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Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives

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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Chemical Processes and Systems".

Deadline for manuscript submissions: closed (30 May 2024) | Viewed by 13931

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Special Issue Editors

Prof. Dr. Maria Rios

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Guest Editor

Department of Mechanical Engineering, Federal University of Ceará, Fortaleza 60440-554, Brazil
Interests: integrated use of biomass; development of multifunctional additives; production, characterization, and performance evaluation of biofuels; thermal analysis; oxidative stability; development of bench-scale equipment; exergy analysis; renewable energy; sustainable development and green chemistry

Prof. Dr. José Cleiton Sousa dos Santos

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Guest Editor

Institute of Engineering and Sustainable Development, University of International Integration of the Afro-Brazilian Lusophony, Redenção 62790-970, Brazil
Interests: enzyme-related processes; biocatalysis; chemistry; biology; materials; energy; environment; food; pharmaceuticals; manufacturing, and related engineering fields
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Special Issue Information

Dear Colleagues,

In recent years, the chemical industry has tried to align with guidelines for sustainable development, working with a new vision to balance environmental, economic, and social factors. Thus, more sustainable innovations have been developed, such as waste-to-energy conversion; waste generation reduces the environmental impact and ensures the production of renewable energy alongside achieving a circular economy. The bio-waste conversion to high-value products such as fuels, chemicals, and materials can play an important role in advancing a circular economy while stimulating the design of products that can be more easily recycled than those currently on the market. The circular economy is a concept that aims to rethink the production system and consumption of goods and services, in addition to reducing waste and preventing damage to the environment caused by air, water, and soil pollution. Its principles are eliminating waste and contamination at the production base, keeping products and raw materials in multiple cycles of use, and regenerating nature. This Special Issue will focus on the green and sustainable chemistry of waste conversion processes, including biomass conversion, the development and application of green chemical products, waste-to-energy processes, thermochemical conversion processes, biomaterials, the life cycle assessment of chemical products and processes, and biomass in the circular economy. Waste biorefinery, as well as circular bioeconomy, will also be covered, which includes bioprocesses; waste for biopolymers; bio-lipids production; bioprocesses for wastewater treatment; and the integrated use of biowaste, biofuels, and renewable feedstocks.

Topics of interest, but not limited, include:

Green and sustainable chemistry of waste conversion;
Bioconversion of wastes into value-added products;
Waste-to-energy conversion;
Waste biorefinery: challenges and perspectives;
Biomass in a circular economy;
Life cycle of chemicals and products;
Integrated use of biowaste;
Treatment technologies for biowaste;
Bioconversion of biowaste into renewable energy and biomaterials.

Prof. Dr. Maria Alexsandra De Sousa Rios
Prof. Dr. José Cleiton Sousa dos Santos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

waste conversion
bioenergy
biorefinery
life cycle analysis
biomaterials
bioprocesses
circular economy
biofuels
green chemistry
sustainability

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Published Papers (10 papers)

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Research

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24 pages, 9062 KiB

Open AccessArticle

Experimental and Statistical Analysis of Concrete Eco-Cobble Using Organic and Synthetic Fibers

by Ricardo Andrés García-León, Jorge Trigos-Caceres, Natalia Castilla-Quintero, Nelson Afanador-García and July Gómez-Camperos

Processes 2024, 12(9), 1936; https://doi.org/10.3390/pr12091936 - 9 Sep 2024

Viewed by 964

Abstract

The environmental impact of traditional construction materials necessitates the development of sustainable alternatives. This study evaluates eco-cobbles as novel building materials designed to reduce environmental footprint while maintaining performance standards. The objectives were to develop an eco-friendly cobble alternative and assess its effectiveness through laboratory tests. Eco-cobbles were synthesized using recycled and bio-based materials and tested for compressive strength, flexural strength, and water absorption at 14 and 28 days. The compressive strength ranged from 11.5 MPa to 26.8 MPa, with a maximum value observed at 28 days in a mixture containing 95% concrete and 5% polyethylene terephthalate (PET). Flexural strength varied from 9.1 MPa to 28.7 MPa, with the highest value achieved in a mixture of 95% concrete and 0% fibers. Water absorption rates ranged from 2.1% to 6.6%, demonstrating an effective balance between performance and durability. Environmental assessments indicated a 30% reduction in resource consumption and a 40% decrease in carbon footprint compared to traditional cobble production methods. The findings demonstrate that eco-cobbles not only meet performance standards but also offer significant environmental benefits with a 99% compliance from the results obtained by response surface methodology plots, confirming that eco-cobbles offer a viable, sustainable alternative to conventional materials, with the potential for broader application in eco-friendly construction practices. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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20 pages, 1529 KiB

