Biochar production and its environmental applications: Recent developments and machine learning insights.

Biochar production through thermochemical processing is a sustainable biomass conversion and waste management approach. However, commercializing biochar faces challenges requiring further research and development to maximize its potential for addressing environmental concerns and promoting sustainable resource management. This comprehensive review presents the state-of-the-art in biochar production, emphasizing quantitative yield and qualitative properties with varying feedstocks. It discusses the technology readiness level and commercialization status of different production strategies, highlighting their environmental and economic impacts. The review focuses on integrating machine learning algorithms for process control and optimization in biochar production, improving efficiency. Additionally, it explores biochar's environmental applications, including soil amendment, carbon sequestration, and wastewater treatment, showcasing recent advancements and case studies. Advances in biochar technologies and their environmental benefits in various sectors are discussed herein.

Metagenomic and physicochemical analysis of Kombucha beverage produced from tea waste.

Kombucha beverage produced through fermentation of sugared tea using bacteria and yeast has gained attention for its beneficial health benefits. However, the cost linked to the raw materials often increases the upstream process expenses, thereby the overall operating expenditures. Thus, there is a need to explore alternative waste and cost-effective raw materials for Kombucha fermentation. The present study, compared the physico-chemical and microbial growth pattern of Kombucha beverage production using tea waste from the tea processing industries with that of the green/black tea, reporting similar trends irrespective of its type. Further, the amplicon sequencing of 16S rRNA showed dominant presence of Komagataeibacter rhaeticus and high throughput sequencing of ITS1 confirmed the presence of yeast species similar to Brettanomyces bruxellensis in the tea waste based Kombucha beverage. Appreciable amount of carbohydrates (8.5/100 g) and energy (34 kcal/100 g) with appropriate organoleptic properties favourable for human consumption were also observed during the nutritional content and qualitative property assessment. The overall study showed a broad taxonomic and functional diversity existing during Kombucha fermentation process with tea waste to maintain a sustained eco-system to facilitate cost-effective beverage production with desired properties for safe consumption. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05476-3.

Hydrothermal processing of microalgal biomass: Circular bio-economy perspectives for addressing food-water-energy nexus.

Hydrothermal processing of microalgae is regarded as a promising technology to generate multitude of energy based and value-added products. The niche of hydrothermal technologies is still under infancy in terms of the technical discrepancies related to research and development. Thus, the present review critically surveyed the recent advancements linked to the influencing factors governing the algal hydrothermal processing in terms of the product yield and quality. The sustainability of hydrothermal technologies as a standalone method and in broader aspects of circular bio-based economy for energy and value-added platform chemicals are comprehensively discussed. Process optimization and strategic integration of technologies has been suggested to improve efficiency, with reduced energy usage and environmental impacts for addressing the energy-food-water supply chains. Within the wider economic transition and sustainability debate, the knowledge gaps identified and the research hotspots fostering future perspective solutions proposed herewith would facilitate its real-time implementation.

Research trends and market opportunities of microalgal biorefinery technologies from circular bioeconomy perspectives.

Microalgae as an alternative feedstock for sustainable bio-products have gained significant interest over years. Even though scientific productivity related to microalgae-based research has increased in recent decades, translation to industrial scale is still lacking. Therefore, it is essential to understand the current state-of-art and, identify research gaps and hotspots driving industrial scale up. The present review through scientometric analysis attempted to delineate the research evolution contributing to this emerging field. The research trends were analysed over the last decade globally highlighting the collaborative network between the countries. The comprehensive knowledge map generated confirmed microalgal biorefinery as a scientifically active field, where the present research interest is focussed on synergistically integrating the unit processes involved to make it enviro-economically feasible. Market opportunities and regulatory policy requirements along with the consensus need to adopt circular bio-economy perspectives were highlighted to facilitate real-time implementation of microalgal biorefinery.

Techno-economic feasibility assessment of bacterial cellulose biofilm production during the Kombucha fermentation process.

