Search Results (32)

In rural Ghana, limited access to affordable, clean cooking fuels drives the need for decentralised waste-to-energy solutions. Anaerobic co-digestion (AcoD) offers a viable route for transforming organic residues into renewable energy, with the added benefit of improved process stability resulting from substrate synergy. This study aims to evaluate the technical feasibility and stabilisation challenges of AcoD, using locally available fruit waste and beet molasses at a secondary school in Bedabour (Ghana). Biological methane potential (BMP) assays of different co-digestion mixtures were conducted at two inoculum-to-substrate (I/S) ratios (2 and 4), identifying the highest yield (441.54 ± 45.98 NmL CH₄/g VS) for a mixture of 75% fruit waste and 25% molasses at an I/S ratio of 4. Later, this mixture was tested in a 6 L semi-continuous AcoD reactor. Due to the high biodegradability of the substrates, volatile fatty acid (VFA) accumulation led to acidification and process instability. Three low-cost mitigation strategies were evaluated: (i) carbonate addition using eggshell-derived sources, (ii) biochar supplementation to enhance buffering capacity, and (iii) the integration of a bioelectrochemical system (BES) into the AcoD recirculation loop. The BES was intended to support VFA removal and enhance methane recovery. Although they temporarily improved the biogas production, none of the strategies ensured long-term pH stability of the AcoD process. The results underscore the synergistic potential of AcoD to enhance methane yields but also reveal critical stability limitations under high-organic-loading conditions in low-buffering rural contexts. Future implementation studies should integrate substrates with higher alkalinity or adjusted organic loading rates to ensure sustained performance. These findings provide field-adapted insights for scaling-up AcoD as a viable renewable energy solution in resource-constrained settings. Full article

This study presents data from Reverse Osmosis (RO) and Nanofiltration (NF) spiral-wound polyamide modules tested in a semi-pilot plant with multicomponent mixtures of Volatile Fatty Acids (VFAs) comprising acetic, propionic, butyric, valeric, and hexanoic acids. A robust method combining film theory and dissociation equilibria was developed to estimate interfacial concentrations, enabling accurate analysis of concentration polarization, real rejection, and effective transmembrane driving force. Concentration polarization strongly affects NF membranes, resulting in real rejections up to 20% higher than apparent values, while its effect is negligible for RO membranes. NF rejections show marked sensitivity to pH and VFA feed concentration: at 20 g/L and highest flux, acetic acid real rejection increases from 80% to 91% as pH rises from 6 to 9. At pH 7, rejections decline with feed concentration, with acetic acid dropping from 55% at 20 g/L to 32% at 63 g/L, at the same flux. These changes correlate with the molecular weight of the acids. Conversely, RO rejections are marginally affected by pH and not influenced by concentration due to dominant steric exclusion. Membrane permeabilities remain unaffected by VFAs and align with pure water values. The data analysis framework is effective and applicable across a wide range of conditions and membranes. Full article

Sewage sludge, characterized by its high organic matter and nutrient content, as well as the presence of microbial pathogens and other contaminants, requires proper management due to its significant generation rate. The table olive sector, which is highly significant in Spain as a global leader in production and export, generates various waste streams such the Organic Solid By-Products from Table Olive Processing (OSBTOP), which are mainly derived from the olive pit after the pitting process. The main aim of this study was to enhance the methane production performance of sewage sludge through co-digestion with OSBTOP as a co-substrate. Batch assays demonstrated that employing OSBTOP as a co-substrate increased methane content by 35–41% across all tested mixtures. While the highest methane yield was produced at a 40:60 (sludge:OSBTOP) ratio, a 60:40 mixture proved to be a more advantageous option for scale-up and practical application. This is attributed to factors such as the higher availability of sludge and its inherent buffering capacity, which counteracts the accumulation of volatile fatty acids and promotes process stability, thereby contributing to the study’s objective of significantly enhancing methane production from sewage sludge through co-digestion. In semi-continuous operation, methane yields in the co-digestion scenario exceeded those of mixed sludge digestion, showing a yield of 180 versus 120 LCH₄⁻¹ · kgVS_added⁻¹, representing a 50% improvement. This study highlights the potential of anaerobic digestion as a strategy for valorizing OSBTOP, a by-product with no prior studies, while demonstrating that its co-digestion with sewage sludge enhances methane generation, offering a sustainable approach to organic waste treatment. Full article

