Biowaste Treatment and Valorization

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Environmental Sciences".

Deadline for manuscript submissions: closed (20 September 2022) | Viewed by 33294

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Special Issue Editor

Department of Water and Environmental Science and Technologies, Universidad de Cantabria, Santander, Spain
Interests: anaerobic digestion; biomethane; wastewater treatment; high-rate anaerobic reactor; biowaste; energy crops
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Special Issue Information

Dear Colleagues,

The socio-economic changes that have occurred in the last several decades due to urban population increase, the development of the food industry, and the rise of consumption trends have resulted in an increase of the generation of municipal wastes in areas of high population density. Within the category of municipal wastes, biowaste is one of the most problematic fractions worldwide, because of the huge amounts generated as well as its polluting potential when biodegrading in the terrain. It poses such a challenge that integral waste management policies now incorporate specific strategies for the management and diversion of the huge amounts taken to landfills. In some countries, mainly in Northern Europe, separate collection of waste strategies were addressed years ago. Therefore, needs are currently related to treatment optimization. However, in most countries, household biowaste is managed as a mixture with the rest of the municipal waste fractions, which subsequently undergo mechanical and biological treatments in order to achieve their exploitation and decontamination. Food waste is the largest component of biowaste and poses a broad range of environmental impacts, such as water and air pollution as well as greenhouse gas emissions, if not properly managed.

Therefore, the general target of the present Special Issue is to contribute to the expansion of knowledge in this field, promoting research focused on both biowaste management strategies and treatment, in particular by biological methods that enable the recovery of nutrients and energy from biowaste.

Dr. Carlos Rico de la Hera
Guest Editor

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Keywords

  • biowaste
  • food waste
  • waste treatment
  • biomechanical treatment
  • anaerobic digestion
  • composting

Published Papers (15 papers)

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Editorial

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3 pages, 194 KiB  
Editorial
Special Issue on Biowaste Treatment and Valorization
by Carlos Rico De La Hera
Appl. Sci. 2022, 12(21), 11217; https://doi.org/10.3390/app122111217 - 05 Nov 2022
Cited by 1 | Viewed by 744
Abstract
Biowaste has been defined as “Biodegradable waste from gardens and parks, food and kitchen waste from homes, restaurants, collective catering services and retail establishments, and comparable waste from food processing plants” (Directive (2008)/98/EC (EC—European Commission, 2008) [...] Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)

