Compost Samples Research Articles

Design, development and evaluation of novel equipment for compost stability tests

Compost stability is a significant quality indicator that needs to be determined before using compost as an organic fertiliser. In this work, a novel device for assessing compost stability based on the oxygen consumption (OC) method was successfully developed. The design of this prototype was created to effectively solve inherent limitations observed in commercially available equipment functioning on the same concept (Oxitop devices). The performance of the device was evaluated in the laboratory to determine the OC of two different types of compost samples (food waste and green compost). The data indicated that the device worked stably and accurately during the test. Between the two types of samples, the compost based on food waste had higher AT4 and OCmax values but with lower K values. According to the EU regulations, both types of samples were considered stable.

Making Biocarno Fertilizer from Marine Organic Waste to Increase the Income of the Abadi Fisherman Farmer Group in Kuala Indah Village

Management of marine organic waste can also be used as a solution to reduce marine waste and prevent global warming considering that the sea has many roles in supporting the life of living creatures and maintaining the ecosystem. The organic fertilizer that will be produced will be called "Biocarno Fertilizer" with good quality. The aim of this activity is to form or develop the Abadi Fishermen Farmer Group which is economically and socially independent, helps create peace and comfort in social life, and increases the skills and income of Farmer Group members in producing Biocarno Fertilizer independently. The result of this activity is the completion of community service in the form of counseling and outreach carried out by the service team to partner farmer groups, namely making Biocarno fertilizer by mixing several raw materials such as marine organic waste, cow dung, rice straw, Azolla, EM4 and molasses as a bioactivator. composting process. The next planned stage that must be carried out is to monitor and evaluate the progress of compost maturation over the next month, then samples of the mature compost will be taken to be taken to the laboratory for nutrient analysis so that farmers can modify the compost raw materials to produce quality compost according to the standards determined by SNI 19-7030-2004.

Upgrade of bio‐oil produced from the sisal residue composting

AbstractThe present work studies the composting effects on the chemical characteristics of bio‐oil produced by pyrolysis of sisal residue. Three systems were composted with sisal residue proportions to sisal fiber powder of 100:0, 90:10, and 75:25, respectively. The systems showed reductions of 33%–48% (extractive), 70%–80% (hemicellulose), and 80%–90% (cellulose) after composting. An increase in lignin content was observed in all systems. The pyrolysis of the composted systems was performed at 450°C and 550°C. At both temperatures, this process was selective in producing a large concentration of hydrocarbons (>160% increase), mainly alkanes and alkenes, reducing the concentrations of ketones, aldehydes, and phenolics (>50%) and eliminating esters, furans, and acetic acid to composted biomasses. The higher temperature favored aromatics and cyclic hydrocarbon production from the pyrolysis of composted samples. In addition to these results, composting helped reduce the oxygenated bio‐oil species by approximately 44%–75% at the lowest and ~69% at the highest temperatures. These results indicate that composted sisal residue can produce bio‐oils that are more suitable for biorefineries since they are rich in aliphatic hydrocarbons and non‐oxygenated species.

Wheat straw biochar as an additive in swine manure Composting: An in-depth analysis of mixed material particle characteristics and interface interactions

In recent research, biochar has been proven to reduce the greenhouse gases and promote organic matter during the composting. However, gas degradation may be related to the microstructure of compost. To investigate the mechanism of biochar additive, composting was performed using swine manure, wheat straw and biochar and representative solid compost samples were analyzed to characterize the mixed biochar and compost particles. We focused on the microscale, such as the particle size distributions, surface morphologies, aerobic layer thicknesses and the functional groups. The biochar and compost particle agglomerations gradually became weaker and the predominant particle size in the experiment group was < 200 μm. The aerobic layer thickness (Lp) was determined by infrared spectroscopy using the wavenumbers 2856 and 1568 cm−1, which was 0–50 μm increased as composting proceeded in both groups. The biochar increased Lp and facilitated oxygen penetrating the compost particle cores. Besides, in the biochar-swine manure particle interface, the aliphatic compound in the organic components degraded and the content of aromaticity increased with the composting process, which was indicated by the absorption intensity at 2856 cm−1 decreasing trend and the absorption intensity at 1568 cm−1 increasing trend. In summary, biochar performed well in the microscale of compost pile.