The Oddy test is an accelerated metal corrosion test used extensively by cultural institutions to determine the suitability of a material for use in museums. Alternatively, the use of gas chromatography-mass spectrometry (GC-MS) to directly identify volatile organic compounds (VOCs) from construction materials is growing in popularity because of its comprehensiveness and speed. Interpreting the reactivity of these potential pollutants, however, relies on ‘chemical intuition’ based on observed functional groups since the reactivity of only a handful of common VOCs has been studied intensively with regard to artworks. While short chain organic acids are known to be deleterious to some metals, polymers, and other culturally relevant materials, the common observation of lower volatility acids as well as their complementary aldehydes and esters in these offgassing experiments do not have clear indicators of their potential for artwork damage. In this work, the lead coupon, known to be a sensitive indicator of damaging organic acids, was exposed to known concentrations of a homologous series of organic acids, aldehydes, and esters from C2 to C18. Analysis of the coupon surface by infrared and Raman spectroscopies, and of the headspace within an Oddy jar by GC-MS, provides insights into the corrosion processes of these potential pollutants. Humidity was identified as a necessary component for corrosion to occur, and very volatile and semi-volatile compounds up to C9 created the corresponding lead carboxylate on the coupon surface in addition to lead carbonate. For higher order acids, and to a far lesser extent the esters and aldehydes, a high concentration of the VOC was necessary to induce small amounts of corrosion. In some instances, the gas phase chemistry of the reactor was particularly complex, suggesting mixtures of pollutants may prove more problematic to artist materials than single offgassed species. Full article

Pyrolysis coupled with gas chromatography–mass spectrometry (Py-GC/MS) is a novel technology capable of detecting micro- and nanoplastics without a size limit. However, the application of Py-GC/MS to airborne microplastic analysis remains inconsistent. This study explores optimal Py-GC/MS procedures using a domestic Henxi^TM PY-1S pyrolyzer-based Py-GC/MS. The initial weight loss of PVC occurs at approximately 260 °C, indicating that the maximum thermal desorption temperature prior to pyrolysis should not exceed 250 °C. To avoid interference from semi-volatile organics present in the sample and injected air, it is essential to purge the sample with pure helium at elevated temperatures before pyrolysis. Microplastic standards can be prepared by ultrasonicating a water–microplastic dispersion system. Significant interactions between microplastic mixtures were observed during co-pyrolysis, indicating that the interactions of mixtures cannot be ignored during the optimization of quantitative references. The optimal procedure features good linearity (R² > 0.98), low detection limit (0.06~0.0002 μg), and acceptable precisions (RSD < 10% in 8 days). Microplastics determined by the domestic PY-1S pyrolyzer coupled with a GC/MS system are comparable to those of the well-established PY-3030D-based Py-GC/MS, indicating that the domestic pyrolyzer coupled with GC/MS is a reliable and powerful tool for microplastic analysis. Full article

The paper presents the possibility of using carbon dioxide as a carrier gas in capillary gas chromatography (with a stationary liquid phase) to analyze semi-volatile compounds (boiling points of up to 400 °C). Based on the experiments carried out for compounds from the group of organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), the maximum volumetric flow rate (2.4 mL/min for CO₂) was determined, enabling the correct separation of the tested standard mixtures (except for two compounds from the OCP group: 4,4′-DDD and Endrin aldehyde and two other pairs of compounds with Rs slightly less than 1.5). Compared to using helium as a carrier gas (and makeup), carbon dioxide produces wider (about 1.6 times) and lower (about 1.8 times) peaks of analytes; these values can vary depending on the separation efficiency of the column. Carbon dioxide can also be effectively used as a makeup gas for the FID detector. The signal increase is comparable to that obtained with helium used as makeup (on average 40–50% depending on the carrier gas). When high sensitivity and high resolution are not required, CO₂ can be an alternative carrier and makeup gas to helium under the same flow conditions. The paper also describes practical aspects related to the implementation of CO₂ as a carrier and makeup gas in GC. Full article