Research

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19 pages, 2091 KiB  
Article
Extraction of Antioxidants from Grape and Apple Pomace: Solvent Selection and Process Kinetics
by Jorge Garcia-Montalvo, Alberto Garcia-Martín, Jon Ibañez Bujan, Victoria E. Santos Mazorra, Pedro Yustos Cuesta, Juan M. Bolivar and Miguel Ladero
Appl. Sci. 2022, 12(10), 4901; https://doi.org/10.3390/app12104901 - 12 May 2022
Cited by 6 | Viewed by 1650
Abstract
Polyphenols have become a research target due to their antioxidant, anti-inflammatory and antimicrobial activity. Obtention via extraction from natural sources includes the revalorization of food wastes such as grape pomace (GP) or apple pomace (AP). In this work, GP and AP were submitted [...] Read more.
Polyphenols have become a research target due to their antioxidant, anti-inflammatory and antimicrobial activity. Obtention via extraction from natural sources includes the revalorization of food wastes such as grape pomace (GP) or apple pomace (AP). In this work, GP and AP were submitted to a liquid–solid extraction using different solvents of industrial interest. Process kinetics were studied measuring the total phenolic content (TPC) and antioxidant capacity (AC), while the extraction liquor composition was analyzed employing chromatographic methods. Extraction processes using water-solvent mixtures stood out as the better options, with a particular preference for water 30%–ethanol 70% (v/v) at 90 °C, a mixture that quickly extracts up to 68.46 mg GAE/gds (Gallic Acid Equivalent per gram dry solid) and 122.67 TEAC/gds (TROLOX equivalent antioxidant capacity per gram dry solid) in case of GP, while ethylene water 10%–ethylene glycol 90% (v/v) at 70 °C allows to reach 27.19 mg GAE/gds and 27.45 TEAC/gds, in the case of AP. These extraction processes can be well-described by a second-order kinetic model that includes a solubility-related parameter for the first and fast-washing and two parameters for the slow mass transfer controlled second extraction phase. AP liquors were found to be rich in quercetin with different sugar moieties and GP extracts highlighted flavonols, cinnamic acids, and anthocyanins. Therefore, using identical extraction conditions for AP and GP and a comparative kinetic analysis of TPC and AC results for the first time, we concluded that ethanol/water mixtures are adequate solvents for polyphenols extraction due to their high efficiency and environmentally benign nature. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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11 pages, 957 KiB  
Article
Bio-Augmentation as an Emerging Strategy to Improve the Textile Compost Quality Using Identified Autochthonous Strains
by Saloua Biyada, Hamada Imtara, Karima Elkarrach, Omar Laidi, Asmaa Saleh, Omkulthom Al Kamaly and Mohammed Merzouki
Appl. Sci. 2022, 12(6), 3160; https://doi.org/10.3390/app12063160 - 20 Mar 2022
Cited by 7 | Viewed by 1776
Abstract
The present investigation is devoted, for the first time, to the potential of autochthonous inoculums through bio-augmentation tests to improve the compost quality and to decrease the composting time during composting of textile waste. For this reason, three strains were isolated from a [...] Read more.
The present investigation is devoted, for the first time, to the potential of autochthonous inoculums through bio-augmentation tests to improve the compost quality and to decrease the composting time during composting of textile waste. For this reason, three strains were isolated from a mixture of textile waste, green waste, paper, and cardboard waste, and therefore identified as Streptomyces cellulosae, Achromobacter xylosoxidans, and Serratia liquefaciens, employed using bio-augmentation test. The organic matter decaying was assessed according to three different inoculums doses, separately and in consortium (4%, 6%, and 8%), to describe the effect of bio-augmentation process on the organic matter decaying. Indeed, these three strains and their consortium have shown a strong potential of organic matter degradation, equally the bacterial consortium showed a total organic carbon degradation of 20.3%, total Kjeldahl nitrogen of 1.52%, and a Carbon/Nitrogen ratio of 13.36. Compost maturity has been completed after only 12 weeks of treatment instead of 44 weeks using the classical treatment by composting. Ultimately, according to these results, bio-augmentation could be an emerging and promising strategy to accelerate the composting process of solid waste, especially in the case of industrial waste. Equally, it could be an effective tool to avoid the accumulation of industrial waste disposal in public landfills and/or nature while allowing their treatment. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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11 pages, 3587 KiB  
Article
Comparative Study of Different Production Methods of Activated Carbon Cathodic Electrodes in Single Chamber MFC Treating Municipal Landfill Leachate
by Pavlos K. Pandis, Theofilos Kamperidis, Konstantinos Bariamis, Ilias Vlachos, Christos Argirusis, Vassilis N. Stathopoulos, Gerasimos Lyberatos and Asimina Tremouli
Appl. Sci. 2022, 12(6), 2991; https://doi.org/10.3390/app12062991 - 15 Mar 2022
Cited by 6 | Viewed by 2617
Abstract
