Biochar-Assisted Catalytic Pyrolysis of Oily Sludge to Attain Harmless Disposal and Residue Utilization for Soil Reclamation.

Pyrolysis of oily sludge (OS) is a feasible technology to match the principle of reduction and recycling; however, it is difficult to confirm the feasible environmental destination and meet the corresponding requirements. Therefore, an integrated strategy of biochar-assisted catalytic pyrolysis (BCP) of OS and residue utilization for soil reclamation is investigated in this study. During the catalytic pyrolysis process, biochar as a catalyst intensifies the removal of recalcitrant petroleum hydrocarbons at the expense of liquid product yield. Concurrently, biochar as an adsorbent can inhibit the release of micromolecular gaseous pollutants (e.g. HCN, H2S, and HCl) and stabilize heavy metals. Due to the assistance of biochar, pyrolysis reactions of OS are more likely to occur and require a lower temperature to achieve the same situation. During the soil reclamation process, the obtained residue as a soil amendment can not only provide a carbon source and mineral nutrients but can also improve the abundance and diversity of microbial communities. Thus, it facilitates the plant germination and the secondary removal of petroleum hydrocarbons. The integrated strategy of BCP of OS and residue utilization for soil reclamation is a promising management strategy, which is expected to realize the coordinated and benign disposal of more than one waste.

Emerging Strategies for Enhancing Propionate Conversion in Anaerobic Digestion: A Review.

Anaerobic digestion (AD) is a triple-benefit biotechnology for organic waste treatment, renewable production, and carbon emission reduction. In the process of anaerobic digestion, pH, temperature, organic load, ammonia nitrogen, VFAs, and other factors affect fermentation efficiency and stability. The balance between the generation and consumption of volatile fatty acids (VFAs) in the anaerobic digestion process is the key to stable AD operation. However, the accumulation of VFAs frequently occurs, especially propionate, because its oxidation has the highest Gibbs free energy when compared to other VFAs. In order to solve this problem, some strategies, including buffering addition, suspension of feeding, decreased organic loading rate, and so on, have been proposed. Emerging methods, such as bioaugmentation, supplementary trace elements, the addition of electronic receptors, conductive materials, and the degasification of dissolved hydrogen, have been recently researched, presenting promising results. But the efficacy of these methods still requires further studies and tests regarding full-scale application. The main objective of this paper is to provide a comprehensive review of the mechanisms of propionate generation, the metabolic pathways and the influencing factors during the AD process, and the recent literature regarding the experimental research related to the efficacy of various strategies for enhancing propionate biodegradation. In addition, the issues that must be addressed in the future and the focus of future research are identified, and the potential directions for future development are predicted.

Triple combination of natural microbial action, etching, and gas foaming to synthesize hierarchical porous carbon for efficient adsorption of VOCs.

Fungi residue, vinasse, and biogas residue differ from general biomass waste due to natural microbial action. Microbial fermentation helps create natural channels for the permeation of activators and produces proteins for natural nitrogen doping. Inspired by these advantages on porous carbon synthesis, this study adopted dual activators of KOH and KHCO3 to synthesize porous carbon with different pore ratios for efficient adsorption of volatile organic compounds (VOCs). The fungi residue possessed the least lignin due to the most severe microbial action, contributing to the best pore structures after activation. The etching effect from potassium compounds and gas foaming from the carbonate decomposition contributed to creating hierarchical porous carbon with ultra-high surface area, ca. 1536.8-2326.5 m2/g. However, KHCO3 addition also caused nitrogen erosion, such that lower adsorption capacity was attained even with a higher surface area when the mass ratio of KOH/KHCO3 decreased from 2.5:0.5 to 2:1. The maximum adsorption capacities of chlorobenzene (CB) and benzene (PhH) reached 594.0 and 394.3 mg/g, respectively. Pore structure variations after adsorption were evaluated by freeze treatment to discover the adsorption mechanism. The surface area after CB and PhH adsorption decreased 40.3% and 34.5%, respectively. Most of the mesopores might transform into micropores due to the mono/multilayer stacking of adsorbates. The VOC adsorption kinetics were simulated by the Pseudo-first- and -second-order models and Y-N model. This paper provides a new approach for high-value biomass waste utilization after microbial action to synthesize efficient adsorbents for VOCs.

