Utilization of agricultural waste biomass and recycling toward circular bioeconomy

Comparative assessment on lignocellulose degrading enzymes and bioethanol production from spent mushroom substrate of Calocybe indica and Volvariella volvacea

In the current study, we compared the production of extracellular lignocellulose degrading enzymes and bioethanol from the spent mushroom substrate (SMS) of Calocybe indica and Volvariella volvacea. From SMS at different stages of the mushroom development cycle, ligninolytic and hydrolytic enzymes were analysed. The activities of lignin-degrading enzymes, including lignin peroxidase (LiP), laccase, and manganese peroxidase (MnP) were maximal in the spawn run and primordial stages, while hydrolytic enzymes including xylanase, cellobiohydrolase (CBH), and carboxymethyl cellulase (CMCase) showed higher activity during fruiting bodies development and at the end of the mushroom growth cycle. SMS of V. volvacea showed relatively lower ligninase activity than the SMS of C. indica, but had the maximum activity of hydrolytic enzymes. The enzyme was precipitated with acetone and further purified with the DEAE cellulose column. The maximum yield of reducing sugars was obtained after hydrolysis of NaOH (0.5 M) pretreated SMS with a cocktail of partially purified enzymes (50% v/v). After enzymatic hydrolysis, the total reducing sugars were 18.68 ± 0.34 g/l (SMS of C. indica) and 20.02 ± 0.87 g/l (SMS of V. volvacea). We observed the highest fermentation efficiency and ethanol productivity (54.25%, 0.12 g/l h) obtained from SMS hydrolysate of V. volvacea after 48 h at 30 ± 2 °C, using co-culture of Saccharomyces cerevisiae MTCC 11,815 and Pachysolen tannophilus MTCC 1077.

Pine needle gasification-based electricity production: Understanding the effect of supply chain

Pine needles (pine tree leaves), found abundantly across continents such as North America, Asia, Europe, South America, Africa, and parts of the Southern Hemisphere, are a significant global concern due to their high susceptibility to catching fire, especially in dry and hot climates. The same issue persists in the Uttarakhand state of India, which boasts ample pine forests, yielding a substantial 1.67 × 109 kg of pine needles annually. In the present study, the annual potential emissions from forest fires in Uttarakhand were estimated to be 58.37 × 109 kg of CO2 equivalent. Therefore, the present research aims to unlock pine needles' potential via gasification for green electricity and biochar production, offering an alternative to coal-based plants while reducing forest fire frequencies. Nevertheless, obstacles hindering pine needle gasification include an unsteady supply chain, limited collection windows (100 days), and plant expenses, including transportation and operational costs. The primary focus of the research is to design and assess the performance of a gasification-based supply chain for pine needles in the Almora District of Uttarakhand. Ten plant capacity scenarios were considered, ranging from 25 to 250 kW. The study incorporated critical factors, encompassing diverse losses within the supply chain, selecting potential plant sites, minimizing transportation distance, and evaluating the supply chain's economic and environmental performance. The economic analysis revealed that the 250-kW plant scenario exhibited a minimum discounted payback period (DPP) of 3.93 years, alongside an internal rate of return (IRR) of 19% and a net present value (NPV) of 653.32 million INR without government subsidies. With subsidies included, the DPP decreased to 1.30 years, improving the IRR to 69% with an NPV of 916.17 million INR. The emission analysis indicated that gasification plant capacity scenarios could potentially reduce 44.63 × 106 to 46.16 × 106 kg of CO2 equivalent emissions annually compared to grid electricity while meeting nearly 5.5% of the electricity demand of Almora district. The present study aligns with SDG-7 (Affordable and Clean Energy), SDG-13 (Climate Action), SDG-9 (Industry, Innovation, and Infrastructure), SDG-11 (Sustainable Cities and Communities), SDG-3 (Good Health and Well-being), and SDG-15 (Life on Land).

