Recycled PET Outperforms PLA in Sustainability Assessment
Updated: Feb 11, 2020
A comprehensive sustainability assessment revealed that recycled content polyethylene terephthalate (RPET) is a more sustainable packaging alternative to that offered by corn-derived polylactic acid (PLA) packaging. This assessment compared packaging derived from RPET and PLA in two broad categories: production and end-of-life. The results revealed RPET as the clear winner when considering impacts on climate, energy, effluents, toxicity and disposal
Two common offerings for packaging are derived from two sources: post consumer recycled content and compostable plastic resin. The first source, RPET, utilizes the existent recycling infrastructure to repurpose plastic products. The second source, PLA, is fabricated by chemical manufacturers into compostable resins that are derived from corn. Thus, the question that emerges for vendors is which packaging, RPET or PLA, is the more sustainable choice. Viewed through the lens of sustainability it is clear that RPET is a better choice because it requires less energy, releases less carbon dioxide, and is safer for our waterways and air.
To determine the most sustainable packaging, the entire lifecycleof the item must be assessed from inputs and production, to use and disposal. The product must be produced in a manner that limits its impact on the environment and does not contribute to increasing accumulation of pollutants, in the air, water and soil. While both RPET and PLA claim to be within these parameters of sustainability, RPET-based packaging emerges, as a sustainable product while PLA –based packaging appears to be a chemical innovation lacking end-of-life considerations.
In order to compare PLA with RPET in a sustainability assessment, it is important to consider the environmental impact of the conversion of the input material into consumer products. While PLA and RPET can be used in similar applications, their lifecycles differ, specifically within the production process and input materials. Each process has its own inherent characteristics and environmental effects. For the purposes of fair comparison, the entire lifecycle of virgin PET, RPET and PLA were considered.
Energy & Climate
Comparing the energy and climate impacts of both PET and PLA are essential to this sustainability assessment. Energy use during production coupled with carbon dioxide emissions is a key indicator of the environmental impact of the product.
PET v. RPET
To gauge the value in utilizing post consumer waste in the production of RPET, it is essential to calculate the energy and greenhouse gas (GHG) savings that occur when comparing virgin PET and its second life as 100% rPET. This data reveals an energy savings per pound of 84% and a GHG reduction per pound of 71%(NAPCOR, 2010). These savings demonstrate the environmental benefits of repurposing virgin PET into new packaging. Figure 1, shows that RPET production consumes significantly less energy than virgin plastic resulting in lower greenhouse gas emissions
Figure 1. Energy Use and GHG Emissions for PET: Virgin and Varying Levels of RPET(NAPCOR, 2010).
PLA v. rPET
Understanding the value in using RPET over PLA requires a comparison to be drawn between the two resins and their impact on climate and energy use. A German firm on behalf of a large producer of PLA products, recently completed a lifecycle assessment of PLA and various content levels of PET. This analysis, as seen in figure 3-5, revealed that only in the category of fossil resources did PLA score better than 100% RPET. It is important to note that this score was achieved by placing a statistical burden on RPET for its first life cycle as virgin PET. If one discounts this burden (as seems appropriate since the repurposing reduces the environmental impact associated with it) then RPET becomes a better choice because it’s fossil resources use less than PLA. Finally, within the category of contribution to climate change and energy impacts, 100% RPET outperforms PLA. Figure 4 and 5 demonstrate that carbon emissions and energy use during the input conversion for PLA is higher compared to that of RPET.
Figure 3. Fossil Resources. Fossil fuel utilization during production(Kruger, 2009).
Figure 4. Climate Change. CO2released during production(Kruger, 2009).
Figure 5. Energy. Gigajoules utilized during production(Kruger, 2009).
Water & Terrestrial Pollution
The comparison of PLA and RPET within the category of water and land pollutants reveals both subtle and obvious environmental impacts, ultimately RPET is found to be less detrimental to waterways and land.
PET v. RPET
Both RPET and PLA require manufacturing processes that are water intensive as well as produce solid waste and water pollution. Figure 6 reveals that despite the use of irrigation water during the corn growing process and manufacturing processes, the total amount of water required for PLA production is more than PET SSP( soda/water bottle grade resin which is the main input for RPET).
Figure 6. Water Use. Process, cooling and irrigation water used during production(Vink, 2002).
PLA v. RPET
Figure 7 shows the phosphate build up within water and on land for both PLA and RPET production. Within the water category of the comparison, the PLA process releases nearly 5 times as much phosphate than the100% RPET process(Kruger, 2009). Whereas, the terrestrial pollution analysis reveals that that PLA releases nearly 3 times as much phosphate(Kruger, 2009). It is abundantly clear that within the water and terrestrial pollutant category, PLA is more environmentally detrimental.