Transcriptome sequencing and functional analysis of Sedum lineare Thunb. upon salt stress.

Soil salinization is one major constraint to plant geographical distribution, yield, and quality, and as an ideal plant for the "greening" of flat-roofed buildings, Sedum lineare Thunb. has strong tolerance against a variety of environmental adversities including salinity with the underlying mechanism still remaining unknown. In this study, we performed de novo transcriptome sequencing on leaf and root samples of NaCl-treated S. lineare Thunb. and identified 584 differentially expressed genes (DEGs), which were further annotated by gene function classification and pathway assignments using the public data repositories. In addition to the increased gene expression level verified by qRT-PCR, the elevated activities of the corresponding enzymes were also demonstrated for peroxidase (POD), glutathione peroxidases (GPX), and cysteine synthase (CSase) in the NaCl-treated roots. Furthermore, two highly inducible genes without known functions related to salt tolerance were selected to be overexpressed and tested for their effects on salt tolerance in the model plant, Arabidopsis thaliana. Upon 150 mM NaCl treatment, 35S:SlCXE but not 35S:SlCYP72A transgenic Arabidopsis seedlings exhibited improved salt resistance as shown by the increased seed germination rates and longer primary roots of transgenic seedlings when compared to wild-type plants. Taken together, this work laid a foundation for a better understanding of the salt adaptation mechanism of S. lineare Thunb. and genes identified could serve as useful resources for the development of more salt-tolerant varieties of other species through genetic engineering.

Gain-of-function analysis of poplar CLE genes in Arabidopsis by exogenous application and over-expression assays.

Among 50 CLE gene family members in the Populus trichocarpa genome, three and six PtCLE genes encode a CLE motif sequence highly homologous to Arabidopsis CLV3 and TDIF peptides, respectively, which potentially make them functional equivalents. To test and compare their biological activity, we first chemically synthesized each dodecapeptide and analysed itsi n vitro bioactivity on Arabidopsis seedlings. Similarly, but to a different extent, three types of poplar CLV3-related peptides caused root meristem consumption, phyllotaxis disorder, anthocyanin accumulation and failure to enter the bolting stage. In comparison, application of two poplar TDIF-related peptides led to root length promotion in a dose-dependent manner with an even stronger effect observed for poplar TDIF-like peptide than TDIF. Next, we constructed CaMV35S:PtCLE transgenic plants for each of the nine PtCLE genes. Phenotypic abnormalities exemplified by arrested shoot apical meristem and abnormal flower structure were found to be more dominant and severe in 35S:PtCLV3 and 35S:PtCLV3-like2 lines than in the 35S:PtCLV3-like line. Disordered vasculature was detected in both stem and hypocotyl cross-sections in Arabidopsis plants over-expressing poplar TDIF-related genes with the most defective vascular patterning observed for TDIF2 and two TDIF-like genes. Phenotypic difference consistently observed in peptide application assay and transgenic analysis indicated the functional diversity of nine poplar PtCLE genes under investigation. This work represents the first report on the functional analysis of CLE genes in a tree species and constitutes a basis for further study of the CLE peptide signalling pathway in tree development.

Identification and expression analysis of the LRR-RLK gene family in tomato (Solanum lycopersicum) Heinz 1706.