Key fuel characteristics and techno-economic aspects of torrefied rubberwood biomass pellets produced by incorporating various cassava-based binders at varied doses

Improving energy content and hydrophobic nature of woody biomass can be pursued through torrefaction. This gives torrefied biomass with a low bulk density, potentially increasing storage and transport costs. To overcome this issue, densifying the torrefied biomass is necessary. However, poor binding of particles makes densification challenging without using a binder. Therefore, the aim of this study was to investigate the physicochemical characteristics and techno-economic aspects of torrefied rubberwood biomass (TRWB) when pelletized using various cassava-based binders at different blending ratios. The selected binders included cassava starch (CS), cassava pulp (CP), and cassava chip (CC). Each binder at 5%, 10%, or 15% (wt.) was mixed with TRWB and water before pelletizing using a flat die machine. The results revealed that pelletizing TRWB with different cassava-based binders at various blending ratios influenced the physicochemical characteristics of the TRWB pellets, particularly dimensions, bulk density, fuel and atomic ratios, and energy content. The TRWB pellets demonstrated energy densities in the range of 7.95-11.39 GJ/m3, and their mechanical durability and fine content fell within acceptable ranges. The TRWB pellets maintained their shape during 120 min of water soaking, with water absorption levels varying by binder dose. The pelletizing ability, material, and energy costs of TRWB pellets depend on binder type and dose. CP can be applied as a binder for pelletizing torrefied rubberwood biomass. However, the mechanical durability of the product needs to be above the user requirement or standard.

Promoting the disassemble and enzymatic saccharification of bamboo shoot shells via efficient hydrated alkaline deep eutectic solvent pretreatment

Pretreatment is a key process restricting the development of biorefinery. This work developed a pretreatment process based on an ethanolamine/acetamide alkaline deep eutectic solvent (ADES). Under microwave assistance, pure ADES pretreatment at 100 °C for 10 min achieved 95.9 % delignification and 95.2 % hemicellulose removal of bamboo shoot shells (BSS). Further, when 75 % water was added to pure DES to prepare hydrated DES (75 %-HADES), impressive delignification (93.2 %), hemicellulose removal (92.2 %) and cellulose recovery (94.8 %) were still achieved. The cellulose digestibility of the 75 %-HADES pretreated solid residue was significantly increased from 12.2 % (the control) to 91.2 %. Meanwhile, the structural features of hemicellulose and lignin macromolecules fractionated by 75 %-HADES pretreatment were well preserved, offering opportunities for downstream utilization. Overall, this work proposes an effective pretreatment strategy with the potential to enable the utilization of all major components of bamboo shoot shells.

Managing the low carbon transition pathways through solid waste electricity

The potential of solid waste as an energy source is clear, owing to its wide availability and renewable properties, which provide a critical answer for energy security. This can be especially effective in reducing the environmental impact of fossil fuels. Countries that rely heavily on coal should examine alternatives such as electricity from solid waste to provide a constant energy supply while also contributing to atmospheric restoration. In this regards, Low Emissions Analysis Platform (LEAP) is used for simulation the entire energy system in Pakistan and forecasted its capital cost and future CO2 emissions in relation to the use of renewable and fossil fuel resources under the different growth rates of solid waste projects like 20%, 30% and 40% for the study period 2023-2053. The results revealed that, 1402.97 TWh units of energy are generated to meet the total energy demand of 1193.93 TWh until 2053. The share of solid waste based electricity in total energy mix is increasing from a mere 0.81% in 2023 to around 9.44% by 2053 under the 20% growth rate, which then increase to 39.67% by 2053 under the 30% growth rate and further increases to 78.33% by 2053 under the 40% growth rate. It is suggested that 40% growth rate for solid waste based electricity projects is suitable for Pakistan until 2053 because under this condition, renewable sources contributes 95.2% and fossil fuels contributed 4.47% in the total energy mix of Pakistan. Hence, CO2 emissions are reduced from 148.26 million metric tons to 35.46 million metric tons until 2053 but capital cost is increased from 13.23 b$ in 2023 to 363.11 b$ by 2053.

Chemical Composition and Biological Activities of the Essential Oil from Citrus reticulata Blanco Peels Collected from Agrowastes