Determination and quantification of microplastics in compost

AbstractAlthough microplastics (MPs) in solid organic waste have been intensively studied, the presence of MPs in organic fertilizer and their potential as new emerging pollution to environment because of their use in agriculture has not been explained completely. Therefore, the identification and quantification of MPs in commercially available compost is important. This study aimed to estimate the quantity of MPs in commercial composts. The characteristics of MPs (shape, color, size, and type of polymers) were identified. This study found that MPs in commercial compost samples were found, reaching up to 160 particles/200 g of compost with various colors (blue, black, red, yellow, and white). The identified MPs had various sizes (0.1–1 mm) and shapes (81.8% fragment, 16.2% fiber, and 2% filament). The findings of this study are very important and significant to inform community and policymakers regarding the presence of MPs in commercial compost, hence, their intensive use in agriculture must be controlled and careful.

Nutrient Properties of Fresh and Composted Cotton Gin Byproducts and Cattle Manure for Soil Amendment

Highlights N and P concentrations in composted vs. fresh Cotton Gin Byproducts (CGB) were at least 55% (dry basis) higher. P concentrations in composted vs. raw Beef Manure (BM) were approximately 25% higher. Characterization informs product formulations and process parameters for co-pelleting CGB with BM. Accurate formulation would enhance the potential for sustainable utilization of both byproducts. Abstract. Applications of fresh and composted Cotton Gin Byproducts (CGB) and cattle manure as soil amendments are very common practices in the industry. However, composting and direct application of the materials are often limited by factors such as bulkiness, varying nutrient composition and application rates, and handling/transportation costs. This study was conducted to characterize fresh and composted CGB and beef manure (BM) for subsequent co-pelletization and utilization as soil amendments, and to investigate the effects of composting on the nutrient composition and agronomic values. Raw and composted samples of CGB and BM at different storage periods and composting ages were sourced from two commercial gins and a beef farm. Nutrient content, acidity, and compost maturity indices such as carbon/nitrogen (C/N) and ammonium/nitrate (NH4-N/NO3-N) ratios were determined and compared. All samples were obtained at four sampling points on the respective storage or composting piles. The results showed that composted CGB generally contained at least 55% more total-N and phosphorus oxide (P2O5), but approximately 35% less potassium oxide (K2O) than fresh CGB. Composted BM had approximately 3% less total-N, but at least 25% more P2O5 than raw BM. The nutrient compositions affirm the potential for co-pelletizing both forms of CGB and BM to improve the agronomic values and enhance the utilization as soil amendments. In addition, establishing the various properties of CGB and BM is crucial for determining product formulations and selecting process parameters for co-pelletization. Keywords: Beef manure, Composting, Cotton ginning, Nutrient composition, Soil fertility.

Microplastic emissions via air and compost from an industrial composting facility in England

ABSTRACT Composting provides a sustainable method of processing biodegradable waste but is often contaminated with plastic. We quantified and characterised microplastics in air and compost samples from an industrial aerobic green waste composting facility in England. Compost samples were taken at different stages of the process; air samples were taken onsite, upwind, and downwind. Microplastics were found in compost from all stages of the process at levels comparable to those reported for marine sediments; higher concentrations were found in the screening stages of the composting process (mean 9.0 (IQR: 7.1) and 9.0 (IQR: 7.4) MPs 5 g-1 (dw), for 30 mm and 10 mm screened material, respectively). Airborne microplastics were found onsite (32–49 MP m−3), upwind (1 MP m−3) and downwind (3 MP m−3). Composting facilities represent a potential source of microplastics and point of entry to the wider environment. Further investigation into other sites and processes is warranted.

Identification of bacterial community in a rapid composting method using 16SrDNA genes sequencing.

