The rapid increase in
global plastic production has generated severe environmental concerns due to
the persistence of petroleum-based polymers in natural ecosystems. Conventional
plastics contribute significantly to landfill accumulation, marine pollution,
and the formation of microplastics that pose risks to both environmental and
human health. In response to these challenges, biodegradable plastics derived
from waste biomass have emerged as a sustainable alternative aligned with
circular economy principles. This theoretical review presents a comprehensive
analysis of waste-derived biodegradable plastics, focusing on feedstock
valorization strategies, biochemical synthesis pathways, material performance
characteristics, and lifecycle dynamics.
Second-generation
feedstocks such as agricultural residues and food-processing waste, along with
third-generation sources including algae and chitinous shellfish waste, are
examined for their potential to reduce dependence on food-grade raw materials.
The microbial synthesis of polyhydroxyalkanoates and the
fermentation–polymerization route for polylactic acid production are discussed
in detail. In addition, chemical and enzymatic pathways for chitosan production
from chitin-rich waste are analyzed. The mechanical, thermal, and degradation
properties of these bioplastics are evaluated in comparison with conventional
polymers. Life cycle assessment studies indicate that waste-derived bioplastics
can significantly lower greenhouse gas emissions and fossil resource
consumption, although energy-intensive pretreatment processes remain a
limitation. This review highlights current challenges, research gaps, and
future directions necessary for the large-scale adoption of biodegradable
plastics within a sustainable circular economy framework.