Clean Energy 101: All Plastics Aren’t Created Equal
Why capturing plastic emissions on a life-cycle basis means going further than recycling potential.
News articles referencing carbon footprint reduction strategies abound as sustainability initiatives gain global focus. Many of these pieces focus on ways individuals or corporations can reduce their climate impact, but collective interest in a more detailed understanding of the carbon footprints of products is desired. A product’s carbon footprint accounts for climate pollution produced in a complete life cycle — from manufacturing all the way through disposal.
Understanding the climate impact of plastics gets a little more complicated. Plastics and other petrochemicals contribute a significant amount of greenhouse gas emissions when aggregated and the share of emissions embodied in each product can be very different. Understanding these emissions differences at the product level empowers purchasers, product developers, and regulators to make cleaner decisions.
A complex petrochemical supply chain is no longer justification for climate inaction. Often the retailer who stocks the product, the supplier who delivers it to market, the fabricator who molds it into shape, the producer who supplies resin pellets, and the operator who extracts oil and gas feedstocks are different companies that have minimal interaction with other parts of the supply chain. That level of fragmentation hinders companies from understanding climate risks in their supply chains. Research into life cycle emissions provides compelling evidence that plastic emissions vary widely across products and producers.
Plastic Emissions Begin with Product Design
Design decisions have a significant impact on a product’s life cycle emissions before production even starts. Thermoplastics make up about 80 percent of plastic production and consist of six main resin types: (1) PET, or polyethylene terephthalate (think soda bottles and polyester); (2) HPDE, or high-density polyethylene (think cleaning chemical bottles and laundry detergent); (3) PVC, or polyvinyl chloride (think plastic pipes and credit cards); (4) LDPE/LLDPE, or low/linear low-density polyethylene (think plastic film and bags); (5) PP, or polypropylene (think food storage containers and car parts); and (6) PS, or polystyrene (think Styrofoam and car cushions). Each of these resins has a unique manufacturing process that affects the range of possible emissions. The chart below compares several literature sources’ cradle-to-polymer pellet emissions factors for traditional plastic production processes.
Designing products with materials that have lower emissions from the very beginning can have significant impacts on the overall emissions footprint of the industry. HDPE, LDPE, LLDPE, and PP resins are known as polyolefins and are among the simplest plastics to produce, leading to a similar range of average life cycle emissions. PS and PET, however, combine several separation and catalytic conversion steps for production, resulting in higher average life cycle emissions compared to the simpler polyolefin resins.
Similar Products. Different Emissions Profiles.
Embodied emissions can vary significantly within the same plastic type. The method of extraction, type of oil or gas being extracted, and flaring procedures of upstream operators can drastically affect the emissions from upstream feedstocks. The complexity and efficiency of the refinery and steam crackers that turn crude oil into propylene plastic precursors can impact the product’s emissions footprint. Further down the supply chain as processes are heavily electrified, the source of electric power can have significant emissions impacts. To quantify these impacts, we modeled the potential life cycle emissions of two polypropylene reusable home food containers using the following inputs:
Modeling these fictional supply chains demonstrated a 350 percent difference in emissions between two functionally identical products with the same processing technology. These differences are not reflected in the recycled content of a product, the leading plastic sustainability metric. Choosing different commercial-scale process technologies and fossil-based feedstocks, such as mechanical recycling and coal-to-chemicals, can further increase the emissions difference of the processes to nearly 30 times. Product carbon footprint transparency can even show if new recycling methods produce more emissions than landfill.
On the shelf, these two food containers would appear identical but have drastically different carbon footprints. Consequently, production methods transparency is essential for differentiating plastic products based on increasingly important climate performance metrics. Climate-conscious consumers are turning to producers and brands to provide this type of information on their products to make climate-informed decisions. This provides valuable information not just to consumers but also for producers and brands looking to understand and reduce their products’ carbon footprint. With more detailed supply chain information, they can identify high-impact opportunities to reduce emissions, such as purchasing lower emissions-intensity oil and gas or using renewable power at their production facilities. Making these changes can drive large emissions reductions and help create cleaner supply chains.
A Climate-Differentiated Future
Some first movers are already moving forward with providing climate footprints on labeling to end consumers, disclosures in business-to-business sales, and calculations for international carbon border adjustment mechanisms. Producers should be actively looking to understand the emissions along their products’ supply chains in advance of regulatory pressure. By providing reliable and independently verifiable emissions data to consumers, first-mover producers and brands can confidently differentiate their products’ environmental impact and sell to climate-conscious consumers. The plastics landscape is complex and diverse, but with improved transparency and traceability there can be real emissions reductions across the supply chain. Contact Meghan Peltier (mpeltier@rmi.org) for additional insights on transforming this research into operational action.