Composting is a process of microbial degradation of organic waste and is commonly applied for waste management. This is a slow process and requires a lot of land and human resources. The present study investigated mechanical augmentation with required microbial culture for composting municipal solid waste (MSW). Thirty isolates were subjected to 16S rDNA PCR amplification and gene sequencing. The isolates' sequencing from the compost samples was processed on BLASTn. Fourteen strains were identified for further experiments. The results divulge that Empedobacter (04), Bacillus (02), Proteus (02), Lactiplantibacillus (01), Klebsiella (01), Citrobacter (01), Brevibacillus (01), E. coli (01) and one unidentified strain were growing during composting. Eleven combinations of bacterial consortium and respective additives were applied for the organic waste decomposition in the next stage, resulting in varied completion periods ranging from 3 to 14days. Two combinations were completed within 3days, which are considered ideal combinations for composting. The microbial consortium was significantly diverse, which is a reason for rapid biodegradation. The present study reveals that the technology will be highly feasible for municipal solid waste management in tropical/subtropical countries.

Effects of biochar combined with MgO desulfurization waste residue on nitrogen conversion and odor emission in chicken manure composting

ABSTRACT Aim: Chicken manure is known to produce strong odors during aerobic composting, which not only pollutes the surrounding environment but also leads to the loss of valuable nutrients like nitrogen and sulfur, thus reducing the quality of the fertilizer. Methods: In this study, we explored the use of biochar combined with MgO desulfurization waste residue (MDWR) as a novel composting additive. Our approach involved conducting composting tests, characterizing the compost samples, conducting pot experiments, and examining the impact of the additives on nitrogen retention, deodorization, and compost quality. Results: Our findings revealed that the addition of biochar and MDWR significantly reduced ammonia volatilization in chicken manure compost, demonstrating a reduction rate of up to 60.12%. Additionally, the emission of volatile organic compounds (VOCs) from chicken manure compost treated with biochar and MDWR decreased by 44.63% compared to the control group. Conclusions: The composting product treated with both biochar and MDWR (CMB) exhibited a 67.7% increase in total nitrogen (TN) compared to the blank control group, surpassing the other treatment groups and showcasing the synergistic effect of these two additives on nitrogen retention. Moreover, the CMB treatment facilitated the formation of struvite crystals. Furthermore, our pot experiment results demonstrated that the CMB treatment enhanced vegetable yield and quality while reducing nitrate content. These findings highlight the significant impact of MDWR on nitrogen retention, deodorization, and compost quality enhancement, thereby indicating its promising application prospects.

Comprehensive discovery and migration evaluation of antimicrobial drugs and their transformation products in a swine farm by target, suspect, and nontarget screening

Swine farms contaminated the surrounding environment through manure application and biogas slurry irrigation, hence causing the wide residual of multiple antimicrobial drugs (ADs) and their transformation products (TPs). This study performed target, suspect, and nontarget screening methods to comprehensively investigate the pollution profiles of ADs in a typical swine farm, and characterize the potential transformed pathway of TPs and distinguish specific reactions of different catalog of ADs. Samples of fresh feces, compost, biogas slurry, topsoil, column soil, groundwater and plants were analyzed using the database containing 98 target analytes, 679 suspected parent ADs, and ∼ 107 TPs. In total, 29 ADs were quantitively detected, and tetracyclines (TCs) were mostly frequently detected ADs with the concentrations up to 4251 ng/g in topsoil. Soil column investigation revealed that doxycycline (DOX) and tetracycline (TC) in soil could migrate to depths of approximately 1 m in soil. Suspect screening identified 75 parent ADs, with 10 being reported for the first time in environmental media. Semi-quantification of ADs revealed that one of the less-concerned ADs, clinafloxacin, was detected to exceed 5000 ng/L in biogas slurry, suggesting that significant attentions should be paid to these less-concerned ADs. Moreover, 314 TPs was identified, and most of them were found to undergo microbial/enzymatic metabolism pathways. Overall, our study displays a comprehensive overview of ADs and their TPs in swine farming environments, and provides an inventory of crucial list that worthy of concern. The results emphasize the need to quantify the levels and distribution of previously overlooked ADs and their TPs in livestock farms.

