Active microbial communities during biodegradation of biodegradable plastics by mesophilic and thermophilic anaerobic digestion

Analyzing performance and microbial mechanisms in an incineration leachate treatment after waste separation: Integrated metagenomic and metaproteomic analyses

The absence of food waste after separation poses a significant challenge to incineration leachate treatment, as it decreases the C/N ratio and COD of leachate, greatly impacting the biological treatment process. A one-year in-situ study was systematically conducted in an incineration leachate treatment plant that experienced waste separation, focusing on the variations in carbon and nitrogen removal performance as well as the involved microbial mechanism of the "anaerobic digestion (AD) + two-stage A/O" process. Results indicated that the biodegradability of leachate significantly decreased over time, with COD concentration decreasing by 10 times and the average C/N ratio decreasing from 12.3 to 1.4. The AD process was maintained stable, achieving a COD removal efficiency exceeding 92 %. The nitrification process also remained stable; while the denitrification process was significantly affected, and a nine-fold increase in external glucose addition was required to achieve a nitrogen removal efficiency of 85 %. Metagenomic analysis indicated that comammox Nitrospira (contributing 90 % to ammonia monooxygenase) occupied the dominant position over Nitrosomonas for nitrification due to the low NH4+-N concentration in A/O tanks (<35 mg/L), and Methanothrix was substituted by Methanosarcina for methanogenesis in AD unit. Metaproteomic results further elucidated that the expression of enzymes responsible for denitrification process, i.e., Nir, Nor, Nos (convert NO2- to N2), was decreased significantly, although the expression of enzymes related to glycolysis and TCA cycle were stimulated by glucose addition. The expression of Nar (convert NO3--N to NO2--N) remained stable, while the imbalance expression within denitrifying enzymes might have facilitated occurrence of partial denitrification, attributed to the low C/N ratio. The results prove that the function robustness and metabolic versatility were achieved in leachate treatment plant after waste separation but at the cost of the high external carbon resource addition, highlighting the urgent requirement for low-carbon nitrogen removal technologies.

Programming aliphatic polyester degradation by engineered bacterial spores

Enzymatic degradation of plastics is a sustainable approach to addressing the growing issue of plastic accumulation. The primary challenges for using enzymes as catalysts are issues with their stability and recyclability, further exacerbated by their costly production and delicate structures. Here, we demonstrate an approach that leverages engineered spores that display target enzymes in high density on their surface to catalyze aliphatic polyester degradation and create self-degradable materials. Engineered spores display recombinant enzymes on their surface, eliminating the need for costly purification processes. The intrinsic physical and biological characteristics of spores enable easy separation from the reaction mixture, repeated reuse, and renewal. Engineered spores displaying lipases completely degrade aliphatic polyesters and retain activity through four cycles, with full activity recovered through germination and sporulation. Directly incorporating spores into polyesters results in robust materials that are completely degradable. Our study offers a straightforward and sustainable biocatalytic approach to plastic degradation.

Alkali, thermal, or thermo-alkali pre-treatment to improve the anaerobic digestion of poly(lactic acid)?

Replacing petroleum-based plastics with biodegradable polymers is a major challenge for modern society especially for food packaging applications. To date, poly(lactic acid) represents 25 % of the total biodegradable plastics and it is estimated that, in the future, it could become the main contributor to the biodegradable plastics industry. Anaerobic digestion is an interesting way for the poly(lactic acid) end of life, even if its biodegradability is limited in mesophilic conditions. The aims of this study were to identify the best pre-treatment for maximizing the methane yield, minimizing the anaerobic digestion duration and limiting residual plastic fragments in the digestate. A systematic comparison was carried out between thermal, chemical, and thermo-chemical pre-treatment. Pre-treatment with 4 M KOH for 48 h at 35°C was effective in improving the mesophilic anaerobic digestion of the poly(lactic acid). Such pre-treatment allows obtaining 90 % of the theoretical methane potential, in 24 - 30 days. Importantly, such pre-treatment completely solubilized the poly(lactic acid), leaving no solid residues in the digestate. In addition, using KOH permits to avoid the sodication of the soil due to the digestate application as fertilizer.