Citrus fruits have a thick outer coat which is often discarded due to its low economic value and usually contributes to the waste. So this work focused on exploring the potential pharmacological properties of the discarded citrus peels. In the present study, we extracted the essential oil from peel wastes of Citrus reticulata Blanco (CREO) from the local market. The antioxidant, antibacterial, and anticancer properties of essential oil were evaluated. The CREO exhibited a strong antioxidant property with DPPH radical scavenging, ABTS radical scavenging, H2 O2 radical scavenging, Ferric reducing antioxidant power and for Lipid peroxidation inhibition respectively. Antibacterial properties of CREO was indicated against different pathogenic microbial strains like E. coli, P. aeruginosa, S. aureus, and S. enterica in terms of disc diffusion method and minimum inhibitory concentration (MIC). Further, anticancer properties studied on breast cancer cell lines MCF7 and MDA-MB-231 showed dose-dependent cytotoxicity with IC50 of 56.67±3.12 μg/mL and 76.44±2.53 μg/mL respectively. The GC-MS analysis of CREO revealed the presence of major compounds like S-limonene, α-pinene, α-myrcene, and cis-terpinene which might have played a significant role in strong antioxidant, antibacterial and anticancer properties. The study thus identified the potential health benefits of Citrus reticulata peel waste.

Trends and social aspects in the management and conversion of agricultural residues into valuable resources: A comprehensive approach to counter environmental degradation, food security, and climate change

The circular economy is essential as it encourages the reuse and recycling of resources while reducing waste, which ultimately helps to reduce environmental pollution and boosts economic efficiency. The current review highlights the management of agricultural and livestock residues and their conversion into valuable resources to combat environmental degradation and improve social well-being. The current trends in converting agricultural residues into useful resources emphasize the social benefits of waste management and conversion. It also emphasizes how waste conversion can reduce environmental degradation and enhance food security. Using agricultural residues can increase soil health and agricultural output while reducing pollution, greenhouse gas emissions, and resource depletion. Promoting sustainable waste-to-resource conversion processes requires a combination of strategies that address technical, economic, social, and environmental aspects. These multiple strategies are highlighted along with prospects and considerations.

Comparative study on thermo-mechanical, structural and functional properties of pectin extracted from immature wasted apples and commercial pectin

Pectin yield of 22.22 ± 0.98 % (dry basis) was achieved from prematurely dropped Golden Delicious apples, having a light orange hue (hue value: 78.08 ± 0.04) and an overall color difference (ΔE) of 9.92 ± 0.01 compared to commercial pectin (CP). Extracted AP exhibited a lower equivalent weight (725.24 ± 29.73) and higher methoxy content (8.36 ± 0.28 %) in contrast to CP. However, a similar degree of esterification of 71.57 ± 0.79 and 70.55 ± 0.59 %, was observed in AP and CP respectively. Apple pectin demonstrated slight lower galacturonic acid (GalA) content of 68.10 ± 3.94 % in comparison to 72.31 ± 4.62 % of CP, which was further corroborated by reduced intensity in FTIR fingerprint region (912-1025 cm-1). Morphology revealed a sheet-like cloudy appearance indicating a significant presence of associated sugars whereas X-ray diffraction highlighted the highly amorphous nature of AP. AP and CP solutions (3-9 %) displayed a shear-thinning flow and viscoelastic behavior where the loss (G') moduli dominated over the storage moduli (G"). Owing to high degree of esterification, galacturonic acid content (>65 %) that aligns with commercial standards and viscoelastic behavior, the extracted AP holds promise for potential utilization in commercial applications. This study underscores the potential for sustainable utilization of prematurely dropped apples through pectin extraction, contributing to valorization of the wasted bioresource.

Mechanisms and factors affecting the removal of minocycline from aqueous solutions using graphene-modified resorcinol formaldehyde aerogels

In recent years, concerns about the presence of pharmaceutical compounds in wastewater have increased. Various types of residues of tetracycline family antibiotic compounds, which are widely used, are found in environmental waters in relatively low and persistent concentrations, adversely affecting human health and the environment. In this study, a resorcinol formaldehyde (RF) aerogel was prepared using the sol-gel method at resorcinol/catalyst ratio of 400 and resorcinol/water ratio of 2 and drying at ambient pressure for removing antibiotics like minocycline. Next, RF aerogel was modified with graphene and to increase the specific surface area and porosity of the modified sample and to form the graphene plates without compromising the interconnected porous three-dimensional structure of the aerogel. Also, the pores were designed according to the size of the minocycline particles on the meso- and macro-scale, which bestowed the modified sample the ability to remove a significant amount of the minocycline antibiotic from the aqueous solution. The removal percentage of the antibiotic obtained by UV-vis spectroscopy. Ultimately, the performance of prepared aerogels was investigated under various conditions, including adsorbent doses (4-10 mg), solution pHs (2-12), contact times of the adsorbent with the adsorbate (3-24 h), and initial concentration of antibiotic (40-100 mg/l). The results from the BET test demonstrated that the surface area of the resorcinol formaldehyde aerogel sample, which included 1 wt% graphene (RF-G1), exhibited an augmentation in comparison to the surface area of the pure aerogel. Additionally, it was noted that the removal percentage of minocycline antibiotic for both the unmodified and altered samples was 71.6% and 92.1% at the optimal pH values of 4 and 6, respectively. The adsorption capacity of pure and modified aerogel for the minocycline antibiotic was 358 and 460.5 mg/g, respectively. The adsorption data for the modified aerogel was studied by the pseudo-second-order model and the results obtained from the samples for antibiotic adsorption with this model revealed a favorable fit, which indicated that the chemical adsorption in the rapid adsorption of the antibiotic by the modified aerogel had occurred.

