Biodegradable plastics offer environmental benefits but require careful material selection and understanding of real-world composting conditions. This guide covers major bioplastic types, certification standards, and practical selection advice.
1. Major Bioplastic Types
PLA (Polylactic Acid) - Source: Corn starch, sugarcane - Properties: Rigid, transparent, good barrier - Processing: Injection molding, extrusion, thermoforming - Biodegradation: Industrial composting only (58-60°C) - Cost: 2-3x conventional plastic - Applications: Food packaging, disposable cups, trays
PBAT (Polybutylene Adipate Terephthalate) - Source: Petroleum-based (but biodegradable) - Properties: Flexible, tough, good elongation - Processing: Blown film, extrusion - Biodegradation: Industrial and home composting - Cost: 3-4x conventional plastic - Applications: Compostable bags, film, flexible packaging
PLA/PBAT Blends - Most common biodegradable blend - PLA provides rigidity, PBAT provides flexibility - Typical ratio: 60-70% PLA / 30-40% PBAT - Properties adjustable by ratio - Cost: 2.5-3.5x conventional plastic
PHA (Polyhydroxyalkanoates) - Source: Bacterial fermentation - Properties: Variable (rigid to flexible) - Biodegradation: Marine, soil, composting - Cost: 5-10x conventional plastic - Applications: Specialty (marine-degradable, medical)
Starch-Based - Source: Corn, potato, tapioca - Properties: Limited mechanical, moisture sensitive - Blended with: PLA or PBAT for improvement - Cost: 1.5-2x conventional plastic - Applications: Loose fill, agricultural mulch
2. Certification Standards
EN 13432 (EU) - Requirements for packaging recoverable through composting - Biodegradation: >90% in 6 months (industrial composting) - Disintegration: >90% pass through 2mm sieve in 12 weeks - Ecotoxicity: No negative effect on compost quality - Heavy metals: Below specified limits
ASTM D6400 (US) - Standard specification for compostable plastics - Similar requirements to EN 13432 - Biodegradation: >90% in 180 days - Recognized by BPI (Biodegradable Products Institute)
OK Compost / OK Compost Home (TÜV Austria) - OK Compost: Industrial composting (58±2°C) - OK Compost Home: Home composting (20-30°C) - Home composting is more stringent (lower temperature, longer time)
Key Distinctions: - "Biodegradable" ≠ "Compostable" (no time frame specified) - "Compostable" = Certified to degrade within specified time - "Oxo-degradable" = NOT biodegradable (fragmentation only) - Marine biodegradable: Additional certification (ASTM D7081)
3. Practical Selection Guide
Rigid Packaging (cups, trays, clamshells) - Material: PLA or PLA/PBAT (80/20) - Processing: Thermoforming, injection molding - Note: PLA is brittle; add PBAT for improved toughness - Certify: EN 13432 for EU market, ASTM D6400 for US
Flexible Packaging (bags, wraps) - Material: PLA/PBAT (40/60) or PBAT + starch - Processing: Blown film - Note: Higher PBAT content for flexibility and tear resistance - Certify: OK Compost Home for consumer bags
Agricultural Applications (mulch film) - Material: PBAT/PLA/starch blend - Processing: Blown film (thin, 8-15μm) - Note: Must degrade in soil, not just industrial composting - Soil biodegradation standard: EN 17033
Food Service (cutlery, straws) - Material: PLA or PLA/PBAT - Processing: Injection molding - Note: Heat resistance limitation (PLA softens at 55°C) - Consider: Crystallized PLA for improved heat resistance
Cost Optimization: - Starch blending reduces cost by 20-30% - Thickness optimization (thinner = less material) - Source locally to reduce logistics cost - Volume commitment for better pricing