Carbon Recycling of High Value Bioplastics: A Route to a Zero-Waste Future

Today, 98% of all plastics are fossil-based and non-biodegradable, and globally, only 9% are recycled. Microplastic and nanoplastic pollution is just beginning to be understood. As the global demand for sustainable alternatives to conventional plastics continues to rise, biobased and biodegradable plastics have emerged as a promising solution. This review article delves into the pivotal concept of carbon recycling as a pathway towards achieving a zero-waste future through the production and utilization of high-value bioplastics. The review comprehensively explores the current state of bioplastics (biobased and/or biodegradable materials), emphasizing the importance of carbon-neutral and circular approaches in their lifecycle. Today, bioplastics are chiefly used in low-value applications, such as packaging and single-use items. This article sheds light on value-added applications, like longer-lasting components and products, and demanding properties, for which bioplastics are increasingly being deployed. Based on the waste hierarchy paradigm-reduce, reuse, recycle-different use cases and end-of-life scenarios for materials will be described, including technological options for recycling, from mechanical to chemical methods. A special emphasis on common bioplastics-TPS, PLA, PHAs-as well as a discussion of composites, is provided. While it is acknowledged that the current plastics (waste) crisis stems largely from mismanagement, it needs to be stated that a radical solution must come from the core material side, including the intrinsic properties of the polymers and their formulations. The manner in which the cascaded use of bioplastics, labeling, legislation, recycling technologies, and consumer awareness can contribute to a zero-waste future for plastics is the core topics of this article.

Characterization of Ralstonia insidiosa C1 isolated from Alpine regions: Capability in polyhydroxyalkanoates degradation and production

This study ventures into the exploration of potential poly-3-hydroxybutyrate (PHB) degradation in alpine environments. PHB-degrading bacteria were identified in both campus soil, representing a residential area, and Mt. Kurodake soil, an alpine region in Hokkaido, Japan. Next-generation sequencing analysis indicated that the campus soil exhibited higher microbial diversity, while Ralstonia insidiosa C1, isolated from Mt. Kurodake soil, displayed the highest proficiency in PHB degradation. R. insidiosa C1 efficiently degraded up to 3% (w/v) of PHB and various films composed of other biopolymers at 14 °C. This bacterium synthesized homopolymers using substrates such as 3-hydroxybutyric acid, sugars, and acetic acid, while also produced copolymers using a mixture of fatty acids. The analysis results confirmed that the biopolymer synthesized by strain C1 using glucose was PHB, with physical properties comparable to commercial products. The unique capabilities of R. insidiosa C1, encompassing both the production and degradation of bioplastics, highlight its potential to establish a novel material circulation model.

From waste to protein: a new strategy of converting composted distilled grain wastes into animal feed

Distilled grain waste (DGW) is rich in nutrients and can be a potential resource as animal feed. However, DGW contains as much as 14% lignin, dramatically reducing the feeding value. White-rot fungi such as Pleurotus ostreatus could preferentially degrade lignin with high efficiency. However, lignin derivatives generated during alcohol distillation inhibit P. ostreatus growth. Thus, finding a new strategy to adjust the DGW properties to facilitate P. ostreatus growth is critical for animal feed preparation and DGW recycling. In this study, three dominant indigenous bacteria, including Sphingobacterium thermophilum X1, Pseudoxanthomonas byssovorax X3, and Bacillus velezensis 15F were chosen to generate single and compound microbial inoculums for DGW composting to prepare substrates for P. ostreatus growth. Compared with non-inoculated control or single microbial inoculation, all composite inoculations, especially the three-microbial compound, led to faster organic metabolism, shorter composting process, and improved physicochemical properties of DGW. P. ostreatus growth assays showed the fastest mycelial colonization (20.43 μg·g-1 ergosterol) and extension (9 mm/d), the highest ligninolytic enzyme activities (Lac, 152.68 U·g-1; Lip, 15.56 U·g-1; MnP, 0.34 U·g-1; Xylanase, 10.98 U·g-1; FPase, 0.71 U·g-1), and the highest lignin degradation ratio (30.77%) in the DGW sample after 12 h of composting with the three-microbial compound inoculation when compared to other groups. This sample was relatively abundant in bacteria playing critical roles in amino acid, carbohydrate, energy metabolism, and xenobiotic biodegradation, as suggested by metagenomic analysis. The feed value analysis revealed that P. ostreatus mycelia full colonization in composted DGW led to high fiber content retention and decreased lignin content (final ratio of 5% lignin) but elevated protein concentrations (about 130 g·kg-1 DM). An additional daily weight gain of 0.4 kg/d was shown in cattle feeding experiments by replacing 60% of regular feed with it. These findings demonstrate that compound inoculant consisting of three indigenous microorganisms is efficient to compost DGW and facilitate P. ostreatus growth. P. ostreatus decreased the lignin content of composted DGW during its mycelial growth, improving the quality of DGW for feeding cattle.