Socio-economic sustainability with circular economy - An alternative approach

As the global population and living standards rise, it pushes the demand for basic amenities like food, health, and energy resources. Additionally, manufacturing automation has led to mass production and consumption, triggering waste production. The existing linear economy approach has led to increasing waste production and resource depletion, posing significant environmental and public health threats. To overcome these impediments, an alternative model called the circular economy concept has gained popularity in the global industry community. This closed-loop, restorative, waste-free concept has the potential to protect the environment and improve economics by reducing energy and resource consumption. Thus, major impetus should be given to strengthening the backbone of the economy where tools such as green technologies, decarbonization strategies, bio refinery processes, material flow analysis, life cycle assessment, ecological footprints (water, carbon, and material), substance flow analysis, circularity index, eco-designing, bioresource management, new business models, and policy play an essential role in the areas of socio-economic sustainability, ecological facts, and industrial aspects to enhance socio-economic growth in a sustainable manner. Sectoral awareness, collaborations, and partnerships among the Government, stakeholders, policymakers, and competent authorities are also essential to enabling circularity within the eco-systems.

A mini review on microwave and contemporary based biohydrogen production technologies: a comparison

Hydrogen gas, along with conventional fossil fuels, has been used as a green fuel with enormous potential. Due to the rapid depletion of fossil fuels, a new dimension of hydrogen production technology has arrived to reduce reliance on nonrenewable energy sources. Microwave-based hydrogen production is a more promising and cost-effective technology than other existing green hydrogen production methods such as fermentation and gasification. Microwave heating may be superior to traditional heating due to several advantages such as less power consumption compared to other methods, higher yield, and a higher rate of conversion. Compared to another process for hydrogen production, the microwave-driven process worked efficiently at lower temperatures by providing more than 70% yield. The process of production can be optimized by using properly sized biomass, types of biomass, water flow, temperature, pressure, and reactor size. This method is the most suitable, attractive, and efficient technique for hydrogen production in the presence of a suitable catalyst. Hot spots formed by microwave irradiation would have a substantial impact on the yield and properties of microwave-processed goods. The current techno-economic situation of various technologies for hydrogen production is discussed here, with cost, efficiency, and durability being the most important factors to consider. The present review shows that a cost-competitive hydrogen economy will necessitate continual efforts to increase performance, scale-up, technical prospects, and political backing.

Exploration of characteristics and synthesis gas suitability for heat generation of coffee biomass pellets produced by single and co-pelletization

Production of coffee beans generates various types of biomass that can be applied as bioenergy for drying and roasting the beans. Thus, the aims of this study were to explore the characteristics of coffee biomass pellets (CBPs) produced from coffee cherry pulp (CCP), coffee parchment (CPM), and expired green coffee beans (ECB) by single and co-pelletization. The CBPs were then used to produce the synthesis gas in a downdraft gasifier, and the syngas properties were investigated for further heat applications. The results showed that single and co-pelletization of CCP and CPM performed well. The CBPs had good physiochemical properties in shape, size, and atomic ratios. The higher heating value and energy density of CBPs were 19.25-24.29 MJ/kg and 12.09-14.87 GJ/m3. The ash from CBPs was rich in K2O, CaO and MgO oxides, and the CPM ash had the lowest initial deformation temperature at 1136 °C. The ash samples from CBPs also had different slagging and fouling indexes. The syngas from CBPs mainly contained H2 (6.85-9.30%), CO (12.15-18.85%), and CO2 (10.85-13.75%). The heating value and tar concentration of syngas from CBPs were 3.24-4.32 MJ/m3 and 21.75-30.92 g/m3. The main chemical compounds in tar were styrene, phenol, caffeine, and pyrrole according to GC-MS. These results indicate that CCP and CPM have potential for pelletization and gasification to generate heat needed for coffee bean processing.