Multiresidue method for the determination of critically and highly important classes of antibiotics and their metabolites in agricultural soils and sewage sludge

In this paper, a method is proposed for the determination of antibiotics classified by the World Health Organization as critically important (four macrolides and three quinolones) and highly important (one tetracycline, one diaminopyridine, and three sulfonamides) and eight of their metabolites. The method is based on ultrasound-assisted extraction, dispersive solid-phase extraction clean-up, and analytical determination by liquid chromatography–tandem mass spectrometry. Variables affecting each stage of the analytical method were thoroughly optimised. The method was validated for its application to sewage sludge from different treatment stages (non-treated sludge: primary and secondary sludge; and treated sludge: digested sludge and compost) and to agricultural soil. Limits of quantification were in the range of 0.03–7.50 ng g−1 dry weight (dw) for most of the compounds. Accuracy values were in the range of 70–102%. Precision was below 17%. The application of the method to real samples revealed that macrolides and fluoroquinolones were the antibiotic classes at the highest concentrations in all types of samples. The lowest concentrations of antibiotics were measured in compost (highest concentration: 27 ng g−1 dw, corresponding to norfloxacin) and soil samples (highest concentration: 93 ng g−1 dw, corresponding to a metabolite of clarithromycin). The proposed method is the first developed to date for the determination of multiclass antibiotics and their main metabolites in sludge from different treatment stages. The method can provide a useful tool for obtaining information about antibiotics in sewage sludge prior to its application to agricultural soils and in agricultural soils.Graphical

Determining the extraction conditions and phytotoxicity threshold for compost maturity evaluation using the seed germination index method

The phytotoxicity of the compost aqueous extracts determines the maturity. To improve the accuracy of compost maturity evaluation using the seed germination index (GI) method, different extraction methods (different moisture content and extraction ratio) were designed to obtain samples with various phytotoxic level. This study analyzed the effects of different extraction condition of compost samples on GI, and established the relationship between phytotoxicity and GI. The results showed that the moisture content and extraction ratio of the compost significantly affected the GI. The extraction ratio for the compost with 60–70 % moisture content was 1:10 (ratio of compost mass to extract volume). However, commercial compost, which must have a moisture content of 30–45 %, had an extraction ratio of 1:30 (w:v). More importantly, compost extraction based on dry weight, with a moisture content of 10–15 %, more effectively reflected the phytotoxicity variations during composting. In such cases, the extraction ratio should be at least 1:30 (w:v) but not exceed 1:50 (w:v). The relationship between phytotoxicity and GI showed that dissolved organic carbon and dissolved nitrogen were the most important factors influencing GI, followed by NH4+, electrical conductivity, K, volatile fatty acids, Zn, and Cu. For composts with a GI greater than 70 %, the dissolved organic carbon, dissolved nitrogen, and NH4+ concentrations were below 257, 164, and 73 mg/L, respectively. These findings provide an optimized standard method for compost maturity evaluation using GI and a concentration threshold of key phytotoxicity is proposed to achieve accurate control of compost maturity.

Genomic and metabolomic insights into the antimicrobial compounds and plant growth-promoting potential of Bacillus velezensis Q-426