Exploring the hidden environmental pollution of microplastics derived from bioplastics: A review

Bioplastics might be an ecofriendly alternative to traditional plastics. However, recent studies have emphasized that even bioplastics can end up becoming micro- and nano-plastics due to their degradation under ambient environmental conditions. Hence, there is an urgent need to assess the hidden environmental pollution caused by bioplastics. However, little is known about the evolutionary trends of bibliographic data, degradation pathways, formation, and toxicity of micro- and nano-scaled bioplastics originating from biodegradable polymers such as polylactic acid, polyhydroxyalkanoates, and starch-based plastics. Therefore, the prime objective of the current review was to investigate evolutionary trends and the latest advancements in the field of micro-bioplastic pollution. Additionally, it aims to confront the limitations of existing research on microplastic pollution derived from the degradation of bioplastic wastes, and to understand what is needed in future research. The literature survey revealed that research focusing on micro- and nano-bioplastics has begun since 2012. This review identifies novel insights into microbioplastics formation through diverse degradation pathways, including photo-oxidation, ozone-induced degradation, mechanochemical degradation, biodegradation, thermal, and catalytic degradation. Critical research gaps are identified, including defining optimal environmental conditions for complete degradation of diverse bioplastics, exploring micro- and nano-bioplastics formation in natural environments, investigating the global occurrence and distribution of these particles in diverse ecosystems, assessing toxic substances released during bioplastics degradation, and bridging the disparity between laboratory studies and real-world applications. By identifying new trends and knowledge gaps, this study lays the groundwork for future investigations and sustainable solutions in the realm of sustainable management of bioplastic wastes.

Comparison of anaerobic digestion of starch- and petro-based bioplastic under hydrogen-rich conditions

To identify an economically viable waste management system for bioplastics, thermoplastic starch (TPS) and poly(butylene adipate-co-terephthalate) (PBAT) were anaerobically digested under hydrogen (H2)/carbon dioxide (CO2) and nitrogen (N2) gas-purged conditions to compare methane (CH4) production and biodegradation. Regardless of the type of bioplastics, CH4 production was consistently higher with H2/CO2 than with N2. The highest amount of CH4 was produced at 307.74 mL CH4/g volatile solids when TPS digested with H2/CO2. A stepwise increased in CH4 yield was observed, with a nominal initial increment followed by accelerated methanogenesis conversion as H2 was depleted. This may be attributed to a substantial shift in the microbial structure from hydrogenotrophic methanogen (Methanobacteriales and Methanomicrobiales) to heterotrophs (Spirochaetia). In contrast, no significant change was observed with PBAT, regardless of the type of purged gas. TPS was broken down into numerous derivatives, including volatile fatty acids. TPS produced more byproducts with H2/CO2 (i.e., 430) than with N2 (i.e., 320). In contrast, differential scanning calorimetry analysis on PBAT revealed an increase in crystallinity from 10.20 % to 12.31 % and 11.36 % in the H2/CO2- and N2-purged conditions, respectively, after 65 days of testing. PBAT surface modifications were characterized via Fourier transform infrared spectroscopy and scanning electron microscopy. The results suggest that the addition of H2/CO2 can enhance the CH4 yield and increase the breakdown rate of TPS more than that of PBAT. This study provides novel insights into the CH4 production potential of two bioplastics with different biodegradabilities in H2/CO2-mediated anaerobic digestion systems.

Self-assembled B-doped flower-like graphitic carbon nitride with high specific surface area for enhanced photocatalytic performance

Graphitic carbon nitride (g-C3N4) is a promising nonmetallic photocatalyst. In this manuscript, B-doped 3D flower-like g-C3N4 mesoporous nanospheres (BMNS) were successfully prepared by self-assembly method. The doping of B element promotes the internal growth of hollow flower-like g-C3N4 without changing the surface roughness structure, resulting in a porous floc structure, which enhances the light absorption and light reflection ability, thereby improving the light utilization rate. In addition, B element provides lower band gap, which stimulates the carrier movement and increases the activity of photogenerated carriers. The photocatalytic mechanism and process of BMNS were investigated in depth by structural characterization and performance testing. BMNS-10 % shows good degradation for four different pollutants, among which the degradation effect on Rhodamine B (RhB) reaches 97 % in 30 min. The apparent rate constant of RhB degradation by BMNS-10 % is 0.125 min-1, which is 46 times faster compared to bulk g-C3N4 (BCN). And the photocatalyst also exhibits excellent H2O2 production rate under visible light. Under λ > 420 nm, the H2O2 yield of BMNS-10 % (779.9 μM) in 1 h is 15.9 times higher than that of BCN (48.98 μM). Finally, the photocatalytic mechanism is proposed from the results of free radical trapping experiments.