Figure 7. Aquatic Eutrophication. Phosphate effluents emitted during production(Kruger, 2009).
Figure 8. Terrestrial Eutrophication. Phosphate accumulation in during production(Kruger, 2009).
Air contaminates and the related carcinogenic risks are important factors to track when manufacturing plastic resins. Toxins in the air can impact human health and the environment, therefore pollution of this sort is monitored on local, state and federal levels. Based on data in Figure 6, it is clear that PLA has a larger impact on air quality than RPET; releasing nearly 3 times more particulate matter into the atmosphere. However, Figure 10 reveals that PET products cause the most harm to human health based on the carcinogenic risk they pose because their key input is fossil fuel.
Figure 9. Human Toxicity Particulate Matter. Soot released during production(Kruger, 2009).
Figure 10. Human Toxicity Carcinogenic Risk. Known carcinogens released during production(Kruger, 2009).
End of Life
In order to compare PLA with RPET in a sustainability assessment, it is important to consider the environmental impact of their disposal. While PLA and RPET can be disposed of in different ways, RPET emerges the clear leader because of its use of existing disposal infrastructure.
There are a number of disposal options for PLA, PET and RPET products such as landfills, recycling and composting. PET and RPET can be recycled into new PET products and PLA products can be composted if the disposal infrastructure is available for composting. However, if neither of these options is available, these products will most likely end up in a landfill. According to the Environmental Protection Agency (EPA), in 2008, the United States generated 250 million tons of trash, 12% of which was plastics. While recycling rates sit around 33%, the straight to landfill statistics reveal that 135 million tons of waste sees no second life but certain death in municipal waste facilities(EPA, 2008).
PET & RPET
Waste diversion and repurposing is a sustainable way to give a second life too much of the materials disposed of in the US. PET diversion and material reuse is a great example of recycling success, given the efficiencies of the recycling infrastructure. In 2008, 2.4 million pounds of the 5.1 million pounds of plastic bottles available, were recycled, this equates to a recycling rate of 27%(NAPCOR, 2009). These statistics clearly demonstrate the utilization of existent infrastructure to collect, process and divert PET from the waste stream.
PLA packaging’s end of life falls into three categories: composting, landfill or recycling. PLA producers design and manufacture products to be disposed, ideally at composting facilities. According to “Food Composting Facilities Across the US”, over 100 facilities across the country should be able to process PLA products(NatureWorks, 200&). However, it was discovered that only approximately 5% of these facilities processed PLA plastics in the suggested manner. In fact, most of the facilities surveyed indicated that they sort out plastics and dispose of them, as they cannot differentiate standard resin plastic products from PLA products(M. Melick, personal communication, October 25, 2010).
If a PLA product does end up in a landfill, it will most likely remain intact, just like any other plastic. Most landfills will retard the degradation process because of the limited availability of moisture and negligible microbial activity necessary for breakdown(Narayan, 2010). These were never the conditions in which PLA was intended to degrade and will lead to increased plastics accumulation in landfills.
Lastly, PLA is recyclable: however, it can’t be mixed with the current recycling stream, as it must be processed differently than PET. PLA is not visibly different than standard PET packaging, therefore it is challenging to identify and sort it appropriately. This separation, which costs time and money, is essential because PLA is considered a contaminant in the recycling stream(Vidal, 2008). If mixed in with other resin materials, it could harm the quality of future RPET products or inhibit recyclable materials from being recycled(Vidal, 2008).
This environmental assessment has demonstrated RPET as a viable solution to the problem of which plastic packaging is most sustainable. Using an RPET product creates a value-add and a point of differentiation amongst competing options. The verified sustainable story that RPET creates makes for a meaningful purchase that allows vendors to capitalize on growing trends. While PLA has some sustainable characteristics, such as being made from a renewable source, a disposal infrastructure is not widely available for mainstream usage. Therefore at present RPET is the most sustainable option.
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 The Lifestyles of Health and Sustainability (LOHAS) consumer group, the primary purchasers of environmentally conscious and natural products, is estimated to consist of 41 million Americans and is an estimated $US 209 billion marketplace (LOHAS, 2010). LOHAS consumers are aware of the negative health and environmental impacts of single use products. This awareness leads them to seek out sustainable alternatives that fit this lifestyle(French, 2006).  Lifecycle refers to every stages of a process from cradle-to-grave(i.e., from raw materials through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling)(Tester,2005).