Metataxonomy and functionality of wood-tar degrading microbial consortia

A comprehensive review on the production and enhancement techniques of gaseous biofuels and their applications in IC engines with special reference to the associated performance and emission characteristics

The increasing global demand for energy, coupled with environmental concerns associated with fossil fuels, has led to the exploration of alternative fuel sources. Gaseous biofuels, derived from organic matter, have gained attention due to their renewable nature and clean combustion characteristics. The paper extensively explores production pathways for gaseous biofuels, including biogas, syngas, and hydrogen, providing insightful discussions on various sources and processes. The energy content, physical, and chemical properties of gaseous biofuels have been analysed, highlighting their potential as viable alternatives to conventional fuels. Distinctive properties of biogas, producer gas, and hydrogen that impact combustion characteristics and engine efficiency in IC engines are underscored. Furthermore, the review systematically reviews enhancement techniques for gaseous biofuels, encompassing strategies to augment quality, purity, and combustion efficiency. Various methods, ranging from substrate pretreatment for biogas to membrane separation for hydrogen, illustrate effective means of enhancing fuel performance. Rigorous examination of performance parameters such as brake thermal efficiency, specific fuel consumption and emissions characteristics such as NOx, CO, CO2, HC of gaseous biofuels in dual-fuel mode emphasizes efficiency and environmental impact, offering valuable insights into their feasibility as engine fuels. The findings of this review will serve as a valuable resource for researchers, engineers, and policymakers involved in alternative fuels and sustainable transportation, while also highlighting the need for further research and development to fully unlock the potential of gaseous biofuels in IC engines.

Microbial, chemical, and isotopic monitoring integrated approach to assess potential leachate contamination of groundwater in a karstic aquifer (Apulia, Italy)

Landfill sites are subjected to long-term risks of accidental spill of leachate through the soil and consequential contamination of the groundwater. Wide areas surrounding the landfill can seriously be threatened with possible consequences to human health and the environment. Given the potential impact of different coexisting anthropic pollution sources (i.e., agriculture and cattle farming) on the same site, the perturbation of the groundwater quality may be due to multiple factors. Therefore, it is a challenging issue to correctly establish the pollution source of an aquifer where the landfill is not isolated from other anthropic land uses, especially in the case of a karstic coastal aquifer. The present study is aimed at setting in place an integrated environmental monitoring system that included microbiological, chemical, and isotope methods to evaluate potential groundwater pollution in a landfill district in the south of Italy located in Murgia karstic aquifer. Conventional (microbial plate count and physical-chemical analyses) and advanced methods (PCR-ARISA, isotope analysis of δ18O, δ2H, 3H, δ 13C, δ 15N-NO3-, and δ 18O-NO3-) were included in the study. Through data integration, it was possible to reconstruct a scenario in which agriculture and other human activities along with seawater intrusion in the karst aquifer were the main drivers of groundwater pollution at the monitored site. The microbiological, chemical, and isotope results confirmed the absence of leachate effects on groundwater quality, showing the decisive role of fertilizers as potential nitrate sources. The next goal will be to extend long-term integrated monitoring to other landfill districts, with different geological and hydrogeological characteristics and including different sources of pollution, to support the ecological restoration of landfills.

Plant sources, techniques of production and uses of tar: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Throughout history, Humans have always used tar for different purposes such as gluing materials, waterproofing, and conserving wood, but today, it is also used in medicines and cosmetics. Many countries around the world, Norway and Morocco to name a few, obtain tar from endemic trees. In a process of dry distillation, the organic material, endemic trees in this case, is exposed to a high temperature with a restricted amount of oxygen. Eventually, it cracks the large molecules in the matter and turns it into tar.

AIM OF THE REVIEW

This review article sheds light on tar production and the species that have been used in the process. Equal emphasis is placed on its uses, chemical composition, and toxicity.

MATERIALS AND METHODS

Meta-analysis (PRISMA) guidelines have been used to review this article. The review is put together from various articles, theses, documents in "Science Direct", "Hal (Archive ouvert)", "Web of knowledge" without limitation date.

RESULTS

It turns out that tar can be produced by 18 tree taxonomic families, notably Cupressaceae, Pinaceae, and Betulaceae. As for the production techniques, two methods are considered: Per ascensum and Per descensum, which can take different forms. The chemical composition of tar consists of acids, phenols, and aromatic hydrocarbons. The uses of tar have changed over time, while its toxicity is strongly related to its chemical composition.

CONCLUSIONS

The different species used in tar production have been highlighted in this research review. Equal importance has been given to its methods of extraction, uses and its chemical components. We hope that future studies will focus more on these species used to produce tar in other biological activities.