BackgroundThe Q-426 strain isolated from compost samples has excellent antifungal activities against a variety of plant pathogens. However, the complete genome of Q-426 is still unclear, which limits the potential application of Q-426.ResultsGenome sequencing revealed that Q-426 contains a single circular chromosome 4,086,827 bp in length, with 4691 coding sequences and an average GC content of 46.3%. The Q-426 strain has a high degree of collinearity with B. velezensis FZB42, B. velezensis SQR9, and B. amyloliquefaciens DSM7, and the strain was reidentified as B. velezensis Q-426 based on the homology analysis results. Many genes in the Q-426 genome have plant growth-promoting activity, including the secondary metabolites of lipopeptides. Genome mining revealed 14 clusters and 732 genes encoding secondary metabolites with predicted functions, including the surfactin, iturin, and fengycin families. In addition, twelve lipopeptides (surfactin, iturin and fengycin) were successfully detected from the fermentation broth of B. velezensis Q-426 by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC–QTOF–MS/MS), which is consistent with the genome analysis results. We found that Q-426 produced indole-3-acetic acid (IAA) at 1.56 mg/l on the third day of incubation, which might promote the growth of plants. Moreover, we identified eighteen volatile compounds (VOCs, including 2-heptanone, 6-methylheptan-2-one, 5-methylheptan-2-one, 2-nonanone, 2-decanone, 2-undecanone, 2-dodecanone, 2-tridecanone, 2-tetradecanone, 2-nonadecanone, pentadecanoic acid, oleic acid, dethyl phthalate, dibutyl phthalate, methyl (9E,12E)-octadeca-9,12-dienoate), pentadecane, (6E,10E)-1,2,3,4,4a,5,8,9,12,12a-decahydro-1,4-methanobenzo[10]annulene, and nonanal) based on gas chromatograph-mass spectrometer (GC/MS) results.ConclusionsWe mined secondary metabolite-related genes from the genome based on whole-genome sequence results. Our study laid the theoretical foundation for the development of secondary metabolites and the application of B. velezensis Q-426. Our findings provide insights into the genetic characteristics responsible for the bioactivities and potential application of B. velezensis Q-426 as a plant growth-promoting strain in ecological agriculture.

Comprehensive Evaluation and Development of Irish Compost and Digestate Standards for Heavy Metals, Stability and Phytotoxicity

Recent EU circular economy, bioeconomy policies and the New Green Deal promote the recycling of organic wastes into soil improvers and fertilisers, thereby reducing the use of mineral fertilisers. This has renewed interest in the use of compost and digestate as fertilisers. At the same time, the Russian invasion of Ukraine has strengthened the demand for sustainable domestic fertilisers to guarantee the security of supply. It is now more important than ever that quality standards in Ireland are fit for the purpose of aiding the sustainable local production of fertilisers. Quality standards for compost and digestate ensure and protect the environment. This study collated the results of the analysis of Irish compost and digestate samples and made comparisons of the Irish data to databases, reports and standards from other countries, including the EU Fertiliser Products Regulation 2019/1009. This paper, therefore, provides comprehensive information on heavy metal, stability and phytotoxicity standards from a number of European and other countries. In addition, it includes actual data on these parameters from Ireland and a few European countries. From this collation and comparison process, we propose to update the heavy metals and stability limits in the Irish compost standard (IS 441) and heavy metals and stability limits in a new digestate standard (whole, liquid and fibre). Our methodology and collated data can be used as templates for countries, especially in Europe, which have not developed their own standards. Having an updated compost quality standard supports the development of a circular economy while still respecting the precautionary principle of avoiding pollution when compost and digestate are used on the soil.

Recovery of Agricultural Waste to Obtain Compost

The aim of this study is to make compost in a specialized container, using household and agricultural waste from own farm and the physicochemical characterization of obtained compost. The physicochemical characterization of the compost samples was carried out through the following determinations: determination of moisture, pH, determination of total soluble salts, determination of nitrate nitrogen, determination of nitrite, determination of ammonium nitrogen and determination of organic matter content. The compost samples analysed showed a high physicochemical quality. The use of compost offers environmentally friendly solutions with a long-term impact on the environment and quality of life.&#x0D;

Insights into effects of thermotolerant nitrifying and sulfur-oxidizing inoculants on nitrogen-sulfur co-metabolism in sewage sludge composting

In this study, high temperature thermotolerant nitrifying bacteria (TNB) and high temperature thermotolerant sulfide oxidizing bacteria (TSOB) were obtained from compost samples and inoculated into sewage sludge (SS) compost. The effects of inoculation on physical and chemical parameters, ammonia and hydrogen sulfide release, nitrogen form and sulfur compound content change and physical-chemical properties during nitrogen and sulfur conversion were studied. The results showed that inoculation of TNB and TSOB increased the temperature, pH, OM degradation, C/N ratio and germination index (GI) of compost. Compared with the control treatment (CK), the addition of inoculants reduced the release of NH3 and H2S, and transformed them into nitrogen and sulfur compounds, the hydrolysis of polymeric ferrous sulfate was promoted, resulting in relatively high content of sulfite and sulfate. At the same time, the physical and chemical properties of SS have a strong correlation with nitrogen and sulfur compounds.