The treatment of real waste extracts with simultaneous energy production is currently under research. One method of addressing this dual task is using biochemical reactors named microbial fuel cells (MFCs). MFCs consist of a bioanode and a cathode where the oxygen reduction reaction [...] Read more.
The treatment of real waste extracts with simultaneous energy production is currently under research. One method of addressing this dual task is using biochemical reactors named microbial fuel cells (MFCs). MFCs consist of a bioanode and a cathode where the oxygen reduction reaction (ORR) occurs. Cathodes are currently under optimization regarding the nature of their support, their catalytic efficiency and their configurations. In this work, we present facile preparation methods for the production of activated carbon ceramic-supported cathodic electrodes produced with three different techniques (wash-coat, brush-coat, and ultrasound-assisted deposition/infiltration). The produced cathodic electrodes were tested in a single-chamber MFC, filled with the concentrated liquid residue, after the reverse osmosis (RO-CLR) treatment of leachate from a municipal waste landfill, in order to exploit their electrochemical potential for simultaneous waste treatment and energy production. The electrode produced utilizing 20 kHz ultrasounds proved to be more effective in terms of energy harvesting (10.7 mW/g·L of leachate) and wastewater treatment (COD removal 85%). Internal resistances of the ultrasound-produced electrodes are lower, as compared to the other two methods, opening new exploitation pathways in the use of ultrasound as a means in producing electrodes for microbial fuel cells. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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13 pages, 1734 KiB  
Article
Impact of Biochar Application on Germination Behavior and Early Growth of Maize Seedlings: Insights from a Growth Room Experiment
by Liaqat Ali, Wang Xiukang, Muhammad Naveed, Sobia Ashraf, Sajid Mahmood Nadeem, Fasih Ullah Haider and Adnan Mustafa
Appl. Sci. 2021, 11(24), 11666; https://doi.org/10.3390/app112411666 - 09 Dec 2021
Cited by 21 | Viewed by 2646
Abstract
Reduced germination and early crop maturity due to soil compaction, nutrients stress, and low moisture are major constraints to achieve optimum crop yield, ultimately resulting in significant economic damages and food shortages. Biochar, having the potential to improve physical and chemical properties of [...] Read more.
Reduced germination and early crop maturity due to soil compaction, nutrients stress, and low moisture are major constraints to achieve optimum crop yield, ultimately resulting in significant economic damages and food shortages. Biochar, having the potential to improve physical and chemical properties of soil, can also improve nutrients and moisture access to plants. In the present study, a growth room experiment was conducted to assess biochar influence on maize seed germination, early growth of seedlings, and its physiological attributes. Corn cob biochar (CCB) was mixed with soil at different rates (0.5%, 1%, 1.5%, 2%, 2.5%, and 3% w/w) before seed sowing. Results obtained showed that increasing CCB application rate have neutral to positive effects on seed germination and seedling growth of maize. Biochar addition at the rate of 1.5% (w/w) significantly increased shoot dry biomass (40%), root dry biomass (32%), total chlorophyll content (a and b) (55%), germination percentage (13%), seedling vigor (85%), and relative water content (RWC) (68%), in comparison to un-amended control treatment. In addition to this, it also improved germination rate (GR) by 3% as compared to control treatment, while causing a reduction in mean emergence time (MET). Moreover, application of biochar (3%) also resulted in enhancement of antioxidant enzyme activity, particularly superoxide dismutase (SOD) and catalase (CAT) by 13% and 17%, respectively. Conclusively, biochar application is an attractive approach to improve the initial phase of plant growth and provide better crop stand and essential sustainable high yields. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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26 pages, 4131 KiB  
Article
Energy Balance of Turbocharged Engines Operating in a WWTP with Thermal Hydrolysis. Co-Digestion Provides the Full Plant Energy Demand
by José García-Cascallana, Daniela Carrillo-Peña, Antonio Morán, Richard Smith and Xiomar Gómez
Appl. Sci. 2021, 11(23), 11103; https://doi.org/10.3390/app112311103 - 23 Nov 2021
Cited by 6 | Viewed by 2270
Abstract
The energy balance of lean-burn turbocharged engines using biogas as fuel is reported. Digestion data were obtained from the wastewater treatment plant (WWTP) of the city of Burgos (Spain), operating with a thermal hydrolysis unit for sludge pre-treatment. Operational performance of the plant [...] Read more.
