Effects of storage of a mature compost on its potential for biodegradation of plastics

Study on the properties of composite superabsorbent resin doped with starch and cellulose

In order to reduce the damage to soil caused by degradation residues in the application of superabsorbent resin (SAR), the primary target of this study was to improve its biodegradability by doping with starch and cellulose. After that, the water absorption performance of composite SAR doped with starch and cellulose was improved as much as possible by changing the formulation when the biodegradability changed in a narrow range. The degradation percentage in soil and compost after 60 days is much higher than that of the SAR without doping which is 8.42 and 14.17%, but the performance for water absorption depends on the type of starch that was used. Experiments showed that the presence of amylopectin in starch contributes significantly to the performance for water absorption of composite SAR. The more amylopectin content, the better performance for water absorption, but the specific relationship between the degradability and the amylopectin content has not to be proven. Finally, the best mass ratio of starch, cellulose, and acrylic was 4.2:1.8:65, which was determined via the experiments. A kind of composite SAR doped with starch and cellulose with excellent performance was obtained.

Functional interplay between plastic polymers and microbes: a comprehensive review

Escalated production of plastic, their worldwide distribution and persistent nature finally results into their environmental accumulation causing severe threats to the ecological environment and biotic health. Thus, development of suitable measurements for environmental remediation of plastic may be an urgent issue in this plastic age. Some recent reviews have categorized the microbial species able to degrade different plastic polymers and the different factors effecting bio-degradation of plastic are poorly understood. This review comprehensively discusses bio-degradation of traditional and biodegradable plastic polymers both in natural and biological environment (gut microbes and fungi) to understand different factors regulating their degradation, and also shows how degradation of plastic polymers under abiotic factors influence subsequent biological degradation. Different physicochemical modifications like - breaking large polymers into small fragments by pre-treatment, functional groups enrichment, identifying potent microbial species (consortia) and engineering microbial enzymes might be crucial for bio-degradations of plastic. Effects of micro/nanoplastic and other chemical intermediates, formed during the bio-degradation of plastic, on species composition, abundance, growth, metabolism and enzymatic systems of microbes involved in the bio-degradation of plastic should be determined in future research.

Biodegradability standards for carrier bags and plastic films in aquatic environments: a critical review

Plastic litter is encountered in aquatic ecosystems across the globe, including polar environments and the deep sea. To mitigate the adverse societal and ecological impacts of this waste, there has been debate on whether 'biodegradable' materials should be granted exemptions from plastic bag bans and levies. However, great care must be exercised when attempting to define this term, due to the broad and complex range of physical and chemical conditions encountered within natural ecosystems. Here, we review existing international industry standards and regional test methods for evaluating the biodegradability of plastics within aquatic environments (wastewater, unmanaged freshwater and marine habitats). We argue that current standards and test methods are insufficient in their ability to realistically predict the biodegradability of carrier bags in these environments, due to several shortcomings in experimental procedures and a paucity of information in the scientific literature. Moreover, existing biodegradability standards and test methods for aquatic environments do not involve toxicity testing or account for the potentially adverse ecological impacts of carrier bags, plastic additives, polymer degradation products or small (microscopic) plastic particles that can arise via fragmentation. Successfully addressing these knowledge gaps is a key requirement for developing new biodegradability standard(s) for lightweight carrier bags.

Investigating microbial activities during a starch-amended co-composting process at mesophilic and thermophilic temperatures

The aim of this study was to assess the use of functional microbial ecological techniques in detailing processes during composting. Using starch as an amendment for a co-composting process, small-scale individual mesocosms were investigated at two temperatures, 30 degrees C and 60 degrees C, over a five-week period. In order to determine the more exact processes occurring during degradation, extracellular enzyme analysis (EEA) and community-level physiological profiling (CLPP) were used. The EEA demonstrated that, although assay temperature effects were present, no significant difference between the two in situ composting temperatures was observed for the two enzyme substrates, alpha- and beta-glucosidase, used. The CLPP profiling was only performed on the 30 degrees C compost samples. These analyses indicated a dynamic, but broadly predictable, environment, suggesting that the use of this approach may be further applicable to these types of study. By investigating both total dry and organic weights, no difference in organic matter degradation between the two temperatures was observed. These results showed that either starch degradation acted independently of temperature or compensatory effects occurred. The former hypothesis was supported by a second experiment investigating starch degradation at both temperatures with appropriate negative controls. Trying to reconcile the EEA results with the changes in total matter was difficult without making speculative assumptions. The study highlights the need to further develop and evaluate these microbial ecological techniques to address such problems.