Bioplastics & Biodegradable Polymers

Bioplastics are a diverse family of materials with different combinations of bio-based content and biodegradability. They include: bio-based but non-biodegradable plastics (bio-PE, bio-PET, bio-PTT), which are chemically identical to their petrochemical counterparts but derived from biomass; biodegradable plastics that may be bio-based (PLA, PHA, starch blends) or fossil-based (PBAT, PCL); and materials that are both bio-based and biodegradable (PHA, some PLAs). Each combination has specific applications, advantages, and limitations.

Global plastic production exceeds 400 million tonnes per year, with the vast majority from fossil feedstocks and most accumulating in landfills or the environment. Bioplastics represent less than 2% of total plastic production but are growing rapidly, driven by sustainability concerns, regulation, and consumer demand. Realizing the potential of bioplastics requires addressing challenges across the full life cycle: feedstock sourcing, polymer production, material properties, application development, and end-of-life management.

Hrisana Journal welcomes bioplastics research across the full value chain: microbial strain development for monomer or polymer production, fermentation and downstream processing, material science and engineering, biodegradation studies, life-cycle assessment, and applications development.

Polyhydroxyalkanoates are a family of polyesters produced by bacteria as intracellular carbon and energy storage materials. Over 150 different hydroxyalkanoate monomers have been identified, providing a wide range of material properties — from brittle plastics to flexible elastomers — depending on monomer composition. The most common PHA is polyhydroxybutyrate (PHB), a brittle, highly crystalline material; copolymers with 3-hydroxyvalerate (PHBV) have improved toughness and lower melting temperature.

PHA production is typically two-phase: cells grow under nutrient-replete conditions to high density, then nutrient limitation (often nitrogen or phosphorus) triggers PHA accumulation as carbon is redirected to storage. Some organisms, such as Cupriavidus necator (formerly Ralstonia eutropha), can accumulate PHA to over 80% of cell dry weight. Feedstocks include sugars, plant oils, methanol, and even CO₂ and hydrogen for some strains. Production from waste feedstocks — wastewater, food waste, agricultural residues — is an active research direction that improves sustainability and economics.

PHA is attractive because it is both bio-based and biodegradable in a wide range of environments, including marine waters, soil, and home compost. This distinguishes it from PLA, which is industrially compostable but does not biodegrade readily in ambient environments. The main limitation of PHA is cost — at current production scales, PHA is several times more expensive than conventional plastics. Scaling production, developing cheaper feedstocks, and improving extraction processes are the main routes to cost reduction.

Polylactic acid is the most widely produced bioplastic, used in packaging, fibres, 3D printing filament, and a range of other applications. It is produced by polymerization of lactide (the cyclic dimer of lactic acid), which is in turn produced from fermentation of sugars by lactic acid bacteria. Lactic acid fermentation is one of the oldest industrial bioprocesses, with high yields and productivity.

PLA properties depend on stereochemistry. Poly-L-lactide (PLLA) is highly crystalline with a melting point around 170-180°C; poly-D-lactide (PDLA) is similar but mirror-image; racemic PDLLA is amorphous. Stereocomplex PLA, combining PLLA and PDLA, has a melting point above 220°C and improved mechanical and thermal properties. Polymer architecture and blending with other polymers or fillers extends the property range further.

PLA is industrially compostable under conditions of elevated temperature (55-60°C) and humidity, where hydrolysis and microbial degradation proceed in months. Under ambient conditions, PLA degrades very slowly — a limitation for applications where littering is a risk. Research on PLA degradation focuses on: enzyme discovery and engineering for faster hydrolysis; blending with more readily biodegradable polymers; and developing PLA grades with controlled degradation profiles.

Bio-based drop-in plastics — bio-PE, bio-PET, bio-PTT, bio-PA — are chemically identical to their petrochemical counterparts but produced from bio-based feedstocks. They offer the performance and recyclability of conventional plastics with reduced carbon footprint. Bio-PE is produced from sugarcane ethanol by Braskem at commercial scale; bio-PET is produced partially from bio-based ethylene glycol (typically from sugarcane) with the terephthalic acid component still fossil-based, though fully bio-based PET is under development.

The advantage of drop-in plastics is their compatibility with existing infrastructure — they can be processed on the same equipment, used in the same applications, and recycled in the same streams as conventional plastics. This avoids the chicken-and-egg problem of new materials requiring new infrastructure. The disadvantage is that they do not address the end-of-life challenges of plastics; bio-PE in the ocean is just as persistent as fossil PE.

Bio-based drop-ins can reduce greenhouse gas emissions significantly. Bio-PE from sugarcane has a negative cradle-to-gate carbon footprint (carbon sequestration during sugarcane growth exceeds production emissions). The sustainability benefit depends on feedstock sourcing, agricultural practices, and land-use change effects, which must be carefully assessed through life-cycle assessment. Hrisana Journal welcomes LCA studies of bio-based materials that transparently address these complexities.

Beyond the major commercial bioplastics, a range of emerging materials is being explored. Polybutylene succinate (PBS), produced from bio-based succinic acid and 1,4-butanediol, is biodegradable and has properties similar to polyethylene. Polyfurfuryl alcohol (PFA), from furfural derived from hemicellulose, is a biobased thermosetting resin. Bacterial cellulose, produced by Gluconacetobacter and other bacteria, has exceptional mechanical properties and is being explored for applications from biomedical to electronics.

End-of-life management is critical for realizing the sustainability potential of bioplastics. Industrial composting infrastructure is limited in most regions, limiting the value of industrially-compostable materials. Mechanical recycling is feasible for some bioplastics (PLA can be recycled if separately collected) but is complicated by contamination of conventional plastic recycling streams. Chemical recycling — depolymerizing plastics back to monomers for repolymerization — is being explored for PLA, PET, and other polymers and may offer a route to circular materials management.

For researchers developing new bioplastics, attention to end-of-life from the design stage is essential. Materials should be designed for durability in use but controlled degradability at end-of-life, with the end-of-life pathway (industrial composting, recycling, biodegradation in specific environments) explicitly considered. Hrisana Journal welcomes submissions that address these design challenges alongside materials development. Visit our Submit Manuscript page to begin your submission.