The energy balance of lean-burn turbocharged engines using biogas as fuel is reported. Digestion data were obtained from the wastewater treatment plant (WWTP) of the city of Burgos (Spain), operating with a thermal hydrolysis unit for sludge pre-treatment. Operational performance of the plant was studied by considering the treatment of sludge as a comparative base for analyzing global plant performance if co-digestion is implemented for increasing biogas production. The calculation methodology was based on equations derived from the engine efficiency parameters provided by the manufacturer. Results from real data engine performance when evaluated in isolation as a unique control volume, reported an electrical efficiency of 38.2% and a thermal efficiency of 49.8% leading to a global efficiency of 88% at the operating point. The gross electrical power generated amounted to 1039 kW, which translates into 9102 MWh/year, with an economic value of 837,384 €/year which was completely consumed at the plant. It also represents 55.1% of self-consumption regarding the total electricity demand of the plant. The analysis of the system considering the use of the total installed capacity by adding a co-substrate, such as cheese whey or microalgae, reveals that total electrical self-consumption is attained when the co-substrate is directly fed into the digester (cheese whey case), obtaining 16,517 MWh/year equivalent to 1,519,160 €/year. The application of thermal hydrolysis as pre-treatment to the co-substrate (microalgae case study) leads to lower electricity production, but still attains a better performance than a mono-digestion baseline scenario. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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15 pages, 5342 KiB  
Article
Energetic Valorization of Solid Wastes from the Alcoholic Beverage Production Industry: Distilled Gin Spent Botanicals and Brewers’ Spent Grains
by Jesús A. Montes and Carlos Rico
Appl. Sci. 2021, 11(21), 10158; https://doi.org/10.3390/app112110158 - 29 Oct 2021
Cited by 3 | Viewed by 1606
Abstract
In this paper, the authors assess the possibilities of energetic valorization for two solid wastes from alcoholic beverage production. Distilled gin spent botanicals (DGSB) and brewers’ spent grains (BSG) are tested, both by themselves and as co-substrates, for their possibilities as substrates for [...] Read more.
In this paper, the authors assess the possibilities of energetic valorization for two solid wastes from alcoholic beverage production. Distilled gin spent botanicals (DGSB) and brewers’ spent grains (BSG) are tested, both by themselves and as co-substrates, for their possibilities as substrates for anaerobic digestion in a system of box-type digesters, suited for the process. While BSGs show a good performance for anaerobic digestion, DGSBs, despite showing an acceptable biomethanogenic potential result as not suitable for the process. Experiments using DGSBs as substrate in the reactors result in failure. And, as a co-substrate, the biomethanogenic digestion process appears to be hampered and lagged. Possible explanations for this behavior are explored, as well as other possibilities for the use of the material as a power source given its high heating value. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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13 pages, 1733 KiB  
Article
High Purity of α-Lactalbumin from Binary Protein Mixture by Charged UF Membrane Far from the Isoelectric Point to Limit Fouling
by Rosalinda Mazzei, Anna Maria Szymczak, Enrico Drioli, Mohamed Al-Fageeh, Mohammed A. Aljohi and Lidietta Giorno
Appl. Sci. 2021, 11(19), 9167; https://doi.org/10.3390/app11199167 - 02 Oct 2021
Cited by 3 | Viewed by 1550
Abstract
Separation and high recovery factor of proteins similar in molecular mass is a challenging task, and heavily studied in the literature. In this work, a systematic study to separate a binary protein mixture by charged ultrafiltration membranes without affecting membrane performance was carried [...] Read more.
Separation and high recovery factor of proteins similar in molecular mass is a challenging task, and heavily studied in the literature. In this work, a systematic study to separate a binary protein mixture by charged ultrafiltration membranes without affecting membrane performance was carried out. α-lactalbumin (ALA, 14.4 kDa) and β-lactoglobulin (BLG, 18.4 kDa) were used as a binary model system. These two proteins are the main proteins of whey, a very well-known byproduct from the dairy industry. Initially, a systematic characterization of individual proteins was carried out to determine parameters (protein size and aggregation, zeta potential) which could influence their passage through a charged membrane. Then, the influence of operating parameters (such as initial protein concentration, pH, and critical pressure) on the UF process was investigated, so as to identify conditions that limit membrane fouling whilst maximizing protein recovery factor and purity. The study permitted to identify process conditions able to fully separate ALA from BLG, with high purity (95%) and recovery factor (80%), in a single UF step. Compared to studies reported in literature, here, the main approach used was to carry out a charged UF process far from proteins isoelectric point (pI) to limit protein aggregation and membrane fouling. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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11 pages, 2413 KiB  
Article
Effect of Bioaugmentation with Anaerobic Fungi Isolated from Ruminants on the Hydrolysis of Corn Silage and Phragmites australis