Influences of straw alkaline pretreatment on biogas production and digestate characteristics: artificial neural network and multivariate statistical techniques

Anaerobic digestion is one of the best options for producing valuable end products (biogas and biofertilizer). The aim of this study was to investigate the influences of thermoalkaline pretreatment of wheat straw on biogas production and digestate characteristics from codigestion with waste-activated sludge. Different alkaline conditions (NaOH, KOH and Na2CO3) and pretreatment durations (1, 3 and 5 h) were used for straw pretreatment. Batch anaerobic codigestion of sludge and pretreated straw was conducted under different pretreatment conditions. A feedforward neural network (FFNN) model, logistic model and statistical analysis were applied to the experimental data to predict biogas and investigate the significance and relationships among the variables. NaOH pretreatment for 5 h showed the best treatment conditions: biogas yield was 6.59 times higher than that without treatment. Moreover, the proportions of total solids, total volatile solids, chemical oxygen demand and microbial count removed reached 63.52%, 74.60%, 78.15% and 82.22%, respectively. The methane content was 67.50%, indicating that the biogas had a high quality. The thermoalkaline pretreatment significantly affected biogas production and digestate characteristics, allowing it to be used as a biofertilizer. Experimental data were successfully modelled for predicting biogas production using the applied models. The R2 values reached 0.985 and 0.999 for the logistic and FFNN models, respectively.

Feasibility of anaerobic co-digestion of biodegradable plastics with food waste, investigation of microbial diversity and digestate phytotoxicity

The effects of biodegradable plastics of different thicknesses (30 and 40 μm) and sizes (20 × 20, 2 × 2, and 1 × 1 mm) on anaerobic digestion of food waste and digestate phytotoxicity were investigated. Methane productions (38 days) for the groups with 20 × 20, 2 × 2, and 1 × 1 mm of 30 μm plastics were 92.46, 138.27, and 259.95 mL/gVSremoval, respectively which are nearly 58 % higher than the control group (58.86 mL/gVSremoval). Methane production in 40 μm plastics groups was lower than in 30 μm groups of equal size. All sizes of 30 µm plastics promoted substrate hydrolysis, acidification, and relative abundance of key hydrolytic bacteria and methanogens. Phytotoxicity tests results showed that seed root elongation was inhibited in groups with 40 μm plastics. In conclusion, 30 μm biodegradable plastics were more suitable for anaerobic digestion with food waste than 40 μm.

A hot topic: thermophilic plastic biodegradation

Biological degradation of plastic waste is an environmentally and economically friendlier alternative to current recycling practices and enables the cycling of plastic monomers back into virgin-quality plastics. However, due to slow reaction rates, there is a lack of an industrially viable biodegradation strategy for most plastics. Here, we highlight the applicability of a thermophilic biodegradation strategy over a mesophilic approach, to enhance enzyme accessibility and catalyze plastic biodegradation. Thus, at reactions closer to the melting temperature or glass transition temperature of plastics, thermophilic reactions can offer an alternative direction to conventional plastic biodegradation strategies.

Assessing labelled carbon assimilation from poly butylene adipate-co-terephthalate (PBAT) monomers during thermophilic anaerobic digestion

PBAT (poly butylene adipate-co-terephthalate) is a widely used biodegradable plastic, but the knowledge about its metabolization in anaerobic environments is very limited. In this study, the anaerobic digester sludge from a municipal wastewater treatment plant was used as inoculum to investigate the biodegradability of PBAT monomers in thermophilic conditions. The research employs a combination of ¹³C-labelled monomers and proteogenomics to track the labelled carbon and identify the microorganisms involved. A total of 122 labelled peptides of interest were identified for adipic acid (AA) and 1,4-butanedio (BD). Through the time-dependent isotopic enrichment and isotopic profile distributions, Bacteroides, Ichthyobacterium, and Methanosarcina were proven to be directly involved in the metabolization of at least one monomer. This study provides a first insight into the identity and genomic potential of microorganisms responsible for biodegradability of PBAT monomers during anaerobic digestion under thermophilic conditions.