As the largest subfamily of receptor-like kinases (RLKs), leucine-rich repeat receptor-like kinases (LRR-RLKs) regulate the growth, development, and stress responses of plants. Through a reiterative process of sequence analysis and re-annotation, 234 LRR-RLK genes were identified in the genome of tomato (Solanum lycopersicum) 'Heinz 1706', which were further grouped into 10 major groups based on their sequence similarity. In comparison to the significant role of tandem duplication in the expansion process of this gene family in other species, only approximately 12% (29 out of 234) of SlLRR-RLK genes arose from tandem duplication. Using the multiple expectation maximization for motif elicitation (MEME) method, the motif composition and arrangement were found to be variably conserved within each SlLRR-RLK group, indicating their different extent of functional divergence. Expression profiling analyses by qRT-PCR data revealed that SlLRR-RLK genes were differentially expressed in various tomato organs and tissues, and some SlLRR-RLK genes exhibited preferential expression in fruits at distinct developmental stages, suggesting that SlLRR-RLK may take important roles in fruit development and ripening process. The results of this study provide an overview of the LRR-RLK gene family in tomato Heinz 1706, one important species of Solanaceae, and will be helpful for future functional analysis of this important protein family in fleshy fruit-bearing species.

Impact of heavy metal stresses on the growth and auxin homeostasis of Arabidopsis seedlings.

The phytohormone auxin is an essential mediator in many aspects of plant development. Its dynamic and differential distribution within the plant is regulated by a variety of environmental cues including heavy metal stimuli. In the present study, we first evaluated the toxic effects of seven heavy metals including Pb(2+), Cd(2+), Hg(2+), Ni(2+). Zn(2+), Co(2+) and Cu(2+) in their excess on the model plant, Arabidopsis thaliana. Various morphological defects including loss in fresh weight and leaf area, decrease of the primary root length and stimulation of the lateral root density occurred to a different extent among seven heavy metals. Next, using an indicative DR5:GUS reporter line of Arabidopsis, the auxin accumulation and distribution within plant seedlings were found to be dramatically and differentially affected by these heavy metals. We further analyzed the transcriptional changes of 27 selected auxin homeostasis-related genes by qRT-PCR technique and found that upon various heavy metals, the expressions of the candidate genes were distinctly altered in shoots and roots. Our data indicated that when confronted with excessive heavy metals, plants could dynamically and differentially regulate the transcription of auxin-related genes to adjust the location and effective accumulation of auxin within the plant for better adaptation and survival under the adverse environment.

Genome-wide characterization, expression and functional analysis of CLV3/ESR gene family in tomato.

BACKGROUND: By encoding a group of small secretory peptides, the members of the CLAVATA3/EMBRYO-SURROUNDING REGION (CLE) family play important roles in cell-to-cell communication to control the balance between stem cell proliferation and differentiation in plant development. Despite recent identification and characterization of members of this gene family in several plant species, little is known about its functional role in plants with fleshy fruits. RESULTS: In total, fifteen CLE genes (SlCLE1-15) were identified from tomato (Solanum lycopersicum cv. 'Heinz-1706') genome and their multiple characters including phylogeny, gene structures, chromosome locations, conserved motifs and cis-elements in the promoter sequences, were analyzed. Real-time PCR analysis showed that 13 out of 15 identified SlCLE genes are transcribed and exhibit remarkably unique expression patterns among tissues and organs. In particular, SlCLE12, the homologue of Arabidopsis CLE41/44 gene, appears to be the dominant CLE gene in most of tested tissues with its maximum expression found in vascular tissues. Meanwhile, SlCLE1, 10, 13 exhibit specific but distinct expression in flower bud, root and shoot apex, respectively. More notably, several SlCLEs are dramatically regulated in their transcriptional levels during fruit development and ripening, indicating significant role these genes may potentially play in the critical physiological process. Upon the treatment with synthetic peptides corresponding to the 12-aa CLE domains of SlCLE 10, 12 and 13, tomato seedlings exhibit a clear reduction in root length to varying degrees. CONCLUSIONS: This study provides a comprehensive genomic analysis of CLE gene family in tomato, a crop species with fleshy fruit. Differential expression patterns of various SlCLEs provide important insights into the functional divergence of CLE signaling cascade in Solanaceae species, especially their potential involvements in the regulation of fruit development and ripening.