Optimization of biomethane production from sweet sorghum bagasse using artificial neural networks combined with particle swarm algorithm

In the face of international movement away from fossil fuels caused pollution menace, many research labs are rushing towards next big breakthrough via effective biorefinery development employing non-edible agro-residues as feedstock. This work aims to evaluate and optimize the methane potential of underutilized full strength sweet sorghum bagasse (SSB) via anaerobic digestion (AD). Biochemical methane potential assays are set up for SSB AD under mesophilic and thermophilic conditions at four substrate-o-inoculum ratios (SIR) 3, 5, 7, and 9 with pH 6.5, 7.5, and 8.5 and with 80, 90, and 100 rpm mixing speed over 50 days. SIR 5 produced the highest cumulative biomethane yield of 4.25 L methane g-1 VS with a shorter lag time of 7.5 days and technical digestion time of 24 days. The influence of physio-chemical parameters on AD process dynamics is supported with 16s rRNA metagenomic sequencing. Based on complete experimental data sets, two artificial neural network (ANN) models are developed to identify the relevant significance of process parameters and to predict bagasse methane potential. Further, the developed ANN model is integrated with particle swarm optimization algorithm to create ideal AD process operating conditions which maximize the target variable, biomethane. The trained and cross-validated ANN-PSO model showed good-fit-accuracy with R2 > 0.995 and demonstrated satisfactory performance in the biomethane yield prediction from AD of non-edible agri-residues.

Financing the hydrogen industry: exploring demand and supply chain dynamics

The hydrogen industry has garnered substantial attention as a pivotal solution in addressing the intricate challenges of energy transition and achieving decarbonization across diverse sectors. The efficacy of deploying hydrogen technologies hinges upon the availability of robust financing mechanisms that can adequately support the dynamic demands and intricate supply chain intricacies inherent in the hydrogen sector. This comprehensive study is underpinned by a rigorous and systematic review of prior research on the hydrogen economy, leveraging authoritative databases including Web of Science, Scopus, and a range of consultancy-based reports. The study meticulously assesses the escalating interest in hydrogen as a paramount clean energy alternative, emphasizing its significance in propelling the multifaceted development and expansion of hydrogen supply chain dynamics. Furthermore, this research critically scrutinizes the intricate financial facets of the hydrogen sector, with a specific focus on delineating the drivers of demand and unraveling the complexities interwoven within the supply chain. Building upon this analysis, the study offers a forward-looking perspective on hydrogen financing, which considers emerging technologies, evolving policy landscapes, and dynamic market trends. In the face of existing global constraints within the hydrogen supply chain, innovative financing mechanisms such as green bonds, project financing underwritten by risk guarantees through public-private partnership paradigms, venture capital-equity models, and carbon pricing mechanisms emerge as indispensable tools poised to address these challenges effectively.

Enhancing biohydrogen production from mono-substrates and co-substrates using a novel bacterial strains

The staggering increase in pollution associated with a sharp tightening in global energy demand is a major concern for organic substances. Renewable biofuel production through simultaneous waste reduction is a sustainable approach to meet this energy demand. This study co-fermentation of dairy whey and SCB was performed using mixed and pure bacterial cultures of Salmonella bongori, Escherichia coli, and Shewanella oneidensis by dark fermentation process for hydrogen production. The maximum H2 production was 202.7 ± 5.5 H2/mL/L, 237.3 ± 6.0 H2/mL/L, and 198 ± 9.9 H2/mL/L obtained in fermentation reactions containing dairy whey, solid and liquid hydrolysis of pretreated sugarcane bagasse as mono-substrates. The H2 production was greater in co-substrate by 347.3 ± 18.5 H2/mL/L under optimized conditions (pH 7.0, temperature 37 °C, substrate concentration 30:50 g/L) than expected in mono-substrate conditions, which confirms that co-fermentation of different substrates enhances the H2 potential. Fermentation medium during bio-H2 production under GC analysis has stated that using mixed cultures in dark fermentation favored acetic acid and butyric acid. Co-substrate degradation produces ethyl alcohol, benzoic acid, propionic acid, and butanol as metabolic by-products. The difference in the treated and untreated substrate and carbon enrichment in the substrates was evaluated by FT-IR analysis. The present study justifies that rather than the usage of mono-substrate for bio-H2 production, the co-substrate provided highly stable H2 production by mixed bacterial cultures. Fabricate the homemade single-chamber microbial fuel cell to generate electricity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03687-9.