Microplastics in waste management systems: A review of analytical methods, challenges and prospects

Numerous studies have reported the presence of microplastics (MPs) in waste collection and disposal systems. However, current scientific studies on measuring MP occurrence in a waste management context are not comparable due to a lack of standardized methodologies. Consequently, the impact of MPs on ecosystems and human health remains largely unclear. To address the inconsistencies, present in published studies, this review thoroughly examines sample preparation techniques for transfer stations, landfill leachate, recycling, compost, and incineration ash samples. Furthermore, various analytical approaches such as flotation, filtration, and organic matter digestion, as well as morphological categorization, identification, and quantification, are subsequently rigorously assessed. The benefits and limitations of each methodology are evaluated to facilitate the development of accurate and effective methods for detecting and characterizing nanoplastics. Recent research suggests that plastic recycling and composting facilities are the primary environmental sources of microplastic pollution among different waste treatment methods. The most prevalent microplastic types discovered in waste management were polyethylene (PE) and polypropylene (PP), with fragment and fiber being the most frequently reported morphologies. The review highlights a number of tactics that could be integrated into the methodology development for detecting microplastics in waste management systems (WMS), ultimately leading to better consistency and reliability of data across different studies. In essence, this will advance our comprehension of potential risks associated with microplastics.

Multitarget and suspect screening of antimicrobials in soil and manure by means of QuEChERS — liquid chromatography tandem mass spectrometry

The present work aimed to develop an accurate analytical method for the simultaneous analysis of twenty-four antimicrobials in soil:compost and animal manure samples by means of ultra-high performance liquid chromatography coupled to a triple-quadrupole mass spectrometer (UHPLC-QqQ). For this purpose, the effectiveness of two extraction techniques (i.e. focused ultrasound solid–liquid extraction (FUSLE) and QuEChERS (quick, easy, cheap, effective, rugged and safe)) was evaluated, and the clean-up step using solid-phase extraction (SPE) was also thoroughly studied. The method was successfully validated at 10 μg·kg−1, 25 μg·kg−1, and 50 μg·kg−1 showing adequate trueness (70–130%) and repeatability (RSD < 30%), with few exceptions. Procedural limits of quantification (LOQPRO) were determined for soil:compost (0.45 to 7.50 μg·kg−1) and manure (0.31 to 5.53 μg·kg−1) samples. Pefloxacin could not be validated at the lowest level since LOQPRO ≥ 10 μg·kg−1. Sulfamethazine (7.9 ± 0.8 µg·kg−1), danofloxacin (27.1 ± 1.4 µg·kg−1) and trimethoprim (4.9 ± 0.5 µg·kg−1) were detected in soil samples; and tetracycline (56.8 ± 2.8 µg·kg−1), among other antimicrobials, in the plants grown on the surface of the studied soil samples. Similarly, sulfonamides (SAs), tetracyclines (TCs) and fluoroquinolones (FQs) were detected in sheep manure in a range of 1.7 ± 0.3 to 93.3 ± 6.8 µg·kg−1. Soil and manure samples were also analysed through UHPLC coupled to a high-resolution mass-spectrometer (UHPLC-qOrbitrap) in order to extend the multitarget method to suspect screening of more than 22,281 suspects. A specific transformation product (TP) of sulfamethazine (formyl-sulfamethazine) was annotated at 2a level in manure samples, among others. This work contributes to the efforts that have been made in the last decade to develop analytical methods that allow multitarget analysis of a wide variety of antimicrobials, including TPs, which is a complex task due to the diverse physicochemical properties of the antimicrobials.