Effect of heterogeneous fenton-like pretreatment on semi-permeable membrane-covered co-composting: Humification and microbial community succession.

This study focused on the impacts of heterogeneous Fenton-like pretreatment on the humification and bacterial community during co-composting of wheat straw with cattle dung covered with a semi-permeable membrane. In this study, FeOCl and low concentration of H2O2 were used for pretreatment and composting, which lasted for 39 days. The results showed that the pretreatment promoted the humification process, with degree of polymerization and percentage of humic acid increasing by 53.2 % and 7.3 %, respectively. Furthermore, the diversity and structure of bacterial communities were altered by pretreatment. During the thermophilic phase, pretreatment considerably promoted the metabolism of carbohydrate. According to redundancy analysis, C/N, moisture and organic matter were the key environmental factors that dominated the microbial community. In summary, heterogeneous Fenton-like pretreatment provided a novel idea for improving the humic acid content and maturity of the compost pile.

Enhancement of methane production from anaerobic digestion of Erigeron canadensis via O2-nanobubble water supplementation.

Malignant invasive Erigeron canadensis, as a typical lignocellulosic biomass, is a formidable challenge for sustainable and efficient resource utilization, however nanobubble water (NBW) coupled with anaerobic digestion furnishes a prospective strategy with superior environmental and economic effectiveness. In this study, influence mechanism of various O2-NBW addition times on methanogenic performance of E. canadensis during anaerobic digestion were performed to achieve the optimal pollution-free energy conversion. Results showed that supplementation of O2-NBW in digestion system could significantly enhance the methane production by 10.70-16.17%, while the maximum cumulative methane production reached 343.18 mL g-1 VS in the case of one-time O2-NBW addition on day 0. Furthermore, addition of O2-NBW was conducive to an increase of 2-90% in the activities of dehydrogenase, α-glucosidase and coenzyme F420. Simultaneously, both facultative bacteria and methanogenic archaea were enriched as well, further indicating that O2-NBW might be responsible for facilitating hydrolytic acidification and methanogenesis. Based on Kyoto Encyclopedia of Genes and Genomes (KEGG) cluster analysis, provision of O2-NBW enhanced the metabolism of carbohydrate and amino acid, translation as well as membrane transport of bacteria and archaea. This study might offer the theoretical guidance and novel insights for efficient recovery of energy from lignocellulosic biomass on account of O2-NBW adhibition in anaerobic digestion system, progressing tenor of carbon-neutral vision.

Preparation of iron oxide-modified digestate biochar and effect on anaerobic digestion of kitchen waste.

Two kinds of Fe2O3-modified digestate-derived biochar (BC) were prepared and their effects on anaerobic digestion (AD) of kitchen waste (40.0 g VS/L) were investigated, with BC and Fe2O3 addition used as a comparison. The results showed that Fe2O3-modified BC (Fe2O3-BC1 prepared by co-precipitation and Fe2O3-BC2 by impregnation) significantly increased methane yield (20.8 % and 16.4 %, respectively) and reduced volatile fatty acid concentration (35.6 % and 29.6 %, respectively). Microbial high-throughput analysis revealed that Fe2O3-modified BC selectively enriched Clostridium (47.3 %) and Methanosarcina (72.2 %), suggesting that direct interspecies electron transfer contributing to improved biogas production performance was established and enhanced. Correlation analysis indicated that biogas production performance was improved by the larger specific surface area (83.4 m2/g), pore volume (0.101 cm3/g), and iron content (97.4 g/Kg) of the BC. These results offer insights for enhancing the efficacy of AD processes using Fe2O3-modified BCs as additives.

Genome-wide identification, characterization and expression analysis of populus leucine-rich repeat receptor-like protein kinase genes.