Bacterial cellulose produced during Kombucha fermentation has recently received lots of attention owing to its desirable mechanical and physicochemical properties and is exploited for different food, textiles and environmental applications. However, lack of information on process feasibility often hinders large-scale manufacturing of Kombucha-based cellulose. Therefore, the current study assesses techno-economic feasibility of a 60-ton annual capacity Kombucha-based cellulose production facility using SuperPro designer. Economic feasibility analysis showed an estimation of 13.72 million US$ as total investment and 3.8 million US$ as operating costs with 89% expenses associated with facility dependent and labour costs. The process feasibility is revealed with a payback time of 4.23 years, 23.64% return on investment and 16.48% internal rate of return. Sensitivity analysis presented that increased volume of fermentation units and automating the process can significantly reduce input costs. Such research is necessary to aid policymakers in facilitating the commercialization of Kombucha-based cellulose at field scale.

Experimental and modelling studies of convective and microwave drying kinetics for microalgae.

Conventional microalgal drying consumes huge time and contributes to 60-80% of downstream process costs. With the aim to develop an effective and rapid drying process, the present study evaluated the performance of microwave based drying (MWD) with a power range of 360-900 W and compared with the conventional oven drying (OD) at 40-100 °C. MWD was found to be efficient due to uniform and volumetric heating because of dipolar interaction, with an effective diffusivity of 0.47 × 10-9-1.63 × 10-9 m2 s-1, comparatively higher than OD. Activation and specific energy of 32.43 W g-1 and 42.9-56.07 kWh kg-1 was projected respectively, and a falling rate period with best fit for Newton and Henderson-Pabis model was observed for MWD. Uniform heating from internal sub-surface avoided cell distress, resulting in 14.4% higher lipid yield and significant preservation of biochemical components that can be processed into bioenergy and valuable products in microalgal biorefinery.

Integrated microalgal biorefinery for the production and application of biostimulants in circular bioeconomy.

Adverse detrimental impacts of environmental pollution over the health regimen of people has driven a shift in lifestyle towards cleaner and natural resources, especially in the aspects of food production and consumption. Microalgae are considered a rich source of high value metabolites to be utilized as plant growth biostimulants. These organisms however, are underrated compared to other microbial counterparts, due to inappropriate knowledge on the technical, enviro-economical constrains leading to low market credibility. Thus, to avert these issues, the present review comprehensively discusses the biostimulatory potential of microalgae interactively combined with circular bio-economy perspectives. The biochemical content and intracellular action mechanism of microalgal biostimulants were described. Furthermore, detailed country-wise market trends along with the description of the existing regulatory policies are included. Enviro-techno-economic challenges are discussed, and the consensus need for shift to biorefinery and circular bio-economy concept are emphasized to achieve sustainable impacts during the commercialization of microalgal biostimulants.

Algal biodiesel production with engineered biochar as a heterogeneous solid acid catalyst.

This study evaluates the use of engineered biochar as a heterogeneous solid acid catalyst for transesterification of algal oil derived from a native microalgal consortium. Biochar derived from sugarcane bagasse, coconut shell, corncob and peanut shell were evaluated for catalytic activity following surface modification. Peanut shell pyrolyzed at 400 °C with the sulfonic acid density of 0.837 mmol/g having 6.616 m2/g surface area was selected for efficient catalysis. The efficiency of transesterification was evaluated with 1-7 wt% catalyst loading, methanol: oil ratio of 6:1 to 30:1 at 55-85 °C over 2-8 h. Biodiesel yield of 94.91% was obtained with 5 wt% catalyst loading, MeOH: oil ratio of 20:1 at 65 °C after 4 h. Spectral analysis of algal biodiesel showed the presence of functional groups corresponding to esters. GC-MS analysis revealed the prominent presence of palmitic and oleic acids, further advocating the suitability of the technology for commercial application.

Biological nutrient recovery from human urine by enriching mixed microalgal consortium for biodiesel production.

