Biodegradation of Wasted Bioplastics in Natural and Industrial Environments: A Review

Abstract

The problems linked to plastic wastes have led to the development of biodegradable plastics. More specifically, biodegradable bioplastics are the polymers that are mineralized into carbon dioxide, methane, water, inorganic compounds, or biomass through the enzymatic action of specific microorganisms. They could, therefore, be a suitable and environmentally friendly substitute to conventional petrochemical plastics. The physico-chemical structure of the biopolymers, the environmental conditions, as well as the microbial populations to which the bioplastics are exposed to are the most influential factors to biodegradation. This process can occur in both natural and industrial environments, in aerobic and anaerobic conditions, with the latter being the least researched. The examined aerobic environments include compost, soil, and some aquatic environments, whereas the anaerobic environments include anaerobic digestion plants and a few aquatic habitats. This review investigates both the extent and the biodegradation rates under different environments and explores the state-of-the-art knowledge of the environmental and biological factors involved in biodegradation. Moreover, the review demonstrates the need for more research on the long-term fate of bioplastics under natural and industrial (engineered) environments. However, bioplastics cannot be considered a panacea when dealing with the elimination of plastic pollution.

A Review of Bioplastics and Their Adoption in the Circular Economy

“…It can be noticed that the biodegradability evaluation is carried out by different experimental methodologies, such as release of carbon dioxide and oxygen demand measurements. Indeed, the main indicators of biodegradation adopted by these standards are the measurement of BOD (the biological oxygen demand) or the measurement of evolved CO 2 , though also mass loss measurements, measurements of CH 4 evolution, as well as surface morphology and spectroscopy analysis are methodologies in use [ 101 ]. Biodegradability standards describe a series of well-defined conditions under which biodegradability or compostability tests are to be carried out, for example temperature, microbial activity and humidity.…”

“…The microorganisms inhabiting the biofilm secrete enzymes that can be broadly defined as intracellular and extracellular depolymerase [ 28 , 101 , 103 , 106 , 110 ]. These enzymes are responsible for the second step in biodegradation, the depolymerization step, during which the polymer chains are broken down into shorter oligomers and eventually monomers, though this process can also result from abiotic phenomena which are covered later in this section.…”

pH-Stat Titration: A Rapid Assay for Enzymatic Degradability of Bio-Based Polymers

“…Accordingly, temperature may become a limiting factor in the decomposition of biodegradable plastics in natural habitats [ 38 ]. Consequently, industrial composting processes typically utilize temperatures of 50 to 65 °C to accelerate the degradation process [ 16 , 39 , 40 ].…”

Natural Polymeric Materials: A Solution to Plastic Pollution from the Agro-Food Sector

“…During photodegradation, both molar mass and crystal structure are affected. The plastics that have the capacity to biodegrade by hydrolytic mechanisms such as biopolymers made of cellulose, starch, and polyesters such as PHA are known ad hydro-biodegradable bioplastics [ 73 ].…”

“…The experiments carried out in compost or in anaerobic digestion environments show a biodegradability over 50% in 65 and 68%, respectively. For those carried out in aquatic environments, this share is 44%, and for experiments carried out in soil, it is 33% of the cases [ 73 ].…”