Fast screening of total nutrient contents in strawberry leaves and spent growing media using NIRS.

In closed-loop soilless cultivation, the main nutrient sinks are nutrients retained either by the crop or in spent growing media. Measurement of nutrients in spent growing media and in the aboveground vegetative plant biomass at crop termination can be a tool for assessing and optimizing nutrient efficiency. The first aim of this study was to test the potential of near-infrared reflectance spectroscopy (NIRS) to forecast the various nutrient contents in strawberry leaves, which would then allow for assessment of crop nutrient status and total nutrient uptake by strawberry plants. The second aim was to test NIRS as a high throughput technique for assessing the N, K, Ca, Mg and organic matter (OM) content and the pH, EC and C:N and C:P ratios for a dataset of composts, plant fibers and spent growing media. The NIRS prediction model for fast screening of the total nutrient contents in spent growing media was compared with a single extraction method. A database with 369 dried and ground strawberry leaf samples with known contents of N, P, K, Ca, and Mg were scanned using NIRS. The database covered a range of leaf contents of 6-35 g N/kg dry matter (DM), 0.7-6.3 g P/kg DM and 2-29 g K/kg DM. A dataset of 458 samples of different types of materials used in growing media was validated with a dataset of 109 samples. Validation for the strawberry leaves indicated potential for this application, with R2 values of 0.90 or higher for N, K and Ca, and R2 values higher than 0.85 for P and Mg. Validation for the dataset of composts, plant fibers and spent growing media also indicated the potential for this application, with R2 values of 0.90 or higher for organic matter, and with R2 values of 0.85 or higher for total Ca, pH and C:N. A first test indicated potential for the calibration based on fresh samples of compost, plant fiber as well as spent growing media or dried (not ground) samples. Use of NIRS on fresh samples would eliminate the need for drying and grinding the samples and would reduce screening time. The ammonium acetate extraction is a reliable alternative to NIRS for fast screening of the total P, K, Ca, and Mg contents in composts, plant fibers and spent growing media.

Functional and sequence-based metagenomics to uncover carbohydrate-degrading enzymes from composting samples

The renewable, abundant, and low-cost nature of lignocellulosic biomass can play an important role in the sustainable production of bioenergy and several added-value bioproducts, thus providing alternative solutions to counteract the global energetic and industrial demands. The efficient conversion of lignocellulosic biomass greatly relies on the catalytic activity of carbohydrate-active enzymes (CAZymes). Finding novel and robust biocatalysts, capable of being active under harsh industrial conditions, is thus imperative to achieve an economically feasible process. In this study, thermophilic compost samples from three Portuguese companies were collected, and their metagenomic DNA was extracted and sequenced through shotgun sequencing. A novel multi-step bioinformatic pipeline was developed to find CAZymes and characterize the taxonomic and functional profiles of the microbial communities, using both reads and metagenome-assembled genomes (MAGs) as input. The samples’ microbiome was dominated by bacteria, where the classes Gammaproteobacteria, Alphaproteobacteria, and Balneolia stood out for their higher abundance, indicating that the degradation of compost biomass is mainly driven by bacterial enzymatic activity. Furthermore, the functional studies revealed that our samples are a rich reservoir of glycoside hydrolases (GH), particularly of GH5 and GH9 cellulases, and GH3 oligosaccharide-degrading enzymes. We further constructed metagenomic fosmid libraries with the compost DNA and demonstrated that a great number of clones exhibited β-glucosidase activity. The comparison of our samples with others from the literature showed that, independently of the composition and process conditions, composting is an excellent source of lignocellulose-degrading enzymes. To the best of our knowledge, this is the first comparative study on the CAZyme abundance and taxonomic/functional profiles of Portuguese compost samples.Key points• Sequence- and function-based metagenomics were used to find CAZymes in compost samples.• Thermophilic composts proved to be rich in bacterial GH3, GH5, and GH9 enzymes.• Compost-derived fosmid libraries are enriched in clones with β-glucosidase activity.