by Bhargavi Ravi, Valentine Nkongndem Nkemka, Xiying Hao, Jay Yanke, Tim A. McAllister, Hung Lee, Chitraichamy Veluchamy and Brandon H. Gilroyed
Appl. Sci. 2021, 11(19), 9123; https://doi.org/10.3390/app11199123 - 30 Sep 2021
Cited by 2 | Viewed by 1675
Abstract
Anaerobic fungi produce extracellular hydrolytic enzymes that facilitate degradation of cellulose and hemicellulose in ruminants. The purpose of this work was to study the impact of three different anaerobic fungal species (Anaeromyces mucronatus YE505, Neocallimastix frontalis 27, and Piromyces rhizinflatus YM600) on [...] Read more.
Anaerobic fungi produce extracellular hydrolytic enzymes that facilitate degradation of cellulose and hemicellulose in ruminants. The purpose of this work was to study the impact of three different anaerobic fungal species (Anaeromyces mucronatus YE505, Neocallimastix frontalis 27, and Piromyces rhizinflatus YM600) on hydrolysis of two different lignocellulosic substrates, corn (Zea mays L.) silage and reed (Phragmites australis (Cav.) Trin. ex Steud.). Biomass from each plant species was incubated anaerobically for 11 days either in the presence of live fungal inoculum or with heat-inactivated (control) inoculum. Headspace gas composition, dry matter loss, soluble chemical oxygen demand, concentration of volatile fatty acids, and chemical composition were measured before and after hydrolysis. While some microbial activity was observed, inoculation with anaerobic fungi did not result in any significant difference in the degradation of either type of plant biomass tested, likely due to low fungal activity or survival under the experimental conditions tested. While the premise of utilizing the unique biological activities of anaerobic fungi for biotechnology applications remains promising, further research on optimizing culturing and process conditions is necessary. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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15 pages, 3034 KiB  
Article
Diagnosis and Monitoring of Volatile Fatty Acids Production from Raw Cheese Whey by Multiscale Time-Series Analysis
by Antonio Lara-Musule, Ervin Alvarez-Sanchez, Gloria Trejo-Aguilar, Laura Acosta-Dominguez, Hector Puebla and Eliseo Hernandez-Martinez
Appl. Sci. 2021, 11(13), 5803; https://doi.org/10.3390/app11135803 - 23 Jun 2021
Cited by 3 | Viewed by 1436
Abstract
Anaerobic treatment is a viable alternative for the treatment of agro-industrial waste. Anaerobic digestion reduces organic load and produces volatile fatty acids (VFA), which are precursors of value-added products such as methane-rich biogas, biohydrogen, and biopolymers. Nowadays, there are no low-cost diagnosis and [...] Read more.
Anaerobic treatment is a viable alternative for the treatment of agro-industrial waste. Anaerobic digestion reduces organic load and produces volatile fatty acids (VFA), which are precursors of value-added products such as methane-rich biogas, biohydrogen, and biopolymers. Nowadays, there are no low-cost diagnosis and monitoring systems that analyze the dynamic behavior of key variables in real time, representing a significant limitation for its practical implementation. In this work, the feasibility of using the multiscale analysis to diagnose and monitor the key variables in VFA production by anaerobic treatment of raw cheese whey is presented. First, experiments were carried out to evaluate the performance of the proposed methodology under different operating conditions. Then, experimental pH time series were analyzed using rescaled range (R/S) techniques. Time-series analysis shows that the anaerobic VFA production exhibits a multiscale behavior, identifying three characteristic regions (i.e., three values of Hurst exponent). In addition, the dynamic Hurst exponents show satisfactory correlations with the chemical oxygen demand (COD) consumption and VFA production. The multiscale analysis of pH time series is easy to implement and inexpensive. Hence, it could be used as a diagnosis and indirect monitoring system of key variables in the anaerobic treatment of raw cheese whey. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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14 pages, 3398 KiB  
Article
Olive Mill and Olive Pomace Evaporation Pond’s By-Products: Toxic Level Determination and Role of Indigenous Microbiota in Toxicity Alleviation
by Houda Ben Slama, Ali Chenari Bouket, Faizah N. Alenezi, Ameur Khardani, Lenka Luptakova, Armelle Vallat, Tomasz Oszako, Mostafa E. Rateb and Lassaad Belbahri
Appl. Sci. 2021, 11(11), 5131; https://doi.org/10.3390/app11115131 - 31 May 2021
Cited by 8 | Viewed by 2283
Abstract
Diverse vegetable oils are extracted from oleagenic trees and plants all over the world. In particular, olive oil represents a strategic socio-economic branch in the Mediterranean countries. These countries use either two or three-phase olive oil extraction systems. In this work, we focus [...] Read more.