This paper presents the results of analytical studies of the combustion process of semi-coke, cedar sawdust, and their mixtures using the TGA method at three different heating rates with the determination of the main characteristics of heating: the presence of synergetic interaction between the components of the mixture affecting the maximum rate of combustion and kinetic parameters. Calculations of activation energy and pre-exponential multiplier of the Arrhenius equation by the Friedman and Ozawa–Flynn–Wall priori methods for initial combustibles and their mixtures have been carried out. Semi-coke was obtained by thermal treatment of brown coal at 700–900 °C to remove volatile substances, which makes it more environmentally friendly than the original coal. Semi-coke has a higher heat of combustion than biomass, and biomass has a higher reactivity than semi-coke. The combustion process of biomass occurs in a lower temperature range, and adding biomass to semi-coke shifts the combustion process to a lower temperature range than such for biomass. Adding at least 50% of biomass to semi-coke increases the combustion index by at least 1.1 times. Regardless of the heating rate of mixtures, synergetic interaction between the mixture’s components increases the maximum combustion rate of coke residue by 20%. Full article

To expand the development of characteristic extension products of Yunnan tea and improve the utilization rate of Yunnan tea resources, in this study, we compared the metabolite composition among raw Pu-erh tea, ripe Pu-erh tea prepared with glutinous rice (according to tea to glutinous rice ratio of 1:3), and ripe Pu-erh tea prepared with a mixture of sorghum, rice, glutinous rice, wheat, and corn as raw materials (according to a tea to glutinous rice ratio of 1:3). Rice flavor liquor prepared with 100% glutinous rice served as a control. The raw Pu-erh tea liquor (RAWJ), ripe Pu-erh tea liquor (RIPEJ), ripe Pu-erh tea mixed grain liquor (HHLSJ), and rice-flavor liquor (MJ) were all brewed by semi-solid fermentation. The non-volatile components of the liquor samples were analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry as a broadly targeted metabolomics technique. A total of 691 metabolites were identified from the four samples. Among them, 674, 671, 633, and 667 species were detected in RAWJ, RIPEJ, HHLSJ, and MJ samples, respectively. Venn diagram analysis demonstrated 19, 21, and 14 unique metabolites in RAWJ, RIPEJ, and HHLSJ, respectively, compared with the metabolite composition of MJ. Flavonoids are the most important differential metabolite between tea liquor and rice-flavor liquor. This study provides a theoretical basis for the development of tea liquor products and offers insight into the difference in non-volatile components between tea liquor and rice-flavor liquor. Full article

The existence of fecal coliform microorganisms (FCs) resistant to antibiotics in the domestic wastewater of an urban and semi-urban locality was determined, along with the effect of two types of treatment plants for wastewater on the resistance of coliform, an aerated lagoon (AL) and a stabilization lagoon (SL). Samples were taken from the affluent and effluent of each treatment plant. FC content, pH, electrical conductivity, dissolved oxygen, total solids, total volatile solids, and several types of ions were determined. Resistant FCs were quantified by plate count in bright green bile agar with ampicillin, amoxicillin, sulfamethoxazole-trimethoprim, amikacin, gentamicin, cefixime and their mixtures. The isolated strains were evaluated against other antibiotics using antibiograms. The relationship between the variables was validated with an analysis of variance factorial design, and Fisher’s means test (α = 0.05) and Pearson’s correlation were used to establish it. The community that presented more resistant FCs was the urban one, but when the wastewater passed through the systems of AL and SL, this fact changed. The resistance of the FCs to ampicillin, amoxicillin, trimethoprim, sulfamethoxazole and cefixime was higher in the SL, with values of 67, 48, 2 and 25.8%, while those for the AL were 20, 13, 22 and 5.3%, respectively. Full article