BACKGROUND: Leucine-rich repeat receptor-like kinases (LRR-RLKs) comprise the largest group within the receptor-like kinase (RLK) superfamily in plants. This gene family plays critical and diverse roles in plant growth, development and stress response. Although the LRR-RLK families in Arabidopsis and rice have been previously analyzed, no comprehensive studies have been performed on this gene family in tree species. RESULTS: In this work, 379 LRR-RLK genes were retrieved from the Populus trichocarpa genome and further grouped into 14 subfamilies based on their structural and sequence similarities. Approximately 82% (312 out of 379) of the PtLRR-RLK genes are located in segmental duplication blocks indicating the role of duplication process in the expansion of this gene family. The conservation and variation in motif composition and intron/exon arrangement among PtLRR-RLK subfamilies were analyzed to provide additional support for their phylogenetic relationship and more importantly to indicate the potential divergence in their functions. Expression profiling of PtLRR-RLKs showed that they were differentially expressed in different organs and tissues and some PtLRR-RLKs were specifically expressed in meristem tissues, which indicated their potential involvement in tissue development and differentiation. For most AtLRR-RLKs with defined functions, Populus homologues exhibiting similar expression patterns could be identified, which might indicate the functional conservation during evolution. Among 12 types of environmental cues analyzed by the genome-wide microarray data, PtLRR-RLKs showed specific responses to shoot organogenesis, wounding, low ammonium feeding, hypoxia and seasonal dormancy, but not to drought, re-watering after drought, flooding, AlCl3 treatment and bacteria or fungi treatments. CONCLUSIONS: This study provides the first comprehensive genomic analysis of the Populus LRR-RLK gene family. Segmental duplication contributes significantly to the expansion of this gene family. Populus and Arabidopsis LRR-RLK homologues not only share similar genetic structures but also exhibit comparable expression patterns which point to the possible functional conservation of these LRR-RLKs in two model systems. Transcriptome profiling provides the first insight into the functional divergence among PtLRR-RLK gene subfamilies and suggests that they might take important roles in growth and adaptation of tree species.

Impact of microplastic pollution on coastal ecosystems using comprehensive beach quality indices.

Previous studies of Microplastics (Mps) pollution focused on abundance, effect on organisms, and origins. Mps could also be indicators to evaluate pollution level. Beach Quality Indices (BQIs) are useful in understanding Mps pollution level. This study is to assess magnitude, impact and quality of beaches using BQIs, by determining abundance, shape, and size of Mps in beach sediments, which is the first effort in China. Three BQIs, i.e. Microplastic Pollution Index (MPPI), Environmental Status Index (ESI), Coefficient of Microplastic Impact (CMPI), were employed involving Sector Analysis Approach. All beaches had "very high" abundance by MPPI, were classified "bad" by ESI, and fell in "red" sector using Sector Analysis Approach by intergradation of MPPI and ESI. The impact of fiber morphology was "extreme" based on CMPI. The average abundance was 664±80 Mps/kg. Fibers occupied >97 % of Mps, with 31 % of black Mps. A model was proposed to determine Mps origins.

Recent advancements in strategies to improve anaerobic digestion of perennial energy grasses for enhanced methane production.

Perennial energy grasses (PEGs) are supposed to be a momentous heading to the development of biomass energy on account of their characteristic superiorities of high yield, strong adaptability and no direct competition with food crops. Anaerobic digestion of PEGs with great biogas-producing potential occupies an irreplaceable status despite a variety of pathways for conversion to renewable energy. However, efficient digestion of PEGs suffers from severe challenges in connection with feedstock properties such as recalcitrant structures. This review highlights recent research in anaerobic digestion of PEGs and focuses on essential aspects enhancing anaerobic digestion performance: types and properties of grasses, diverse pretreatments, various co-feedstocks for co-digestion, dosing of different additives, and improvements in reactors. General discussions on the future prospects of anaerobic digestion of PEGs are proposed. Overcoming knowledge gaps and technical limitations will facilitate further application of PEGs on an industrial scale.