Diverse vegetable oils are extracted from oleagenic trees and plants all over the world. In particular, olive oil represents a strategic socio-economic branch in the Mediterranean countries. These countries use either two or three-phase olive oil extraction systems. In this work, we focus on the by-products from three-phase olive oil extraction, which are the liquid olive mill wastewater (OMW) and the solid olive mill pomace (OMP) rejected in evaporative ponds. The disposal of this recalcitrant waste poses environmental problems such as the death of different species of insects and animals. In-depth ICP-OES analysis of the heavy metal composition of OMW and OMP revealed the presence of many metals ranging from non-toxic to highly toxic. The LC-HRMS characterization of these by-products indicated the presence of several secondary metabolites harmful to humans or to the environment. Thus, we aimed to identify OMW and OMP indigenous microbiota through metagenomics. The bacterial population was dominated by the Acetobacter (49.7%), Gluconobacter (17.3%), Gortzia (13.7%) and Nardonalla (5.3%) genera. The most abundant fungal genera were Nakazawaea, Saccharomyces, Lachancea and Candida. These microbial genera are responsible for OMW, OMP and soil toxicity alleviation. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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17 pages, 958 KiB  
Article
Analysis of Quality of Backyard Compost and Its Potential Utilization as a Circular Bio-Waste Source
by Apolka Ujj, Kinga Percsi, Andras Beres, Laszlo Aleksza, Fernanda Ramos Diaz, Csaba Gyuricza and Csaba Fogarassy
Appl. Sci. 2021, 11(10), 4392; https://doi.org/10.3390/app11104392 - 12 May 2021
Cited by 2 | Viewed by 2107
Abstract
The use and quality analysis of household compost have become very important issues in recent years due to the increasing interest in local food production and safe, self-produced food. The phenomenon was further exacerbated by the COVID-19 pandemic quarantine period, which gave new [...] Read more.
The use and quality analysis of household compost have become very important issues in recent years due to the increasing interest in local food production and safe, self-produced food. The phenomenon was further exacerbated by the COVID-19 pandemic quarantine period, which gave new impetus to the growth of small home gardens. However, the knowledge associated with making high-quality compost is often lacking in home gardeners. Therefore, the objective of this research was to find answers to the following questions: can the quality of backyard compost be considered safe in terms of toxicity and nutrient content? Can weed seed dispersion affect the usability of backyard compost? In general, can the circulation of organic matter be increased with the spread of home composting? In this study, 16 different house composts were analysed for stability, weed seed contamination, toxic elements, and nutrient content using analysis of variance. The results of the research showed that the quality properties of the composts (including their weed seed dispersion effect) were greatly influenced by the different techniques and raw materials used. The toxicity levels, as well as the content of macro and microelements, were within the parameters of safe-quality compost. The specific macronutrient (Ca, Mg) and micronutrient (Fe, Mn) contents of the tested composts have a similar and, in some cases, more favorable nutrient supply capacity in crop production than the frequently-used cow manure-based composts. With a plan of basic education on composting, there is potential to encourage farmyard composting. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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18 pages, 5177 KiB  
Article
Influence of Digester Temperature on Methane Yield of Organic Fraction of Municipal Solid Waste (OFMSW)
by Gregor Sailer, Martin Silberhorn, Johanna Eichermüller, Jens Poetsch, Stefan Pelz, Hans Oechsner and Joachim Müller
Appl. Sci. 2021, 11(7), 2907; https://doi.org/10.3390/app11072907 - 24 Mar 2021
Cited by 4 | Viewed by 1838
Abstract
This study evaluates the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) and digested sewage sludge (DSS) at lowered temperatures. AD batch tests for CH4 yield determination were carried out with DSS as inoculum between 23 and 40 [...] Read more.
This study evaluates the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) and digested sewage sludge (DSS) at lowered temperatures. AD batch tests for CH4 yield determination were carried out with DSS as inoculum between 23 and 40 °C. All results were related to organic dry matter and calculated for standard conditions (1013 hPa, 0 °C). The AD experiments at 40 °C and at 35 °C delivered specific CH4 yields of 325 ± 6 mL/g and 268 ± 27 mL/g for OFMSW alone. At lower temperatures, specific CH4 yields of 364 ± 25 mL/g (25 °C) and 172 ± 21 mL/g (23 °C) were reached. AD at 25 °C could be beneficial regarding energy input (heating costs) and energy output (CH4 yield). Plant operators could increase AD efficiencies by avoiding heating costs. The co-digestion of OFMSW together with DSS could lead to further synergies such as better exploitation of the energy potentials of DSS, but the digestate utilization could become problematic due to hygienic requirements. Efficiency potentials through lowered operating temperatures are limited. In further research, lowered process temperatures could be applied in the AD of energy crops due to large numbers of existing plants. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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Review

