodiesel in this study. The effect and interaction of four independent factors such as methanol to oleic acid molar ratio (MOMR), time, catalyst loading, and temperature were investigated using response surface methodology (RSM). After doing the thirty experiments given by the central composite design (CCD), the optimized reaction condition using RSM was found to be MOMR of 21:1, 60 min, 8 wt % catalyst loading, and temperature of 80 ◦C that predicted 96.77% biodiesel yield under microwave irradiation, whereas, 97.6 ± 0.2% yield was observed experimentally. The kinetic study of the esterification reaction showed that it followed a pseudo first order reaction. The activation energy of the esterification was found to be relatively low at 49.19 kJ mol− 1 . The catalyst showed good recyclability when explored up to the 5th reaction cycle. The SEM analysis of the recycled catalyst showed its stability for at least 5 reaction cycles. Therefore, it can be promoted for sustainable production of biodiesel due to its moderate preparation method, good catalytic efficiency, and excellent recyclability.