In recent decades, numerous studies have indicated the substantial role semiconductors could play in photocatalytic processes for environmental applications. Materials that contain a semiconductor as a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. In this paper, the focus is on TiO₂. Heterogeneous photocatalysis using TiO₂ leads to the degradation of NO/NO₂, benzene, toluene, and other priority air pollutants once in contact with the semiconductor surface. Preliminary evidence indicates that TiO₂-containing construction materials and paints efficiently destroy the ozone precursors NO and NO₂ by up to 80% and 30%, respectively. Therefore, the development of innovative coatings containing TiO₂ as a photocatalyst was in the foreground of research activities. The aim of this was for coatings to be used as building and construction materials, mainly outdoors, e.g., on building façades on high-traffic roads for the degradation of priority air pollutants (NOx and volatile organic compounds) in the polluted urban atmosphere. Though there are advantages connected with the application of TiO_2, due to its band gap of 3.2 eV, these are limited. TiO₂ is effective only in the UV region (ca. 5%) of the solar spectrum with wavelengths λ < 380 nm. Hence, efforts are made here, as in many research studies, to dope TiO₂ with transition metals to increase its activity using visible light, which will extend its application to indoor environments. In our studies, experiments were conducted with 0.1% (w/w) and 1% (w/w) Mn-TiO₂ admixtures, and the ability of the modified photocatalysts to degrade NO by both solar and indoor illumination was evaluated. The surface chemistry at the air/catalyst interface, governed by the photoelectric characteristics of TiO₂ and the formation of reactive oxygen species with co-occurring redox reactions, is reviewed in this paper. The factors affecting the application of TiO₂ for the degradation of priority air pollutants as single compounds or mixtures are discussed. We investigated, particularly, the degradation of mixtures of priority compounds at typical concentrations in ambient air and confined spaces. This is a realistic approach, because pollutants are present as mixtures, rather than as individual compounds in ambient and indoor air. Moreover, organic polymers as paint constituents were found to be the primary source for carbonyl formation, e.g., formaldehyde, acetaldehyde, etc., during the heterogeneous photocatalytic processes conducted on TiO₂-enriched coatings. Full article

During the production and laying phases of hot-mixing asphalt (HMA), various volatile organic compounds (VOCs) and noxious gases such as H₂S are released into the atmosphere. These emissions are a serious environmental problem, a risk to human health, and expose workers and residents to unfriendly odours. The aim of this study was the development of a fast and sensitive analytical method to detect the H₂S emitted from hot bituminous binder that is generally used in the various stages of asphalt production, processing, handling and during road construction. The method consisted in the analysis of evolved H₂S from a flask with molten bitumen, using nitrogen as a carrier gas to lead the volatile compounds into a residual gas analyser equipped with a quadrupole mass spectrometer. The analysis was performed following the H₂S-specific signals at m/z 33 (HS⁺) and at m/z 34 (H₂S⁺) in real time, directly on the sample without laborious and expensive pre-treatments and with short response times (<6 s). Calibration with a standard mixture of 1000 ppm of H₂S in nitrogen allows semi-quantitative H₂S detection. The sensitivity and rapidity of the method were evaluated by quenching the release of sulphur compounds with commercial odour-suppressing agents. Upon addition of 0.1% of additive in two minutes, the H₂S signal drops about 80% in two minutes, confirming the good response of the method, even with a very complex matrix. Full article