Levels and risk assessment of polycyclic aromatic hydrocarbons in wood vinegars from pyrolysis of biomass

A method quantifying 16 polycyclic aromatic hydrocarbons (PAHs) in wood vinegars (WVs) obtained from slow pyrolysis of biomass with ultrasonic-assisted liquid-liquid extraction/gas chromatography-mass spectrometry (USALLE/GC-MS) was established. The recovery range was 83-128%, and the relative standard deviations (RSD%) were less than 15% except naphthalene, acenaphthylene and acenaphthene. Acenaphthylene, acenaphthene, fluorene, anthracene, phenanthrene, fluoranthene, and pyrene were observed in all samples and the other 9 compounds, including benzopyrene (B[a]P), were not detected. The concentration of ∑PAHs referred to the sum total of 7 PAHs mentioned above was 22.0-498.3 μg L^-1. The PAHs concentration increased with the increasing pyrolysis temperature in bamboo willow WV, pinus sylvestris WV, and corncob WV, while it increased initially, and then decreased with a maximum at 550 °C in rice husk WV. The ∑PAHs concentration increased with a higher heating rate in the white pine WV, while rice husk WV and cornstalk WV showed the opposite trend. The varied condensed aromatic ring number showed that 3-ring PAHs relatively were the main component in all kind WVs. 3-ring PAHs increased with increasing temperatures, while 4-ring PAHs showed an opposite trend in sawdust WV and corncob WVs. A higher cellulose content in sawdust enhanced the reaction of lignin leading to a higher concentration of PAHs than that in straws and leaves. Calculations of the toxicity equivalents of PAHs in WVs indicated that anthracene was the most toxic among the PAHs, and the pinus sylvestris WV had the highest risk of ∑PAHs toxicity in all WVs.

Combined Effects of Microplastics and Biochar on the Removal of Polycyclic Aromatic Hydrocarbons and Phthalate Esters and Its Potential Microbial Ecological Mechanism

Microplastics (MPs) have been attracting wide attention. Biochar (BC) application could improve the soil quality in the contaminated soil. Currently, most studies focused on the effect of MPs or BC on the soil properties and microbial community, while they neglected the combined effects. This study investigated the combined effects of BC or ball-milled BC (BM) and polyethylene plastic fragments (PEPFs) and degradable plastic fragments (DPFs) on the removal of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) from the PAH-contaminated soil and the potential microbial ecological mechanisms. The results showed that BC or BM combined with PEPF could accelerate the removal of PAHs and PAEs. PEPF combined with BM had the most significant effect on the removal of PAHs. Our results indicating two potential possible reasons contribute to increasing the removal of organic pollutants: (1) the high sorption rate on the PEPF and BC and (2) the increased PAH-degrader or PAE-degrader abundance for the removal of organic pollutants.

Steam reforming of toluene and naphthalene as tar surrogate in a gliding arc discharge reactor

Steam reforming of mixed toluene and naphthalene as tar surrogate has been investigated in an AC gliding arc discharge plasma, with particular emphasis on better understanding the effect of steam and CO₂ on the reaction performance. Results show that H₂, C₂H₂ and CO are the major gas products in the plasma steam reforming of tar for energy recovery. The addition of a small amount of steam remarkably enhances the conversions of both toluene and naphthalene, from 60.4% to 76.1% and 57.6% to 67.4%, respectively, as OH radicals formed by water dissociation create more reaction pathways for the conversion of toluene, naphthalene and their fragments. However, introducing CO₂ to this process has a negative effect on the tar reforming. Optical emission spectroscopic diagnostics has shown the formation of a variety of reactive species in the plasma process. Trace amounts of monocyclic and bicyclic aromatic condensable by-products are also detected. The destruction of toluene and naphthalene can be initiated through the collisions of tar surrogates with energetic electrons, N₂ excited species, OH and O radicals etc. Further optimization of the plasma tar destruction is still needed because the complexity of the tar component in a practical gasifier could decrease the tar conversions.

Linking initial soil bacterial diversity and polycyclic aromatic hydrocarbons (PAHs) degradation potential

The aim of this study was to understand the role of indigenous soil microbial communities on the biodegradation of polycyclic aromatic hydrocarbons (PAHs) and to determine whether PAHs degradation potential in soils may be evaluated by analysis of bacterial diversity and potential metabolisms using a metagenomics approach. Five different soils were artificially contaminated with seven selected PAHs and the most abundant bacterial taxa were assessed by sequencing the 16S rRNA gene, and linking them to PAH biodegradation efficiencies. A PICRUSt approach was then led to estimate the degradation potentials by metagenomics inference. Although the role of bacteria in PAHs degradation is not directly established here, the presence of a large number of bacteria belonging to the Betaproteobacteria class correlated to a higher degradation of LMW PAHs. A link with specific bacterial taxa was more difficult to establish concerning HMW PAHs, which seemed to require more complex mechanisms as shown by PICRUSt.