Not all recycled content materials are created equal - especially when it comes to recycled plastics. In a new report released by StopWaste and the Healthy Building Network, we take an in-depth look at the health implications, supply chain considerations, and potential to scale up recycling of the world’s most common plastic: Polyethylene (aka PE).  This report, Post-Consumer Polyethylene in Building Products, is the latest installment in our Optimizing Recycling series.
Polyethylene is a material widely used in product packaging, beverage containers, and myriad consumer products. High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), and Linear Low Density Polyethylene (LLDPE) are all readily recyclable in California. Polyethylene plastic scrap bottles and plastic bags usually have minimal contents of concern and are easily processed into feedstock for new products, including building materials. Despite the great potential for recovery of PE, sizeable barriers stand in the way of a lot more recycling.
The explosive growth in virgin ethylene production on the U.S. Gulf Coast, driven by cheap energy, has meant that most post-consumer scrap PE is either landfilled, incinerated, or sent overseas for processing. 
Industry trends in recycling collection technology are also undermining the value of post-consumer polyethylene feedstocks. Pipe and plastic lumber manufacturers in the U.S. require supplies that have minimal amounts of contaminants such as volatile residual substances in packaging and other types of plastics. Yet proportionally less “good material” is coming out of the plastic waste recycling stream due to the rising use of municipal single stream recycling over the past decade. Mixed and low quality scrap materials that come from single-stream recycling centers are more likely to be exported than sorted and screened for high-quality polyethylene scrap. As a result, more recovered plastic bags are exported than processed domestically. 
Additives used for plastics can turn into contaminants when recycled. As seen with other recycled content materials, feedstocks with less contamination have an increased potential for recyclability as well as increased value to purchasers.  For PE, contaminants come in the form of residual materials from packaging (residue from bottles that contained pesticides, for example), or from additives used in manufacturing to achieve certain product characteristics. Perhaps the most problematic additive to PE products are so-called biodegradation additives used in plastic packaging. These additives (but not the rest of the plastic) degrade when exposed to sunlight or other environmental conditions. When these products are collected and used as post-consumer recycled feedstocks in products like pipes and decking, however, these additives can lower the reliability and value of a manufacturer’s product. This is why, in our report, we recommend that plastic manufacturers stop using degradability additives in all new polyethylene.
Despite the challenges, polyethylene has the potential to be a recycling success story. For example, in November voters in California will consider a ban on single-use plastic bags that would also mandate the use of post-consumer content in reusable bags, including bags made of polyethylene.  Further, the Association of Plastic Recyclers is developing protocols to standardize screening of incoming polyethylene feedstocks, which should foster more consistent supplies. These types of product standards and policy drivers will create demand for recycled polyethylene plastics and close the loop on a high value feedstock.
Post-Consumer Polyethylene in Building Products is the fifth paper in the Optimizing Recycling series we launched last year. Prior papers established our evaluation framework, and examined polyvinyl chloride (PVC), glass cullet, and flexible polyurethane feedstocks. All are available on our website, https://healthybuilding.net/content/optimize-recycling.
This article was authored by both Wes Sullens and Jim Vallette. Wes Sullens of StopWaste supports progressive green building policies, codes, standards and legislation on behalf of Alameda County, California. Jim Vallette is Research Director for the Healthy Building Network.
 Polyethylene sales accounted for 35% of all USA plastic resin sales in 2014. The next most common resins, polypropylene and polyvinyl chloride, accounted for 15 percent and 14 percent, respectively. (American Chemistry Council. “2015 Resin Review,” April 2015.)
 CalRecycle cautions that “contamination of collected materials” and “export trends of recycled materials” may greatly impact future job growth. (Limacher, Frank. “AB 341 Goal: 75% Recycling by 2020 Creating New Jobs Through Increased Recycling, Processing and Remanufacturing.” CalRecycle, April 16, 2013. http://bit.ly/2cNkglR)
 In 2005, the Healthy Building Network and the Institute for Local Self-Reliance examined the market for lumber made from recycled plastic. The report rated fourteen plastic lumber products as “most environmentally preferable” because they contained only polyethylene plastics and, according to the manufacturer at the time, at least 50% of the polyethylene was from post-consumer sources. (Platt, Brenda, Tom Lent, and Bill Walsh. “The Healthy Building Network’s Guide to Plastic Lumber.” Institute for Local Self-Reliance, June 2005. https://www.greenbiz.com/sites/default/files/document/CustomO16C45F64528.pdf.) At least eight of these fourteen products remain on the market, but current literature reveals that most if not all have decreased post-consumer content in favor of pre-consumer (factory-generated) scrap or even virgin polyethylene. Plastic lumber products listed in the report that are still on the market include: SelectForce; PlasTEAK; TRIMAX; American Plastic Lumber’s HPDE decking; Perma-Deck Advantage+; Eco-Tech; Enviro-Curb; and MAXiTUF. Resco Plastics, manufacturer of MAXiTUF plastic lumber, explains, “Due to the current price increases for our raw material, Resco Plastics, Inc. is no longer able to guarantee its post consumer content.” (Resco Plastics Incorporated. “Plastic Lumber Warranty,” 2016. http://rescoplastics.com/warranty/.)
 Plastic scrap exports to Asia have soared since 2000. This trend continued through 2013, the most recent year for which data are available from the Society of the Plastics Industry. Of the plastic film collected for recycling in the US, only 42 percent was processed in the U.S. or Canada. Shippers exported the remaining 58 percent. (Taylor, Michael D. “The State of Plastics Recycling in the U.S.” presented at the 11th China International Forum on Development of the Plastics Industry & China Plastics Recycling/ Reutilization Forum, Yuyao, China, October 2015. http://www.slideshare.net/mdairtaylor/the-state-of-plastics-recycling-in-the-us.)
 See our report Optimizing Recycling: Criteria for Comparing and Improving Recycled Feedstocks in Building Products for more on how additives and contaminants can affect common post-consumer recycled feedstock materials markets.
 California plans to require that reusable plastic grocery bags contain a minimum of 20% post-consumer recycled material, a requirement that would double to 40% in the year 2020.