Browsing by Subject "Biodegradation"

Now showing 1 - 2 of 2

Bioplastics for food packaging: Environmental impact, trends and regulatory aspects
(2022) Cruz, Rui M. S.; Krauter, Victoria; Krauter, Simon; Agriopoulou, Sofia; Weinrich, Ramona; Herbes, Carsten; Scholten, Philip B. V.; Uysal-Unalan, Ilke; Sogut, Ece; Kopacic, Samir; Lahti, Johanna; Rutkaite, Ramune; Varzakas, Theodoros
The demand to develop and produce eco-friendly alternatives for food packaging is increasing. The huge negative impact that the disposal of so-called “single-use plastics” has on the environment is propelling the market to search for new solutions, and requires initiatives to drive faster responses from the scientific community, the industry, and governmental bodies for the adoption and implementation of new materials. Bioplastics are an alternative group of materials that are partly or entirely produced from renewable sources. Some bioplastics are biodegradable or even compostable under the right conditions. This review presents the different properties of these materials, mechanisms of biodegradation, and their environmental impact, but also presents a holistic overview of the most important bioplastics available in the market and their potential application for food packaging, consumer perception of the bioplastics, regulatory aspects, and future challenges.
Microplastics interactions with soil organisms
(2022) Schöpfer, Lion; Kandeler, Ellen
Microplastics (MP) are plastic particles from 100 nm to 5 mm with different shapes and chemical compositions. In aquatic ecosystems, MP have proven to affect the biological fitness of aquatic organisms, enter the food web, and act as vectors of pollutants. Agricultural soils are sinks for MP due to inputs via sewage sludges, plastic mulches, and organic fertilizers. However, ecological consequences of MP in agricultural soils are unknown. This doctoral thesis aimed to evaluate the risk of conventional and biodegradable MP for soil organisms in agricultural soils. A microcosm study was combined with a field study and a nematode study to investigate background concentrations, the persistence, and the biodegradation of MP in the soil, and effects of MP on soil microorganisms and nematodes. In the microcosm study, the influence of plastic type, particle size, and soil moisture on the biodegradation of MP in the soil and on effects on soil microorganisms were examined under controlled conditions (25 °C, 230 days). The abundance and composition of the main soil microbial groups was analyzed via phospholipid fatty acids (PLFAs) as biomarkers; activities of C cycling enzymes driving the decomposition of differently complex substances were analyzed as proxies for C turnover. To understand better the role of MP as an interface for specific microbial processes in the soil, e.g. the enzymatic hydrolysis of MP, enzyme activities of individual MP particles extracted from the soil were measured. The site of the field study was a conventionally managed agricultural soil (silt-loam Luvisol) of the Heidfeldhof, University of Hohenheim. No practices associated with significant inputs of MP have been conducted at the site in the past (sewage sludge, organic fertilizers, plastic mulch). In a randomized complete block design, the effects of MP, organic fertilizers (digestate and compost), and their interactions on soil microbiological indicators (microbial biomass, soil enzymes) were studied. Before the setup of the field study, MP background concentrations (particle-based) in the soil were analyzed. The persistence of added MP in the soil was evaluated by comparing MP concentrations in the soil after 1 month and 17 months with initial MP concentrations after addition. In the nematode study, the soil-dwelling nematode Caenorhabditis elegans was exposed to MP feed suspensions on agar plates. The uptake of MP through nematodes and the influence of plastic type and concentration on MP effects on nematode reproduction and body length were examined. In all studies, artificially fragmented MP from a conventional polymer (low-density polyethylene, LDPE) and a biodegradable polymer blend (poly(lactic acid) and poly(butylene adipate-co-terephtalate), PLA/PBAT) were used. The occurrence of both LDPE- and PLA/PBAT-MP is likely in agricultural soils because these are used for plastic mulches and compost bags. Results from this thesis suggest that (1) agricultural soils, including those without management practices related to significant MP entry, contain various MP, indicating diffuse MP inputs via atmospheric deposition, littering, and the abrasion of machinery coatings (a possible newly identified pathway), (2) also biodegradable MP persist and are slowly biodegraded in the soil implying a long term exposure risk for soil organisms to MP, (3) MP have no acute negative effects on microorganisms and C turnover, (4) MP form a specific habitat in the soil, the plastisphere, where MP-specific processes take place, e.g. the enzymatic hydrolysis of PLA/PBAT, (5) MP can enter the soil food web via nematodal uptake and affect nematode reproduction, which could destabilize the soil food web.