Open AccessArticle

Influence of Thermal and Chemical Treatment on Biosorbent from Rice Husk and Its Application in Removal of Resorcinol from Industrial Wastewater

by Salaha Saeed, Muhammad Yousaf Arshad, Ahsan Raza, Faisal Mahmood, Agnieszka Urbanowska, Anam Suhail Ahmed and Lukasz Niedzwiecki

Processes 2023, 11(12), 3344; https://doi.org/10.3390/pr11123344 - 30 Nov 2023

Cited by 3 | Viewed by 1092

Abstract

The removal of phenolic compounds is of great importance because of their toxic nature and potentially harmful effects on the environment and human health. This study examines the use of rice husk as a biosorbent for eliminating phenolic compounds, particularly resorcinol, from industrial wastewater. Three types of rice husk, namely raw rice husk (RRH), chemically treated rice husk (CTRH), and thermally treated rice husk (TTRH), are utilized after grinding and methanol treatment. Characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and optical microscopy are used to analyze the rice husk-based adsorbents. The microscopic analysis reveals the presence of nano-pores in TTRH and the existence of carbonyl and hydroxyl groups in all sorbent samples. XRD analysis confirms the presence of silica in biosorbents. This study also examines the influence of dosage and initial concentration on resorcinol sorption. Optimized dosages of 0.5 g (RRH), 0.5 g (CTRH), and 1.5 g (TTRH) result in sorption capacities of 14 mg/g (RRH), 11 mg/g (CTRH), and 5 mg/g (TTRH). Isotherm analysis indicates that the Langmuir isotherm best describes the sorption behavior of TTRH, while the Freundlich isotherm is observed for CTRH, and both RRH and CTRH follow the Temkin isotherm. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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12 pages, 13717 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Physicochemical Characterization of Potassium Hydroxide Pretreated Chestnut Shell and Its Bioconversion to Lactic Acid by Lacticaseibacillus rhamnosus

by Jeongho Lee, Seunghee Kim, Hyerim Son, Kang Hyun Lee, Chulhwan Park and Hah Young Yoo

Processes 2023, 11(12), 3340; https://doi.org/10.3390/pr11123340 - 30 Nov 2023

Cited by 3 | Viewed by 1549

Abstract

Lactic acid (LA) is an important platform chemical with a wide range of applications, including bioplastic materials, and demand for it is growing rapidly. However, the high cost of feedstock for LA production is a major barrier to industrial production. This study designed a process to produce LA from chestnut shell (CS), a low-cost biomass. The entire process includes KOH pretreatment, enzymatic saccharification, and fermentation. This study investigated the chemical compositions and physicochemical properties of raw CS and KOH pretreated CS (KpCS) to evaluate the impact of the pretreatment process that enhances the conversion of cellulose into glucose. The results showed that KOH affected the lignin removal and surface morphological changes of CS, and FT-IR and TGA patterns correlated to increased cellulose fractions were found. In the fermentation process, Lacticaseibacillus rhamnosus was selected as a prominent LA producer, and the fermentation using KpCS hydrolysate was carried out. As a result, cell growth (27%), glucose consumption (23%), and LA production (21%) were all achieved higher than the control group. The LA production yield from our suggested process was estimated to be 187 g/kg CS, and we concluded that CS has a high potential as a feedstock for LA production. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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16 pages, 2274 KiB

Open AccessArticle

Evaluation of Adsorbent Biomaterials Based on Coconut Mesocarp for Treatment of Wastewater Contaminated with Tartrazine Dye

by Candelaria Tejada-Tovar, Ángel Villabona-Ortiz, Fabián Aguilar-Bermúdez, Yerardin Pájaro-Moreno and Ángel Darío González-Delgado

Processes 2023, 11(11), 3115; https://doi.org/10.3390/pr11113115 - 31 Oct 2023

Viewed by 1480

Abstract

The presence of synthetic dyes in industrial wastewater poses significant environmental and health concerns due to their persistent nature and potential toxicity. Tartrazine is a synthetic yellow dye known for its stability and resistance to conventional treatment methods. As a result, its discharge into natural water bodies can lead to adverse ecological impacts and can jeopardize public health. The objective of this work was to functionalize coconut shells (CSs), coconut cellulose (CC), and modified coconut cellulose (MCC) bioadsorbents with cetyl trimethyl ammonium chloride (CTAC) for their use in the elimination by adsorption of the dye tartrazine in aqueous solutions. CC was synthesized through a double extraction with sodium hydroxide, and a chemical treatment was performed with CTAC at 100 mmol L⁻¹. The final dye concentration was determined through UV-Vis at 500 nm. An FTIR analysis showed multiple active sites, represented in groups such as hydroxyl, COO-, NHx-, and hydrocarbon compounds. Increasing the initial concentration had a positive effect on the efficiency of the process, reaching 99% removal with an adsorption capacity of 11.89 mg/g at equilibrium using MCC. The test showed that equilibrium was reached after 30 min. Initially, the removal of the dyes was rapid, about 97% of the contaminant being removed in the first 5 min. The Langmuir and Freundlich models were satisfactorily fitted to the adsorption isotherm, showing physical and chemical adsorption. It can be concluded that MCC is a promising bioadsorbent for the removal of tartrazine dye in aqueous solutions. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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18 pages, 3397 KiB