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27 pages, 651 KiB  
Review
Development and Characterization of Bioadsorbents Derived from Different Agricultural Wastes for Water Reclamation: A Review
by Julián Aguilar-Rosero, María E. Urbina-López, Blanca E. Rodríguez-González, Sol X. León-Villegas, Itza E. Luna-Cruz and Diana L. Cárdenas-Chávez
Appl. Sci. 2022, 12(5), 2740; https://doi.org/10.3390/app12052740 - 07 Mar 2022
Cited by 13 | Viewed by 3901
Abstract
The presence of dangerous pollutants in different water sources has restricted the availability of this natural resource. Thus, the development of new low-cost and environmentally-friendly technologies is currently required to ensure access to clean water. Various approaches to the recovery of contaminated water [...] Read more.
The presence of dangerous pollutants in different water sources has restricted the availability of this natural resource. Thus, the development of new low-cost and environmentally-friendly technologies is currently required to ensure access to clean water. Various approaches to the recovery of contaminated water have been considered, including the generation of biomaterials with adsorption capacity for dangerous compounds. Research on bioadsorbents has boomed in recent years, as they constitute one of the most sustainable options for water treatment thanks to their abundance and high cellulose content. Thanks to the vast amount of information published to date, the present review addresses the current status of different biosorbents and the principal processes and characterization methods involved, focusing on base biomaterials such as fruits and vegetables, grains and seeds, and herbage and forage. In comparison to other reviews, this work reports more than 60 adsorbents obtained from agricultural wastes. The removal efficiencies and/or maximum adsorption capacities for heavy metals, industrial contaminants, nutrients and pharmaceuticals are presented as well. In addition to the valuable information provided in the literature investigation, challenges and perspectives concerning the implementation of bioadsorbents are discussed in order to comprehensively guide selection of the most suitable biomaterials according to the target contaminant and the available biowastes. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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18 pages, 448 KiB  
Review
Biodegradable Solvents: A Promising Tool to Recover Proteins from Microalgae
by David Moldes, Elena M. Rojo, Silvia Bolado, Pedro A. García-Encina and Bibiana Comesaña-Gándara
Appl. Sci. 2022, 12(5), 2391; https://doi.org/10.3390/app12052391 - 25 Feb 2022
Cited by 8 | Viewed by 3352
Abstract
The world will face a significant protein demand in the next few decades, and due to the environmental concerns linked to animal protein, new sustainable protein sources must be found. In this regard, microalgae stand as an outstanding high-quality protein source. However, different [...] Read more.
The world will face a significant protein demand in the next few decades, and due to the environmental concerns linked to animal protein, new sustainable protein sources must be found. In this regard, microalgae stand as an outstanding high-quality protein source. However, different steps are needed to separate the proteins from the microalgae biomass and other biocompounds. The protein recovery from the disrupted biomass is usually the bottleneck of the process, and it typically employs organic solvents or harsh conditions, which are both detrimental to protein stability and planet health. Different techniques and methods are applied for protein recovery from various matrices, such as precipitation, filtration, chromatography, electrophoresis, and solvent extraction. Those methods will be reviewed in this work, discussing their advantages, drawbacks, and applicability to the microalgae biorefinery process. Special attention will be paid to solvent extraction performed with ionic liquids (ILs) and deep eutectic solvents (DESs), which stand as promising solvents to perform efficient protein separations with reduced environmental costs compared to classical alternatives. Finally, several solvent recovery options will be analyzed to reuse the solvent employed and isolate the proteins from the solvent phase. Full article
(This article belongs to the Special Issue Biowaste Treatment and Valorization)
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