Co-composting of cattle manure and wheat straw covered with a semipermeable membrane: organic matter humification and bacterial community succession.

Semipermeable membrane-covered composting is one of the most commonly used composting technologies in northeast China, but its humification process is not yet well understood. This study employed a semipermeable membrane-covered composting system to detect the organic matter humification and bacterial community evolution patterns over the course of agricultural waste composting. Variations in physicochemical properties, humus composition, and bacterial communities were studied. The results suggested that membrane covering improved humic acid (HA) content and degree of polymerization (DP) by 9.28% and 21.57%, respectively. Bacterial analysis indicated that membrane covering reduced bacterial richness and increased bacterial diversity. Membrane covering mainly affected the bacterial community structure during thermophilic period of composting. RDA analysis revealed that membrane covering may affect the bacterial community by altering the physicochemical properties such as moisture content. Correlation analysis showed that membrane covering activated the dominant genera Saccharomonospora and Planktosalinus to participate in the formation of HS and HA in composting, thus promoting HS formation and its structural complexity. Membrane covering significantly reduced microbial metabolism during the cooling phase of composting.

Conversion and impact of dissolved organic matters in a heterogeneous catalytic peroxymonosulfate system for pollutant degradation.

Dissolved organic matters (DOM) are widely present in different water sources, causing significant effects on water treatment processes. Herein, the molecular transformation behavior of DOM during peroxymonosulfate (PMS) activation by biochar for organic degradation in a secondary effluent were comprehensively analyzed. Evolution of DOM was identified and inhibition mechanisms to organic degradation were elucidated. DOM underwent oxidative decarbonization (e.g., -C2H2O, -C2H6, -CH2 and -CO2), dehydrogenation (-2H) and dehydration reactions by ·OH and SO4·-. N and S containing compounds witnessed deheteroatomisation (e.g., -NH, -NO2+H, -SO2, -SO3, -SH2), hydration (+H2O) and N/S oxidation reactions. Among DOM, CHO-, CHON-, CHOS-, CHOP- and CHONP-containing molecules showed moderate inhibition while condensed aromatic compounds and aminosugars exhibited strong and moderate inhibition effects on contaminant degradation. The fundamental information could provide references for the rational regulation of ROS composition and DOM conversion process in a PMS system. This in turn offered theoretical guidance to minimize the interference of DOM conversion intermediates on PMS activation and degradation of target pollutants.

Overexpression of poplar wounding-inducible genes in Arabidopsis caused improved resistance against Helicoverpa armigera (Hübner) larvae.

Four highly inducible genes of poplar trees, PtdKTI5, PtdWIN4, PtdPOP3 from hybrid poplar (Populus trichocarpa × P. deltoides) and PtKTI2 from trembling aspen (Populus tremuloides Michx.) have been individually transformed into Arabidopsis thaliana for overexpression. High transcriptional level of each transgene in transgenic Arabidopsis lines was confirmed by RT-PCR analysis. The development, body weight and survivorship of cotton bollworm (Helicoverpa armigera) fed on four types of transgenic Arabidopis plants were evaluated in the laboratory. Our data indicated that these four Populus defense-related genes exhibited various degree of insectital activity on larval and postlarval development of cotton bollworm and may be utilized for herbivore resistance improvement in plant genetic engineering.

Tunable active sites on biogas digestate derived biochar for sulfanilamide degradation by peroxymonosulfate activation.

