ALT LLC

Sustainability: Reusing and Recycling Plastics in AM

ALT now offers sustainability in 3D printed objects using recycled plastics!

Sustainability is more important than ever.

Sustainability

“A true conservationist is a man who knows that the world is not given by his fathers, but borrowed from his children.” —John James Audubon

Why is Sustainability Important?

Sustainability is more important than ever because today, landfills and waterways are inundated with tons of non-degradable plastics derived from petrochemicals. Jambeck et al. estimated that of the 275 million tons of plastic produced in 2010, about eight million tons wound up in the ocean, impacting the health of marine life and poisoning the water with toxins [1]. Statistically, each square mile of ocean has 46,000 pieces of plastic floating in it [2]. Strict mandates in California’s recent commercial recycling law AB 341 are now requiring cities and counties in the state to divert 75 percent of waste from landfills by 2020.

For over a decade, the U.S. has been shipping 50 to 75 percent of the material collected from curbside recycling programs to China each year for processing there [3]. In an effort to clean up China’s atrocious pollution, China’s government has implemented a new directive called “Operation Green Fence,” where Chinese port inspectors allow no more than 1.5% contamination per bale of scrap and now much less material is being shipped overseas [3]. This is seriously impacting recycling in the U.S. and many recycling companies have gone out of business (>20%) due to the 44% reduction in price that the plastic commands ($1.19/lb) and the lack of a demand in the U.S. for the scrap, leading to 2 billion plastic containers now going into American landfills [4].

Shipping recycled plastics halfway around the world requires significant fuel and emission of greenhouse gasses; this is not a solution [5].  ALT is working on solutions to this problem through local reuse of plastic materials directly into new objects.

Background and Sustainability

Plant-based plastics, such as Polylactic acid (PLA), have emerged as a good alternative to petrochemical-based plastics because they are renewable and biodegradable. The majority of plastics, such as polyethylene terephthalate (PET), PLA and others, are manufactured in OPEC countries close to the raw material source. The largest manufacturer of PLA is NatureWorks, which uses mostly corn from the Midwest. Early lifecycle assessments of PLA by DOW/Cargill have shown low CO2 emissions, water usage, and fossil fuel energy requirements [6].

NatureWorks has reduced its dependence on fossil fuel-based energy in the commercial production of PLA by supplanting it with wind power and biomass-driven strategies. They report that a kilogram of PLA uses only 27.2 MJ of fossil fuel-based energy and anticipate a drop to 16.6 MJ/kg in their next generation plants [6]. Despite these clear advantages, there has been some controversy over PLA with respect to compostability and recyclability. For instance, the Plastic Redesign Project, the Container Recycling Institute, Eco-Cycle, the Ecology Center, Eureka Recycling, the Grassroots Recycling Network, and the Institute for Local Self-Reliance, joined together to call for a moratorium on PLA in bottles because it was contaminating PET feedstocks due to challenges in sorting the two clear plastics. This has led to newer technologies that utilize IR spectroscopy to sort materials at recycling stations.

An additional complexity is that PLA is a mixture of two stereoisomers L-Lactide and D-Lactide, which have different degrees of crystallization, molecular weights, colorants or other additives and as a result, the material properties can be significantly different in varying PLA products further contaminating the plastic feedstock. According to Madival et al, 23.5% of PLA is incinerated, and 76.5% of PLA ends up in the landfill, rather than being recycled, primarily due to the lack of commercially available centers for recycling PLA [7].

Local Sustainability

Marborg in Santa Barbara will compost PLA cups that have an identifying green stripe but all other PLA and unidentified objects are put into the landfill. Additionally, composting of PLA is challenging because PLA is largely resistant to attack by microorganisms in soil or sewage under ambient conditions.

Thus, industrial systems are required in order to first hydrolyze PLA at elevated temperatures (~58C) in order to reduce the molecular weight before biodegradation occurs. As pointed out by researchers Brandrup and others in 1999 [8] and Ohkita and Lee in 2006 [9], PLA will not degrade in typical garden compost. Vink concluded that if all produced PLA articles enter into composting processes, the CO2 absorbed by the starch plant would be re-emitted into the atmosphere [10]. According to Shen, the lifecycle would be much more desirable if the PLA was recycled [11] instead of composted. In addition, if manufacturing is done in close proximity to the point of use, transportation costs are reduced and result in positive economic and environmental impacts [7].

The bottom line is we have a responsibility to be part of the solution and engineer for a sustainable green future. ALT has recently developed green process technology that can turn recycled plastics, such as PET, PP, PLA, etc. from plastic water bottles, packaging, and other waste, into new 3D printed objects. See how you can fabricate your next cell phone case or drone with recycled plastics! Get a quote today.

References:

[1] J. R. Jambeck, R. Geyer, C. Wilcox, T. R. Siegler, M. Perryman, A. Andrady, R. Narayan and K. L. Law, “Plastic Waste Inputs from Land into the Ocean,” Science, vol. 347, no. 6223, pp. 768-771, 2015.

[2] N. Nuttall, “Action Urged to Avoid Deep Trouble in the Deep Seas,” United Nations Environment Programme, 16 June 2006. [Online]. Available: http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=480&ArticleID=5300&l=en. [Accessed 3 10 2016].

[3] E. Royte, “onearth.org,” [Online]. Available: http://archive.onearth.org/articles/2013/10/china-to-u-s-we-dont-want-your-stinking-trash. [Accessed 3 10 2016].

[4] J. Nash, “California’s Recycling Industry is in the Dumps,” Blumberg, pp. 19-20, 10 October 2016.

[5] C. Pacanha, “Evaluation of Life-Cycle Air Emission Factors of Freight Transportation,” Environmental Science Technology, vol. 41, pp. 7138-7144, 2007.

[6] E. T. Vink, K. R. Rabago, D. A. Glassner and P. R. Gruber, “Applications of life cycle assessment to NatureWorksTM polylactide (PLA) production,” Polymer Degradation and Stability, vol. 80, pp. 403-419, 2003.

[7] S. Madival, R. Auras, S. P. Singh and R. Narayan, “Assessment of the environmental profile of PLA, PET and PS clamshell containers using LCA methodology,” Journal of Cleaner Production, vol. 17, pp. 1183-1194, 2009.

[8] J. Brandrup, Polymer Handbook, John Wiley & Sons, Incorporated, 1999.

[9] T. Ohkita and S.-H. Lee, “Thermal Degradation and Biodegradability of Poly (lactic acid)/Corn Starch Biocomposites,” Journal of Applied Polymer Science, vol. 100, no. 4, p. 3009 – 3017, 15 May 2006.

[10] E. T. Vink, K. R. Rabago, D. A. Glassner and P. R. Gruber, “Applications of life cycle assessment to NatureWorksTM polylactide (PLA) production,” Polymer Degradation and Stability, pp. 403-419, 2003.

[11] J. J. Shen, “Comparative Life Cycle Assessment of Polylactic acid (PLA) and Polyethylene terephthalate (PET),” 2011.

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