Understanding Different Types of Plastic: What Those Recycling Numbers Mean - Part 2

markets. Oil price fluctuations can flip these economics overnight. Physical properties determine processing difficulty and cost. High-melting plastics require more energy to process. Brittle plastics create fines and material loss. Low-density plastics cost more to transport. Plastics that absorb contaminants require extensive cleaning. These factors compound—foam PS is low-density, brittle, contamination-prone, and low-value, making recycling economically impossible. Infrastructure investment creates recycling momentum or barriers. PET bottle recycling has decades of investment in collection, sorting, and processing equipment. This infrastructure creates economies of scale that improve economics. Conversely, lack of infrastructure becomes self-fulfilling—without processing capability, collection makes no sense; without collection, investing in processing makes no sense. Market demand for recycled plastic varies dramatically by type and quality. Clear PET flakes have global commodity markets. Black PS has virtually no market. Brand owners' commitments to recycled content create demand and improve economics. Legislation mandating recycled content or banning virgin plastic could transform recycling economics, as seen with bottle bills achieving 90% return rates. ### The Truth About Biodegradable and Compostable Plastics Biodegradable and compostable plastics promise to solve plastic pollution but often create more problems than they solve. These materials, usually marked as number 7, require specific conditions to break down and contaminate both traditional recycling and composting streams when mishandled. "Biodegradable" doesn't mean what consumers think. Many biodegradable plastics only break down at temperatures above 50°C with specific humidity and microorganisms—conditions not found in landfills or oceans. Oxo-degradable plastics fragment into microplastics rather than truly biodegrading. These materials can persist in the environment for years despite biodegradable labels. Compostable plastics require industrial composting facilities operating at 60°C with controlled humidity and microbial populations. Home compost bins don't reach these conditions. Even industrial facilities often reject compostable plastics because they slow composting processes and leave residues. The lack of composting infrastructure means most compostable plastics become landfill waste. Contamination issues plague both directions. Compostable plastics in recycling streams cause defects and degradation. Traditional plastics in composting streams don't break down and contaminate compost. Consumers can't distinguish between plastic types by appearance, leading to systematic contamination. The similar appearance of PET and PLA exemplifies this problem. Life cycle analyses reveal complex environmental tradeoffs. Producing PLA from corn requires agricultural land, water, and energy. The total environmental impact may exceed traditional plastics depending on disposal method. If compostable plastics end up in landfills, they generate methane—a potent greenhouse gas. The promise of biodegradable plastics often distracts from reduce and reuse strategies. ### Mixed Plastics and Contamination Issues Mixed plastics and contamination represent recycling's greatest challenges. Even small amounts of wrong plastic types can ruin entire batches, while contamination from food, labels, and additives reduces quality and value. Understanding these challenges explains why recycling rates remain low despite technical capability. Polymer incompatibility creates fundamental challenges. Different plastics have different melting points, densities, and properties. PET melts at 260°C while PP melts at 160°C—processing mixed plastics at any temperature leaves some unmelted or some degraded. Even chemically similar plastics like HDPE and LDPE don't mix well due to different molecular structures. Mixed plastics create weak points, discoloration, and processing problems. Sorting technology has limits despite advances. Near-infrared spectroscopy identifies plastic types but can't see through labels or contamination. Black plastics absorb infrared, making identification impossible. Multilayer plastics show only the surface layer. Small items fall through sorting screens. Wet plastics reflect differently than dry. These limitations mean perfect sorting remains impossible. Food contamination particularly challenges recycling. Grease absorbs into plastics, especially polyolefins, and resists washing. Dairy residues create odors that persist through recycling. Sugar residues caramelize during melting, creating brown specks. Even thorough washing can't remove all contamination. Food-contact regulations require higher cleanliness standards than technical applications, limiting recycled plastic use. Labels, adhesives, and inks create unexpected problems. Paper labels don't melt, creating defects in recycled plastic. Adhesives can degrade at processing temperatures, creating odors and discoloration. Inks contain heavy metals and organic compounds that concentrate during recycling. Even "recyclable" labels may use adhesives incompatible with recycling processes. ### How to Actually Recycle Plastics Properly Proper plastic recycling requires understanding both the technical aspects and local infrastructure. Consumer actions significantly impact recycling success, but the most environmentally responsible choice often isn't recycling—it's avoiding single-use plastics entirely. Check local recycling guidelines, not just numbers. Recycling capability varies dramatically by location. Some areas accept all numbers 1-7, others only 1-2. Some want caps on bottles, others off. Some accept plastic bags, most don't. Contamination from non-accepted items costs recyclers money and can contaminate good materials. "Wishcycling"—putting items in recycling hoping they'll be recycled—causes more harm than good. Preparation matters more than people realize. Rinse containers to remove food residue—dishwasher clean isn't necessary, but visible contamination is problematic. Remove labels if they come off easily. Sort plastics if your program requires it. Flatten bottles to save space but don't crush them completely—automated sorting needs three-dimensional shape recognition. Recognize recycling limitations and alternatives. Most plastics can only be recycled 2-3 times before properties degrade too much. Recycling requires energy and creates emissions. Reducing consumption and reusing containers provides greater environmental benefit than recycling. Choose products with minimal packaging, buy in bulk, use reusable containers. Support systemic change beyond individual recycling. Advocate for bottle bills and extended producer responsibility laws that make manufacturers responsible for plastic waste. Support businesses using recycled content and minimal packaging. Push for standardized recycling systems and better labeling. Individual recycling helps, but systemic change is essential for solving plastic pollution. Consider the entire lifecycle when making choices. A durable plastic item used for years may be more environmental than single-use alternatives. Lightweight plastic packaging might reduce transportation emissions compared to heavier alternatives. Local factors matter—in areas with landfill methane capture, landfilling might be better than contaminating recycling streams. Environmental choices are complex and context-dependent.