Open AccessArticle

Experimental Study and Mathematical Modeling under Various Hot-Air Drying Conditions of Thin Layer Olive Pomaces

by Chafaa Nsibi and Marzouk Lajili

Processes 2023, 11(9), 2513; https://doi.org/10.3390/pr11092513 - 22 Aug 2023

Cited by 2 | Viewed by 1108

Abstract

The present work studies the convective drying of a granular porous medium in a bed of olive pomace. The experimental tests were conducted in a closed convection drying loop of hot air. The experimental tests measured the mass loss over time. Tests were carried out for five temperature values: 60 ± 0.1 °C, 70 ± 0.1 °C, 80 ± 0.1 °C, 90 ± 0.1 °C and 100 ± 0.1 °C, respectively. Moreover, three values of velocities of the drying air, 1 ± 0.01 ms⁻¹, 1.5 ± 0.01 ms⁻¹ and 2 ± 0.01 ms⁻¹, were considered. The effects of initial humidity, bed thickness and pomace composition on the drying process were studied. The results show that the moisture content decreases when the temperature and the velocity of the drying air increase. In addition, the composition of olive pomace (pulp, pits and raw pomace) significantly affects the drying time. A characteristic drying curve and its equation were determined. Seven thin layer drying models were tested, and the Midilli et al.’s model produced the best agreement. The effective moisture diffusivity coefficient (D_eff), the activation energy (E_a) and the pre-exponential coefficient of the Arrhenius law were evaluated. The results could be of great help for the pretreatment of crude olive pomace when moving to industrial scale and before passing to the step of biofuel (pellets, briquettes or logs, Syngas) production. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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17 pages, 7026 KiB

Open AccessArticle

Analysis of the Fuel Properties of the Seed Shell of the Neem Plant (Azadirachta indica)

by Francisco Simão Neto, Maria Melo Neta, Ana Sousa, Luana Damasceno, Bruna Sousa, Samuel Medeiros, Rafael Melo, Ada Lopes, José Santos and Maria Rios

Processes 2023, 11(8), 2442; https://doi.org/10.3390/pr11082442 - 14 Aug 2023

Cited by 2 | Viewed by 1842

Abstract

The energetic potential of the seed shell of the Neem plant (Azadirachta indica) was investigated using proximate analysis, Higher Heating Value (HHV), thermal analysis (TG-DTG and DSC) in inert and oxidative atmospheres, and X-ray fluorescence (XRF). The results of ash (3.80% ± 0.44), volatile matter (81.76% ± 1.30), fixed carbon (14.44% ± 1.74), and estimated HHV (18.791 MJ/kg: average value) are compatible with other biomasses already used as fuels in the bioenergy industry. Thermograms showed three main degradation events in synthetic air and two in nitrogen, attributed to the moisture, release of volatile materials, and decomposition of hemicellulose, cellulose, and lignin. The elements positively detected by the XRF were Ca, K, S, P, Fe, Ti, Zn, Rb, and Sr. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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31 pages, 18864 KiB

Open AccessReview

The Heteropolyacid-Catalyzed Conversion of Biomass Saccharides into High-Added-Value Products and Biofuels

by Márcio Jose da Silva and Pedro Henrique da Silva Andrade

Processes 2024, 12(11), 2587; https://doi.org/10.3390/pr12112587 - 18 Nov 2024

Viewed by 503

Abstract

The industrial processes used to produce paper and cellulose generate many lignocellulosic residues. These residues are usually burned to produce heat to supply the energy demands of other processes, increasing greenhouse gas emissions and resulting in a high environmental impact. Instead of burning these lignocellulosic residues, they can be converted into saccharides, which are feedstock for high-value products and biofuels. Keggin heteropolyacids are efficient catalysts for obtaining saccharides from cellulose and hemicellulose and converting them into bioproducts or biofuel. Furfural, 5-hydroxymethylfurfural, levulinic acid, and alkyl levulinates are important platform molecules obtained from saccharides and raw materials in the biorefinery processes used to produce fine chemicals and biofuels. This review discusses the significant progress achieved in the development of the processes based on heteropolyacid-catalyzed reactions to convert biomass and their residues into furfural, 5-hydroxymethylfurfural, levulinic acid, and alkyl levulinates in homogeneous and heterogeneous reaction conditions. The different modifications that can be performed to a Keggin HPA structure, such as the replacement of the central atom (P or Si) with B or Al, the doping of the heteropolyanion with metal cations, and a proton exchange with metal or organic cations, as well as their impact on the catalytic activity of HPAs, are detailed and discussed herein. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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23 pages, 3750 KiB