The rumen contains a complex mixture of microbes, crucial for the animal’s ability to degrade feed. Some of the feed-derived carbon is released as methane, a potent greenhouse gas, into the atmosphere. There is growing interest in reducing the loss of feed-derived carbon, making it available to the animal and improving animal productivity. Artificial rumen systems (ARSs) have been widely used to evaluate novel feed additives in terms of their ability to reduce methane production in the rumen and their effect on the rumen microbiome function prior to conducting resource-intensive animal trials. While the value of ARSs is widely acknowledged, it remains unclear which of these in vitro systems simulate the natural system most accurately. Here, we evaluated three different ARSs and compared them to in vivo rumen metrics. The results showed that all systems were capable of maintaining stable pH, redox potential, and temperature over time. The batch-style ARS simulated the rumen over 48 h. The semi-continuous ARS mimicked the volatile fatty acid profile and microbiota of the in vivo rumen for up to 120 h. Similarly, all ARSs maintained the prokaryotic and eukaryotic rumen populations over the duration of the study, with the semi-continuous ARS maintaining the natural rumen microbiome more accurately and for up to 120 h. In sum, our results suggest that three of the widely used ARSs simulate the rumen ecosystem adequately for many short-term rumen microbiome studies, with the more advanced semi-continuous ARS being more accurate when rumen simulation is extended to over 48 h. Full article

Textile waste contributes to the pollution of both terrestrial and aquatic ecosystems. While natural textile fibres are known to be biodegraded by microbes, the vast majority of textiles now contain a mixture of processed plant-derived polymers and synthetic materials generated from petroleum and are commonly dyed with azo dyes. This presents a complex recycling problem as the separation of threads and removal of dye are challenging and costly. As a result, the majority of textile waste is sent to landfill or incinerated. This project sought to assess the potential of fungal bioremediation of textile-based dye as a step towards sustainable and environmentally-friendly means of disposal of textile waste. Successful development of an agar-independent microcosm enabled the assessment of the ability of two fungal species to grow on a range of textiles containing an increasing percentage of elastane. The white rot fungus Hypholoma fasciculare was shown to grow well on semi-synthetic textiles, and for the first time, bioremediation of dye from textiles was demonstrated. Volatile analysis enabled preliminary assessment of the safety profile of this process and showed that industrial scale-up may require consideration of volatile capture in the design process. This study is the first to address the potential of fungi as bioremediation agents for solid textile waste, and the results suggest this is an avenue worthy of further exploration. Full article

The objective of this work was to develop an automated anaerobic biodigester capable of operating in a semi-continuous or batch system for biogas production. Low biodegradability biomass has little efficiency in the production of biogas by anaerobic digestion processes and an efficient alternative is the use of bioprocesses in semi-continuous system. Two experiments were carried out in the same proportions but in different processes, and all control and automation parameters were tested and evaluated. For testing, mixtures of organic waste, anaerobic sludge (inoculum) and raw sewage without any treatment from the sewage treatment plant, in mesophilic phase (37 °C), were used during the 60 days of experiment. The semi-continuous system showed the greatest reduction in organic matter, expressed by the removal of 80.7% Total Solids Volatile (TVS) and the greatest volume (68.5 L) and methane percentage (78.5%). Finally, with these and other results found, it is possible to conclude that the biodigester developed for semi-continuous system, with the automation and control system, was satisfactory for the reduction in organic matter and biogas production. In addition, all operating system worked properly and with the use of current, low-cost technologies, the application and development on a larger scale becomes viable in the future. Full article

Essential oils (EOs) are complex mixtures of volatile and semi-volatile organic compounds that originate from different plant tissues, including flowers, buds, leaves and bark. According to their chemical composition, EOs have a characteristic aroma and present a wide spectrum of applications, namely in the food, agricultural, environmental, cosmetic and pharmaceutical sectors. These applications are mainly due to their biological properties. However, EOs are unstable and easily degradable if not protected from external factors such as oxidation, heat and light. Therefore, there is growing interest in the encapsulation of EOs, since polymeric nanocarriers serve as a barrier between the oil and the environment. In this context, nanoencapsulation seems to be an interesting approach as it not only prevents the exposure and degradation of EOs and their bioactive constituents by creating a physical barrier, but it also facilitates their controlled release, thus resulting in greater bioavailability and efficiency. In this review, we focused on selecting recent articles whose objective concerned the nanoencapsulation of essential oils from different plant species and highlighted their chemical constituents and their potential biotechnological applications. We also present the fundamentals of the most commonly used encapsulation methods, and the biopolymer carriers that are suitable for encapsulating EOs. Full article