Environment friendly emerging techniques for the treatment of waste biomass: a focus on microwave and ultrasonication processes

In the recent past, an increasing interest is mostly observed in using microwave and ultrasonic irradiation to aid the biological conversion of waste materials into value-added products. This study is focused on various individual impacts of microwaves and ultrasonic waves for the treatment of biomass before the synthesis of value-added products. Following, a comprehensive review of the mechanisms governing microwaves and ultrasonication as the treatment methods, their effects on biomass disruption, solubilization of organic matter, modification of the crystalline structure, enzymatic hydrolysis and production of reducing sugars was performed. However, based on the lab-scale experiments evaluated, microwaves and ultrasonication were studied to be economically and energetically ineffective despite their beneficial effects on the waste biomass. This article reviews some of the difficulties associated with using microwaves and ultrasonic irradiation for the efficient processing of waste biomasses and identified some potential directions for future study.

Statistical optimization, characterization and effect of process variables on cotton stalk pellets using tractor drive pelleting machine

In present study, the development, production, characterization and economic analysis of pellets made from cotton stalk in a tractor PTO-based pelleting machine are investigated. The cotton stalk is widely available in the southern part of India and has a huge potential in bioenergy generation due to its salient physicochemical composition. Many regions of Southern India are suffering from an electricity shortage, and therefore to overcome on this issue, an energy-efficient, portable, tractor PTO-operated pelleting machine was developed that can be operated directly on the field to reduce the transportation cost of agro-residues. The Box-Behnken design using response surface methodology (RSM) was employed to evaluate the performance of the pelleting machine. Based on the ANOVA results, the pelleting efficiency, pelleting capacity, bulk density of pellet and fuel consumption were obtained to be 87.06%, 42.65 kg/h, 614.09 kg/m³ and 1.12 lit/h, respectively. In order to examine the physicochemical properties of cotton stalk pellets, the proximate, ultimate, physical, TG-DTG, FTIR and SEM analysis have been carried out. As a result, the ash content, calorific value, shattered index and durability of cotton stalk pellets were found to be around 2.73%, 18.92 MJ/kg, 92.80% and 93.75%, respectively. A combustion characteristic of pellets using TGA analysis exhibited a maximum mass loss (43.5%) observed in between 180 and 350 °C due to the degradation of cellulose and hemicellulose, whereas a SEM analysis of cotton pellets justified its homogeneous morphology along with rich concentration of minerals. The benefit-cost ratio and payback period of developed tractor PTO-operated pelleting machine for cotton stalk were found to be 1.11 and 33.1 months, respectively. The internal return of rate was observed to be 74%.

Production of antifungal iturins from vegetable straw: A combined chemical-bacterial process

A combined chemical-bacterial process was developed to convert vegetable straw waste to high value antifungal iturins. Straws from three widely cultivated vegetable (cucumber, tomato and pepper) were evaluated as feedstocks for iturin production. Microwave assisted hydrolysis with very dilute acid (0.2% w/w H₂SO₄) achieved efficient reducing sugar recovery. The high glucose concentration in non-detoxified hydrolysate from pepper straw facilitated the optimal growth of Bacillus amyloliquefaciens strain Cas02 and stimulated the production of iturin. The fermentation parameters were optimised to enhance the iturin production efficiency. The obtained fermentation extract was further purified using macroporous adsorption resin, resulting in an iturin-rich extract that exhibited strong antifungal activity against Alternaria alternata with an IC50 of 176.44 μg/mL. Each iturin homologue was identified using NMR. Overall, 1.58 g iturin-rich extract containing 164.06 mg/g iturins was obtained from 100 g pepper straw, illustrating the great potential of valorising pepper straw via this process.