Open AccessReview

The Green Synthesis of Nanostructured Silicon Carbides (SiCs) from Sugarcane Bagasse Ash (SCBA) as Anodes in Lithium-Ion (Li-Ion) Batteries: A Review Paper

by Sandy U. Pesulo, Lyle A. September, Ntombizonke Kheswa, Ntalane S. Seroka and Lindiwe Khotseng

Processes 2024, 12(9), 1817; https://doi.org/10.3390/pr12091817 - 27 Aug 2024

Viewed by 1363

Abstract

Silicon is a promising anode material for the increased performance of lithium-ion batteries because of its high elemental composition and specific capacity. The application of silicon on a commercial scale is restricted due to the limitation of volume expansion. Silicon is also expensive, making it difficult for large-scale commercialisation. Different methods were used to address these issues, including a sintering process and the sol–gel method, to form silicon carbide (SiC), a hard chemical compound containing silicon and carbon. The silicon carbide anode not only acts as a buffer for volume expansion but also allows for better infiltration of the electrolyte, increasing charge and discharge capacity in the battery. Like silicon, silicon carbides can be costly. The development of renewable energy systems is very important, especially in the development of energy storage systems that are not only efficient but also cost-friendly. The cost of the energy storage devices is lowered, making them easily accessible. Silicon carbides can be synthesised from sugarcane, which is the fibrous waste that remains after juice extraction. This could be beneficial, as we could never run out of such a resource, and it offers low carbon with a high surface area. Silicon carbides can be synthesised by carbothermal reduction of silica from sugarcane bagasse. This review provides a comprehensive understanding of silicon carbides and synthetic processes. The innovative use of waste to synthesise materials would reduce costs and comply with Sustainable Development Goals (SDGs) 7 (affordable and clean energy) and 13 (climate action). Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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15 pages, 2799 KiB

Open AccessReview

Cupuassu Fruit, a Non-Timber Forest Product in Sustainable Bioeconomy of the Amazon—A Mini Review

by Jeane Santos da Rosa, Paula Isabelle Oliveira Moreira, Ana Vânia Carvalho and Otniel Freitas-Silva

Processes 2024, 12(7), 1353; https://doi.org/10.3390/pr12071353 - 28 Jun 2024

Viewed by 1211

Abstract

This study examines the importance of cupuassu, a tropical fruit native to the Amazon, to Brazil’s biodiversity, the Amazon biome, and its potential for economic development. Cupuassu is a Non-Timber Forest Product and a fruit of the Theobroma genus, which also includes cocoa. Just in the state of Pará alone, cupuassu production in 2019 was over 4100 t with a gross value of 2.6 million USD produced. However, cupuassu cultivation still needs investment through technological advances to overcome threats such as witches’ broom disease and mycotoxin contamination. Cupuassu fruit is composed of pulp, seeds, and a shell; all these parts have a chemical composition with numerous bioactive compounds, especially the seeds, which also contain stimulant compounds, besides lipids and proteins. The processing of the whole cupuassu fruit has its economic value in the commercialization of the pulp, the extraction of cupuassu butter, and a product called Cupulate^®. However, in this process, the cake resulting from the oil pressing, often considered a waste product, has potential as a source of proteins, peptides, lipids, and bioactive molecules with functional and nutritional properties. Recycling this fruit processing waste can create high-value-added products for various industries and promote a circular economy. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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17 pages, 1439 KiB

Open AccessReview

Recent Advances in Biochar: Synthesis Techniques, Properties, Applications, and Hydrogen Production

by Evan D. Visser, Ntalane S. Seroka and Lindiwe Khotseng

Processes 2024, 12(6), 1111; https://doi.org/10.3390/pr12061111 - 28 May 2024

Viewed by 1963

Abstract

The field of material sciences has evolved vastly in the last two decades, largely due to the discovery of carbon nanomaterials such as graphene and its derivatives. Although they offer positive characteristics, the cost of production and material processing of these carbon nanomaterials has limited their application. However, scientists have started searching for cheaper and more environmentally friendly alternatives. Biochar, a carbonaceous material derived from biowaste, is the most viable alternative, as it offers characteristics on par with traditional carbon nanomaterials. This review will discuss the production of biochar from biomass, methods of production, the effects various conditions have on the production of biochar, biomass selection, current biochar applications, and the potential biochar has to produce hydrogen as an energy carrier. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

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