Exploring the Influence of Growth-Associated Host Genetics on the Initial Gut Microbiota in Horses

The influences of diet and environmental factors on gut microbial profiles have been widely acknowledged; however, the specific roles of host genetics remain uncertain. To unravel host genetic effects, we raised 47 Jeju crossbred (Jeju × Thoroughbred) foals that exhibited higher genetic diversity. Foals were raised under identical environmental conditions and diets. Microbial composition revealed that Firmicutes, Bacteroidetes, and Spirochaetes were the predominant phyla. We identified 31 host-microbiome associations by utilizing 47,668 single nucleotide polymorphisms (SNPs) and 734 taxa with quantitative trait locus (QTL) information related to horse growth. The taxa involved in 31 host-microbiome associations were functionally linked to carbohydrate metabolism, energy metabolic processes, short-chain fatty acid (SCFA) production, and lactic acid production. Abundances of these taxa were affected by specific SNP genotypes. Most growth-associated SNPs are found between genes. The rs69057439 and rs69127732 SNPs are located within the introns of the VWA8 and MFSD6 genes, respectively. These genes are known to affect energy balance and metabolism. These discoveries emphasize the significant effect of host SNPs on the development of the intestinal microbiome during the initial phases of life and provide insights into the influence of gut microbial composition on horse growth.

Anaerobic biodegradation of disposable PLA-based products: Assessing the correlation with physical, chemical and microstructural properties

In the present study commercial Polylactic Acid-based disposable cups and plates were selected for lab scale anaerobic degradability tests. The experiments were carried out under thermophilic conditions at different inoculum to substrate ratios and test material sizes, and the specific biogas production and associated kinetics were evaluated. Maximum biogas production was comparable for almost all the experimental runs (1620 and 1830 NmL/gTOC_PLA) and a biodegradation degree in the range 86-100% was attained. Moreover, physical, chemical and microscopical analyses were used to characterize the tested materials before and after the degradation. The products composition was assessed and the presence of some additives (mainly Ca-based) was detected. Potential correlations among the process parameters and product composition were derived and a delay in process kinetics with increasing amount of additives embedded in the polymeric matrix was observed, confirming the relevant influence of the chemical blend on the biodegradation process.

Conductive materials enhance microbial salt-tolerance in anaerobic digestion of food waste: Microbial response and metagenomics analysis

Previous studies have shown that high salinity environments can inhibit anaerobic digestion (AD) of food waste (FW). Finding ways to alleviate salt inhibition is important for the disposal of the growing amount of FW. We selected three common conductive materials (powdered activated carbon, magnetite, and graphite) to understand their performance and individual mechanisms that relieve salinity inhibition. Digester performances and related enzyme parameters were compared. Our data revealed that under normal and low salinity stress conditions, the anaerobic digester ran steady without significant inhibitions. Further, the presence of conductive materials promoted conversion rate of methanogenesis. This promotion effect was highest from magnetite > powdered activated carbon (PAC) > graphite. At 1.5% salinity, PAC and magnetite are beneficial in maintaining high methane production efficiency while control and the graphite added digester acidified and failed rapidly. Additionally, metagenomics and binning were used to analyze the metabolic capacity of the microorganisms. Some species enriched by PAC and magnetite possessed higher cation transport capacities and were to accumulate compatible solutes. PAC and magnetite promoted direct interspecies electron transference (DIET) and syntrophic oxidation of butyrate and propionate. Also, the microorganisms had more energy available to cope with salt inhibition in the PAC and magnetite added digesters. Our data imply that the promotion of Na+/H+ antiporter, K+ uptake, and osmoprotectant synthesis or transport by conductive materials may be crucial for their proliferation in highly stressful environments. These findings will help to understand the mechanisms of alleviate salt inhibition by conductive materials and help to recover methane from high-salinity FW.