An integrated biorefinery approach for the valorization of water hyacinth towards circular bioeconomy: a review

Water hyacinth (WH) has become a considerable concern for people across the globe due to its environmental and socio-economic hazards. Researchers are still trying to control this aquatic weed effectively without other environmental or economic losses. Research on WH focuses on converting this omnipresent excessive biomass into value-added products. The potential use of WH for phytoremediation and utilizing waste biomass in various industries, including agriculture, pharmaceuticals, and bioenergy, has piqued interest. The use of waste WH biomass as a feedstock for producing bioenergy and value-added chemicals has emerged as an eco-friendly step towards the circular economy concept. Here, we have discussed the extraction of bio-actives and cellulose as primary bioproducts, followed by a detailed discussion on different biomass conversion routes to obtain secondary bioproducts. The suggested multi-objective approach will lead to cost-effective and efficient utilization of waste WH biomass. Additionally, the present review includes a discussion of the SWOT analysis for WH biomass and the scope for future studies. An integrated biorefinery scheme is proposed for the holistic utilization of this feedstock in a cascading manner to promote the sustainable and zero-waste circular bio-economy concept.

Food Waste Utilization for Reducing Carbon Footprints towards Sustainable and Cleaner Environment: A Review

There is world-wide generation of food waste daily in significant amounts, leading to depletion of natural resources and deteriorating air quality. One-third of global food produced is wasted laterally with the food value chain. Carbon footprint is an efficient way of communicating the issues related to climate change and the necessity of changing behavior. Valorization or utilization of food wastes helps in resolving issues related to environment pollution. Reduction in the carbon footprint throughout the chain of food supply makes the whole process eco-friendly. Prevailing food waste disposal systems focus on their economic and environmental viability and are putting efforts into using food waste as a resource input to agriculture. Effective and advanced waste management systems are adopted to deal with massive waste production so as to fill the gap between the production and management of waste disposal. Food waste biorefineries are a sustainable, eco-friendly, and cost-effective approach for the production of platform chemicals, biofuels, and other bio-based materials. These materials not only provide sustainable resources for producing various chemicals and materials but have the potential to reduce this huge environmental burden significantly. In this regard, technological advancement has occurred in past few years that has proven suitable for tackling this problem.

Chemical Composition, Antioxidant, Anti-Bacterial, and Anti-Cancer Activities of Essential Oils Extracted from Citrus limetta Risso Peel Waste Remains after Commercial Use

Citrus plants are widely utilized for edible purposes and medicinal utility throughout the world. However, because of the higher abundance of the antimicrobial compound D-Limonene, the peel waste cannot be disposed of by biogas production. Therefore, after the extraction of D-Limonene from the peel wastes, it can be easily disposed of. The D-Limonene rich essential oil from the Citrus limetta risso (CLEO) was extracted and evaluated its radical quenching, bactericidal, and cytotoxic properties. The radical quenching properties were DPPH radical scavenging (11.35 ± 0.51 µg/mL) and ABTS scavenging (10.36 ± 0.55 µg/mL). There, we observed a dose-dependent antibacterial potential for the essential oil against pathogenic bacteria. Apart from that, the essential oil also inhibited the biofilm-forming properties of E. coli, P. aeruginosa, S. enterica, and S. aureus. Further, cytotoxicity was also exhibited against estrogen receptor-positive (MCF7) cells (IC₅₀: 47.31 ± 3.11 µg/mL) and a triple-negative (MDA-MB-237) cell (IC₅₀: 55.11 ± 4.62 µg/mL). Upon evaluation of the mechanism of action, the toxicity was mediated through an increased level of reactive radicals of oxygen and the subsequent release of cytochrome C, indicative of mitotoxicity. Hence, the D-Limonene rich essential oil of C. limetta is useful as a strong antibacterial and cytotoxic agent; the antioxidant properties exhibited also increase its utility value.