Utilization of waste resources is necessary to harness the long-term sustainability of algal technology. The study focused on the use of human urine as the basic nutrient source for culturing native microalgal consortium and further optimized the process parameters using response surface methodology. A full factorial, central composite rotatable design (CCRD) with three variables: urine concentration (1-10% vol of urine/vol of distil water [%v/v]), pH (6.5-9) and light intensity (50-350 µmolphotonsm-2sec-1) was used to evaluate the microalgal biomass and lipid content. Results indicated that at 95% confidence limits, the selected factors influence the biomass and lipid productivity. The maximum biomass productivity of 211.63 ± 1.40 mg l-1 d-1 was obtained under optimized conditions with 6.50% v/v of urine, pH of 7.69 and at light intensity of 205.40 µmolphotonsm-2sec-1. The lipid content was found to increase from 18.96 ± 1.30% in control media to 26.27 ± 1.94% under optimal conditions. The interactive effect of variables over the microalgal biomass and lipid content has also been elucidated. The data obtained were comparable to the BG11 media (control). Optimized diluted urine media in the presence of ammonium ions and under limited nitrate showed better lipid yields. Significant lipid biomolecules were detected in the algal oil extracts obtained from the diluted urine media characterized by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (NMR). Gas chromatography-mass spectrometry (GCMS) revealed the presence of several monounsaturated and polyunsaturated fatty acids in the transesterified algal oil. Such studies would aid in technically realizing the field scale cultivation of microalgae for biofuels.

Optimization of process variables on two-step microwave-assisted transesterification of waste cooking oil.

Scale-up and commercialization of biodiesel is often delimited by costly feedstock that adds up to the process costs. These underlying issues demand the exploration of unconventional cheap feed to improve the process economics. Conversion of waste cooking oil (WCO) into biodiesel could reduce the process costs by 60-70%. However, the continuous exposure to heat during frying leads to oxidation as well increase in the free fatty acid (FFA) content which intensifies the time and energy required for transesterification. The present study analyzes the effect of parameters over the conversion of WCO (with 8.17% FFA) into biodiesel via two-step acid-alkali-based microwave-assisted transesterification. Response surface methodology (RSM) was used to optimize the oil:methanol volume ratio, microwave power, and reaction time during the acid-catalyzed esterification to bring down the FFA below 1%. Microwave irradiation of 250 W, with methanol:oil molar ratio of 19.57:1 [oil:methanol volume ratio of 1.31 (expressed as decimal)] and reaction time of 35 s, resulted in 0.082% of FFA. Alkali-catalyzed transesterification with methanol:oil molar ratio of 5:1 with 2% sodium hydroxide at 65 °C thereby produced fatty acid methyl esters (FAMEs) with the volumetric biodiesel yield of 94.6% in 30 min. Physiochemical properties of the transesterified WCO were well comparable with the biodiesel standards. The study highlights the essentiality of multivariate optimization for the esterification process that could aid in understanding the interactive effects of variables over FFA content. Such studies would benefit in scaling up of the transesterification process at industrial level by improving the economics of the overall bioprocess.

Natural plant extracts as an economical and ecofriendly alternative for harvesting microalgae.

The study investigated the ability of plant based natural coagulants from Azadirachta indica; Ficus indica; Moringa oleifera; Citrus sinensis; Punica granatum and Musa acuminata to harvest the microalgal biomass. Influence of eluent type (water and NaCl) and concentration (1-5 N) on coagulant extraction; coagulant dosage (1-5 g) and volume (20-100 ml); pH (6-12) and algal concentration (0.1-1 g l-1) on harvesting were analyzed. The results obtained were compared with alum and chitosan. FTIR and biochemical analysis confirmed the presence of bioactive compounds to aid coagulation. Biomass removal efficiency of 75.50% was obtained with M. oleifera extracts (8 mg ml-1) at pH 7.5-7.8, within 100 min. The harvesting efficiency increased to 95.76% when 4 mg ml-1M. oleifera extracts was combined with 0.75 mg ml-1 chitosan. The life cycle and cost analysis acknowledged the eco-friendly coagulants as strong alternative for conventional coagulants used in microalgal harvesting, thereby improvising the overall bioprocess.