Enhancement of biogas production rate from bioplastics by alkaline pretreatment

The effect of alkali-based pretreatment on the methanization of bioplastics was investigated. The tested bioplastics included PHB [poly(3-hydroxybutyrate)], PHBH [poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)], PHBV [poly(3-hydroxybutyrate-co-3-hydroxyvalerate], PLA (polylactic acid), and a PLA/PCL [poly(caprolactone)] 80/20 blend. Prior to methanization tests, the powdered polymers (500-1000 μm) at a concentration of 50 g/L were subjected to alkaline pretreatment using NaOH 1 M for PLA and PLA/PCL, and NaOH 2 M for PHB-based materials. Following 7 days of pretreatment, the amount of solubilized carbon for PLA and its blend accounted for 92-98% of the total initial carbon, while lower carbon recoveries were recorded for most PHB-based materials (80-93%), as revealed by dissolved total organic carbon analysis. The pretreated bioplastics were then tested for biogas production by means of mesophilic biochemical methane potential tests. Compared to unpretreated PHBs, methanization rates of pretreated PHBs were accelerated by a factor of 2.7 to 9.1 with comparable (430 NmL CH₄/g material feed) or slightly lower (15% in the case of PHBH) methane yields, despite featuring a 1.4-2.3 times longer lag phases. Both materials, PLA and the PLA/PCL blend, were only extensively digested when pretreated, yielding about 360-380 NmL CH₄ per gram of material fed. Unpretreated PLA-based materials showed nearly zero methanization under the timeframe and experimental conditions tested. Overall, the results suggested that alkaline pretreatment can help to enhance the methanization kinetics of bioplastics.

Differential effects of petroleum-based and bio-based microplastics on anaerobic digestion: A review

The number of plastics is increasing owing to the rapid development of the plastics industry. Microplastics (MPs) are formed during the use of both petroleum-based plastics and newly developed bio-based plastics. These MPs are inevitably released into the environment and are enriched in wastewater treatment plant sludge. Anaerobic digestion is a popular sludge stabilization method for wastewater treatment plants. Understanding the potential impacts of different MPs on anaerobic digestion is critical. This paper provides a comprehensive review of the mechanisms of petroleum-based MPs and bio-based MPs in anaerobic digestion methane production and compares their potential effects on biochemical pathways, key enzyme activities, and microbial communities. Finally, it identifies problems that must be solved in the future, proposes the focus of future research, and predicts the future development direction of the plastics industry.

Antibiotic resistance genes proliferation under anaerobic degradation of polylactic acid and polyhydroxy butyrate bioplastics

As the global concern over plastic pollution grows, efforts are underway to find environmentally friendly alternatives to traditional plastics. Bioplastics are being extensively researched and developed as a possible solution. This study compared the impact of two bioplastics, polylactic acid (PLA) and polyhydroxy butyrate (PHB), on the proliferation of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) during anaerobic digestion (AD). Both bioplastics (250-500 particles) could be degraded to a certain extent over 79 days, as indicated by higher methane production than the control without bioplastic particles. The PHB 500 reactor showed the highest methane yield along with the highest biodegradation efficiency (91 %) than other reactors amended with PHB and PLA particles. The highest ARG and MGE abundances were also observed in PLA 500, and the lowest ARG abundance was in PLA 250. Conversely, PHB reactors showed a relatively lower ARG abundance than the control. The correlation analysis suggested that most ARGs were positively correlated with PLA and negatively correlated with PHB (except for tetA, tetB, and tetX). Moreover, a correlation between MGEs and ARGs in PLA and PHB reactors was revealed by correlation analysis. These results show that AD responds differently to the different types/levels of bioplastics, which can ultimately influence the behavior of ARG proliferation. Thus, bioplastics may also pose a potential risk for spreading antibiotic resistance. These findings can be used as a basis for setting environmental standards for bioplastics and creating monitoring and control measures to prevent potential negative impacts on public health.

Anaerobic Biodegradability of Commercial Bioplastic Products: Systematic Bibliographic Analysis and Critical Assessment of the Latest Advances

Bioplastics have entered everyday life as a potential sustainable substitute for commodity plastics. However, still further progress should be made to clarify their degradation behavior under controlled and uncontrolled conditions. The wide array of biopolymers and commercial blends available make predicting the biodegradation degree and kinetics quite a complex issue that requires specific knowledge of the multiple factors affecting the degradation process. This paper summarizes the main scientific literature on anaerobic digestion of biodegradable plastics through a general bibliographic analysis and a more detailed discussion of specific results from relevant experimental studies. The critical analysis of literature data initially included 275 scientific references, which were then screened for duplication/pertinence/relevance. The screened references were analyzed to derive some general features of the research profile, trends, and evolution in the field of anaerobic biodegradation of bioplastics. The second stage of the analysis involved extracting detailed results about bioplastic degradability under anaerobic conditions by screening analytical and performance data on biodegradation performance for different types of bioplastic products and different anaerobic biodegradation conditions, with a particular emphasis on the most recent data. A critical overview of existing biopolymers is presented, along with their properties and degradation mechanisms and the operating parameters influencing/enhancing the degradation process under anaerobic conditions.