The evaluation of the performance of rice husk and rice straw as potential matrix to obtain the best lipase immobilized system: creating wealth from wastes

India generates 126.6 and 42 million tons of Rice straw (RS) and Rice husk (RH) annually, respectively. These agro-processing wastes feedstock are dumped in landfills or burnt, releasing toxic gases and particulate matter into the environment. This paper explores the valorization of these wastes feedstock into sustainable, economic products. We compare these wastes as matrices for lipase immobilization. These matrices were characterized, different parameters (pH, temperature, ionic strength, and metal ion cofactors) were checked, and the selected matrix was analyzed for reusability and hydrolysis of vegetable oils. Lipase immobilized Rice straw (LIRS) showed the highest activity with 72.84% protein loading. Field emission scanning electron microscopy (FESEM) demonstrated morphological changes after enzyme immobilization. FTIR showed no new bond formation, and immobilization data was fitted to Freundlich adsorption isotherm (with K = 12.18 mg/g, n_F = 4.5). The highest activity with protein loading, 91.05%, was observed at pH 8, 37 °C temperature, 50 mM ionic strength, and lipase activity doubled in the presence of Mg²⁺ ions. The LIRS retained 75% of its initial activity up to five cycles and efficiently hydrolyzed different oils. The results reflected that the LIRS system performs better and can be used to degrade oily waste.

Producing aromatic amino acid from corn husk by using polyols as intermediates

Agricultural biomass remains as one of the commonly found waste on Earth. Although valorisation of these wastes has been studied in detail, the fermentation-based processes still need improvement due to the high cost of hydrolysing enzymes, and the presence of growth inhibitors which constrains the fermentation to produce high-value products. To address these challenges, we developed an integrated process in this study combining abiotic- and bio-catalysis to produce l-tyrosine from corn husk. The first step involved a one-pot hydrolytic hydrogenation tandem reaction without the use of the expensive enzymes, which yielded a mixture of polyols and sugars. Without any purification, these crude hydrolysates can be almost completely utilized by an engineered Escherichia coli strain, which did not exhibit any growth inhibition. The strain produced 0.44 g/L l-tyrosine from 10 g/L crude corn husk hydrolysates, demonstrating the feasibility of converting agricultural biomass into a valuable aromatic amino acid via an integrated process.

Microbial originated surfactants with multiple applications: a comprehensive review

Microbial synthesized surfactants are used in contaminated soil bioremediation processes and have multiple applications in various industries. These compounds minimize the negative influences in soil via absorption by detoxifying the toxic metals or compounds. Further, applications of biosurfactants are detected in treating chronic diseases or synthetic drugs alternatives in current periods. Various surfactant molecules can provide many benefits due to their diversities in structural and functional groups. These compounds showed a wide array of applications in multiple sectors such as biomedical or pharmaceutical fields. Agricultural, food processing, laundry, or other sectors. Many microbial systems or plant cells are utilized in biosurfactant production as confirmed by biochemical analysis of genome sequencing tools. Biosurfactant compounds can alter drug transport across the cell membrane. Different nature of biosurfactant compounds exhibited their antifungal, antibacterial, antiviral activities, or antiadhesive coating agents used in reduction of many hospital infections. These distinct properties of biosurfactants pushed their broad spectrum applications in biomedical, agriculture sectors and bioremediation tasks. Additionally, many strains of fungi or bacteria are utilized for biosurfactant synthesis involved in the detoxification of soil/other components of the environment. In these reviews, authors explained various biosurfactants molecules and their mode of actions. Also, applications of microbial originated biosurfactants along with their process technologies are described. Future perspectives of biosurfactants and their scope are also critically explained so that this review paper can be used as a showcase for production and application of biosurfactants.

A Comparative Photographic Review on Higher Plants and Macro-Fungi: A Soil Restoration for Sustainable Production of Food and Energy

The Kingdom of Plantae is considered the main source of human food, and includes several edible and medicinal plants, whereas mushrooms belong to the Kingdom of fungi. There are a lot of similar characteristics between mushrooms and higher plants, but there are also many differences among them, especially from the human health point of view. The absences of both chlorophyll content and the ability to form their own food are the main differences between mushrooms and higher plants. The main similar attributes found in both mushrooms and higher plants are represented in their nutritional and medicinal activities. The findings of this review have a number of practical implications. A lot of applications in different fields could be found also for both mushrooms and higher plants, especially in the bioenergy, biorefinery, soil restoration, and pharmaceutical fields, but this study is the first report on a comparative photographic review between them. An implication of the most important findings in this review is that both mushrooms and plants should be taken into account when integrated food and energy are needed. These findings will be of broad use to the scientific and biomedical communities. Further investigation and experimentation into the integration and production of food crops and mushrooms are strongly recommended under different environmental conditions, particularly climate change.