Conversion of digestate into biochar-based catalysts is an effective strategy for disposal and resource utilization. The active sites on biochar correlated with reactive species formation in peroxymonosulfate (PMS) system directly. Clarifying the structure-performance relationship of digestate derived biochar in PMS system was essential for decomposition of contaminants. Herein, dairy manure digestate derived biochar (DMDB) was prepared for PMS activation and sulfamethoxazole (SMX) degradation. The higher pyrolysis temperature could promote effective sites generation. Especially, the DMDB-800 catalyst exhibited excellent performance for PMS activation, achieving 90.2% degradation of SMX within 60 min. Based on the correlation analysis between log (k) values and active sites, defects, graphite N and CO were identified as dominant sites for PMS activation. The 1O2 oxidation and surface electron transfer were critical routes for SMX degradation. Besides, the degradation pathways of SMX were proposed according to DFT calculations and intermediates determination. The cleavage of the sulfonamide bond, hydroxylation of the benzene ring and oxidation of the amino group mainly occurred during SMX degradation. Overall, this study provides deep insights into the enhanced mechanism of tunable active sites on DMDBs for PMS activation, boosting the application of digestate biochar for water treatment in advanced oxidation systems.

Hydrothermal carbonization of garden waste by pretreatment with anaerobic digestion to improve hydrohcar performance and energy recovery.

Sustainable and resourceful utilization of garden waste with high lignocellulosic content remains a huge challenge, anaerobic digestion (AD) and hydrothermal treatment provide prospective technologies with achieving environmental and economic benefits. In this study, a 7-28 d AD was provided as a biomass pretreatment means and combined with hydrothermal carbonization (HTC) to treat three typical garden wastes (leaves, branches, grass). The results showed that AD pretreatment could effectively change the surface composition and structure properties of the feedstocks and thus modulating the properties of the hydrochar downstream. Compared to the unpretreatment samples, the specific surface area (SSA), higher heating value (HHV), energy density and nutrient elements (P and K) of hydrochar obtained by AD pretreatment were significantly improved and enriched, respectively. Specifically, the highest HHV of hydrochar obtained from leaves, branches, and grass were 25.71, 25.63, and 23.81 MJ/kg, which obtained with 21, 14, and 7 d of AD pretreatment respectively. The P contents of hydrochar of leaves and grass pretreated with AD for 14 and 7 d were 205% and 15% higher than those without AD pretreatment, respectively. Additionally, in this coupled system, the biomass energy recovery of 90.2% (78.2% biochar and 12.0% CH4) was achieved on leaves pretreated with AD for 21 d. Energy recovery of 81.2% (66.8% biochar, 14.4% CH4) and 71.3% (39.7% biochar, 31.6% CH4) was obtained by 14 d of AD pretreatment on branches and grass, respectively. Thus, this study enhances energy utilization efficiency and reduces secondary waste generation, providing valuable new insights into AD coupled with HTC technology.

Biochar from constructed wetland biomass waste: A review of its potential and challenges.

Constructed wetland is considered a promising approach for water remediation due to its high efficiency, low operation costs, and ecological benefits, but the large amounts of wetland plant biomass need to be properly harvested and utilized. Recently, wetland plant derived biochar has drawn extensive attention owing to its application potential. This paper provides an updated review on the production and characteristics of wetland plant derived biochar, and its utilization in soil improvement, carbon sequestration, environmental remediation, and energy production. In comparison to hydrothermal carbonization and gasification, pyrolysis is a more common technique to convert wetland plant to biochar. Characteristics of wetland plant biochars varied with plant species, growth environment of plant, and preparation conditions. Wetland plant biochar could be a qualified soil amendment owing to its abundant nutrients. Notably, wetland plant biochar exhibited considerable sorption capacity for various inorganic and organic contaminants. However, the potentially toxic substances (e.g. heavy metal and polycyclic aromatic hydrocarbons) retained in wetland plant biochar should be noticed before large-scale application. To overcome the drawbacks from the scattered distribution, limited productivity, and seasonal operation of constructed wetlands, the economic feasibility of wetland plant biochar production system could be improved via using mobile pyrolysis unit, utilizing local waste heat, and exploiting all the byproducts. Future challenges in the production and application of wetland plant derived biochar include the continuous supply of feedstock and proper handling of potentially hazardous components in the biochar.